1979 Marshall JMP 2203 - the 'Bright Cap' revisited!!

[@RDamps]

When I have this, I tell the customer if you don’t like it, you’ve got the wrong amp or speakers. That amp is perfect as is. What a gem.

[@HeadfirstAmps]

💯 agree! He imported it from the UK! Dead mint.

[@Johnsormani]

It can only be stock once.

[@chrisjones8592]

You are exactly right. Take out the highs it gets lost in the mix. I think many people don’t understand these amps. This amp sounds great bone stock.

[@MoOvertones]

Great video! I Fantastic sounding Marshall! I 100% agree with your suggestion about leaving this amp like it is!

[@scottpayne33]

I one million percent agree it sounds like a great JMP leave it alone.

[@MichaelSorensen-bl3ec]

I really don't understand why anyone would be trying to dial back the gain to get a clean sound from these amps. They sure weren't designed with that use in mind. People say they are a one trick pony, but damn, what a trick! Good to see you using a chopstick to point out things in the chassis. My father was an old school military radio electrician, he emphasised to me to never go randomly touching things with your bare hands. He was trained to use a non conductive tool in one hand, and have his other hand in his pocket. That way even if he did get a shock, it wouldn't be as serious as if he was holding the chassis with his other hand so the voltage wouldn't pass through his body and potentially kill him.

[@yessitsme6884]

Never bothered me, if I need to clean up I just roll down my guitar's volume. The tone is in the bright cap, stop clipping them!!!

[@tonehound671]

Plug into the low input if he needs clean

[@PerfectCircle91]

​@@tonehound671THANK YOU!!!! FINALLY SOME ONE KNOWS WTF THEY'RE TALKING ABOUT.

[@lousekoya1803]

Another great one Jason ! Here in Quebec , I'm lucky enough to have a great Electronic Engineer as a tech . He was the designer for all the pedals at Radial Engineering and invented the amp stage switcher for the big names in the 80's. Anyway , all this to say that I had him build me a 2204 JMP with SS and Tube Rectifier on a three way standby switch , standby being middle position . He also drew a schematic years ago so a knob on the back would blend the Bright cap less or more so you can adjust it to taste depending on the guitar or cab you're using and it's brilliant . There is so many forum threads on the subject of clipping or leaving the bright cap in but having a knob to add the brightness and grit you want is fantastic and it works great ! Just wanted to share my story on your wonderful channel . Have a great weekend everyone !

[@HeadfirstAmps]

Hey Lou, great story man - thank for sharing!

[@notasilicaanimus]

That amp sounds absolutely fantastic.

[@StellanAlm]

Sounds as it should, even better after being biased. I think a lot of guitarist listen to their amp without putting them into the mix. Good explanation as usual 😊

[@BradRocker]

Wow...what an amp. I liked it stock too.

[@marcogiampa283]

Thanks for servicing the amp for me Jason! Sounds killer especially biased well. As mentioned by @unclebensrice you cant really treat it like a gain control. I initially dialled it in like I would my jubilees (this is my first 2203 circuit) with the gain somewhere between 4-6, and yeah its pretty damn bright. Cranking the gain up to 8 really fills it out and doesnt really add that much more gain.

[@HeadfirstAmps]

Hey Marco, you got a great amp here man. Looking back at the video, it’s super clean. Very rare to find them like this…it will only go up in value!

[@johnmurphy6707]

Killer sound from your amp!

[@andyhayes7828]

Agreed, that is a GREAT sounding 2203. Alot of the horizontal input 2204's could be OVERLY brittle/bright, but like in another Headfirst video, they can be made to SHINE (just wish I knew NOW what I DIDN'T know back then). A Jubilee is middy/muddy conpared to the clear/crisp crunch of a 2203/2204 🤘

[@IrakliySherozia]

Thank you very much for your love for the amps and tones! It makes everyting so beautiful

[@jeanpierre72]

I bought two of these about 14 years ago ... picked one and kept it. Sounds at least as good as this one ❤ Incredible instruments

[@superman-el9jd]

Sounds Killer-Rock on Jason 😎

[@eds4754]

Ideal sounding 2203 to me, in great condition too. Love those pointer knobs!

[@HeadfirstAmps]

Hell yeah, how cool!

