Lower Voltage JCM 800 Build

[davesi]

Been almost 40 years since I owned one of these. I forgot how loud they are! Had most of the parts accumulating over the years and after the Marshall section was added to the forum, and reading all the impressive ideas here, managed to assemble another working amp.

In the spirit of keep it simple, and with kudos to everyone here, this all went together in a blank JTM 45 chassis. It's very nearly identical to Jana's specifications with Trainwreck/Bassman type transformers and a modified power rail (closer to Trainwreck). It is indeed a very sweet sounding amp! Much better cleans than I remember with harmonics to rival anything I have ever built. Did I mention it is loud?

D

[Colossal]

Dave,

That looks very clean. Great build! What does the mod switch under the input jack do?

[davesi]

That's the low input switch I borrowed from Jana. Puts a 100k in series with the 470K on V2a (before CF), grid to ground. Two distinct gain options through one jack. Very versatile.

[davesi]

Correction ...100K in parallel with 470k....

[Structo]

Very nice build!

You have some nice parts there!

Mustards

Takmans

looks like the voltages are fairly close.

Is this the 2204?


Does the master volume on those work well?

And it goes to 11!

[M Fowler]

Very nice amp Looks killer and I bet is does sound great too.

I built something like this a few years back using TW PT and Dynaclone A-470-S OT 4k3 into a BF Champ chassis very cool amp for sure.

Mark

[davesi]

Thanks guys. Yes, it is based on a 2204. It's all preamp with this master and it does sound best opened up into the PI. Running it through a 100 watt MASS right now, trying to decide if I want to add a PPIMV. Do you guys think this would benefit with a second master?

[Smokebreak]

I've got 1 with both a normal and PPIMV . PPIMV just stays all the way up You can get some different sounds out of it though(not all good!) I'm biased though Ive never met a PPIMV I liked.

[Bob S]

That there is a nice looking build - well done.
I'm also not a fan of a PPIMV in this circuit.
Jana's hi/low switch is a nice option.
Bet this amp sounds killer.

[davesi]

Thanks for the input. Think I will let it ride for a while and use the MASS to appease the neighbors.

D

[deeder]

Thanks guys. Yes, it is based on a 2204. It's all preamp with this master and it does sound best opened up into the PI. Running it through a 100 watt MASS right now, trying to decide if I want to add a PPIMV. Do you guys think this would benefit with a second master?

The lead dress is very neat. I use both Pre and Post MV's with my 2203 and it works great at any level. I beleive some are pro and others are con but according to me it is the best of two worlds.
If you don't like it, it's easy backing your amp to what it was, but you know that mate