Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Seduction => Topic started by: denti alligator on January 09, 2012, 03:23:16 AM
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In trying to locate the source of my turntable hum I got me some shorting plugs. Putting these in the input jacks, with the output going to my SEX amp I'm hearing noticeable hum when the volume pot is at 60 or higher. Normal?
It gets more noticeable when the turntable is plugged in.
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Sam,
Very little hum is normal. How does the SEX do with shorting plugs in the input and the volume at 60?
If that sounds very quiet then you have vindicated your table/arm/cartridge with the shorting plugs and located the hum to the Seduction (you lifted the TT ground wire, right?). I'll post all the ground/circuit common terminals and you can check them.
Any terminal with a bunch of solder should be "wicked" then resoldered. I'm a big fan of making a tight mechanical joint first. That requires crimping the wire end with a pair of needle nosed pliers first.
The fact that the hum increases with the TT on says you might not have a good ground. Or that the TT needs the power cord flipped, rotated 180 degrees. If you can't do that get a "cheater plug" and try flipping.
We can beat this if you persist!
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What kind of listening level is that setting? Too loud, or just right? Also, does the noise have a buzzy component or is it a soft 60 cycle hum? If it's buzzy you may have a ground loop with other gear that can be found by unplugging the other gear and seeing of the hum changes. Is the preamp near any equipment with a power transformer? If so try moving the preamp to see if it's picking up 60Hz from another piece of gear.
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Shorting plugs in the SEX inputs gives me ZERO hum. None at all. But that doesn't tell me anything about the turntable, which then isn't plugged in.
The hum is kind of buzzy with some hum. The volume level is just right for me, which is maybe a little loud, but not too loud. It's right where I like it.
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If it's buzzy then you usually have ground problem somewhere. I can't recommend it for liability reasons but some folks try cheater plugs to lift the ground on one piece of gear in order to break a ground loop.
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Like a ground loop isolator? I've got one of those from Radio Shack. It doesn't appear to be making much of a difference, but let me try again.
I should say that I had a pretty nasty buzzing that was mostly eliminated by running a wire from the ground bus on the Seduction to the external power supply unit of the turntable.
Lifting that ground makes for an unbearable buzzing.
With that ground in place, I'm still getting buzzing. But I should also note that I have plugged a different turntable into the Seduction and heard almost no buzzing/humming, which seems to locate the problem elsewhere. Shorting plug experiment says otherwise...
I'm confused. And a bit frustrated.
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More info:
The Seduction is sitting right next to the SEX on a glass shelf. Turntable above them. Turntable power supply a shelf below.
Cheap switch being used, but I'm not getting noise from the other two inputs, so I doubt this is the problem. Switch is behind the subwoofer, which is not turned on during listening. Also near wall power. Nothing else beside a floor light nearby. Phone on other side of the wall.
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Ground loop problems imply two pieces not working together. So actually the experiment with the other turntable not making noise tells you that the problem is between the current turntable and Seduction. When you shorted the inputs on the Seduction was that wire still connected between the ttable and Seduction? If so try the Sed again without the Ttable connected to it at all. If the buzz goes away it may be that a cheater plug on the ttable cord (if it is three prong) will help.
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Sam,
To be certain that nothing is radiating hum/buzz try spreading all electronics out with a foot of two between each using shielded interconnects. This is a situation of it can't hurt.
Try unplugging the power supply for the table with it still connected to the Rega and the Seduction. Does it still hum/buzz? It should since the shorting plugs didn't remove the problem.
When you tried the shorting plugs did you lift the grounding wire from the turntable power supply? You want no other connections except the interconnects to the SEX.
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It's so hard to tell now, but I moved the Seduction just an extra 10-12" or so from the SEX and I think it's better. I'm still getting hum at 70/75+ on the volume pot (shorted SEX or from TT), but I think this is normal, no? Playing Neil Young's Zuma right now at about 70 and hum is inaudible in between tracks (well, not the cleanest record, but...) and it's plenty loud.
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So, yes, the buzz is gone. But again, a deep hum is present. So I put that ground loop isolator in between the turntable and the Seduction input and it got rid of the deep hum. Now there's only a higher pitched buzzy-humming that is very quiet, and only really noticeable at 90+.
So I guess I'm happy...
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The RS Ground Loop Isolator ... like this? ... http://www.radioshack.com/product/index.jsp?productId=2062214#
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Sam,
You might have to stop at a hardware store or Home Depot and find a "cheater." This is a grounded to phased plug adapter. It removes the ground on one component, this would be your TT power supply (PS). The first thing to try is removing the ground from the PS. Then you should try rotating the plug 180 degrees, this swaps the hot and neutral. Both are standard hum busting techniques.
Then there is a whole permutation of grounding wires. You have one from the PS to the Seduction. Have you run a ground wire from the table/arm to the Seduction? (I know we went through this before but I don't remember the answers.)
I would expect that the ground on the PS is carried on to the TT, but maybe not. You just have to seek out the combination that works for you.
The grounded terminals are T3, T8, T13, T18, T23, T28, T33, T38 & T43. These are all connected to the chassis/safety ground.
The circuit common terminals are T7, T10, T11, T14, T16, T20 and tube pins 4.
Somewhere they are tied together with a wire or jumper, but I'm not sure where. It may be at the ground buss at the inputs.
You should go over all these and check.
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Laudanum, yes, that's the one I have. I have a feeling now that the hum appears to be mostly eliminated with the ground loop isolator that the entire sound of my records has been 'thinned out,' that is, there's less bass. But maybe that's a misperception.
Can these devices affect the sound significantly? Well, I know they can, because the hum was eliminated, and also because I hid it behind some other wires that happen to have been near the switch I'm using, and this only brought the hum back. Keep the isolated itself isolated took care of that.
Grainger, thanks for the tips. I'll report back when I've found the time to investigate further.
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Yeah, that ground loop isolator was killing the sound. Out it goes. I can live with hum if removing it means losing the heart and soul of the music.
The PS goes into the wall with a wall wart, so there's no ground. And anyway the hum is there whether it's plugged in or not.
But now I've moved the Seduction back next to the SEX and the hum does not increase, nor does the buzzing return. Weird, though it's now on the other side, so the inputs are no longer close to the other amp. Not sure if that makes a difference. Or rather, I guess that makes a difference...
