JCM/Plexi/Clean ch.switch fx loop, attenuator rebuild (Pictures)!

[cboysen]

Hi Guys!

I lightly promised a friend last summer to build him a heavy rock amp. I had reasonly built an El84 cathode based plexi style amp, I could modify to his specs and wishes. The primary mods are as follows:

1) FX loop (LND150 TT kit)
2) 2 Button Ch.switch System (Dual Relay TT kit):
          a) Clean(single triode to PI) or Dirty(plexi style w/ cathode follower & TMB),
          b) Cold clipper stage on/off in Dirty mode
3) Fixed Bias & Choke
4) Reactive Attenuator (M2 John Hewitt style) w/ line out option

The clean channel sounds tweed'ish, with 1 triode and no Tonestack. It pairs well with the other channels, and breaks up the PA/PI around 2-3 o'clock. The dirty channel sounds like a classic rock amp, with the CC boost giving you Iron Maiden and beyond. The Attenuator doesn't color the sound (to my ears) at any level, and makes it easy to dial in a good power amp compression in the Dirty channel, down to speaking volume. The Fx loop is practically transparent and in test drove 30m of cable, without any significant reduction in highs. Finally, for a medium to tight build like this, the noise floor is surprisingly low, even at the heaviest of gain settings. Although the mods were more extensive and time consuming than anticipated, the amp turned out great I think. Overall I'm very pleased with the outcome, and hope my friend will too.

Kind regards
Christian

[tubeswell]

Did you hand-drill that awesome front grille?

[tubenit]

Very impressive build! Congrats!  Thanks for sharing.

With respect, Tubenit

[d95err]

Very impressive and creative!

I’ve been thinking about integrating a reactive attenuator into an amp. Your build gave me more inspiration there!

[cboysen]

Thanks all!

Did you hand-drill that awesome front grille?

Nope, I made a 3D model of the cabinet in fusion, and borrowed a friends cnc, to make the front grill and finger joint cut outs :)