Built my Crack, but have some buzzing I can't figure out.

[BaksideAttak]

Hi all,

I built my Crack plus Speedball about three weeks ago, and it sounds great with one exception - some slight buzz. I've been trying to get access to the forums to get technical assistance from some of you gurus, so I would really appreciate some insight into the issue. I will go ahead and try and give you all the information I have, though some of it may be irrelevant:

• After building the Crack (base, no Speedball), it passed all resistance and voltage tests within 10% of target
• When plugging in my heaphones without music, I heard a very low buzzing. This buzzing DOES change with turning of the volume knob.
• https://mega.co.nz/#!VQtS0JQY!CdVUcU5epwLMN_wx3lqJLAlto15Wdx1PoqsN-7EMKNo This is a link to an audio recording of the buzzing. I put my iPhone up to my headphones and recorded, and it captured the buzz pretty well. Note that this was captured at full volume of the Crack
• I was hoping that this could be an issue that could be resolved by installing the Speedball upgrade. I did so, passed all voltage and resistance checks within 10% margin of target. The buzz was still there (but the amp sounded a LOT better after Speedball! I was very impressed.)
• I tried cleaning the tube pins by removing and reinserting several times.
• I went through the manual for both the base Crack and Speedball three times to ensure each connection was in the right place.
• I then tried reheating all the solder joins and retesting the resistance and voltages. Everything checked out within 10% again.
• In case that last step wasn't enough, I reheated and added a little more solder to the joints to ensure connectivity. Resistance and voltages checked out, but the buzz is still there.
• I tried several cables, another amp, and removed my DAC from the setup, and the problem seems isolated to the Crack.

That's the point where I stopped trying to troubleshoot and decided to come to the forum and ask for help. Does anyone have any ideas as to what could be causing this sound? I can barely hear it at normal listening levels, and when music is on I can't hear it at all.

Any and all advice/help would be appreciated! For context, I'm using a JDSLabs ODAC, HD 650s, hand-made cables (I did the cable project to learn how to solder before doing the Crack. I have tested these on multiple devices and proven they work. I also used commercial cables to test the Crack), and have a JDSLabs O2 as my other amp.

Thank you!

 

[jrebman]

Sounds like it may be interference from something like flourescent or LED lightbulbs, a light dimmer, electric motors and things like that.  Can you move the crack and dac to another room and try it there and see if the buzzing persists?

 

[Alonzo]

To echo Jim,
Do you have a cordless phone or wireless router near the amp?  I picked up interference from my ASUS router when my Crack amp was on a shelf below it.

 

[Doc B]

short the inputs and see if the buzz goes away.

 

[BaksideAttak]

Interestingly enough, I found out some new information. I moved everything into another room and used my laptop for the setup - no more buzzing. I moved it back to where it was, still plugged into my laptop - no buzzing. I swapped back to the USB cable to my desktop - buzzing. I then changed USB ports on my desktop and tried a different USB cable, but every feed from my desktop had the buzzing.

So basically, it's my desktop. I'm not sure what exactly could be causing this, though, or how to fix it. Any ideas?

Good news is that it's not my amp!!!

 

[Doc B]

Check what else is connected to your desktop. When I charge my iPhone from my desktop it generates so much god awful buzzing/clicking garbage that I can't listen to the the desktop's audio thru headphones.

 

[Guy Boisvert]

Make sure that the transformer screw that holds down the ground connection is tight [one of four on the top of the transformer]  . Give it a turn or so, and see what happens.

 

[BaksideAttak]

@Doc:
I only have mouse, keyboard, microphone, and DAC in my desktop. I tried unplugging each individually, but none made a difference. I noticed that the buzzing happens when Windows goes into its login screen - maybe it's one of my accessory hard drives? I'll try unplugging those later today.

Any other possible ideas?

I'll try tightening the screw later today, as well.

 

[jrebman]

One thing that has also helped with this situation is to go through the computer and tighten every single bolt and nut you can find.  It's no guarantee, but it has worked for more people than you would ever think.

Also, try using one of the usb ports that are closest to the motherboard -- again sometimes the ports at the end of long ribbon cables can also pick up radiated noises inside the computer.

HTH,

Jim

 

[Doc B]

If it goes noisy at a particular screen, maybe try turning off the monitor and see if the sound changes.

 

[BaksideAttak]

Ok, so I've tried:

• Tightening all screws in the computer
• Removing every cable from the computer individually and restarting each time while listening
• Disconnecting my monitor on start
• Moving the desktop while listening to the buzzing (it should change when I move it a foot or so if it's an interference issue, right?)

