Bottlehead Forum
Bottlehead Kits => Crack => Topic started by: mosshorn on January 13, 2012, 09:31:48 AM
-
First of all, let me thank this forum for how much help it's been. You guys really know your stuff :)
Anywho, to the problem. I've had this occuring hum since I initially built my Crack. I thought it was the tubes, but remove the RCA plugs, no hum. Several things has been possible culprits, and I've taken them out:
New tubes
switching DAC to different circuit
different DAC
different RCA cables
Well, I go outside to resolder the RCA's solder pot (in other news, I hate soldering soldering pots!). It seems successful. I go inside, plug everything back in, turn it on and wait.
I plug in my headphones, and the nasty "this is probably not good" cracking goes on. I promptly turn it off and unplug my headphones. Could this be due to that RCA jack REALLY not being well grounded? What else could that hum come from?
Thanks,
Brian
-
Did you use the insulating washers for the RCAs? The RCAs should not be grounded to the chassis plate. Also, did you paint or powdercoat the plate, and if so, did you make sure to scrape all paint off at the main grounding point (near the power inlet, and at the tube sockets?
Assume all your voltage and resistance measurements are ok.
-- Jim
-
The plate on the transformer? or the main plate?
-
He's talking about the top plate, the white washers around the input RCA jacks and your top plate finish.
-
Clarification time-
Only happened with cables plugged in - is that the hum or the crackle? Or both?
If the crackle only happens with the cables plugged in it could very likely be a broken cable. That break could be causing the hum too. If it is caused by the RCA jack itself the jack probably needs to be replaced.
-
The hum was the original sound, that happened only when the RCA plugs were connected. Tried 3 different pairs of cable (including the monoprice pair that I just got in the mail) to no avail. The crackling happened when I tried to fix the black RCA jack by resoldering the wire into the pot.
From there I resoldered the ground buss and wire B8U (which apparently I didn't solder before), and now I'm getting crazy readings from not having a ground. So it goes, time to retest joints lol
-
Alright, update. It powers on now, and everything seemed ok, my voltage checks were okay, but the TRS check came out odd at first (peaked at 10v or so on the ring, then nothing really, nothing much on the tip).
I plugged in my headphones, and it still made the crackle noise. Also, I've been using my 6080 tube that came with my Crack to test (keeping my 6AS7's to the side), and it got hot, fast. It also started smelling like burning (not the typical hot smell at all), so I promptly turned it off.
Any ideas? I'm lost at this point, and kind of worried to plug in one of my 6AS7's to test and see if it was just that tube :/
EDIT: Just put in my RCA 6AS7 tube, and the crackle/fuzz noise is still there. Since my voltages check out, I'm guessing it might be the RCA jack that I messed up. Any way to confirm this?
Even more EDIT: I'm noticing I have more hum than I did before, and even remotely moving the pot causes for some nasty, nasty popping. Hope this helps.
-
Bump if anyone knows. I'm going to mess around with it more tomorrow afternoon.
-
moss-first -ck what you have done with the directions-take your time doing this-second ck your soldering-when you say you resoldered the rca wire into the pot-i take it you mean resoldered the input wire from the rca at the voume pot-you may have dropped solder into the pot or over heated the pot-if you have large blobs of solder -get a solder sucker and suck them clean then resolder-at your rca's make sure you did not melt the inner insulation or blob solder from the inner part[positive] of the rca to the outer part[ ground ]
-
Thanks for the help Howard, you named off what I was thinking of doing as my short list. I suppose I had a short around my RCA jacks, but I resoldered quite a bit of stuff tonight.
Everything works! But I still have the hum. Oh well, I'll try resoldering some of the driver tube section tomorrow.
By the way, I found I enjoy the sound of my stock Electro-Harmonix ECC82 more than my old Telefunken 12AU7, with a significantly greater soundstage. Who woulda knew? :S
Thanks for everyone for all the help!
-
This is a long shot, but if your rectifier circuit is bad, it may. be passing AC which will sound like what you are describing. Might start there next....
