Bottlehead Forum
Bottlehead Kits => Legacy Kit Products => Seduction => Topic started by: rebbi on July 19, 2010, 05:17:55 PM
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Hi, Guys,
I need some troubleshooting help with my Seduction preamp. Hope somebody can help me with this.
I have a Seduction preamp with the C4S upgrade. I've been using it for quite some time with no real issues. It feeds into a Manley Shrimp preamp, and that, in turn, drives a Bel Canto S300 amp. My TT is a SOTA Sapphire with an Ortofon 2M Blue cartridge.
I recently rearranged the physical layout of my gear as part of setting up a new pair of speakers (Merlin TSM-mmi's). And since doing so, I have been having the following issues.
There's a slight hum in the speakers when the electronics are fired up; this is only true when running the phono gear; the CD part of the rig is dead quiet. But when I turn on the motor on the turntable, a rather prominent buzzing noise crops up. I've tried moving some of the cables around, as well as relocating the outboard power transformer of the SOTA, but no luck.
How would I go about troubleshooting this?
I've also noticed that right now, my CD gear sounds better than my analogue gear - more alive and dynamic, if you will. I know that's vague... so right now, I'd settle for getting the buzzing issue sorted out.
Thanks in advance,
Steve
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Sounds to me like a grounding issue with the phono cables and/or turntable internal wiring.
The simple test is to disconnect the phono cable at the Seduction and use shorting plugs at the Seduction input, then repeat the experiments. If the hum and buzz go away, then it's coming in from the turntable; otherwise there may be some other source.
Is everything, including the turntable, plugged into the same power outlet?
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Sounds to me like a grounding issue with the phono cables and/or turntable internal wiring.
The simple test is to disconnect the phono cable at the Seduction and use shorting plugs at the Seduction input, then repeat the experiments. If the hum and buzz go away, then it's coming in from the turntable; otherwise there may be some other source.
Is everything, including the turntable, plugged into the same power outlet?
Paul,
Thank you very much for the speedy reply. Excuse my ignorance, but what are shorting plugs?
Thank you,
Steve
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Although some recommend using resistance, I have always just used some cheap RCAs and shorted the center pin to the outside shell.
They are useful for inserting into the inputs of amplifiers in order to measure self-noise, among other things.
THEY SHOULD NEVER BE USED ON OUTPUTS!
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In this case I am probably on the safe side with the following answer: take an old cheap RCA plug and solder a resistor from the center tab to ground. Good values for typical RCA inputs are about 5 kOhm. Plug those into your amp's inputs. Keep them around. They have many uses.
Paul,
Thank you very much for the speedy reply. Excuse my ignorance, but what are shorting plugs?
Thank you,
Steve
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As PJ mentions you should check the placement of the Seduction. The audio circuits of it are susceptible to pickup of hum from transformers or power supplies that are too close, but not its own The Seduction's transformer is well shielded). So first if the Seduction is next to any other piece of equipment you should move it. The hum field drops with the square of the distance so even a few inches can make a difference, a foot a huge difference.
The cabling from the turntable to the Seduction (the most sensitive) and from the Seduction to the preamp (less sensitive) are also prone to hum and buzz pickup. So your routing should be changed next.
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I think PJ's question of whether or not everything is plugged into the same outlet may well be the key, particularly when you mention the noise happening when you start the TT motor. If the Seduction and ttable are are in different outlets around the room try setting them up so they both run from the same power strip. If they are all in the same power strip, try using a cheater plug on the turntable motor power cord. You can also try connecting the turntable/motor chassis to the Seduction ground post
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I think PJ's question of whether or not everything is plugged into the same outlet may well be the key, particularly when you mention the noise happening when you start the TT motor. If the Seduction and ttable are are in different outlets around the room try setting them up so they both run from the same power strip. If they are all in the same power strip, try using a cheater plug on the turntable motor power cord. You can also try connecting the turntable/motor chassis to the Seduction ground post
I will check all this out when I get home -- I'm at work now. I think it's all in the same surge protector strip, but I'll check. IIRC, the SOTA TT power transformer has only a two-pronged plug. And I do have the ground wire from the TT attached to the ground post on the Seduction.
