Hum at high volume [Resolved]

[shrapnel]

Hello,
I finished building my Crack and resistance and voltages checked out great. I plugged it into my Oppo cd player and it sounds just great, but ....

Case 1) I hear hum when the pot is turned beyond 75% volume position. I don't hear this below that level. Also I hear this when no music is playing. I haven't tested the volume beyond 75%. So is this hum normal ?

Case 2) I plugged my computer audio jack into the Crack using a EPA-RCA cable and in this case I hear a hum even at low volume levels. When I remove the cable from the computer I observer behavior as in Case 1. So is this related to the cable ?

Thanks much,
A

[Paul Birkeland]

The answer to number 1 is well covered under the Crack FAQ:
http://bottlehead.com/smf/index.php?topic=4295.0

As far as number two goes, what's an EPA cable? 

Computers are noisy sources generally, what kind of noise is there with your phone as the source?

[shrapnel]

Thank you for pointing me to the FAQ.

I meant a standard stereo jack to RCA

The noise I hear is a low hum, basically the same hum I hear at higher volumes in case 1.

[Paul Birkeland]

The noise I hear is a low hum, basically the same hum I hear at higher volumes in case 1.

The noise either originates from your computer, or from interference picked up by the cable between your computer and the Crack.

If your computer has a toslink output, an inexpensive external DAC cabled to your computer with a toslink cable will eliminate many common noise issues folks experience similar to what you're describing.

-PB

[shrapnel]

You are right, experimenting with other sources it is clear to me that it is either my computer or other electrical interference. Unfortunately it is a MAC book laptop and I don't have TOSLink. I have however ordered a DAC and will experiment with USB.

Thanks for the suggestions.

[Tom-s]

A Macbook normally has a toslink connection.
The 3.5mm audio ouput can be used with a mini toslink connector.
This is the way i use my macbook (Mac mini etc etc) -> DAC.

[shrapnel]

I got a Schiit Modi Multibit in the mix and lost the hum. Thanks for tthe help guys.