[@Johnsormani]

Many people are running these JMP‘s with vintage 30 speakers , which are overly bright anyway. I used to run a graphic eq to sculpt the input to my taste as well. My bright cap is untouched since 1980

[@andyhayes7828]

This is one of the best sounding amps I've heard on your channel 👍

[@masonlocksmiths3690]

Awesome. Mods are great, but a stock MV rips, when you dial it into it's sweet spot. Almost exactly how I run mine. Wise old Mr. Ho once told me "master at 4, preamp at 6" when I had him service it shortly after buying it for $750. He closed shop, gonna miss him. For a guy that didn't play guitar he new exactly what we wanted.

[@vintagesound8112]

That would sound great. There’s a problem though, I have a 2204 and gig it regularly at small clubs/ bars etc and outside pubs and there is nowhere I would get away with playing it on 4 MV. The highest I got away with was 3 and the owner moaned then. 4 is too loud for any small venue these days.

[@ScottyBrockway]

Looks factory to me, I've seen a few weird things in JMP's. They do tend to be stupidly bright sometimes, I remember back in the day we used to try them out and find one that sounded "good". The 800s were more consistent when they were new, but they can drift wildly. Sometimes that sounds good too so I don't usually change them unless the out of spec is going to cause problems.

[@vox1966]

the early 800 amps are the same as the jmp amp

[@davidkervin]

The brightness is what makes it sound great. All those upper mid and high harmonics. My 2203 from 1983 is amazing because of this. You can always turn down treble but it's hard to add without mods.

[@zachariahwade8482]

I’ve had my stock 79 JMP for nearly 10 years now. It was my all time fave for most of that time and beat out 2203’s from 80 and 82(as well as a Ceriatone 2203 and a few ‘800 killer’ boutiques)for the top spot. Yes, it is a bright amp and like in the video I tend to run the Preamp around 7 to take the edge off the stock brightcap. Fantastic sounding amp that cleans up great and gobbles up boosts. That said, lately I’ve been going for a more Malcolm rather than Angus sound and the Preamp needs to be a little lower for that, say 5, and that can be a little edgy. So my stock 71 1987 became my go to for that sound and a few weeks ago I got a stock 70 Super Bass, and that is instant Malcolm.

[@eyedunno8462]

Okay

[@smellytele9629]

Yeah, that's one great sounding amp! I set mine up pretty much exactly like how you dialed this one, though it can also depend on the guitar I use and/or speaker cab. With my Bogner os2x12 with Scumback m75's I can run the P, M, and T up higher as that is a darker sounding cab. For smaller gigs I bring a 1x12 with a Cream Alnico and that cab is a brighter cab, so I roll back the P and T a bit (and keep the master lower so that I don't get fired).

[@UncleBensRice]

I've always found that the preamp volume on these Master Volume amps behaves much more like a tight loose control than a "real" gain control. Even by changing the bright cap to something smaller like 500p or 250p it still behaves somewhat like this. So instead of changing the bright cap I like to use a 250k pot and change the 470p on the 470k to a 2200p. To tackle the high end harshness on these amps I like to change the negative feedbackresistor to something like 39k or 47k off of the 4 or 8Ohm tap and add in a resonance pot. It makes the amp much more usuable (especially at lower volumes) in my opinion.

[@HeadfirstAmps]

Don’t disagree, but these days I’m avoiding modding these old amps unless the owner really demands it.

[@UncleBensRice]

​@@HeadfirstAmpsTotaly understandable. This is definitely something you should rather do to a clone/reissue or an amp that has already been heavily modified in the past.

[@HeadfirstAmps]

💯

[@dylanjastle]

Cool mod ideas for my 2204 china clone!

[@antilaw9911]

Had one of these. 79 JMP 100. Bought from willies American guitars st paul, Mn about 20 years ago. $500. Mint. Thing could really thump! I was trying for the Randy Rhoads sound. Like a fool, didnt know and i got rid of it for JMP-1 setup, which was killer!! What they ask for these now.... i had a piece of valuable history.

[@HeadfirstAmps]

…and they are only going up in value now!

[@leiferickson3183]

I think it sounds great, but please mention to the customer that it might help them to run the preamp high and turn down on the guitar - that way it minimizes the treble boost of that stage and also makes for a cleaner guitar sound, if that is what is desired. It may lead to it sounding a bit noisy though...