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Alright, back to the start. The Seduction is definitely humming. It's a low, deep hum, not buzzy.
I'll go ahead and check those ground terminals and see if anything is loose. What else can I try? And again, how normal is this? Grainger, you're first response to this question could be read in two different ways:
1. It is normal to have a little bit of hum
Or
2. Normal is to have very little, i.e. almost no, hum.
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I go with normal is to have very little hum, almost no hum. Part of it has to do with the S/N ratio with your cartridge being the signal. IIRC it is around 4mV, right?
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Yes, that ground isolator is a pair of tiny transformers. They are probably designed to work best at 1K or 2K ohms, not 47K like the Seduction input.
The good thing is, now you know it is a ground current problem - there is hum current in the ground side of the interconnects between the turntable and the Seduction. The puzzle is where does it come from. You say that removing the power supply from the wall socket has no effect, so it has to be capacitive coupling from something else, or a ground loop within the turntable/power supply/interconnect/ground wire system. Sometimes the "cold" side of the cartridge wires is grounded at the turntable, which allows some (or all if you don't have the separate ground) of the current to go through the interconnect grounds. Does the ground wire (turntable to Seduction)run close to the interconnects? If not, that would allow for magnetic hum pickup in the loop area.
Since this is a puzzle - the obvious ones have not helped - consider the possibility of old-style flourescent lights, light dimmers, etc.
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The arm on his table is a Rega. Internally, there is a ground wire for the arm tube and the arm base, both are carried on the shield of the left channels cable. There is no seperate, external ground wire.
For the record, liberating the grounds from the left channel RCA and using a seperate ground wire with my Rega arm didnt make much difference if any at all. Re-wiring the arm did but that was because the internal wiring was a mess with atleast two cold solder joints.
Denti --- I was going to tell you that I tried that RS ground loop islolator in a car audio system installation many years ago. It kills the bass as you already found out.
It's been mentioned to flip two prong plug for TT if possible. If you havent tried it yet, try flipping two prong plugs for everything. The culprit of the last bit of low level hum and buzz in my headphone system ended up being the CDP. Strange because the CDP and the digital player were quiet but selecting the TT as source, I still had a little bit of hum and buzz. Once I unplugged the CDP it was gone. There may be a little bit still there with FPIII and Crack wide open but I would never come close to listening that loud and I doubt that my HP's would survive it. For all intents and purposes, it's quiet. I havent heard anything between tracks even at my highest listening levels. Also, I noticed that there was more hum from an Ortofon OM10 compared to the other carts I tried ... Shure, Pickering, Music Hall. But I havent tried the Ortofon again since the fix. This is on my headphone system - Rotel TT (RB250 arm) - Seduction - FPIII - Crack. Keep at it, it can be very quiet if not silent.
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Thanks, guys, but the turntable can't have anything to do with it, since the hum is there when it isn't even plugged in to the Seduction. That's how I've been using the shorting plugs, at least: they go in the inputs, the outputs are still going to the SEX.
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The normal noise floor of the Seduction has a very slight bit of 60Hz (soft low hum, not buzzy) in the right channel (due to the right channel circuit components proximity to the power transformer) This is usually only heard when the system is really cranked up to excessive loudness. As Grainger points out, whether it intrudes or not will depend upon the output level of your cartridge. If it is down around 2mV it might. If it is up around 4-5mV as we recommend it shouldn't be a problem.
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Output voltage of the cart I'm using is 5. But again, I'm getting the hum even when the table is not connected to the Seduction.
Should I check out the grounding at the terminals Grainger suggests or is there another troubleshooting tip you might suggest?
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If it's just low (60Hz) hum, not buzzy, it's not grounding issues. That would be magnetic coupling, similar to the kind of problem one can run into when using a step up transformer. I'd suggest trying to move the Seduction away from the SEX and other gear with power transformers as far as possible, and also try rotating the Sed relative to the other gear. Sometimes you can null out the magnetic fields that are coupling with the circuit that way.
Another possibility is to try different tubes if you have any handy. Some might be a wee bit less susceptible to picking up hum, though I don't know if the tubes are really the main culprit in picking up the magnetic field so I don't know that you would hear a night and day kind of difference.
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Switched out tubes. Same.
Moved the Seduction. There's a very, very low hum that goes away when it's placed right, but the main noise is still there. What is this noise? Well, it's a kind of sshhhhh white-noise-ish sound. Not really buzzing, and not just a low hum. Somewhere between the two. Again, it's only audible at 70+ on the volume pot. But that's where I listen, a lot of the time.
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The shhhh part of the noise is tube rush, pink noise coming from the tube itself. The only cure for that is to look for tubes that do it less (or use a cartridge with a higher nominal output level). Unfortunately the tube price often tends to be inversely proportional to the noise level. Tubes like 7308s were designed for lower noise output and may help.
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OK, I've played around with this a bit. I think what I'm hearing is a combination of three noise sources: 60hz hum, tube rush, buzzing from poor grounding.
The hum is reduced when I move the Seduction to the floor, but only to the floor. I don't really want to leave it there, so I'll have to figure out a way of positioning it to assure reduced hum.
The tube rush is minimal, especially once I plugged in the turntable again (I was testing with the shorting plugs in).
That leaves the buzzing. Yes, there's still some buzzing. But I know where it's coming from. It's the turntable power supply. I've already soldered alligator clips to the ends of a piece of wire (leftover Teflon coated from the Sed kit) and attached one end to the ground bus of the Sed and the other to a screw at the back of the TTPS. This reduces buzzing significantly. However, not fully. If I hold the other end of this wire in my hand and touch the power supply it goes away entirely. So my attempt at grounding is not good enough. How might I make a more solid grounding?
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If I hold the other end of this wire in my hand and touch the power supply it goes away entirely.
Oh man, that is one effect that makes me nuts, when somehow touching a ground wire works better than actually grounding it. I can't quite wrap my head around what is happening that isn't working when the wire is directly connected, but I have sure experienced it many times. I'm guessing that somehow the path through the Seduction chassis and safety ground wire is actually allowing the injection of noise into the preamp as it passes thru it. Maybe try touching the wire from the screw on the TTPS right to the safety ground in the wall socket? (REALLY CAREFULLY)
I'll say it's 50/50 whether it makes it better or a lot worse... Grounding issues are a challenge indeed.
