Marshall JMP MV '77 2204--Best Tubes?

[David Root]

Just checked out my above amp closely for the first time. Its paper chassis sticker reads 1/31/77. It appears to be a transition preamp between the plexi type design of '76 and the full three stage 2203 cascaded design of '78. It looks like someone changed a couple of parts and rerouted a little bit but it is now the full 2203 circuit.

Sounds very good, has relatively recent F&T blue can caps, mostly mustards otherwise.

It has three Beijing silver top 12AX7s, the ones labeled for Mesa, Mesa STR 12AX7-A on the glass. Power tubes are a pair of '02 Winged C EL34s. It's a US spec amp set up for 6550s that has the bias resistor changed from 22K to 27K. The power tube grid leaks are 150K, for 6550s.

I have heard that RFT 12AX7 in V1 and RFT or Tesla EL34s rock in these amps. How about Mullards, they should be good in a British amp?

How about a NOS Tungsram 12AX7 in V1? What works real well in the PI?

[selloutrr]

Stock voicing would be GEC 6550's if it's a north american amp.
Probably a canadian import. with Mullard or Brimar preamp tubes

Telsa / telefunken / Winged =C= / Mullard ... etc

They will all sound good.
What are you trying to achive?
How much you want to spend?

[David Root]

I'm just curious, it sounds pretty good now.

How could one tell if it were a "Canadian import"? I thought Marshall exported directly to the US in the '70s.

The power tube spots are rubber stamped 6550.

Would a chassis pic help?

[selloutrr]

serial number

I've own several 6550 marshalls over the years and work on a couple around town (southern california) and they have all been canadian. It's funny cause I was under the impression they where sent directly to the USA side of the border but I have yet to actually hold a USA verision in my hands that was pre '79.

[David Root]

S/A 00458J

[selloutrr]

Looks like you have a USA import The ones I've come across have a "C" following the serial number several spaces behind. Very Cool!

[David Root]

Here's some pics. Note the S/N is also stamped on the edge of the chassis near the inspection chassis. No C anywhere, same on the backplate S/N.

[selloutrr]

here are a couple pics of the last canadian amp I had on the bench.

Notice different Iron, no chassis tube model stamps, and different caps used on the same ST1 card.

[David Root]

Wooo! Almost looks like a different amp! What are those rectangular caps, they are different? Only the .68 is the same, they must have bought a s**tload of those. The iron looks like new! Choke looks a bit smaller.

How does it sound with those Fat Boy 6CA7s?

[selloutrr]

Original GEC 6550's It sounded very smooth and bluesy. very similar to my late 60's bluesbreaker when it's cocked back around "7".

It's doesn't have that "marshall" crunch with the 6550. but still one of the top 10 marshalls I've heard.

I don't remember but the block caps manufacture but they look to be wima or panasonic?

everything on it was stock.

[David Root]

OOps, my mistake! I missed the nickel bases. I have no idea about those caps.

Sounds like a lot different than mine with the Beijing Mesas and the Winged C EL34s. What preamp tubes were in it? Were they original Mullards?

I'd like to do mine with the European tubes.

[selloutrr]

I don't remember the pre tubes off hand when it came in. I do remember they were NOS but i want to say Brimar? they were pretty much dead. I do remember how low they tested on the Amplitrex - under 10% life.
I was amazed the amp still made sound. The output tubes still had 85%+ life.

The amp ended up with a hand selected JJ/telsa preamp and PI compliment from Eurotubes.
(I called and explained what the client was looking for in his tone)
I can't put in words how pleased the client was with the tone it truly sounds jaw dropping for classic rock and blues.

[David Root]

Interesting stuff. Smooth old top line 6550s with modern aggressive 12AX7s. I learn new things every day!

Would that tone be a personal favorite? Sure sounds like it!

[selloutrr]

As far as marshall amps go yes it's a personal favorite.

I own Marshall's because like Fender they are must have, but since I've always felt forced to own them I've been a bit jaded, my personal interest has always been vintage off beat amps.

I own 180+ amps and I've heard/ worked with probably... 2000+ amps in an intimate studio climate and live stages.

This marshall would easily be in the top 15 amps. taking the amp for what it does, not trying to make it do a tone outside of it's range. i.e. it's not an 80's metal machine, or a modern gain monster. But for where the amp voices in on it's own it's perfect for blues, classis rock, and the more new counrty tries to be a depressing pop rock act, it would be the finishing touch in a layer track.

I have to give eurotubes credit on making that amp great they really know how to hand pick tubes!