Marshal Major?

[mAx___]

Thanks a lot Reeltarded. I recently installed a Power Scaling kit in my AC30 and thought of maybe doing the same to the 1987 kit. What are your thoughts compared to the two master solution and how does PS affect NFB?

[Reeltarded]

I think it depends on how you implement the power scaling, but I have no experience with any power scaling other than variacs.

With that experience, it would have no effect on the NFB with the whole amp scaled. I commonly run Marshalls and Fenders til the pilot lights are dark. (55-65vac) this is how I don't worry about the tubes in my Majors as well. Never lost a tube to cathode stripping, whatever that is supposed to be.

Looks like Detroit, but not as loud.

[renshen1957]

The preamp is the same as a JMP 50 (1987/1986) of the same vintage.

Just do like I said above and turn a 50 into a "sounds like". Totally go overboard with the NFB to make it sound more like the completely unforgiving UL Major output.

Hi

Well yes and no about the same as a Plexi/JMP 50.

The V1a and V1b are similar to a Plexi first stage, yes.

And No:

V2a/V2b are a concertina splitter Phase Inverter with the EQ for the preamp in between amplifier section and before the splitter proper. The NFB from the PA is connected the amplifiers stage (V2a).

As the feedback loop is on V2a, it is no longer a free running stage as in a Plexi.

Valve three is 12AT7 a driver section, a paraphase used as a full time differential amplifier (looks more Schmidt PI without the long tail) to supply the oomph to drive the 4 KT88s

You might be able to simulate the preamp by a Plexi first stage with an Active (as in transistors) EQ system.

Best Regards

[Reeltarded]

Sure you are right. I meant more generally, and talking about 'kind of sounds like', but if you add a simple loop, the output of the loop basically sounds like a stale 50 watt preamp.

It's a sight to see though. They have as much (the later style) stuff in there to keep them from blowing up as they do to make them blow up!

[mAx___]

Hi

Well yes and no about the same as a Plexi/JMP 50.

The V1a and V1b are similar to a Plexi first stage, yes.

And No:

V2a/V2b are a concertina splitter Phase Inverter with the EQ for the preamp in between amplifier section and before the splitter proper. The NFB from the PA is connected the amplifiers stage (V2a).

As the feedback loop is on V2a, it is no longer a free running stage as in a Plexi.

Valve three is 12AT7 a driver section, a paraphase used as a full time differential amplifier (looks more Schmidt PI without the long tail) to supply the oomph to drive the 4 KT88s

You might be able to simulate the preamp by a Plexi first stage with an Active (as in transistors) EQ system.

Best Regards

I've already found a Hammond UL OT for my "Mini" Major project. Now if I wire a cathodyne PI, change values in the preamp section to match the Major schematic and put an ECC82 driving two EL34s in a 50W 1987 kit, would that get me "close enough"?