Noise from crack [resolved]

[Lexusspike]

Hello everyone!

First off, let me say i love my crack. From building it to the sound, it had been an experience i didn’t get from any other amp.

I have run into an issue though. Yesterday i noticed a buzzing, so i reflowed some connections around the pot (i recently replaced the stock one with an audio note 100k and rolled in a 5998) and it went away.

Afterwards i noticed a static-like noise coming from my headphones when i turn the volume up to about 30%, increasing when i turn the knob up. This seems to be the same noise i used to get when i turned the knob up to about 80%. I read that this was to be expected, however the noise now starts just above listening level instead of way above it. When i disconnect the rca jacks this noise is replaced with buzzing (that’s louder in the left channel if that matters). Could this be because of the audio note pot?

Thanks in advance, Lex

[Thermioniclife]

I think I would start by removing the 5998 and reinstall the 6080 and listen.

[Lexusspike]

Hi Thermioniclife,

Yes, that was the first thing i did but that didn’t help. The sound still starts at about the same level. I also ran the 5998 for a couple days to cook it in before this started happening.

[Paul Birkeland]

You could also try this mod:
https://forum.bottlehead.com/index.php?topic=11676.0

Is this noise present with a source connected?

[Thermioniclife]

Hello Lexusspike
The next thing I would try is reflowing the connections on the volume pot, perhaps you have a bad signal ground.
I would also reflow the connections on the 12au7 socket, it's possible you had a connection that worked but when installing the audio note the manipulation of the wires could have exposed a bad connection.

[Lexusspike]

You could also try this mod:
https://forum.bottlehead.com/index.php?topic=11676.0

Is this noise present with a source connected?

Hi paul,

Yes the noise (not the low, loud buzz, that is only without a source) is present with a source connected, however it gets softer when i turn my pc off. It still starts at the same point on the pot though. This used to be at a way later point.

Lex

[Paul Birkeland]

If the noise is dependent on your PC, then you'll want to perform that modification.

[Lexusspike]

Alright thanks Paul! It’s awesome that you respond so quickly, truly amazing customer service. I have already ordered the exact diodes you recommended, they arrive tuesday. I will let you know how it goes.

Lex

[Lexusspike]

I have a question; is it normal to get a loud buzz without rca’s plugged in? The buzz starts around 50% and gets very loud when i turn the knob to 100%

Lex

[Paul Birkeland]

Yes, that is the amplifier picking up ambient noise at the inputs. 

[Lexusspike]

Okay great. And do you have an explanation for why my crack suddenly started picking up my pc’s sound like crazy when it didnt before?
It is awesome to get responses from you after lurking on this forum for months

Lex

Edit: i’m using a schiit modi over usb if that helps, i just ordered a toslink cable this afternoon.

[Paul Birkeland]

Okay great. And do you have an explanation for why my crack suddenly started picking up my pc’s sound like crazy when it didnt before?

Something had to change, but it wouldn't surprise me if it's very difficult to figure out.  Fortunately the diode mod should kick this noise out. It could be something obscure like moving something around or buying some new component.  I don't remember the specifics on the Modi, but if it has the option to be USB powered or externally powered, that could certainly account for the difference. 

Edit: i’m using a schiit modi over usb if that helps, i just ordered a toslink cable this afternoon.

The toslink cable should also eliminate the noise.

[Lexusspike]

Okay so the toslink cable actually eliminated all the unwanted noise i was getting. I guess using one usb cable for signal and power is not smart. Now it's silent from 0 to 100%, great! Should i still do the diode mod or is that not necessary?

The only thing is, when i try to put windows at 192khz instead of 96khz it doesnt output sound anymore, just a nasty buzz. I guess this is the dac's fault and all my music is 96khz or lower so it doesnt really matter. Just curious.

A lot of thanks, Lex

[Paul Birkeland]

If you do the diode mod, it's very likely that you can go back to the USB cable.

[Doc B.]

TOSLINK does not usually work with 192kHz.