Noise issues with Crack [resolved]

[Patrick_P]

Hello everyone,

Disclaimer: I'm fairly new to the audiophile experience so please have patience I've finished my built of the crack a while ago (speedball upgrade not done yet) and had some interference issues in the beginning. Read a bit in the forum and found out about cell phone interference and so on... helped my issues quite a bit. But now after using it for about a month, some new noises have popped up.

About my setup:
Sennheiser HD650s plugged into the Crack, Crack receives input from my audio interface which is connected via USB to my laptop. Connection between audio interface and Crack is a very simple TRS to RCA cable with a 3.5mm 1/4" adapter plugged into the AI.

First thing I noticed with no input to the crack, if I jack up the volume all the way, there's a very audible amount of static noise with the addition of something that sounds a bit like a buzzing sawtooth. I would think it's somewhat normal when cranking it up all the way but maybe that's already a first hint to something wrong.

Now the real problem is a very high pitched constant static noise in one of the channels as well as a sudden crackling/ noisy type of sound that comes and goes every now and then, lasts a couple of seconds and then vanishes again. The high pitch static noise changes the channel as I flip my TRS inputs and the crackling noise can somewhat be manipulated by slightly touching the bigger of the two tubes. I am also using a USB controller for music production and whenever I turn it on via USB, a static low pitch humming appears.

 I am not an expert in soldering but I paid a lot of attention to create clean solder joints. I can also post pictures if necessary. Could it be some grounding issues of some sort? Is it a problem that I'm using rather cheap cables and adapters? Is the whole setup with other electronic components an issue?

I'd be very grateful for any pointers. Thank you.

Cheers,
Patrick

[Doc B.]

You may have two or three different things going on. Noise at full volume with nothing plugged into the inputs is pretty typical. The noise that comes and goes when you touch a tube could be a bad solder joint on the sockets or dirty tube pins. The USB noise might be cured with some distance between components, better cables or connecting the Crack chassis to the chassis of the USB source.

[Patrick_P]

Ok the crackling noise is kind of gone I would say. But there is still this very high pitch constant sound that is really annoying. Is there any indication as to where it might be coming from? It's volume independent and has this metallic character to it. When I switch the amp on and off it keeps rising steadily for a few seconds and then stays constant. During the rise it has some small fluctuations.

Edit: Hmmm, actually the buzzing noise still keeps coming in every now and then, no touching of the tubes or nothing. Could this also be interference related? Is this sth. that all amps have in common, being so sensitive?
I also didn't quite get what you meant with the connection between chassis, could you please elaborate a bit? Thank you.

[fullheadofnothing]

Try another source to figure out if it's a problem with your Crack or your whole setup.

[Doc B.]

The description sounds like outside interference. The best way to work this out is to unplug any connected RCA cables and short the center pins of input jacks to the ground tabs of the RCA jacks. Then listen to see if the noise is still present. If not, it's coming from something besides the Crack.

[Deluk]

What happens if you simplify things and you route some music straight from your laptop audio out to the Crack?

[Patrick_P]

Hello everyone,

thanks for the suggestions.

"Try another source to figure out if it's a problem with your Crack or your whole setup."
Tried using my phone as a source, didn't change, still constant high pitch noise and crackling every now and then (intervalls of 10 minutes maybe??). The high pitch tone sounds to me like people describe a tinnitus. Very annoying.

"What happens if you simplify things and you route some music straight from your laptop audio out to the Crack?"
Good idea, tried it, things remain unchanged so it's not the audio interface that's introducing the noise, I would guess it's the crack itself/ interference.

"The description sounds like outside interference. The best way to work this out is to unplug any connected RCA cables and short the center pins of input jacks to the ground tabs of the RCA jacks. Then listen to see if the noise is still present. If not, it's coming from something besides the Crack."

I did that and it made me realise that the tinnitus noise is present without even plugging the RCA cables in, so just power and headphones plugged in. Shorting the RCA cables to the ground tabs did not change anything.

