Little help please - Marshall value

[skoora]

I wouldn't say the vertical 2204's are a lot more desirable as the amp, circuit wise, didn't change in any way when they went horizontal. The vert's, IIRC, should be flying leads from chassis mounted pots where the horizontal have pcb mounted pots, so that's a plus for maintenance. Plus this looks to be around an 83/4 when they added the D.I. which is when the real change happened in the 2203's with the filtering layout. A vert 2203 without the D.I. would theoretically be more desirable than 2203's that followed. It's all hit and miss when it comes down to tone. I've played sweet ones and dogs from any period in the 80's. To me the mod makes it worth less. I would offer less knowing the chances I like the mod will be slim and will have to pay to have someone reverse it.

 

[stratjacket]

I wouldn't say the vertical 2204's are more desirable as the amp didn't change in any way when they went horizontal. Plus this looks to be around an 84 when they added the D.I. which is when the real change happened in the 2203's with the filtering layout. A vert 2203 without the D.I. would theoretically be more desirable than 2203's that followed. It's all hit and miss when it comes down to tone. I've played sweet ones and dogs from any period in the 80's. To me the mod makes it worth less. I would offer less knowing the chances I like the mod will be slim and will have to pay to have someone reverse it.

Yeah the guy said it was an 84 and it looks like someone wrote 30-3-84 on the white tag in the pics, which I assume for UK written March 30, 1984. I don't know the diff's between a 2203 and 2204 but this looks like the single channel JCM that's the main one I always see as the classic. But that's why I asked here before I made the deal, to get opinions from all you guys in the know if this was the real deal or a bad rep year/model and a good deal or not. Appreciate the help, you guys rawk

 

[311boogieman]

Yeah the guy said it was an 84 and it looks like someone wrote 30-3-84 on the white tag in the pics, which I assume for UK written March 30, 1984. I don't know the diff's between a 2203 and 2204 but this looks like the single channel JCM that's the main one I always see as the classic. But that's why I asked here before I made the deal, to get opinions from all you guys in the know if this was the real deal or a bad rep year/model and a good deal or not. Appreciate the help, you guys rawk

They are both single channel. The 2203 is 100w. The 2204 is 50w. They will be equally loud

Looking forward to your next steps, but I agree - I would offer a bit less due to the mod but be prepared to pay full price if it sounds good. Can't speak to the extra preamp tube mod.

 

[stratjacket]

Picked the amp up today. Spent about 30 minutes with it. Sounds pretty damn good, fun to play. It rips pretty good, aggressive. The extra gain stage is actually a nice touch. It can get really good gain on it's own, sounds fucking incredible with my pedals and effects chain. Think this is a keeper, glad I finally took the plunge.

It fits right in with it's new bothers:

 

[Fret-Shredder]

Picked the amp up today. Spent about 30 minutes with it. Sounds pretty damn good, fun to play. It rips pretty good, aggressive. The extra gain stage is actually a nice touch. It can get really good gain on it's own, sounds fucking incredible with my pedals and effects chain. Think this is a keeper, glad I finally took the plunge.

It fits right in with it's new bothers:

?
Congrats man. Glad it worked out for you. Nice addition to an already awesome collection.

 

[stratjacket]

For shits and giggles and because I had them sitting in a drawer, I swapped out the preamp tubes. It had Groove Tubes in V1 - V3 plus the extra gain stage. They sounded good but I had a bunch of new Tung-sol 12AX7's and new Sovtek 12AX7LPS's. So I put TS in V1, V2 and extra gain and the Sovtek in V3.

It sounded good before, but holy shit, it's clear now. Notes pop, clear and punchy. Definitely liking.

 

[311boogieman]

Oh man - that is nice. Good work. Wish I could hear it in person. Glad it all worked out

And yeah - you do have a kick ass stable of amps. Killer stuff there.



side note - double check with someone on here about running a Tung Sol in V2 as that may be a cathode follower stage on these amps and they don't mix well.

 

[skullfxr]

I had a buddy with the JCM800 1X12 combo version (not up on Marshall combo numbers) he dropped some old Mullards and a brimar in there one day instead of whatever it had in it. HOLY HELL it woke that amp up.

I would roll some NOS pre amp tubes in there. It would be worth every penny IMO.

 

[stratjacket]

For more shits and giggles, I tried to swap out the power tubes. It came with a set of 6550's, but everything was is smudged out and they look old. Again, not that it was bad, but just playing around with it, I tried to swap in a pair of Tungsol EL34's, but the bias was so low and would not adjust up. Maxed out a 2mA, put the 6550's back in and they would go up as high as in the 60mA. Went ahead and adjusted them down to a 70% level.

Not sure what the deal is, I thought they were swappable. I did notice that extra gain stage seemed to make thing go all over the place if I adjusted it. Not sure if that has something to do with it or not. Anyway, left the 6550's in there until I can figure this out...probably should leave well enough alone...

 

[glpg80]

For more shits and giggles, I tried to swap out the power tubes. It came with a set of 6550's, but everything was is smudged out and they look old. Again, not that it was bad, but just playing around with it, I tried to swap in a pair of Tungsol EL34's, but the bias was so low and would not adjust up. Maxed out a 2mA, put the 6550's back in and they would go up as high as in the 60mA. Went ahead and adjusted them down to a 70% level.

Not sure what the deal is, I thought they were swappable. I did notice that extra gain stage seemed to make thing go all over the place if I adjusted it. Not sure if that has something to do with it or not. Anyway, left the 6550's in there until I can figure this out...probably should leave well enough alone...

The tubes are not hot-swappable. Marshalls require the grid reference resistors to be changed from 150K each to 120K for EL34s. The bias resistor needs to be changed (from memory I believe from 47k to 56k).

