Humming noise on one side (with a twist)

[michte]

Hi,

I've been using my Crack (v1) with speedball for almost 5 years now and have been mostly really satisfied. But lately, it started developing a faint but audible humming noise on one side of the headphones. To be sure, I completely reflowed every connection (without overdoing it) and while doing so, took down the speeball main board to easily access its components. I was shocked to see that I put the board backwards from what was indicated in the manual, but luckily, since it's a mirrored design, I didn't botch my whole setup. So I put the whole thing back together, but sadly the humming noise is still here. However, it did change side !

So my question is : given that I already took down and reflowed the whole thing, and that the humming noise changed side when I put the speedball board the other way around, does it mean that the main culprit sits on the sb mainboard ? Would buying another speedball kit and rebuilding it from scratch be a wise move ?

Thanks for your input

PS : I did try on different main plugs and with other tubes, same humming noise.

[Paul Birkeland]

Can you recheck your voltages?

[michte]

I did, everything seems in order.

[Paul Birkeland]

It is possible that there's a flaky joint on the board itself, and reversing the board moved the impact of that joint to the other channel.  I have never experience a C4S failure that led to just noise and no deviation in predicted operating parameters.