Unfortunately, a new problem arose. I left the amp on while I was at school today, came back, and now there is spontaneous popping/crackling on average once every 5 seconds. Also, the popping/crackling seems to be isolated to the right channel. I read in the manual that this could be a tube issue... is there any way I can test this?

 

[ice9mike]

After I dropped the top plate of my crack I had the popping crackling sound in the left channel only. I could visually see this by watching the 6080 tube with the lights off. The popping and crackling were generated from arcing inside the tube. The tube also became very microphonic picking up the slightest movements and touches on the top plate.

ice9mike

 

[BaksideAttak]

I looked at the 6080 in the dark but didn't see any arcing. I am not sure how the tube could have been damaged, as it was sitting on my desk all day untouched when the popping started, and I'm unbelievably careful around the amp. And the popping is much, much louder than the buzzing (at normal listening levels), as it doesn't go away when the potentiometer is all the way down. I am considering buying replacement tubes, but I'd really like to be able to confirm that it's a tube issue before purchasing expensive tubes. Especially since I saved up for so long for the Crack - I don't really have the money for replacements! But now that I'm listening to my O2 again, everything sounds so hollow Spoiled already.

I can try and get a recording of the popping and the buzzing changing with the potentiometer if anyone sees any value to having those data.

Thanks for everyone's help!!!

 

[Doc B]

It is possible that a tube that went noisy after it cooked in for a while. Another less likely possibility would be a poorly seated tube. You might try shutting the amp off, pulling and reseating the tubes in the sockets and running it again to see if that stopped the noise. Beyond that, the only easy way to see if a tube is making the noise is to try a different tube.

It is also possible for a tube to go through a noisy phase and then get quiet again. Or it may just stay noisy. Tubes are kinda like women that way.

 

[adamct]

And like men...

 

[BaksideAttak]

Update:

So the crackling stopped, but the buzzing continues. It has changed in character, though. When the potentiometer is all the way down, I get a louder buzzing in the right channel only. As I turn it up, the buzzing fades into both channels. I have no idea what this could mean.

• I tried unplugging each cable from the power strip individually to see if it stopped the buzzing. No luck.
• I unplugged each peripheral from the computer one by one. No luck.
• I switched the computer to a different power strip. No luck.
• O2 works fine fed from ODAC plugged into the USB on my desktop (using this now)

So it seems like those tube sounds have gone away (like you said could happen, Doc), but now the buzzing is louder and behaves differently.

Given the channel weirdness, could this be an issue with the cabling from RCA inputs to the potentiometer? I've seen some people use Cardas Star Quad to replace the braid... would this help? I'm by no means an electrical engineer, and I wouldn't even know how to do that.

 

[MDFreaK76]

I have the same problem. I'm pretty sure its due to a Ground Loop. Essentially, the ground from your laptop/USB/DAC/Audio Out and the ground from your Crack have different potentials. This creates interference between the the two circuits, which presents itself as a hum in the 50-60Hz range. Give the youtube link below a listen (its what 60Hz sounds like).

I'm still trying to find an adequate solution for this. Some suggestions i've heard are:

• Try a different plug, maybe on another circuit/breaker (Tried this; somewhat works)
• Use TOSLINK from Source to DAC (Not tried yet)
• Clip the ground on the NEMA 5-15P connector (included for completeness, but a terrible idea. Please DO NOT try this!)
• Clip the +5v and GND leads on the USB cable (Not tried yet)

On a somewhat related note: I've also had CPU interference if my amp is plugged into the same surge protector as my laptop, which creates a much higher pitched buzz/hum that goes away if i keep the CPU busy enough.

Info on Ground Loops: http://en.wikipedia.org/wiki/Ground_loop_(electricity)
YouTube Link to 60Hz Hum: https://www.youtube.com/watch?v=SVZ2P0KsLic


Good luck!
  -Rick

 

[Doc B]

Ground loop hum is usually 120Hz and buzzy sounding, not 60Hz. 60hz is usually due to magnetic coupling and soft sounding.

 

[jrebman]

Don't cut the power lines on your usb cable -- the usb receiver chip needs those to bootstrap even if the dac uses internal power instead of usb power.

-- Jim

 

[Paul Joppa]

The ultimate solution to ground current problems is to eliminate the ground current from the signal lines. That means a transformer, an optical link, or the traditional balanced line. Naturally all of these are compromises, one way or another. Pick your poison!

Non-ultimate solutions involve reducing the resistance of the signal-ground line in which the current is flowing, or reducing the current itself. Naturally, "reducing the current" means sleuthing out the source(s) of that current - never an easy task, but sometimes an interesting challenge!