Thanks, everybody,
Steve
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I'm pulling Carl's problem from rebbi's thread and posting here:
http://www.bottlehead.com/smf/index.php/topic,1512.msg10931.html#msg10931
I have finished it now. I will delete the posts here to clean up the confusion. Well, I'm confused.
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As the original poster from last July, I still haven't managed to sort out this hum/buzz issue. I even took my Seduction to Austin Stereo Service here and Mike, the owner, resoldered a lot of my -- ahem! -- less than lovely solder joints. No difference... the hum's still there.
Like the other poster here, I notice that the hum gets worse if I, for example, touch the tone arm on my SOTA Sapphire.
I still haven't had the chance to make shorting plugs to ascertain if the hum is somehow coming from the Seduction itself.
All in all this is very frustrating! :-/
Steve
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Steve,
You gotta try shorting the inputs of the Seduction. That's the only way to isolate the noise source. Paul mentioned this back in July. If the hum goes away with the shorting plugs in the Seduction inputs, you will have eliminated everything downstream of the Seduction's inputs from "blame".
Please don't just assume that, just because you built the Seduction, it's at fault... (even though I know that I would do that :-) ). Since this problem started after you moved your equipment, I'm thinking that it's a turntable issue... because the turntable is the most delicate piece in the chain, for sure.
The Sapphire has an AC motor. There's a ground issue somewhere in the signal chain, and I'm wondering if something hasn't gone awry with the wiring in the tonearm... the hum increasing in volume when you touch the tonearm could be pointing to this.
I would recommend making up a set of shorting plugs (maybe you can borrow some from Mike at Austin SS?). If the problem goes away, I'd start looking at the interconnects from the Sota to the Seduction, then the tonearm / headshell / cartridge.
Been too long, man. Need to get this fixed... music is life! :-)
-Don
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As the original poster from last July, I still haven't managed to sort out this hum/buzz issue.
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All in all this is very frustrating! :-/
Man, that just sums up hum and buzz issues!
I encourage everyone to never give up though. There is almost always an answer, and it pretty often taken an inordinate amount of trying to find it. Take a break when you have to, but keep coming back to it - this forum has found some pretty amazing solutions to seemingly intractable problems.
OK, if touching the tonearm increases hum, and if the tonearm is properly grounded to the Seduction chassis, then it's logical that touching the Seduction chassis would increase hum. Does it?
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Steve,
You gotta try shorting the inputs of the Seduction. That's the only way to isolate the noise source. Paul mentioned this back in July. If the hum goes away with the shorting plugs in the Seduction inputs, you will have eliminated everything downstream of the Seduction's inputs from "blame".
Please don't just assume that, just because you built the Seduction, it's at fault... (even though I know that I would do that :-) ). Since this problem started after you moved your equipment, I'm thinking that it's a turntable issue... because the turntable is the most delicate piece in the chain, for sure.
The Sapphire has an AC motor. There's a ground issue somewhere in the signal chain, and I'm wondering if something hasn't gone awry with the wiring in the tonearm... the hum increasing in volume when you touch the tonearm could be pointing to this.
I would recommend making up a set of shorting plugs (maybe you can borrow some from Mike at Austin SS?). If the problem goes away, I'd start looking at the interconnects from the Sota to the Seduction, then the tonearm / headshell / cartridge.
Been too long, man. Need to get this fixed... music is life! :-)
-Don
Okay, I will try the shorting plug thing tomorrow and report back. I would really like to get this sorted out so I can enjoy my TT again.
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Steve,
You have been wrestling with this for quite a while. Let's start eliminating components and arrangements so you can get rid of the hum.
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Steve,
You have been wrestling with this for quite a while. Let's start eliminating components and arrangements so you can get rid of the hum.
Can I just solder the cut wire coming out of an RCA plug onto the outer collar of the plug to make a shorting plug? Fry's doesn't have any bare, male RCA plugs in stock.
Steve
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rebbi,
I would go to Radio Shack and buy a pack of "Jumpers." That is a number of short wires with an insulated alligator clip on each end. They are great for measuring voltages and resistances as well as shorting the inputs of an amp, preamp or anything else you need it for.
