Marshall JMP Master Volume 20W Build

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Littlewyan
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Marshall JMP Master Volume 20W Build

Post by Littlewyan »

I've finally got around to starting a topic for my Marshall 20W JMP Master Volume Build. Its basically a standard 2204 Master Volume Amp but with 6V6s instead of EL34s and of course different transformers.

There is actually a different PT in the amp now to what you see in the photo, because that one was overloaded. With the new one (another toroidal) the amp responds even more like a standard Marshall! It runs at 385V idle and at full whack it sags down to 350V.

The PT is the 200mA Toroidal from Ampmaker, the OT is for a Marshall 18W and is from Tube Town and the choke is a Fender 50mA 4H Choke from Modulus Amplification. The Faceplates, chassis, board and a few other bits are also from Michael at Modulus. Headcab is from Chris Uff and was a JTM45 Cab that I had scaled down.

I've been valve swapping tonight as the amp had a very harsh distortion when I tested it on Saturday. Turns out the Chinese 12AX7s don't sound too good in this amp, so it now has an EH12AX7 in V1, JJ ECC803S in V2 and JJ ECC83S in V3. I'm using JJ 6V6S Power valves.
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dcribbs1412
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Re: Marshall JMP Master Volume 20W Build

Post by dcribbs1412 »

Congrats
Great looking build
I bet you can Still get loud with the 6V6's

D
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dorrisant
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Re: Marshall JMP Master Volume 20W Build

Post by dorrisant »

Nice looking build! Very clean.

Got any clips? I was thinking of building one of these. I will want to throw in some mods from an older post too.
"Education is what you're left with after you have forgotten what you have learned" - Enzo
RockinRocket
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Re: Marshall JMP Master Volume 20W Build

Post by RockinRocket »

Very nice build! I was planning on doing a 6v6 vintage Marshall. I also figure 18 watt iron woud be good at what I'm figuring 380v and 8k output.
gldtp99
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Re: Marshall JMP Master Volume 20W Build

Post by gldtp99 »

Here's one I built several years ago:

[IMG:800:600]http://i46.photobucket.com/albums/f112/gldtp99/25%20Watt%20AFD%20Guts/25WattAFD003.jpg[/img]

[IMG:800:600]http://i46.photobucket.com/albums/f112/gldtp99/Mule%20JCM%20800%2025/MuleJCM80025Watt003.jpg[/img]


Heyboer 18 watt PT/OT, JJ 6V6S.
First built stock then a range of different moderate gain mods---- a Metro FX Loop added.
Amp was first bought in stock form by a player who loved it in my shop---- it was returned after he found out it didn't have much clean headroom when playing with his full band. Player bought a 50 watt 2204 clone I built.
Modded for moderate gain boost and FX loop added----- bought by a second player who loved it in my shop----- it was returned when he found out that it didn't have the headroom he expected with his full band---- he bought a 50 watt 2204 based head I built.
Amp was bought by the current owner who uses it for recording/side projects---- he plays another amp with his full band and loves this 20 watt MV type head.
I'm in no hurry to build more of these 20 watt sized 2204 clones---- It seems like a good idea but an EL34 x 2, 50 watter can do everything a 20 watter can do and usually sound better while doing it---- and the 50 can run with a full band on its own--- I've built them with the standard pre-PI MV and also a PPIMV so they can be turned down to living room vol levels while keeping the driven tone mostly intact---- My rebuilt Marshall 4010 is set up this way and it is my "living room amp".
I also built an EL84x2, cathode biased 2204 at about the same time (the 6V6 amp is fixed bias)---- MPS PT and an OT pulled from a McGohan PA amp--- Pentode/Triode switch (pretty much useless, 7 watts is still loud when cranked), and an adjustable NFB pot.
Here it is with AFD-type mods:

https://youtu.be/XiuwSyg_T34

https://youtu.be/dbn9MIcBdzA

good recording amp----- gets buried by a full band.

I suggest just building 50 watt 2204 type amps unless planning on a re-amping rig like a Fryette Power Station or similar.
These lower wattage 2204 type amps are too loud to be cranked up in the house and don't have enough power to compete with a full band unless maxxed out all the time (lacking headroom vs a 50 watter).
But, build whatever you want to............... gldtp99
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M Fowler
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Re: Marshall JMP Master Volume 20W Build

Post by M Fowler »

I've finally got around to starting a topic for my Marshall 20W JMP Master Volume Build. Its basically a standard 2204 Master Volume Amp but with 6V6s instead of EL34s and of course different transformers.
Good looking built.
joeboo88
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Re: Marshall JMP Master Volume 20W Build

Post by joeboo88 »

Ryan: you sure do some nice work.
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Littlewyan
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Re: Marshall JMP Master Volume 20W Build

Post by Littlewyan »

Thank you all for the kind words. I haven't got any clips yet but I will record some soon. Its still pretty dam loud, its only about 4dB quieter than a 50W amp.

18W OT seems to be good, I used Tube Town's own brand. Can't comment on the 18W PT.

Nice looking amp gldtp99, it was actually your's that I looked at when planning mine :D. With my 50W amps I am always attenuating them down to roughly 3-5W anyway so a 20W amp is fine for me. They often get mic'd up at gigs anyway and 20W is easier to attenuate than 50W. I actually have to use max attenuation (-12dB) with my 50W amps at some gigs.