I'd be very grateful for more suggestions. Thank you everyone.

Edit: I'm also hearing some noises that seem tube related somehow, like someone would flick the wire for a second. Hard to describe but sounds very mechanical/ wire-like/ oscillation of a wire. Only lasts for one second and is rarely present but noticeable.

[Doc B.]

Could be a noisy tube. Substituting another pair of tubes might help sort it out.

[Patrick_P]

New tubes have been ordered, will report back. Thanks!

[ChuckWheat]

I have almost exactly the same thing. I just built it yesterday. I haven't installed the speedball yet. I can hear some quiet whine noise every few minutes in the right channel. Often only when there's no sound playing. I find the longer I leave the crack on, the less often it happens. It's not all that bad, but I'm not sure if I should go ahead with the speedball install when there's already noise of this sort. I did notice that all my voltages were within range, but on the lower side. I'm wondering if this might have something to do with it.
If it's one of the tubes, I'll probably end up swapping them for something else eventually, but it kinda sucks if the tubes aren't good out of the box.
If you could let me know if the other set of tubes gets rid of the noise, that would be very helpful.

[Doc B.]

A whining noise is most likely from external interference like a computer, cell phone, light dimmer, etc. You could try the suggestions made to the OP to track it down.

[ChuckWheat]

I just took my phone and waved it around the crack while loading a bunch of youtube videos (using wifi), and found that lo and behold, the noise happened. This time with extra white noise. It is consistent when I hold my phone 6 inches away from the left side of the body. I think that might be it! My computer might also contribute, but it's a good 5 feet away. Do you think it could be possible to install some sort of shielding around the tubes and body of the crack? I've heard that using aluminum and grounding it can help...

Edit: Gently tapping the rectifier tube seems to also cause the same kind of noise. I can seemingly "play" with the noise by wiggling the tube. Could they be two separate issues?

Edit2: It seems to also be linked to the headphone cable (stock hd650). Perhaps the cable is picking up interference?

Edit3: I'm starting to think I should make my own thread. Adding speedball hasn't changed the symptoms.

[Patrick_P]

Hey guys,

just wanted to mention quickly that I've been away for a while and didn't have time yet to change the tubes. They are sitting in my desk and I think I should be able to give it a shot tomorrow. Will report back.

Cheers,
Patrick

@Chuck: Sounds like you're having very similar issues. Especially the noise when moving the tube is exactly what I'm experiencing as well. I also thought that installing the speedball wouldn't really do much so I've put that aside for now. I'll report back if the tubes made it go away.

[Patrick_P]

Ok so I've just installed the new tubes and pretty much all of the issues I had are gone now. There's a slight low frequency buzzing now instead but it's barely noticeable and not really that annoying. Seems to me that the tubes were the issue here. A bit of a shame since I handled them with great care putting my kit together but I'm happy the way it is now. It's also good to know that I know where to get tubes from now I'll try narrowing it down which one seemed to have caused the issue (yep 6080, looking at you) and maybe give another update. For everyone else that runs into the issue, new set of tubes cost me about 40$ including shipment to Europe with one week delivery, worth a try. Good luck everyone. I'll go enjoy my noise free crack now

PS: I can now crank up the volume all the way without hearing any kind of noise at all. Before changing the tubes, it seemed that the noise floor would get amplified a lot by cranking up the volume. Complete silence now. Maybe that's a good pointer for someone else who's wondering.

PPS: Maybe one more question. Since I would ideally like to get rid of the low frequency buzzing as well, are there any pointers as to why I can only hear it on one side? Or single sided noises in general? Is there a chance I messed up one side of the connections?

[Paul Birkeland]

PPS: Maybe one more question. Since I would ideally like to get rid of the low frequency buzzing as well, are there any pointers as to why I can only hear it on one side? Or single sided noises in general? Is there a chance I messed up one side of the connections?

Yes, generally this points to a flaky solder joint that only affects on channel (though it can also be cable/source related).