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Sam,
Let me see if I get this right. With your body as a high value resistor in series with the ground wire from the TT to the TTPS you get no buzzing at all? Do you see where I'm going here, try a 100k resistor in series with the ground wire.
I'm thinking that you should take a meter and see if the chassis of the TTPS is grounded to the TT when plugged into it. It seems to me that the power supply connection should include an integrated ground.
That also makes me wonder how close to the TT the TTPS is. The whole reason for outboard power supplies is to remove the noise producing components (mostly hum) from the audio generating components (cartridge/arm).
After that let's try wrapping the TTPS in aluminum foil and swinging incense above it. Maybe a Voodoo doll? (I'm not really serious with those two.)
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No, ground wire is from the Seduction to the TTPS. And that's where my body adds something to reduce buzz to zero.
The TTPS is over two feet below the turntable.
Should I add a resistor to the ground wire going from the Seduction to the TTPS?
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No, ground wire is from the Seduction to the TTPS. And that's where my body adds something to reduce buzz to zero.
I'm not sure I follow, is the wire secure on both ends but your touching it makes the buzz go away?
The TTPS is over two feet below the turntable.
That should be more than enough distance to keep one from inducing hum into the other. It is something else.
Should I add a resistor to the ground wire going from the Seduction to the TTPS?
I don't think so. It depends on your answer to the first question in this post.
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No, ground wire is from the Seduction to the TTPS. And that's where my body adds something to reduce buzz to zero.
I'm not sure I follow, is the wire secure on both ends but your touching it makes the buzz go away?
The wire is secure at the Seduction end. When I attach the alligator clip to the screw at the back of the TTPS buzzing is significantly reduced, but not entirely eliminated. Only when I take that alligator clip in hand and put my other hand on the TTPS does the buzzing disappear entirely. Alternately, if I hold the alligator clip against the back of the TTPS with my hand (so that my hand too touches the unit) the buzzing also stops entirely.
Note, buzzing is *significantly* reduced by just attaching the ground wire with the alligator clip. The addition of my body reduces buzzing down to zero.
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Yeah, this is the kind of thing I have experienced. My hunch is that your skin might be acting more as a capacitor than a resistor and somehow it is shunting off noise that's carried on the wire. As an experiment see if touching the wire at the Seduction end to the screw next to the IEC power inlet rather than the Seduction ground post gives any improvement.
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How about a ceramic capacitor, 0.1uF, in series with the ground wire?
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How about a ceramic capacitor, 0.1uF, in series with the ground wire?
I tried one of the Teflon caps 0.1uF and it made no difference. Neither did moving the ground closer to the ground nut on the Sed.
Any other ideas?
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Reading through this, I have a couple thoughts. Maybe not good thoughts, but thoughts...
First, is the power supply for this table the kind of thing that is "optional"? I.E. you could plug the table into a wall outlet, but instead you plug it into a box that plugs into the wall? If so, have you tried eliminating the power supply? I know it's a pain to change speeds by moving the belt, but maybe it's worth looking into. If you can clear this, it could point to the culprit being either the power supply or its wall wart.
Also, I don't think anyone has talked about interconnects. Are you using shielded interconnects? How are the shields connected? At both ends or one end. On interconnects with arrows, the arrow points away from the side that has the shield attached. I know in my system, I get less hum if all arrows on my interconnects point away from my Seduction (the shield is attached to the Seduction going to both the Foreplay and the step up, and then all other inputs and outputs point away from the FP).
Hope this helps,
Josh
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Power supply is not optional, due to this specific design of the P3-24.
I'm using cheap interconnects, so this could be the problem, but I doubt it. Any recommendations on fairly inexpensive but quality shielded interconnects?
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The shielding may be over-kill... but I love my interconnects from 'the-music-cable.com' . They are very stiff cables, completely shielded in perforated copper, and should be bent into their correct positions before installation.
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For a cheap option, you could go to your local electronics supplier (Radio Shack or whatever), pick up a spool of shielded twisted pair and some cheap RCAs. Make a couple pairs, one pair with the shield only connected on one side and one with both sides connected. Try both and try the single sided in both orientations. From there, either you're happy with the sound or you can look at commercial designs or DIY recipes using a similar shielding strategy.
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I think Joshua has hit on something.
I tried several shielded and unshielded interconnects from my TT to my Seduction. I got hum with all unshielded interconnects. If the shield is not solidly grounded on the RCA plugs and/or the common is loose somewhere you can get horrible noise, hum, buzz etc.
Sam,
I thought that with the TT disconnected and shorting plugs in you still had hum. Have you fixed that?
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I'm calling what I hear when the TT is unplugged and the Sed shorted tube rush, not hum. The hum seems to be down to a minimum when I place the Sed on the floor. Right now I'm still trying to get the TTPS grounded well enough to eliminate all the buzz.
I don't think the interconnects are the problem here. Though I'm willing to try that at some point.
I'd like to be able to get the same silence I get when I hold the grounding wire with one hand and touch the PS with the other. Should I try another capacitor? A resistor, maybe? How is my body making the difference?
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I think there is a confusion with words. When you say "the TT is unplugged" are you referring to the power supply unplugged from the wall outlet, or the cartridge interconnect unplugged from the turntable, or the cartridge interconnect unplugged from the Seduction?
What led me to this question is a desire to better guess whether the buzz is electric fields (wire or body acting as an antenna, typically for radio-frequency fields) or ground wire currents.
This has become a long thread, and it's difficult to get all the data together to make sense of it. Perhaps we should first concentrate on the buzz, ignoring the hum and the tube rush until the buzz problem is solved. Can you summarize the exact configuration or configurations which have teh buzz, and the one that does not?
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By unplugged, I primarily mean not plugged into the Seduction.
But if we focus on the buzz, that's not an issue. The buzz comes when everything is plugged in as if I would put on a record.
Only when I hold a ground wire attached to the Seduction in one hand and hold the other hand to the PS does the buzz stop. If I attach the wire to the PS without going through me the buzz is significantly reduced, but not entirely.
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. . . Only when I hold a ground wire attached to the Seduction in one hand and hold the other hand to the PS does the buzz stop. . . .