But, yes, you can solder a wire from the center to the RCA jack to the outer conductor.
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My memory is not that good but I do recall that early Foreplays did not have the signal ground attached to the chassis. Making that connection (T13 to T14) reduced hum and buzz in many cases.
I know the earliest Foreplays had 2-wire power cords; I do recommend a 3-wire cord with the ground lead taken to the chassis close to where the power cord comes in. The UL standard is for that ground lead to be the longest, so that if the power cord is ripped out of the preamp by brute force, the ground wire will be the last one to disconnect.
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Well, here it is, November of 2013, and I still haven't sorted out my phono stage hum problems, but now I'm determined to do so! >:(
I recently completely rearranged my components. My power amps (now a pair of Manley Mahi's) are a fair distance from my preamp (a Manley Shrimp) and my Seduction is on a shelf by itself, well underneath the Shrimp preamp.
The buzz in the phono side is still there.
I noticed that if I touch the top plinth of the turntable, the hum becomes somewhat less loud.
Also (and this seems really weird to me) I have figured out that even with the Seduction plugged in but powered off, whatever preamp input I plug the Seduction into will hum. I tried a number of different Shrimp inputs just to make sure it wasn't the preamp, but no: any input will hum with the powered off Seduction plugged into it.
I still haven't made those grounding plugs but will do so.
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Do you have a Rega table? They seem to have a grounding problem brought out by Seductions. I suppose you have used a pair of Sorting Plugs (http://www.bottlehead.com/smf/index.php/topic,586.0.html) to see if it goes away.
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Hi, Grainger,
My turntable is a SOTA Sapphire, not a Rega, so that shouldn't be the issue.
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Hum/buzz is a hard problem to find. Sometimes inverting the power plug on one device cures it. Did you try shorting plugs, the above post includes a link?
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Do you know how shielded your interconnects are? I was getting a lot of hum from my VPI Classic > Seduction > FPIII with some ICs that had foil shields. I made some diy ones with a heavier braided shield that seem to help quiet down whatever I'm picking up.
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I'll just mention here that 3 years ago, there was a first step recommended to sort this problem out. It involves going to a Radio Shack and spending about $10, or placing a parts order online for about the same amount.
I would start by following through on that advice, then we will actually have the information we need to help you sort this out.
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Okay, I looked on eBay for RCA shorting caps and found a guy selling gold-plated brass ones for about $13 for a four-pack, plus shipping from Hong Kong, which seems ridiculous. So I'm gong to sacrifice two of these plugs (as in the photo) and solder the stripped end of the wire to the outside of the round, metal collar on the plug. That's all I need to do, right? (Sorry for being cautious/dense.)
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Go to Radio Shack or your local discount electronics store. Buy a crappy quality RCA to RCA cable. Amputate one plug, strip the insulation. 2 conductors which you can now short using clip leads.
Robert Lees
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Butchering cables is a little harder, since they are designed to be thrown away rather than re-soldered
Plugs:
http://www.radioshack.com/product/index.jsp?productId=2103423&retainProdsInSession=1
4 pack, $3.49 ($0.87 each)
Every RadioShack has these in stock. Ask for part number 274-319 if you can't find them.
http://www.ebay.com/itm/RCA-Plug-Solder-Type-Audio-Cable-Connector-device-Intelligent-info-/300861665368?pt=LH_DefaultDomain_2&var=&hash=item460cc0b058
$0.94, free shipping, get at least two.
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Golly, the customer reviews on those Radio Shack plugs are the angriest I've ever seen (as in "this is the cheapest crap I've ever seen") but I guess for my purposes they'd be fine, eh?
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rebbi!-the problem seems to be from your turntable-i won't say that is for certain-but the buzzing changes when you touch that component-- make sure that your ground wire for your turntable is not broken inside the insulation or rt at the terminal and then have a look at the wires in your headshell
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Howard,
These are good suggestions. The headshell wires look okay; nothing seems to be loose or anything. As for the tonearm cable, what you suggest about a short in the ground wire isn't impossible. The arm (a Linn Basik that I bought, used, in the mid-1980's!) is still using the original cable, so maybe it's gone bad...