John
-
Does the hum increase when you turn up the "volume" or is it the same regardless of where the volume is set?
-
It slightly goes up when turned up, but oddest thing, I'm noticing it makes weird cutting out noises when I wiggle the pot itself via the volume knob. Connection issue?
-
I bookmarked this site when another Bottlehead posted it. It could be some help:
http://www.geofex.com/Article_Folders/potsecrets/potscret.htm
-
Sounds like it. You could try connecting a jumper from the wire from the center of the RCA jack to ground, better yet the end of it that connects to the pot. Do both chanels and see if the hum stops...John
-
Hum is still going, but I did notice that when I twisted the plug in the RCA jacks, it caused more/less hum. I think I'm going to run to Radioshack, pick up some new jacks, and see if that resolves anything.
-
Ok so just got back and installed some new jacks (things are so tiny it's almost funny compared to the stock ones)
Same hum. Well, now to try that again. It sounds almost like an electrical static, which is why I started at the tubes. It goes in pulses kind of. Should I maybe resolder the capacitors? I just can't figure out what it may be :/
Thanks again all,
Brian
-
>>...when I twisted the plug in the RCA jacks, it caused more/less hum
That makes me thing there may be a bad ground inside the interconnect, or the plug's outer shell is not tight enough to make a solid contact with the jack.
>> ...It sounds almost like an electrical static, which is why I started at the tubes.
That could be an iffy solder joint in the signal path somewhere, or an external radio wave such as a current carrying switch - even refrigerators have been known to cause this symptom
>> ...It goes in pulses kind of.
And of course that makes me think of cell phones, flourescent lights, dimmers, and battery-operated motorized devices ...
Sorry to have so many vague possibilities, it's just kind of the nature of sleuthing out hum and noise problems. Frustrating unless you're an amateur detective.
-
>>...when I twisted the plug in the RCA jacks, it caused more/less hum
That makes me thing there may be a bad ground inside the interconnect, or the plug's outer shell is not tight enough to make a solid contact with the jack.
>> ...It sounds almost like an electrical static, which is why I started at the tubes.
That could be an iffy solder joint in the signal path somewhere, or an external radio wave such as a current carrying switch - even refrigerators have been known to cause this symptom
>> ...It goes in pulses kind of.
And of course that makes me think of cell phones, flourescent lights, dimmers, and battery-operated motorized devices ...
Sorry to have so many vague possibilities, it's just kind of the nature of sleuthing out hum and noise problems. Frustrating unless you're an amateur detective.
Detective indeed. I tried resoldering a cap that had a nasty connection since I originally did it (14u if I remember correctly), and reflowed 15u and one of the power connectors, also one of the transformer terminals (terminal 2 to be precise). Strangely enough, it made the static sound worse. Odd.
I DID notice something though. I'm connecting the Crack to my Audioengine D1 via optical. BUT it is powered via USB! So whenever I move the mouse, I can hear a little bit of whirr from the mouse moving. Weird eh? I thought about my DAC being the problem, but it did the exact same thing with a previous DAC as well.
I also turned off all my lights, the router, AND the modem, and still nothing :/ Worth a shot though! Thank you so much for the help so far :)
-
Jumping back, did you short the inputs as 2wo suggests in the last post on the first page? Shorting the inputs will tell you if the crackle is in the crack or elsewhere.
What source(s) is/are you using? It could be within the source. Have you eliminated the source as the problem?
-
I had a crazy problem with interference that was driving me crazy.My Crack is connected to a modded Squeezebox2. I have the SB2 connected to a wireless Ethernet adapter so that I can avoid any RF interference. When I would power on the crack with my SB2 off I would hear a crackling sound every once in while. It was driving me nuts because everything sounded great. When I would turn the SB2 on the crackling would be much worse. I tried the Crack with my sons setup and it was dead quiet. So I knew that he Crack was good. Come to find out that the Ethernet adapter was to close to the Crack and SB2. Once I moved it away the Crack and SB2 were dead quiet.
It just goes to show that there are outside influences that can cause problems with the overall sound.