[@terrydemol5354]

Jason, WRT bright cap the following is worth trying: a/ use a series resistor to tame it, value experimentally derived, b/ connect it said RC network from * before* the 470k // 470p network. This will even out the HF boost response across the gain controls range. No bright cap to me doesn't sound quite right and IMV it needs some amount of HF boost but not too much. You can also connect the bright cap with a pull switched 1M gain control. Plenty of options. Have fun.

[@thechannelforeverything2170]

Man that thing has some amazing high end.

[@Burgschall]

Seen that Plate Snubber in a lot of JMP 22xx, it's also used to prevent oscillation, so I would not really exclude that this is a factory mod.PIHER They did some really awkward things sometimes so I would also consider the stacked resistors as factory, considering that the value is somehow in the ballpark and they are all the same type of PIHER resistors.

[@HeadfirstAmps]

Thanks

[@ianorourke6320]

Sounds excellent

[@charvelshredder]

That’s a cool amp! A local cover band I used to follow played thru these & the lead player, who was a heavy set fella, got a huge fat tone out of that thing lol! I used to think, maybe it’s because of his size? Did he clip the bright cap? Anyway, I really enjoy your videos & greatly appreciate you sharing your knowledge!

[@jenkinses8121]

The factory Celestion speakers in Marshall cabs at the time this head was made were the very warm sounding, low-mid heavy G12-65, there’s a reason for that.

[@MojoMedicineMan]

Say, I have been asking what speakers were used in the cabs with these amplifiers for years now. Are you positive? Many years ago, I once purchased a late 79 JMP MV 2203 that looked completely original, LCR blue caps, 6550's, etc. However, the owner stated that the cab had V30's in it from the factory. Could this be possible? I took the head and left the cab, as he was willing to part. I think back and wish I would have taken the cab with it. I've never read much about speaker rolling with this amplifier. I was advised by a well known Celestion rep at that time to try those BASS speakers with it. Never tried it. Your comments please? Thank you!

[@jenkinses8121]

@@MojoMedicineMan a 79 Marshall would never have come with factory installed Vintage 30’s, seeing as Celestion didn’t invent the V30 until 1986. First amp ever to have a factory-installed V30 was the Marshall 4001 Studio 15 combo, introduced in ‘86

[@jenkinses8121]

Hi, if the cab had V30’s from the factory, then it would not have been manufactured earlier than 1987 (the V30 was introduced in ‘86, first amp ever to ship with them was the Marshall 4001 Studio 15 combo in ‘86, followed by the Silver Jubilee series cabs and combos in ‘87). TL;DR: either the cab was not original to the amp, or the speakers were not original to the cab. The bass cone speakers that sound good with guitar are the 55hZ G12H-30’s from the late 60’s/early 70’s. The later G12-100, G12-80 etc speakers used in the 800 era bass cabs, imo do NOT sound good for guitar (cold, brittle, harsh)

[@MojoMedicineMan]

@@jenkinses8121 Okay, thanks. He was a bit of a salesman and he wanted to unload the cab as well, understandably. You mentioned G12 65 previously, but now think that the G12H's may work better with the 79 JMP MV then? I seen a 78 cab that had G12M black back magnets. Today, a fella is pretty much looking at reissue speakers, clones, etc. Thanks again!

[@jenkinses8121]

@@MojoMedicineMan my personal speaker pref for a cascaded-preamp master volume JMP is the G12-65 (these include the black labelled « Marshall » branded speakers that were stock in Marshall cabs/combos from ca 79 to 81), but you can’t really go wrong w/ G12M, G12H, V30 etc, just adjust EQ/volume levels accordingly (G12H and V30’s will be louder than the others mentioned, which is not necessarily a good thing!)

[@JockeLundgrenTV]

Great video! Thank You! 🙋🏻‍♂

[@kxmrock]

Ends Up sounding good

[@frankquinn1296]

I have an original 800, like this same year, it was super bright , but as you said once the preamp gets passed 12 it eases of a bit. Speaker cab selection is important as well. I used to run mine with the presence and treble at 2 to 3 , the preamp gain at just past Noonish, bass literally full on. I hit the front end with Klon or , surprisingly good effects with this is the Keeley DM drive. Its was still a little harsh. So I had mine modded with a bright switch and a Metropolis loop ( which is switchable). Now it sounds perfect and you can still get that incredible bite. I did have the normal channel modded to be a switchable boost, but it has the wrong value pot , which makes it unusual able. You just need to literally touch it and it adds 3 db.