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well i wouldn't say the cable has gone bad -take a ohm meter and connect to the end of the ground wire and the other to the base of the arm you should get some continuity-that is usually the general vicinity of the other end of the ground wire-i am not sure about cking the continuity further up at the headshell -i know you should not put the meter on a cartridge -
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"Butchering cables is a little harder, since they are designed to be thrown away rather than re-soldered"
With clip leads soldering is unnecessary, and if you have gotten this far without wire cutters and wire strippers you must be exceptionally talented ;) Seriously, you do have some clip leads, don't you? Indispensable for measuring high voltages since it leaves one hand free :) And if you want to simulate a load all you need is a resistor of the desired value.
Robert Lees
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Okay, I finally got me two of these guys, on eBay, all the way from Hong Kong. ;D It also comes with a screw on collar piece.
Now, I solder the center pin to the other tab, yes?
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For crying out loud! You can get shorting plugs at Radio Shack, I did. It needs not be fancy. Just a plug that can have a dummy load or a dead short on it. I have labeled mine so I don't short an output from a source.
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Okay!
I have finally done my shorting plug tests. Time for all of your expertise.
With the shorting plugs on the inputs of the Seduction, I get a rather loud "whooshing" noise in both channels, that oddly seems to be somewhat louder in the right channel than the left.
With the Seduction connected to the turntable, it's the same as before; nasty hum/buzz in both channels that gets buzzier when the table motor is turned on. The noise gets louder when I touch the tonearm and softer when I touch the plinth. By the way, I have tried different preamp inputs just to make sure it's not the preamp itself, and it's not; the noise follows the Seduction.
Ideas?
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A wooshing sound is tube rush, which is generally a normal operating condition. I'm guessing that the hum went away when you inserted the shoring plugs?
We never did hear which arm you have on your turntable. Often times Sota turntables ship with Rega arms, can you confirm?
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The Ortofon 2M series of cartridges have a metal screw on top that is there to ground the cartridge to the arm. In practice, this causes more problems than it solves. You can try not using the arm's ground wire, which might eliminate the ground loop. If that doesn't solve the issue, you can put an insulator between the top of the cartridge and the arm, or replace the cartridge. Both of these will require the skills to mount a cartridge.
Wooshing sound is probably tube rush. Are you testing at higher than normal listening levels? If not, try another set of tubes.
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A wooshing sound is tube rush, which is generally a normal operating condition. I'm guessing that the hum went away when you inserted the shoring plugs?
We never did hear which arm you have on your turntable. Often times Sota turntables ship with Rega arms, can you confirm?
Yes, the hum went away with the shorting plugs.
The arm is a Linn Basik LVX, which I bought with my first good 'table (a Systemdek) in the mid-1980's and later moved to the SOTA when I bought it.
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The Ortofon 2M series of cartridges have a metal screw on top that is there to ground the cartridge to the arm. In practice, this causes more problems than it solves. You can try not using the arm's ground wire, which might eliminate the ground loop. If that doesn't solve the issue, you can put an insulator between the top of the cartridge and the arm, or replace the cartridge. Both of these will require the skills to mount a cartridge.
Wooshing sound is probably tube rush. Are you testing at higher than normal listening levels? If not, try another set of tubes.
Yes, the "whoosh" is with the volume turned up pretty high; I don't hear it normally at all, and it's only with the shorting plugs on the Seduction.
Removing the TT ground wire spade from the Seduction ground screw doesn't affect the hum.
Through the headshell, I think I can see the hole in the top of the Ortofon cartridge that must be intended to receive the grounding screw you mentioned. The SOTA factory mounted the cartridge for me when I sent the TT back to the factory for a refurb a couple of years ago. It seems they didn't use the ground screw, just the two mounting screws on top.
I can also double confirm that it's not the Seduction because a local dealer was nice enough to lend me a cheap little NAD PP 2 phono pre for testing, and the hum's still there with the NAD installed.
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The screw is there to make a physical conmection with the bottom side of the headshell; it should be nearly invisible when the cartridge is mounted. If you are capable of re-installing the cartridge, remove it from the headshell, but leave the wires attached. Check for hum, my guess is it will be gone. If you cannot carry out this experiment, find someone who can.