-
Brad, that is exactly why I asked the questions above your post.
-
I tried a jumper going from one channel to ground, but will try both tomorrow. Doing just one, the crackle was just as bad as before.
I'm using Crack>Audioengine D1>Computer. I'm also going to bring the Crack into another room to see if the problem is isolated.
-
You should try the Crack with an analog source, TT, Tape, FM etc. to rule out digital problems.
-
Just tried it from my turntable, and now I'm really confused. One channel is playing in my headphones thru the amp (left channel), and I can hear some (maybe the other channel) being played out my turntable? It's low but definitely there. I'm pretty much a layman in that area, so I don't even know. Anywho, there was still a noise with the TT plugged in. A tracking buzz, kind of like the record spinning.
-
The stylus in the groove can be microphonic. And it might not be. That is without any amplification on it can make sound. Some TT setups don't do this. Is this what you mean?
So now with your TT you are missing a channel, right? Is the crackle there? You mention a "tracking buzz" can you describe this? That sounds like a buzz caused by a grounding issue that is not that uncommon with first time TT setups. Often it is a loose or missing grounding wire.
To help the helpers you need to continue to answer the questions that are asked.
-
I put my ear up to it, and I'm thinking it is microphonics. I guess I've never heard it before since I always have my headphones on, not to mention I found it weird that is the audible song, just very quiet.
With my TT playing, I can't hear a single pop or crackle, even on quiet passages. If I raise the arm up, about 2 seconds later it starts that tracking buzz, a "tickatickatickaticka" that sounds like the motor perhaps?
Thank you so much for your help by the way, I can't explain how much I appreciate it.
-
I put my ear up to it, and I'm thinking it is microphonics. I guess I've never heard it before since I always have my headphones on, not to mention I found it weird that is the audible song, just very quiet.
That makes sense. I can't hear it across the room but with one ear piece not working the dead ear should hear it.
With my TT playing, I can't hear a single pop or crackle, even on quiet passages. If I raise the arm up, about 2 seconds later it starts that tracking buzz, a "tickatickatickaticka" that sounds like the motor perhaps?
That says the pop/crackle is not the Crack, per se. It is either the source or an interaction between the Crack and the source as a number of posters have suggested.
The buzz is as I mentioned in reply #25 "caused by a grounding issue that is not that uncommon with first time TT setups."
But to find the source of the problems you need to answer all the questions asked. What we have now is that the sound from the TT is microphonic. The pop/crackle is not happening in the TT setup.
Another question that comes up is the "tickatickatickaticka" noise. Does it go away if the table is turned off? How about if you invert the AC plug for the TT? That is, take it out, rotate it 180 degrees and put it back in the socket. Ground loop problems can be minimized this way.
-
When I turned the TT off, it stopped that noise. I'll try inverting the plug when I get home in a few hours, in class right now (love 1 o clock classes this semester)
-
This also says that the Crack is not the problem. It is a problem, but the Crack is innocent. It could be the table/ground/motor. There are a number of problems.
We should get one problem fixed at a time rather than jumping around.
-
Well some excellent news, but still not an answer. I used an RCA to 3.5mm connection with my phone to see if it was causing any of the same issues that my other two devices have been doing (crackling in the DAC, one channel on my TT), and it had both channels, but one was EXTREMELY quiet (the same one on the TT). Perplexed, I flipped it over.....to notice I had my jumper cable down there from the prior troubleshooting! I took it off and both channels came in loud and clear, and no tracking noise from my TT. Dead quiet too. So I'm figuring it's something to do with my DAC, I'm going to try a couple more things and report back with results:
-Change USB cables for the DAC
-move setup closer to computer
-see if running from 3.5mm on computer to RCA on amp resolves anything
EDIT:
From this move, I found out the culprit (at least as far as I can tell) is my own computer (or the sound card I have in, or something else inside it). I swapped everything over, and ran my dac through both USB and optical to see if anything changed. Nothing. So then I unplugged that, and set my RCA to 3.5mm up. Still produced the same noise! It should be noted also that when my DAC is plugged in exclusively to USB (not usb power/optical input) that a clicking noise is also heard.