This would be an inconvenient listening position to me. I would have to run wires from the TTPS and Seduction about 16 feet to me and back. I can see why you don't want to do this. That is all tongue in cheek. I got the picture of that in my mind and had to say it. I had an uncle who watched his TV with his big toe on the tuning knob to keep the picture straight. (The tuner needed cleaning)
Sam, the problem is that this is a very odd situation. Usually hard grounding works. I'm pretty much out of steam here but I'll continue to follow the thread and contribute when I think I have some value to add.
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I think it has been well covered here that hum problems are complicated, and sometimes the fix doesn't make sense and/or isn't really fixing the problem, but moving it around. My point is you have to be willing to try anything, because everyone posting in this thread has dealt with this stuff and there is no panacea.
Things suggested and never tried:
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Been very busy, and haven't been able to troubleshoot this as much as I'd like. But I am very grateful for everyone's input!
Right onow i'mwilling to live with the very slight hum. And with the ground in place the buzzing is really only audible at 90 or higher on the volume. I don't use that often.
I briefly experimented with the ground again, this time putting an alligator clip and wire at the PSU and the other at the Seduction, and indeed the buzz completely goes away when I connect those wire with my hands.
There was speculation about my body acting as either a resistor or capacitor. Putting a .1uf cap in the chain did nothing. Any suggestions for what else I might put in the ground to replicate the effect of my body?
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How about a Mr. Potato Head :), or a very large value resistor, like 10 meg or so...John
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Try a resistor - several values, whatever you have available. I suppose your body is less than 200K and more than 1K ohms.
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I am joining this thread a bit late but I have a question based on an similar experience I had. The question is do you have any fluorescent lights on or wireless phones (not cell)? Another thing to try is using an extension cord and relocating the power for the TT to see if the noise goes away.
Cheers;
Mike
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I'm bumping this thread. I found a little hum in the Quickie (see that thread), which I've mostly dealt with, and am realizing that it's the Seduction that hums to levels I find unacceptable. Moving it 1.5 meters away from my SEX makes little difference, though bringing it within 2 feet definitely makes it worse.
When I pick up the Seduction with both hands and with one finger on the ground lug the hum decreases significantly. Big time. I wish I could get it that way all the time. It's similar to the effect I described earlier in this thread, putting my hand on the TT power unit.
What can I do to get rid of this hum. To clarify, it's a low level hum with some higher buzzing. The buzzing almost completely disappears and the hum drops down in volume when I hold the amp and touch the ground lug.
I've got it grounded to the TT power unit, without which the buzzing is much louder.
But it's definitely the amp. Other sources don't have the same problem, and when I use shorting plugs on it I still get the sound.
Since I'm not using shielded cables, this may still be the best solution. I wish I had some to test out. Maybe I'll get some Blue Jeans cables to hold me over till I can afford the Bottlehead ones...
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OK, so let's simplify to help isolate the source.
I think you hear the hum with the Seduction (shorted inputs) > Quickie > SEX amp > speakers.
First, some checks for ground current issues (also called ground loop):
1) I guess perhaps the CD player is also connected to Quickie? If so, remove its cables from Quickie. Does that help?
2) Are the Seduction and the SEX powered from the same outlet? If not, try that. If they are, try to run the power cables close together as much as possible (minimize loop area).
3) Are the power outlets all grounded (3-wire)? If not, run everything from a 3-wire power strip, so that the Seduction and SEX share a ground connection even if the wall socket does not have one.
4) Are the signal grounds inside the Seduction and SEX well connected to the chassis plate and to the safety ground? Do those connections go all the way to the power plug ground pin (the round one)?
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When I pick up the Seduction with both hands and with one finger on the ground lug the hum decreases significantly. Big time. I wish I could get it that way all the time. It's similar to the effect I described earlier in this thread, putting my hand on the TT power unit.
My hunch is you might (and I certainly could be wrong too) have something going on with the safety ground in your home wiring. Not trying to pass the buck, just observing that phono preamps deal with tiny signal levels and it sounds like a situation where one of the possible issues is a lack of safety ground continuity that is working against you and injecting more hum than usual into the signal path. I deal with that in my own 71 yo house quite often. My Tode sounds great at our 5yo office, but hums a bit at my 71yo house. In my case it's probably time for new ground rods at the house.
If touching with your finger helps, only sometimes using a wire to make the same connection can help. This hum pickup stuff can be fickle...
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Thanks guys.
Paul, yes, the CD player was adding to the buzzing A LOT. Turning it off (instead of leaving it in standby) made a big difference. But not enough.
The amps are going to a power strip/conditioner and into the same outlet.
The outlets are grounded. It's an older house, but I had the same problem just a few months ago in my previous residence, which was a new (<10 years) house. Anyway, why the Seduction and not the other amps?
I will check the ground on the amp tonight.
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. . . When I pick up the Seduction with both hands and with one finger on the ground lug the hum decreases significantly. Big time. . . .
I think this is a big clue. It points to the ground loop hum PJ is guiding you through above.
You say when you use shorting plugs you use shorting plugs on it I still get the sound. Do you remove the ground lug from the TT Power Supply too and still get the sound?
Check that your outlet that you are using is properly grounded. Home Depot has a plug in tester with three LEDs on it. See a picture in my Pictures Of Tools thread, in my corner.
As a follow up to Dan's thought... a quick check is to pull the interconnects out at the Seduction and check the resistance from the ground lug of the power cord to the top plate. It should be under an ohm.
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Can the wall really not be properly grounded if the SEX alone works fine, without noise?
I'll test the grounding and see if I can find anything.
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4) Are the signal grounds inside the Seduction and SEX well connected to the chassis plate and to the safety ground? Do those connections go all the way to the power plug ground pin (the round one)?
OK, without checking the manual (which I'm not even sure I could find so quickly, having moved since I built this), there's the signal ground coming of the solder tabs on the outputs and from the plate on the inputs. This ground runs through all the terminal strip. There's also a ground coming from the ground lug and going to the transformer and the power input. These two ground are not connected, as far as I can tell. But they apear to be solid. Should they be connected somehow?
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I should note that when I spoke of turning off the CD player to reduce the buzzing, I wasn't even referring to a CD player that was plugged in to the Quickie. It was just on. I noticed the amount of noise it was causing when I accidentally brushed up against the RCAs plugged in to it. That caused a hell of a lot more noise. Again, the CD player is there (you can see where by looking at the pic in the Quickie thread I started), but it's not plugged in to anything, except the wall.
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Sam,
Yes, the wall might not have the ground connected properly and the SEX still work properly. It could also have hot and neutral reversed.