Basically in stock marshall platform, they are not hot-swappable.

 

[stratjacket]

For more shits and giggles, I tried to swap out the power tubes. It came with a set of 6550's, but everything was is smudged out and they look old. Again, not that it was bad, but just playing around with it, I tried to swap in a pair of Tungsol EL34's, but the bias was so low and would not adjust up. Maxed out a 2mA, put the 6550's back in and they would go up as high as in the 60mA. Went ahead and adjusted them down to a 70% level.

Not sure what the deal is, I thought they were swappable. I did notice that extra gain stage seemed to make thing go all over the place if I adjusted it. Not sure if that has something to do with it or not. Anyway, left the 6550's in there until I can figure this out...probably should leave well enough alone...

The tubes are not hot-swappable. Marshalls require the grid reference resistors to be changed from 150K each to 120K for EL34s. The bias resistor needs to be changed (from memory I believe from 47k to 56k).

Basically in stock marshall platform, they are not hot-swappable.

Thanks man, I just found that info off a google search on a Marshall forum. Looks like 6550's it is, they sound fine. I may replace them because they do look really old. Still sound good though, just created an itch that must be scratched to see if a new set will improve it. Damn I hate myself.

 

[glpg80]

For more shits and giggles, I tried to swap out the power tubes. It came with a set of 6550's, but everything was is smudged out and they look old. Again, not that it was bad, but just playing around with it, I tried to swap in a pair of Tungsol EL34's, but the bias was so low and would not adjust up. Maxed out a 2mA, put the 6550's back in and they would go up as high as in the 60mA. Went ahead and adjusted them down to a 70% level.

Not sure what the deal is, I thought they were swappable. I did notice that extra gain stage seemed to make thing go all over the place if I adjusted it. Not sure if that has something to do with it or not. Anyway, left the 6550's in there until I can figure this out...probably should leave well enough alone...

The tubes are not hot-swappable. Marshalls require the grid reference resistors to be changed from 150K each to 120K for EL34s. The bias resistor needs to be changed (from memory I believe from 47k to 56k).

Basically in stock marshall platform, they are not hot-swappable.

Thanks man, I just found that info off a google search on a Marshall forum. Looks like 6550's it is, they sound fine. I may replace them because they do look really old. Still sound good though, just created an itch that must be scratched to see if a new set will improve it. Damn I hate myself.

Yep no problem. I have a gained up 2203 I'm building now in the tech corner section of the forum and it came with 6550's in it too that need replacing. For high gain I actually like the 6550 tone more as it's deeper and larger sounding. EL34's are great but when it comes to high gain, I'm more of a 6L6/6550 dude.

 

[SpiderWars]

I just bought a 2204 with 6550s and have those values burnt in my head right now.

6550s
150k grid loads
120k bias supply
47k bias range

EL34s
220k grid loads
220k bias supply
56k bias range

Typically when people change from 6550 to EL34 they often don't change the bias supply resistor and use a lower value for the bias range (I think it's around 27k-33k instead of 56k). The grid loads sometimes get changed sometimes not, it's not that big of a deal if not imo (arguably 150k is 'safer'). FWIW, I'm running KT88 using the original 6550 values; I've read that usually works fine. They seem to have the depth of the 6550 with less of the sizzle. Just another flavor. I've also added a tube and done a Langner mod on it.

 

[SpiderWars]

By the way stratjacket, I just looked at your mod and it looks like you might have a hot-shield on the Hi input. Opinions vary on that. I'd like to hear glpg80's take on it. I'm not sure how I feel about it except I almost never do it (and only in PPIMV bias supply) and my understanding is that its fairly common especially in these.

 

[Thunkful]

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[stratjacket]

By the way stratjacket, I just looked at your mod and it looks like you might have a hot-shield on the Hi input. Opinions vary on that. I'd like to hear glpg80's take on it. I'm not sure how I feel about it except I almost never do it (and only in PPIMV bias supply) and my understanding is that its fairly common especially in these.

That’s interesting, it’d be nice to know exactly what this mod is. It can’t be removed by turning it down, turning the volume pot all the way down, silences the amp. It’s not on the Low input at all though, at least volume out has no effect when plugged into Low input.

 

[SpiderWars]

Yeah, the mod only affects the Hi input. It just shoehorns a gain stage with gain control between the Hi input jack and the normal Hi gain input. I can't see the cathode cap or most of the resistor because they are obscured by the fat grey wire but they look like typical values otherwise.

 

[stratjacket]

Yeah, the mod only affects the Hi input. It just shoehorns a gain stage with gain control between the Hi input jack and the normal Hi gain input. I can't see the cathode cap or most of the resistor because they are obscured by the fat grey wire but they look like typical values otherwise.

Thanks for taking a look. This evening I’ll take a closer and better pic then was in the Craigslist ad.

 

[Racerxrated]

You won’t find amps that are more sensitive to tube rolling than a vintage Marshall...by vintage I mean JCM 800 or older. And newer production tubes pale to what you’ll hear with vintage tubes..I’ve tried them all(most anyway) and this has always been the case from my experience.

 

[glpg80]

The mod was installed haphazardly. Improper shielded wire techniques, poor heater wrap, and non-shielded wires aren't twisted. I'm literally spending the same time fixing stuff like this on my own. They also didn't ground the un-used triode correctly minus the heaters.

I'm also not a fan of drawing extra heater filament current off of original transformers. I have an original Dagnall in mine and I am removing the pre-amp tube filaments completely from the PT to help it run a bit cooler.

If you want to be able to defeat the mod at-will, a push-pull pot in the back could be installed in place of the new pre-gain to bypass it without harm back to stock without much hassle. I'd want the rest of it fixed at the same time though.