Need a bit more help with Mainline [resolved]

[Larpy]

Great idea (why didn't I think of it?!).

Turns out that the problem follows the board, so that's conclusive:  it's that particular C4S board that is the problem.

I removed the board and tried to unsolder all the parts so I could reinstall them, but I mangled the LEDs and a few of the resistors in the process, and I've now soldered and unsoldered and resoldered the IA, OB, and bB pads that I'd like to start over from scratch.  So I just e-mailed Eileen to order a replacement C4S board and components.

Once they arrive and I build and install it, I'll report back.  In the meantime, thank you so much for your assistance.  When I couldn't figure out what the problem was on my own, I felt helpless.

[Paul Birkeland]

I'd recommend sending an e-mail to the replacementparts(at)bottlehead(dot)com e-mail.  Pasting a link to this thread into your email can be helpful as well.

[Larpy]

Replacement C4S board and components arrived and I built and installed it last night.  The amp works perfectly now.  LEDs all aglow and all voltages spot on.  I was hoping there would be an "aha!" moment replacing the old board where I spotted the problem, but nope--some unseen gremlin was the culprit.

In any case, right now I'm listening to the Mainline through Audeze LCD2s and it sounds quite nice.  Neutral-sounding and quite resolving--a much better match for the Audezes than my homemade Wheatfield HA2 (an OTL Pete Millett circuit).  Bass is significantly tighter.

Thank you, PB, for guiding me through troubleshooting. A frustrating couple of weeks, but well worth it now that the amp is finally happy.