Greetings tube heads:
I discovered recently that when my Bottlehead Crack has nothing plugged in (The RCAs,) It produces a noticeable low hum regardless of the position, (with the exception of "0" obviously,) of my stepped attenuator. To clarify, when the RCA's are plugged in, the unit is super quiet and sounds awesome like it always had from the day I finished building it. The unit was built as a stock unit at first, then a few months later I added a stepped attenuator, then after that I added the speedball, finally, I built a shielded power cord with some really nice copper I found at my local electronic surplus store. I'm leaning towards the theory that perhaps the stepped attenuator is at fault here but before I assume things I figured someone here can suggest a quick trouble shooting technique, unless this symptom is normal to the Crack. Again, this is not at all a problem when everything is plugged in and/or while I'm listening to music, the amp is working like it should. I'm attaching some pics of the build in case anyone and catch something weird. Thanks in advance.