I'm looking at my schematic and I don't show a jumper from the power (safety) ground and the signal common, aka signal or circuit ground. I see the power ground to the transformer and to the top plate. I don't see a jumper to the signal common. Edit: A jumper from T10 to T11 does it. At least it looks like those two terminals on the schematic.
Did you measure the resistance from the power plug ground to the chassis plate?
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Resistance measures 0.3 ohms.
So that leaves the wall ground? What else can I check? Would adding a jumper between the two grounds help?
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Ok the chassis is grounded as it should be.
You could see if the hot blade of the wall outlet measures 120V AC, plus or minus a little, to the ground lug. The outlet has three holes. The odd one is ground. The smaller of the other two is hot. Be careful, this voltage will kill you if you touch the hot and a true ground.
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I've got a power strip that tells me if I'm grounded, and it says I am.
I think it's the Quickie amplifying the hum that has returned me to this issue, since it's not that noticeable without the preamp.
Right now it's fine, IF I'm holding the amp. The second I set it on a surface (ground, shelf, etc.) the hum doubles in volume. And when I let go of the ground lug a buzzing is introduced into the hum. So it appears I'm dealing with two different types of noise.
I'm about to give up here.
(Maybe I'm being overly sensitive. The noise isn't that audible, if at all, at normal volumes through speakers. Only with quiet music turned up to a high volume on 'phones can it be heard. I'm testing without music and with volume turned way up with 'phones on, so the hum can sound pretty dramatic.)
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The first question is, do you listen to quiet music with the volume all the way up? This is a sickness brought to us by magazine writers who report that the XXXXXXX was dead quiet in my system even with the volume all the way up. It is not a real world test for most of us. I listen to my Eros at 9:00, used to listen to my Seduction a quarter turn louder. Eros has more gain.
The hum and buzz can be measured at the output jacks of the Seduction with the inputs shorted. That will help put it in perspective. Unplug the table, including ground, from the Seduction and the Seduction from the Quickie then set your meter to AC and measure. There are low level noises that will always be there.
When you asked "Would adding a jumper between the two grounds help?" Which two grounds were you speaking of?
The components of the noise can be seen on an oscilloscope. I have one. It doesn't really measure the RMS value of AC signals but will reveal the peak to peak voltage there.
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I'm measuring 0.00. ???
This is driving me bat crazy.
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Sam,
I edited the post above and were you measuring AC volts?
If you are bat crazy you must retire to the Bat Cave for a cold one.
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Yes, measuring AC.
And yes, I sometimes listen to quiet music with the volume higher than usual. I find that with headphones I the pot ends up around 2/3 up. With quieter music it may go higher. And no, it's not totally blasting my ear off.
What's the next thing to try? By connecting the two grounds I meant the one at the inputs/outputs/terminal strips and the one at the power/transformer/ground lug, which, as I said earlier, do not appear to be connected.
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I know there are other things at play but just out of curiosity, what cartridge are you using? On my Rotel table with Rega arm, the Ortofon cart (Super OM10) exhibited the most hum but it was still low level such that it was not heard at the highest I would listen. On the Technics table I havent tried all my budget carts. I use either an M97 or a Pickering XV-15 and again, whatever low level noise (hum) there is with the Crack volume cranked up, I dont hear it with music playing or between tracks at my highest listening levels. System = Table - Seduction - FPIII - Crack. Still need to make room to be able to add one of my small amps and some speakers.
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The TT is out of the equation. I've tried to isolate the source as much as possible, and it's really the Seduction that is bringing in the most hum/buzz. That is: I'm now using shorting plugs for the input.
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Sam,
The schematic doesn't indicate a connection. Edit, it is between T10 and T20, according to the Bottlehead schematic.
Using a wire touch to the top plate and the ground buss.
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Will try it tonight. What do you mean by "touch to the top plate and ground buss"? I was just going to solder a piece of ground buss from one of the grounds to the other.
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Soldering is good. Touching them together is faster. There should be no voltage difference between them. Touching will answer the question. If it works, solder.
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Looking at this thread, I am very confused about what is being discussed.
All Bottlehead gear uses a few techniques to minimize noise that I don't necessarily understand, but they seem to work for most people. First, all the pieces (except the Quickie) use a ground tab that connects the chassis to earth ground (3rd prong); this makes the basis for the star-ground. The signal ground is connected to the ground at one point. [EDIT: not 100% sure about this being a "single point"] In the Seduction, it's at the inputs
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Joshua,
Just looked at the manual, one wire from the RCA inputs' common lands on the ground plane. Is there a connection between the chassis and the ground plane? Are the inputs connected to the chassis and then through the ground plane?
The FP 2 had no connection between the signal common and the chassis/safety ground. If noise persisted it was a common fix to jumper terminal 13 to terminal 14 which made that connection.
Even with Shielded Twisted Pair (STP) the signal common is usually, but not always, connected to the chassis of the sending and receiving pieces. But the additional shield grounded to a chassis, a grounded chassis, gives additional noise abatement. It sounds like this is redundant. Won't hurt if it is redundant and might help if it isn't.
I think Sam and I are on the same page as I suggested connecting the incoming ground/safety ground to the known signal common.
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Next, Grainger asked if Sam actually listened at a loud enough volume to hear the noise while listening to music. This is the crucial question-all systems make some noise, particularly when they are amplifying very small signals. If you are hearing the noise at full volume but never listening at that level, it does not matter.
Yes, this is key. But I'm persisting because the hum is loud enough that is CAN be heard in quiet passages or when listening to music with few instruments (jazz trios, quartets, folk, classical...). Even if it's not nearly as prominent, it's there. And I don't like it.
Granted, when listening through my speakers I can't tell the difference, unless I'm really cranking it--and then only in between tracks (but hey, that's still annoying). Mostly this is a headphones issue.
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I am working under the assumption that this discussion is based around the S.E.X. Am I right? Please be explicit here, I can only help if I know what we are talking about. My biggest source of confusion is in statements like this "I think Sam and I are on the same page as I suggested connecting the incoming ground/safety ground to the known signal common. " Very specific, yet completely vague.