[@HeadfirstAmps]

Interesting

[@marcogiampa283]

The cab is important, when I first got the amp I was only running it through a cab with v30s. While Jason had the amp I picked up a pair of 55hz blackbacks to go in my v30 cab and a quad of 75hz blackbacks too. Thats what that amp was made for, less harshness of the v30s

[@davidgangemi3314]

I had my amp tech change the value of the bright cap on my 1981 Jmp to get it to sound warmer. Then I run it into a Mesa 2x12 cab loaded with Weber Thames 4 ohm speakers,which are voiced like Fane speakers like you hear with Hiwatts. What a massive difference! I still get the highs I need but they blend in with the Bass and Mids much better. I also got rid of my Vintage30 Celestions in my Mesa cab. Too harsh sounding. I dont understand why people like those speakers at all

[@MrWilly2204]

That sounds like rock n roll to me. Nothing wrong with that tone at all.

[@Turboy65]

It's worth it to make note of the fact that by now any 50 year old Marshall with original plastic/bakelite/phenoloic power tube sockets should be considered for socket replacement with ceramic sockets. I've had more than one 50 year old JMP come across my bench with arced power tube sockets that have a definite burned smell on them. Try to crank the amp and things just go very badly due to more arcing in the sockets. So consider therapeutic socket replacement to keep the amp reliable at high volume. Even better to replace them with high quality ceramics.

[@guitfidle]

I have this exact model and year. Mine is a US version which originally shipped with 6L6s, the only thing I have changed was a setup and rebias for EL34s. Otherwise completely stock. The chouce of rube in V1 can make a huge change to the sound. I typically run my pre gain at 9 or 10, with a Tubescreamer pushing the front. Sounds massive! Plus, I have it paired with one of those oversized Mesa 4x12s with Celestion V30s. Mine does not have stacked resistors BTW.

[@hootowl6354]

Didn't it originally ship with 6550's? 6550's are similar to 6L6's but not the same.

[@HeadfirstAmps]

Yeah, if US delivered would be 6550

[@guitfidle]

@@hootowl6354 hmmm, I haven't looked at the back of the amp in quite a while.... I thought it was 6L6, definitely did not have 6550s when I got it, but I'm not the original owner. Now I'm not sure what it had when I got it.

[@hootowl6354]

@@guitfidle In Europe, they had EL34's. The company that imported them to the U.S. wanted 6550's because they were more durable in shipping. I've read that numerous times. 6L6's are never mentioned. FYI. 😉

[@KahnuevsKrake]

I imagine this guy was trying to play it at bedroom volumes, hence it sounded too bright. They're designed like that so that they don't sound muddy when you crank the tubes. I have a JCM800 studio which I thought sounded too bright, but thanks to an attenuator, I can really crank it up without it getting ear splittingly loud.

[@markkinney5030]

Cool video that is a good sounding marshall with EVH great tone! One of things that got my eye was the guitar you were playing very nice guitar and with great tone! Is it stock?

[@HeadfirstAmps]

Peavey Wolfgang USA hard tail. Pickups have been changed to DiMarzio Transitions

[@markkinney5030]

@@HeadfirstAmps Cool nice man

[@lordgraga]

Isn’t that a Suhr?

[@HeadfirstAmps]

Oh, wrong video sorry! Thought the question was about the Rocker 30 clip. Yeah, a Suhr Modern with a Thornbucker+ set.

[@GL64]

Wow, I just acquired a 76 2203 with the exact same four piggybacked 10K dropping resistors.

[@antilaw9911]

Also, i remember i had savage audio convert the KT88"s? I think stock, to EL34"s. Honestly.... couldnt tell a difference after spending $300. But oh well, we learn.

[@HeadfirstAmps]

I agree. We have to remember that tubes were made to be transparent audio amplifiers….they weren’t made to have ‘tone’.

[@Mark70609]

Surely the EL-34’s would have been correctly bias where the KT-88’s would have been biased cold. I don’t think the Marshall power transformer could handle correctly biasing KT-88, then there is the question that primary impedance of the output transformer wouldn’t suit the KT-88’s.

