Right Channel buzz troubleshoot

[Bullpride]

I've been doing some troubleshooting to figure out why I am getting a buzz.

Current setup:
PC to Liquid Carbon + Grace SDAC

Buzz only when music is playing or PC is making sound of some kind (notifications included)
Buzzes when: 3.5 SDAC output to RCA to Crack
Buzzes when: 1/4 headphone output to RCA to Crack

Clean when 3.5 iPad output to RCA to Crack
Clean when Headphones plugged into headphone out of Liquid Carbon (Crack not in line)

If my DAC was bad, wouldn't I hear the buzz when the headphones are using the Liquid Carbon Amp? 
Would the Crack pick up noise when the liquid carbon wouldn't?

I have inspected and flowed all joints.
Buzz was happening before and after I installed the first board of the speedball.

Any thoughts would be greatly appreciated.

 

[Paul Birkeland]

I would try this mod:
https://forum.bottlehead.com/index.php?topic=11676.0

 

[Bullpride]

Been reading through that thread. 

Would picking up a multi pack like the following be worth while?

Ordering 2 diodes from any site costs at least that in shipping:

https://www.amazon.com/Switching-Rectifier-14-Electronic-Assortment/dp/B07BTY8FD2/ref=sr_1_6?dchild=1&keywords=1N5408&qid=1590420744&sr=8-6

 

[Paul Birkeland]

So, you could certainly buy that pack and use them in this spot.  I wouldn't recommend using off-brand diodes like that anywhere else though.  There's no company name standing behind the performance of those parts, and I've had some off brand UF4007s fail for me before where they were running at below 15% of their ratings.

You could get the Diodes at Digikey and get a PEC pot while you're there.

 

[Bullpride]

Is this still the one to buy?

https://www.digikey.com/product-detail/en/KKA1041S28/KKA1041S28-ND/770961

 

[Paul Birkeland]

Yes, that's what I'd get.

 

[Bullpride]

Diodes and PEC Pot ordered.

By the way, I followed the suggestion in this post, and it almost completely cleared up the noise. I am still going to do the Diode Mode, as I am still getting a very low but audible hum.

A note to potential Crack builders out there: The wires that connect to the headphone socket red and white as seen in my kit are often shown in the manual as running parallel to a bunch of other wires flat against the chassis. I found that having them like that would mean the wire closest to the wire group could pick up a 60 Hz buzz from one of the other wires in that collection: the red right-hand channel wire in my case. Be sure to lift them away from the other wires if you can, buzz gone...

https://www.hificollective.co.uk/blog/bottlehead-crack-headphone-amp-build-and-modification.html?fbclid=IwAR0pPu_oP5EUsHwAC6igbOKKmfhGclqcW0dRfv2VBugCjoIJYfPcR7nBPpY

 

[Paul Birkeland]

It's funny, I've built dozens of Crack kits over the years and I always lay those wires flat against the chassis next to each other with nary a buzz.