Looking over the S.E.X., the chassis plate forms the main ground, it is connected to earth ground via the solder tab near the power inlet. The right input is connected to ground: black from the input goes to the pot, which goes to 12L, which is jumpered to 13L, which is a center terminal on the strip, therefore chassis, therefore ground. The left channel does not repeat this connection, most likely for noise issues of some kind (ask someone smarter than me for full details). Both channels are definitely connected to ground with the jumper from the headphone jack to 23L (again, center terminal). The specifics of this connection will vary depending on the jack used (varied yet again if the Impedance Switch Boards are used), but the connection is made regardless. I will edit my previous post since I'm not so sure about the statement about signal ground being connected only at one point.
As for the STP interconnects, they worked for me. I was having terrible hum with a coax based interconnect, I made something as described, my hum went away. Like I said, YMMV, but a few bucks at Radio Shack and a few minutes at the solder station can go a long way.
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Touch to the top plate and the ground buss.
Is this vague? This will hard wire the safety ground to the signal common.
As the title implies, it is a Seduction hum problem.
You didn't answer the question about the RCA input jacks and the ground plane. Do you have a Seduction near to check?
My comment on STP was to point out that it doesn't remove the ground from signal common. It just adds an additional shield.
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Grainger, it's vague because when you are clearing up a systemic issue, it needs to be said which piece of gear you want to make the connection in. This issue is quite possibly caused by a difference in ground potential between two different pieces of equipment, so there are at least two ground busses and top plates in play.
You said "wire" which made me think you weren't talking about the Seduction, since the inputs aren't connected with wires, but directly to the ground plane (shell) and via resistor leads (pin). I've got my Seduction right in front of me. The ground post is not insulated from the chassis or the ground plane. The RCA inputs are not isolated from the ground plane. Grounded.
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Yes, I have the SEX amp. That is indeed what I'm using with the Seduction. On its own the SEX is dead quiet. Dead. Quiet. Hence also my surprise at the levels of hum coming from the Seduction.
Not home yet, but any suggestions for what to try out when I get home would be welcome.
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Joshua,
We are 5 pages and 74 posts into this thread. Sam and I have been talking back and fourth about only the Seduction, starting today in my reply #52. I don't see my mentioning the SEX amp, since Jan. 9.
In addition I have emailed and PMd him today. I am sure that Sam and I are on the same page. I am sorry if we have confused you. You were not privy to the emails and PMs.
Sam, I think that Joshua is suggesting to also try a wire from the Seduction to the SEX. I believe this is redundant with the interconnects, but it never hurts to try. It is also cheap, quick and might help.
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Ground from Seduction touching chasis plate of SEX makes no difference.
I soldered a ground buss on the Seduction to connect the two grounds. No difference.
And I just put on Coltrane's Live at the Village Vanguard Again. The Jimmy Garrison solo at the end of side A is a perfect test. On the speakers I can turn it up and not really hear the hum. With phones I can, though just barely.
EDIT: By contrast, I'm now listening to a great obscure gem, the self-titled album by Lewis Furey. This record doesn't need the volume very high to get it to my preferred volume, so hum isn't an issue at all. So I guess it will depend on what I'm listening to if I choose the 'phones.
What I want to know is: is what I'm hearing normal, but most of you folks just don't turn the volume WAY up? What do you hear (those of you who have my set-up or something close) when you turn the volume to 10 on pre and main amp but don't play a record. Is there hum? a little buzzing? Does holding the Seduction and putting a finger on the ground lug cut out the buzzing and reduce the hum? If yes, then I'm not alone.
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If, as you describe, the only problem is at the highest end of the volume control and with very quiet music, I would say that is normal.
The Seduction amplifies the lowest voltage level signal in a stereo. It is more likely to introduce hum in the system than any other component.
To me, the problem centers around the low level of the signal (cartridge output), the low signal level (small jazz etc.), low recorded levels (quiet passages or the dead band between cuts) and the amount of gain that is required to make the cartridge's signal usable by the rest of the system.
My comment about equipment reviewers meant to indicate that most of the equipment on the market, except a very few, will have hum when the system is WAO. Wide Assed Open.
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I can accept that. My only question would be: why can I reduce this hum by half just by holding the amp and touching the ground? Shouldn't I be able to do this via some other means?
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I believe it is 120 Hz hum as described by Paul Joppa above. Obviously the Seduction is the source.
Back at answer $46 Paul Joppa suggested that you try grounding through a resistor. I am assuming grounding the turntable. Try a high resistance, 100k to 1M ohms. But I am just not sure where to add the resistance.
I'm going to have to think on this and get back to you.
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Hum and buzz is the single most frustrating problem with systems! Patience and persistence seems to be the best answer there is; experience helps (hence the Forum) but not as much as you might hope.
The signal ground starts at the ground plane which is electrically connected to the chassis plate at the ground post. The power line safety ground is connected to the chassis plate near the IEC socket - that's how the two are connected.
When touching things helps, it is quite possible that the interference is radio frequency pickup. For example, perhaps the CD player has a switch-mode power supply which is not well shielded, or which radiates from its power cord (poor line shielding). Or something else - a light dimmer, flourescent lights, battery vibrator in an adjacent apartment (no kidding, it's happened). Another source used to be television signals, with its 59.94Hz vertical refresh rate. The usual answer is shielding, such as the tube shields and a metal box around the circuitry - the chassis is drilled for it. I can't put my hands on it but there must be a thread or two - can someone find it?
Shielding acts on electric fields by surrounding the circuitry with a metal container which is grounded, draining any induced field to ground. That's one of the reasons I wanted to start the search for causes by making sure all the grounds were in place. Normally I would expect that if the chassis is well grounded, then touching it will just drain whatever your body picks up to ground, and will not have an effect. So I think the jury is still out on what is the real cause of what you are hearing.
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At this point, I would think the Hammond 1590J be worth a shot ... $12.
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At this point, I would think the Hammond 1590J be worth a shot ... $12.
Does it have the right dimensions? Seems small to me. I have a Hammond that I got for the Quickie but never used. It's surely the right W and D dimensions, but is probably not hight enough...
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From the Seduction product description page (and it's also in the manual if memory serves):
"For those who live in RFI rich environments, mounting holes for a die cast Hammond aluminum box (PN 1590J) that you can modify slightly with a file to fit are provided to allow you to shield the entire preamplifier circuit from RF..."
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The modification is to make holes for the power STPs.