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Well, I tried something similar. My local dealer loaned me a few old cartridges, and suggested I remove the lead wires from the pins on the mounted Ortofon and then attach them to one of the loaners and see what happens, to determine if the hum is from the Ortofon having bit the dust. I did this with two of the loaner cartridges and in both cases the hum/buzz was still there. So it's something else.
I'm kind of stumped at this point. I think I'll try to borrow a turntable from a DJ friend of mine and see if the substitute table also has the hum...
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Can you confirm which tonearm you have?
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Can you confirm which tonearm you have?
Linn Basik LVX
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Hmm, can you let us know what the second grounding wire is connected to? (See the link)
Linn Arm Issues (http://www.vinylengine.com/turntable_forum/viewtopic.php?f=18&t=60469&p=480790)
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. . . With the shorting plugs on the inputs of the Seduction, I get a rather loud "whooshing" noise in both channels, . . . .
So we are saying that the shorting plugs remove the ugly hum/buzz. That says it is a problem with the table arm combination not the Seduction. Or at least an interaction between the grounding schemes of the table and arm with the Seduction. The Seduction alone, inputs shorted is quiet.
It is sad when good tables have a bad interaction with a phono stage, but this happens and it is a ground loop somewhere in the table. I blame it on the non-standard grounding practices since the 50s.
As others have mentioned the "whooshing" noise could be the tubes. Give them a four day run without anything else turned on and see if it goes away.
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Hmm, can you let us know what the second grounding wire is connected to? (See the link)
Linn Arm Issues (http://www.vinylengine.com/turntable_forum/viewtopic.php?f=18&t=60469&p=480790)
Paul,
Thanks for the link. The SOTA Sapphire is a heavy beast to move but I will carefully wrangle it and try to see what's going on underneath the table and whether my Linn arm has the "extra" lead. I also want to give a shout out to my local brick and mortar stereo shop, Audio Systems in Austin, TX. They've been great about lending me stuff to help me try to sort this out. Good folks.
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. . . With the shorting plugs on the inputs of the Seduction, I get a rather loud "whooshing" noise in both channels, . . . .
As others have mentioned the "whooshing" noise could be the tubes. Give them a four day run without anything else turned on and see if it goes away.
Hi again, Grainger,
Thanks for the reply.
I'm not worried about the whooshing noise; that seems to only appear when the shorting plugs are on the Seduction inputs. I'm gonna take a few days off from this so I don't break any gear in frustration, and then go back at it in the New Year. >:(
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Okay, here's the latest.
Haven't yet had the chance to look at the underside of the TT, but I did contact Kirk and Donna at SOTA.
Donna said that this type of noise is almost always a tonearm/cartridge problem of some sort. If I cannot find someone local to look at it, they offered to troubleshoot it. I'd have to pack up the arm attached to the arm board and ship it back to them.
So that's where I am.
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Hi have you tried twisting your RCA interconnect cables together? This cleared up similar noise and hum I was picking up with my amp (Crack, not seduction) after fitting the speedball (which I think has similar purpose to the C4S) it became more sensitive to outside interference. Its quick and easy to try.
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Well, Gang, after about 4 years of intermittent fiddling, I finally have my problem solved! ;D
Donna of SOTA was correct when she said that problems like the one I was describing were nearly always a tonearm issue. I took my entire 'table to Mike of austinstereo.com (http://austinstereo.com). He fixed the issue in a couple of hours.
Turns out the grounding wire in the tonearm cable had broken somewhere, so there was no real ground. So Mike snipped the old wire and created a new one. Additionally, he told me that the hum lessened but didn't completely vanish with the new ground wire, so he unmounted the Linn Basik LVX tonearm and tightened all the hardware, including some loose bits that help to ground the arm. That finished the job.
So, in the end, the issue had nothing at all to do with the Seduction.
I suppose I should mention, by the way, that I bought this arm used in 1986, so I guess I should've checked this first. ::)
Many thanks to all of you who helped along the way! :) Now to install the Russian Teflon cap that mingles sent me 5 years ago. ;D