Long time lurker and thought it was time to chime in! I received my #183 from Nik about 2 months ago. I thought it was good but not great. About a month ago, I dropped it off at a local store to consign it. Yesterday, I decided to pick it up because there was no action on it. I also wanted to try a couple of simple mods to see if I could improve it along the lines of what I wanted to hear from it (basically, the stock OD was a bit bloated in the bass that couldn't be dialed out adequately without messing with the clean tone; it started getting fizzy on the top with the OD settings much above 5 and the OD trimmer above about 5 as well).
As I stated, I didn't want to spend a lot of time tweaking it and picked tow basic areas where I thought I might have success.
I changed the slope resistor from 150K to 82K; I removed the 22pF snubber from V2a and I increased the snubber on V2b to 700pF.
When I fired it up I was stunned. It transformed the amp in my opinion. The OD is now fat but not flubby through the bass and lower mids...there is more usable range to the OD as well...all the fizzy stuff on top is gone and it just sings. That elusive "chirp" and "bloom" that everyone speaks of is now there in all it's glorious incarnations. Tons of harmonics are jumping out of it and it sustains for days (at lower Larry Carlton OD levels as well as higher gain). With humbuckers, the amp is a joy and completely controllable from the guitar's volume pot. I tried the amp with several speakers and all sounded great (Marshall 4X12 with Greenbacks) a 2X12 open back with Weber F150a, a 1X12 with a Celestion Blue (yeah, I know...). I think I will ultimately pair this amp with a 1X12 open back cab with a Celestion Gold or a WGS ET65. I just have to decide on what cab to settle on.
I am running a JJ Gold Pin ECC83 in V1, Tungsol RI ECC83 in V2, a JJ ECC803 in V3 and a pair of Winged C EL34s.
I am so glad I did these mods! The amp is now a keeper! If anyone has a #183 and wants a creamier, lush tone out of the OD with no harshness on the top, try these mods!
Oh, one final observation: when the amp was stock, the OD--regardless of settings--always sounded best with the PAB engaged. With the mods, I don't even turn the PAB on! It really is amazing!