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http://www.mouser.com/Search/ProductDetail.aspx?qs=lxPAlgZqN%2FwBkmsjCw3f7A%3D%3D
those dimensions wouldn't work.
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I can definitely say I'm dealing with a low hum. And it isn't THAT bad at the volumes I use my system. BUT, it would be nice to minimize it a la my holding it and touching the ground.... I'm not in a high RF area, I don't think. No dimmers, and really no other electrical things in this side of the house. I'll play around with turning stuff on/off in other rooms to see what difference this makes, and I'll also try completely unplugging the CD player. Turning it from standby to off made a big difference. Maybe unplugging it will do the rest.
If only I could replicate the ground my body serves with something else...
And if someone can tell me which Hammong enclosure to get, I'll try that, too.
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http://www.mouser.com/Search/ProductDetail.aspx?qs=lxPAlgZqN%2FwBkmsjCw3f7A%3D%3D
those dimensions wouldn't work.
I wouldnt think that BH would have named the part and made the holes in the top plate accordingly to line up with those of the Hammond box if it wouldnt work. It doesnt cover the entire bottom of the top plate, just the preamp section. The 4 open mounting holes in the top plate measure out pretty close to the listed dimensions of the box. Granted, I dont have one on hand or installed so I cant guarantee it fits from personal experience. And I dont know if it will help with your problem. But Paul mentioned RFI a few posts up and that's what they state the accomodations for the hammond box were made for. Just thought I'd mention it for what it's worth.
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Sam-google- star grounding-read and possibly implement-also go into your seduction and suck or wick the solder off the grounding points and resolder-ck anything else that gets your attention-ck your turntable ground wire -i have had that as a problem-and this next option always gets me in trouble-get a plug adapter without the ground-if that works -remove the grounding prong with pliers- most houses have the nuetral connected to ground at the panel anyway-now if your listening area has a inch or two of water on the floor -i would not recommend this
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Thanks, Desmond. I see now how it's supposed to work. I might as well try it.
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Star grounding sounds simple, at first, but then I get lost and wouldn't know how to proceed with the few pieces in my system:
http://www.geofex.com/article_folders/stargnd/stargnd.htm
http://www.aikenamps.com/StarGround.html
http://www.lh-electric.net/tutorials/gnd_loop.html
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Unfortunately, the Hammond box won't fit, but only because I have switched out the caps for somewhat larger ones that woudn't fit in the only 1.77" height.
Another potential clue to the source of the hum: if I *just* put my finger on the Sed ground, the hum is only reduced very, very slightly. Only when I also touch the *wooden* base at the same time is the hum reduced significantly.
I've experimented with this, touching the chasis and ground, other amps and ground, other amp bases and ground, etc. Only touching the wooden base and the ground lug does the trick. (This is why holding the amp and touching the ground lug made such a difference.) NBot sure if this helps figure out the source of the hum. To me it suggests a grounding issue, not RF.
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Sam,
I have seen pictures of a Seduction with holes drilled through the box so long leads could be used on the capacitors. The cap leads were fed through the holes, soldered on and then the box screwed to the top plate.
It might work for you.
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sam-- when you touch sed ground and chassis thus reducing hum is your turntable plugged in --is the turntable on the same outlet or string of outlets from one circuit or are they on different circuits--the same question for sex and seduction-turntable
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(Maybe I'm being overly sensitive. The noise isn't that audible, if at all, at normal volumes through speakers. Only with quiet music turned up to a high volume on 'phones can it be heard. I'm testing without music and with volume turned way up with 'phones on, so the hum can sound pretty dramatic.)
You'll drive yourself nuts doing that, turning things all the way up without signal just amplifies the noise floor to its maximum potential, often times "testing" a scenario that you would never encounter while listening.
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sam--if you google --regap3-24 hum problems there is info-some say the tt is picking up hum from amps-others say maybe bad ground in turntable-also google ground loop hums there is info there
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sam-- when you touch sed ground and chassis thus reducing hum is your turntable plugged in --is the turntable on the same outlet or string of outlets from one circuit or are they on different circuits--the same question for sex and seduction-turntable
It's not the TT. With and without TT plugged in = same effect.
I'm gonna learn to be less anal and live with it, knowing I don't hear it most of the time, anyway.
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Two thoughts-
1) Your hand may be providing a radio frequency shield around the side of the box. The ground plane made up of the chassis plate does provide some shielding, but is most effective on parts and wires that are closest to the plate.
2) There is a bit of residual hum in the tube closest to the power transformer; this is the magnetic field of the power transformer affecting the tube, or perhaps bending the electron stream. I don't remember (if it was ever posted) what your cartridge sensitivity is, but that hum is usually OK with carts of 3-5mV or greater. That's because with a higher output cartridge you turn the volume at the amp down.
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What's an effective DIY RF shield that I can use to test with the Sed, before going with the Hammond box, which really will be a pain to install given my cap upgrades?
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You could take a few sheet of heavy duty aluminum foil and fold them into a box shape. And of course, duct tape to hold it together. ;)
Somewhere along the line you mentioned, that if you touched two components, the hum was reduced. Have you tried using a jumper wire to replace your body?
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I haven't suggested aluminum foil because of the risk that a high voltage might touch it. Be careful!
Hammond and others do make 6"x10" boxes 2" deep, which can replace the wooden base. The lip may need some trimming, depending on how wide it is, but it does have a better chance of accommodating the large caps.
Understand, this is low level hum we're talking about. There is no guarantee than ANY particular solution, including this one, will be the right one. Hum busting is pretty frustrating.
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Hum busting is pretty frustrating.
Not as frustrating as mutton bustin!
Have you tried clip leading the chassis of all your gear together? Sometimes I can discover the issue by doing that.
-PB
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I'm having a tough time finding a Hammond that's deeper. If anyone could point me to one or an equivalent, I'd be grateful.
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Start on this page:
http://www.hammondmfg.com/scpg.htm
The first type goes to 3.98" deep.
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http://www.onlinemetals.com/merchant.cfm?id=753&step=2&top_cat=6
i buy from these guys they are excellent-if you search the site you can create anything you want-with thin sheet you could put it inside the wood chassis-and get a perforated bottom
or get plate aluminum and make one to suite yourself-they also have up to 6" square or round tube-trannie covers!!
or vt4c.com--takes awhile to populate
also
http://www.ebay.com/itm/Full-Aluminum-Chassis-for-audio-DIY-Power-amplifier-2109-/230858336808?pt=US_Amplifier_Parts_Components&hash=item35c03aaa28
hope this helps ---howie
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Looks good, Howie, thanks. But what thickness should I get? And how to attach (glue, staples?)
