It's coming up on that time of year...I come here and read when I don't know what else to do...

so, my PPA turned sweet sixteen this year... still working perfectly. Charged it up this morning and let her rip. Coolest thing ever.

I'm gonna assume when you say "central pad" you mean PCB...the PCB is being used to hold the drivers in a certain configuration so it fits in a housing. If you can see the trace and it runs to a solder point for a wire and then to the pin of the driver, then it would be fine to solder directly...

OPA551PA is a buffer, if you look at the first post in this thread, you will see the link that Pete supplied, all your questions will be answered there...

some of my tubes are very old... its an easy place to start...swap them in the sockets.

I actually did try to find a 100k DG AT pot for a few hours on the interwebs, the closest I could get was two singles that allowed the shaft from either pot to be inserted into the back of the other pot. Seemed dubious at best...didn't buy them.

Thanks for the speedy answers, I have gone the other way and used a 50k Ohms pot in place of a 100k pot with great success. It was done on the 6DJ8 "Headwatt" amp by Bruce Heran...

so, the higher Ohms value isn't an issue?

would it be possible to use an Alps "blue velvet" 50k ohms pot with this amp? I have a few spares, I could wire one off board...

Woo Hoo!!! ordered my board, sorting thru the BOM now! Thank you sir for another awesome project!!!

I can only see two possibilities...one is to contact the manufacturer and hope they will sell you one/offer to repair, or try to DIY a more readily available 3.5 that will need to be installed by you in a "best fit" scenario.

I soldered every joint of my B22 and Nate Maher built the stepper... From a true DIY perspective? The B22 is the finest thing I've ever built or listened to.

I etched my boards for this amp, here is what I came up with...  

I do have them... I have to find my external hard drive and locate the files, I will get back to you ASAP...

No more group Buys...for me, those were the golden days of Head-Fi. Gosh...I built every amp that came along, I have the first run Bijou amp PCBs of which maybe a dozen or less boards were produced? same with the Millett Max, I got the last two boards from the original beta GB...I think there...