One mod that I may do to this amp is put a resistor between the MV Wiper and the PI. I want to use my spectrum analyzer to see how much of a difference this makes to lower frequencies.
gldtp99
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Re: Marshall JMP Master Volume 20W Build

Post by gldtp99 »

Ok, I tried to sell the idea of using bigger amps but if low watts is what is called for then maybe for a next build you might consider something like this Single Ended 10 watt Marshall based build I did:

[IMG:800:600]http://i46.photobucket.com/albums/f112/gldtp99/Mule%2010%20Watt%20Single%20Ended/003-1.jpg[/img]

[IMG:800:600]http://i46.photobucket.com/albums/f112/gldtp99/Mule%2010%20Watt%20Single%20Ended/001-2.jpg[/img]

[IMG:800:600]http://i46.photobucket.com/albums/f112/gldtp99/Mule%2010%20Watt%20Single%20Ended/001.jpg[/img]

The preamp, in this one, has four gain stages so it is meant for driven tones and doesn't have much clean tone at all----- You could build a stock type 2204 preamp with only three gain stages if it seemed to be more to your liking.
The Single Ended Class A circuit vs the Push/Pull Class AB1 circuit opens up some interesting possibilities for someone who likes to build/tweak amps.
You did a good job on your 20 watter !!................... gldtp99
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Littlewyan
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Re: Marshall JMP Master Volume 20W Build

Post by Littlewyan »

Very nice build! And an original Marshall!!!! I am jealous. I do want to build a single ended amp. In fact I do plan on building one for my cousin as he needs a valve amp and he only plays at home so doesn't need anything powerful. I have to say though I've never heard a decent recording of a single ended amp. I'm not saying there aren't any, I just can't find them! Have you got any clips?

I must say, I do have a few parts that would be perfect for a single ended amp and I do have a few ideas for a pre amp design.....
gldtp99
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Re: Marshall JMP Master Volume 20W Build

Post by gldtp99 »

The real Marshall is my '76 1987---- it still has orig iron and all the Mustard caps------ 4700pF Bright Cap, Boost cap across V2a cathode resistor, and a PPIMV----- nice classic rock amp.
It's in the pic for size comparison with the SE 10 watter.
I don't have any clips of this 10 watter----- there have been circuit changes since the pics, larger OT and more----- project has been shelved for now because people around here want big amps rather than 10 watters. The white 14 watt, EL84x2 head in the vids above sounds better so far.
And I have very limited bench time until I retire later this year---- I've shut down my repair shop, not taking in any outside amp work (I'll service the amps I've built).
I'll be able to get back to the SE 10 watter later............. gldtp99
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Littlewyan
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Re: Marshall JMP Master Volume 20W Build

Post by Littlewyan »

Awesome. Did you add the V2a Cathode Bypass Cap?

I guess the issue with low wattage amps is they're not always that much cheaper to build than high wattage amps and so a lot of people can't justify buying them. Thats what appears to be the issue anyway.

Where are you based gldtp99?
gldtp99
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Re: Marshall JMP Master Volume 20W Build

Post by gldtp99 »

Yes, I added the V2a cathode bypass cap---- it's either a .47 or a .68---- I did somewhat similar changes (bright cap values/V2a boost cap values) on a 1987 clone I built and a JTM45RI at the same time as the '76 1987 to get a feel for a balance between gain levels and the ability to clean up with the guitar vol pot----- interesting round of experiments but I can't remember exactly what I did to which amp without opening them up and looking inside.
The '76 1987 came to me modded/oscillating/unusable and I proceeded to try out a series of mods (One Wire Mod, etc) and then I had it cleaner than stock with a BF Fender-y take on V1 (that was pretty cool for a Blues/Rock amp---I may build something like that again). It was the very first amp that I did a Lar/Mar PPIMV on (it works well on this amp)
Then I decided it should sound like a Marshall 1987 and re-did it stock and then did the current slight boost/bright cap set up.
The poor amp has been through a lot but it still kicks it out----- I like it.
I now want my real Marshall amps to sound like Marshalls and I'll try out the more extreme mods on clones I build---- for example I built a 5 gain stage "Big 50" vaguely Marshall 2204 based head----- with oversized iron and running KT88 x 2----- modded 80's to Modern Metal type sounds.
Most people I know around here use big amps----- the band next door to my workshop uses two Mesa Triple Recs (150 watts each) at the same time----- you can barely hear the bass player when they practice----- big Peavey old 5150's and 6505's are common------ one friend who plays Grindcore uses a Sound City 120 I rebuilt with another version of the 5 stage preamp (like the Big 50 above---- I call this preamp type the War Elephant) and he also has several Peavey 5150's and an Engl.
They want to feel the amp in their bone marrow and 10, 14, or 20 watt amps (or even 50 watters) are considered "toys".
I'm using a 150 watt, 6L6GC x 6, Hi Gain Channel Switcher prototype I built for the band i'm putting together for after I retire----- a couple of guys that have tried it out want it but I have no time right now to build more of them----- and I like it enough to keep it for me and I can be my own "long term test" player.
I'm in Arlington, Texas------ between Dallas and Ft Worth
gldtp99
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Re: Marshall JMP Master Volume 20W Build

Post by gldtp99 »

Here's a crude vid (with very low audio) of the 150 watt, 6L6GC x 6, Hi Gain channel switcher prototype I built----- played by a customer of mine, Rock Cortez---- He plays a 100 watt single channel hi gain amp I built with his band.

https://youtu.be/uQZ73eHbyMo

In the vid, behind the amp in use, you can see a 100 watt Hiwatt DR103 clone I built @10 years ago (has my "Mule" logo)----- this one has been owned by three different players, toured around the USA, and found its way back to me last year.
It still works/sounds good and I use it in my shop for guitar, bass, testing pedals, etc.
Just a great sounding General Purpose amp------most people here that I know seem to feel at home with big amps------ they like the headroom/depth even at reasonable volume levels.
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deeder
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Re: Marshall JMP Master Volume 20W Build

Post by deeder »

Very impressive Mark, 150W.... :shock:
Both of you Littlewyan are killer guys ;^)
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