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Alright, one last time (I SWEAR):
Going back to phono after a week of only listening to digital, I am surprised again by the background hum.
Normal volume with speakers it's not really noticeable.
But normal volume on 'phones it is. Those using the Seduction with SEX/Crack and 'phones: before the needle hits the record, do you hear a background hum? In between tracks? Again, I just want to be sure this is normal, and that I don't have a more serious problem.
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Sam,
At 8 pages it is going to take a long time to sort it out. Can you post what you have tried? Also, can you measure the hum on each channel, Seduction input shorted. Hum is AC. A quick reading would help.
And maybe you have done that.
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I forget if I've measured, though I think I have and got no reading, or near 0.
Let me do it again. I can say it's definitely the Seduction (i.e. when shorted I still get hum) and that moving it several feet from the other amps doesn't appear to help much. I may just send it to you, Grainger, to check out, if that's OK.
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I'm willing. I agree, we had nailed it to the Seduction. Or at least the Seduction TT/PS combo. But I do think it was finally isolated to the Seduction.
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Sam,
I looked up the Sennheiser HD-600 headphones. The spec is 1k Hz at 1V 112dB. If that were a speaker you could power it from the Quickie alone (I exaggerate)! If I am reading Sennheiser's site right they are very sensitive. So this is part of the problem.
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But isn't this all relative to the volume at which I listen? I hear the hum at normal listening volume.
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Normal listening volume is different for your speakers and headphones, right?
You have said that the noise is not a problem with your speakers but is a problem on phones. Compounding the problem of sensitivity is that you are so close to the transducers with phones, there is only a little air between them and your ears. There is a lot more between the speakers and your ears.
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Another potential clue (for those who are still reading this thread):
With shorting plugs in the input and not powered on, the Seduction buzzes pretty bad. When I switch the power on it is DEAD QUIET until (no buzzing, no humming) for a few seconds until it's fully powered up, at which point the buzzing disappears and is taken over by humming.
I really want to get to the bottom of this. Is this just because my speakers and headphones are so sensitive?
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We can't answer your question with any accuracy unless you can measure the hum level or better yet get a picture of it on a scope. There will be a very small amount of 60Hz in the right channel of some Seductions, based primarily upon the sensitivity of the rear tube to magnetic coupling with the power transformer. But in general the question "is this hum normal" is very difficult to answer without access to the device.
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...With shorting plugs in the input and not powered on, the Seduction buzzes pretty bad. ...
That's a big clue!
I've lost track of the details in this thread, but you can only know that with other things downstream of the Seduction. Most likely, here's what's happening:
Something downstream has a power transformer. That transformer's primary has some capacitance to the secondary which goes to the power supply and signal ground. That capacitive coupling induces a current from the ground of the device power supply, through the grounds of the interconnects, to the chassis ground of the Seduction which is connected to safety ground. The voltage drop across the resistanceof the interconnects, RCK\A jack/plugs, circuitry, etc. creates a voltage which is amplified by the downstream device(s) and is what you hear.
There are other possibilities. It's possible that the neutral and hot are reversed at the power socket, so that the neutral is switched and the hot stays connected when it's switched off, causing some ground current from the Seduction.
It's also possible that it's radio frequency pickup, with various bit of metal acting as an antenna. You can check this by unpluggin the Sediction from the wall. If it still buzzes, you are picking up an environmental sgnal which is detected by some device downstream - probably the first one.
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I'm not sure I entirely understand you, Paul. But would the buzzing-when-not-turned-on be related to the hum-when-turned-on?
I'm pretty sure I heard the buzzing when the power cord when not plugged in.
Recall that my SEX/Quickie is mostly very quiet with the CD or digital input. No hum or buzz.
I need to get a cheater plug to flip the hot-neutral on the Seduction. This is one test I haven't tried yet. Could it really be what clears this up?
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Cheater plugs can clear up buzzy 120Hz from ground loops. But they won't do much for soft 60Hz hum, because that is from coupling between the power transformer and another component. You seem to be describing the latter as what you hear after the amp comes to life and the buzzy component goes away. Am I following you correctly?
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Yes, except distance to the other amps doesn't seem to make all that much difference.
My shielded interconnects aren't that long, though. I'm assuming interference with the SEX would be the main culprit, right? So if I can get it 6 feet from the SEX and 3 feet from the Quickie and still get hum, then can I rule this out as a source?
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Actually I meant another electronic component in the circuit. For example a wire or a tube in the Seduction itself could be picking up transformer hum of the PT-1. This is measurable in a Seduction in the right channel due to the proximity of the circuit components to the power transformer, though it is seldom noticed by ear unless the cartridge is a very low output type. But variations in sensitivity to hum pickup can vary quite a bit from tube to tube. That's why it is difficult to quote a "normal" figure. Since this problem only seems to be present when you listen with headphones and not with speakers it seems like it may be right on the threshold of what could be considered normal. And that is why I feel that I would have to listen and measure it myself to give a more confident answer about whether it is typical or atypical performance.
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HOLY MOLE!! O M G !! :o
The hum is gone!
Gone, I say.
Yep, the amp is quiet. I can't tell you how good this feels. I sent the amp to Bottleheadquarters to get looked at and it got damaged in the mail. So it's hard to say what the source of the hum was (I'll let PB chime in with details), but whatever they did it's better now.
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I wish I knew what specifically made the difference, but all that shipping damage didn't leave me a particularly accurate picture of what was going on before.
I'm sure shortening the leads a bit helped, but it's anybody's guess I suppose!
-PB
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For me what's most important is that what I was hearing was NOT normal. I was concerned that I was just overly sensitive. Nope, it was not normal. [phew]
Now I can get back to nitpicking about other minor imperfections in my phono set up ;)
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Just noticed this. Congrats Sam. Very happy to hear that you finally got it all sorted out. Leave it to the Bottlehead gang, if they can design it, they can surely fix it ;)
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Sam,
How close to the s.e.x. can you place the seduction without getting any interference or noise from the power amp?
Thanks,
Jim
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Lemme get back to you on that. Right now it's about 1 1/2 feet away and no problems.