Metropoulos Forum

I've read that the negative feedback loop on early Marshall 2203 amps running EL34s was on the 8Ohm tap instead of the 4Ohm tap. Has anyone seen this first hand?

I've been trying to find gut shots of 76-80 2203s but I can't find much at all! I think 2204s were still 100K on 4Ohm tap, but again I haven't seen many 76-80 2204s so don't know for sure.

That's the way it's on my '77. Apparently normal on the early ones, even though mine was for 6550's originally.
Cheers.

Was that a 2203? Do you mean the NFB was on the 8ohm tap?

Yeah sorry, a 2203 with 100k to 8 ohm nfb. Although I did have a tech convert it to el34's so he could have changed it. In the schematic from '78 it is on the 8 ohm tap so pretty sure he didn't.

Great, thanks mate . The schematic from 78 has 6550s on it, unless you have another?

I'm just curious more than anything.

Littlewyan wrote: ↑

Wed Nov 08, 2017 7:23 pm

Great, thanks mate . The schematic from 78 has 6550s on it, unless you have another?

I'm just curious more than anything.

No that's true, has 6550's. Didn't notice before. 150k grid leak resistor too. My print out is so blurry it's hard to be sure.

However I came across George's Master Volume 100W Build guide today which states that you use 8Ohm Tap for EL34s and 4Ohm Tap for 6550s. George has probably seen more Marshalls than anyone else so he's probably right! I believe the reason is that 6550s have more headroom than EL34s.

Wonder when they changed to 4ohm all together, Jcm's? I'd like to get an early 800 too but don't know if it's really justified tonally.

I'm not sure. I'm really struggling to find photos of the Master Volume amps. Even on the Amparchives site! I think they did it in the 70s as there was always variation from the Marshall factory.

I serviced a late 70s 2203 which used the 4 ohms tap

Did it have EL34s or 6550s?

el34s. no 6550s here