So now that I've taken the DAC out of the picture, the grounding issue is out (at least I believe the TT/phone resolved this) , and the DAC isn't the issue (resolved by bypassing the DAC itself). I'll try going through a laptop that's plugged in, just to see if I can localize it to my PC individually. If it is that, what would my options be?
Once again, thank everybody for being so helpful.
EDIT 2:
So I finally isolated (as far as I can tell) where the noise is coming from: a ground loop from my amp through my dac to my computer, in particular my power supply. I'm thinking of picking up a ground loop isolator from radio shack (most affordable option at the moment) before class tomorrow to see if that helps. I've heard horror stories of severely degraded performance, but also heard they don't affect the sound at all. Anyone have any experience with these?
-
Yesh, it may very well eliminate some or all "hum" but also the bass, and probably more, with it. I tried one years ago in car audio installation. A member here recently tried one as well. Seems they havent changed much if at all over the years. Keeping working on a real solution. The ground loop isolator is probably going to be a bandaid, and not a good one.
link to recent thread in Seduction forum ... http://www.bottlehead.com/smf/index.php/topic,2491.0.html
-
Worse come to worst I might try one of those cheater plugs, it's worth a shot, as long as it doesn't burn my house down at least :P
Just tried something else with very unenjoyable results. I thought "hey, what if I isolated the noise by plugging the dac usb power in via an external source, since its data is run via toslink?
Called up Audioengine, guy was like "sure, that would work"
SO I decided to experiment using my phone's charger as the usb psu. Plugged it in, light turned on, no issues. Turn my Crack on, everything seems fine. Plug in headphones and start playing a track, and I'm noticing there's no sound. I adjust the volume pot and touch the metal....
.....and apparently that usb power was still coming, because I got quite the shock (the creepy chill one) coming from my amp. Safe to say, I promptly turned everything off and dismissed that idea. Maybe running a lower current power supply would work (it's specced to 200mA, this one is 700mA, same voltage reading though)
-
Do you have an electrical out let polarity tester? Do you know if your outlets are wired correctly? That's certainly not a safe assumption these days.
-- Jim
-
No, but I can ask around to see if someone does. the usb power was plugged in a power strip, so maybe inverting the way it was plugged in would produce a difference?
Also, I'm giving a usb isolator a thought. Since it's just for the power, and not for audio, I don't "think" it would affect quality like a rca based ground loop isolator would.
-
I don't think that will help -- sounds like you may have your house wiring backwards -- hot and neutral reversed -- a unsafe situation no matter what and really not good with audio gear.
Those power supplies are also typically isolated because of the internal transformer, and something just sounds very wrong.
The outlet testers can be had at rat shack or harbor freight for probably $5 or so -- the little gizmos that plug into an outlet and have lights on them to indicate if there is a problem or not. Every audio person should have one.
HTH,
Jim
-
If I can't find anybody with one, I'll pick one up today or tomorrow :) Thanks for that idea, if it brings anything to light I'll let you know!
-
The 700ma shouldnt matter as long as the voltage it correct. The device only draws the current that it needs. Yep, something isnt right if you are getting shocked by touching the chassis plate. Definitely check the wiring suggested. Home Depot and Lowes also sells the simple plug in testers. Ive seen them at Walmart as well.
-
Thank you so much for the help all! That truly sounds like the culprit, but is there any way to alleviate this situation other than messing with the house's electrical? I don't know if I'll be able to change that.
-
So I figured out the issue (well 99% of it, I hear a very tiny tiny bit left.)
If anyone has these issues:
tighten the screws in your PC. After checking everything as good, I tightened every screw I could find. This allowed for a better ground, and the problem is almost entirely gone (I'll check for more screws tomorrow). Thank you so much for everyone that has helped, I cannot believe how much of a difference this made to my music :)
-
moss-i just can't help myself--i always thought you had a few loose screws!!!!
all in fun--- howie
-
haha thanks :P