[@lechstryzewski9350]

Awesome amp !!

[@PeteKaltsa]

I put the 330uf fat cap across a resistor that Friedman recommended and it beefed up the low and top end. Gives it more girth I guess

[@gregbear123]

Love removal machine!

[@davidbucket]

Sounds just killer 😎

[@nicolasrivera5310]

Killer background!!!

[@MarzLast]

The preamp on 7 sounded where i would want to be ,the solder on the resisters looked new i have never seen marshall solder add on resistors like that on top of the board when they have had the board out doesnt look factory at all .

[@RozsaAmplificationLLC]

Hey Jason, as you indicated and voltages I saw...this amp is spot on the epitome of a Marshall! NO changes needed. Bias it for tone/life and if the customer feels something is off...it's gotta be something else, like speaker/cab or upstream and guitar/pickups, because this Marshall is healthy as fuck!👍 I've seen stacked resistors in Marshall amps I think factory, but not as many as this one. But I do think looking at them and era specific n solder joints that they are in fact factory original!?

[@HeadfirstAmps]

Robb! Yeah man, after closer examination I’m certain those droppers are factory. Even that 27pF over the first plate looks factory!

[@RozsaAmplificationLLC]

@@HeadfirstAmps ...and why there is inconsistency in Marshall products over time n you have to find a "good" one!! 😂 Just over 460 on the plates and 335 at the PI....very nice, and you can tell by the tone.

[@SVATTIMO]

Nice tone, I had some 800's back in the day but prefer the Plexi

[@johnmurphy6707]

Hi Jason..love your videos.....Ive got a stock 2204 and theres a snubber cap on the plate resisitor of V1, though I think ive seen others without..strangely my volt drop of 2x 10k resistors next to the bias pot theres only a 10k and a bare wire in place of the other??..I know its stock as I bought it from new.

[@HeadfirstAmps]

What year is your 2204?

[@johnmurphy6707]

@@HeadfirstAmps 1979 B+ is under 400 and its (from memory) 320v after first dropper (1x 10k plus bare wire)

[@HeadfirstAmps]

Cool amp. The 2 x 10k droppers is for those with the higher B+. You want that voltage after those first dropper(s) in the 320 to 330 range, so you are right on it!

[@Nightjar726]

That’s the only thing missing from the Suhr 68 amp. It NEEDS the bright cap. If people don’t like the stock bright cap just throw in a 470pf. Good in between.

[@PainterDans]

I think you fixed in the first minute and a half. That thing sounds great

[@jcwoodstl]

Sounded perfect when he dropped it off. He just has the wrong amp for him

[@PainterDans]

Great video, what do you think of the new 20 watt JCM 800 SC20 ?

[@HeadfirstAmps]

They are ok actually

[@f4solutionsinc.6]

I have a 79 jmp 2204 and it is exactly the same with a snubber cap and doubled up dropping resistors that add to 8.9k. It must have been done at the factory.

[@TheAxe4Ever]

I have a feeling you could take a Pignose and make it RAWK!

[@HeadfirstAmps]

Hahaha

[@obicross]

which suhr pickup did you use? sounds very dynamic and rock n roll! i like it!

[@HeadfirstAmps]

Thornbuckers!

[@obicross]

@@HeadfirstAmps ahhh i was thinking, "was it thornbucker?" But asked just to be clear 😁 wish could hear the neck position too. Any other videos with the suhrs?

[@HeadfirstAmps]

Lots. I have a set in my 81 gold top too

[@rocker8692]

Maybe put a tube rectifier might take out some harshness.

[@brightfalls6788]

These late 70’s Marshall’s are the coolest ever. People (especially modern amp designers) don’t seem to understand how a Marshall is supposed to sound. The lack of presence and sparkle is why I’ve returned almost every new Plexi clone I’ve ever tried out. They all sound like there’s an inch of cement and 4 blankets over the cabinet, just total mud. Friedman’s are the worst about this. Plus, people act like it’s almost impossible to get proper AC/DC tone at low volume and it’s some kind of unachievable holy grail tone, but that’s probably because they’re playing through these dark and dull modern plexi “interpretations”. The Brent Hinds Terror is the only one I’ve tried that gets it right, and was predictably discontinued and hated for being too bright and also improperly advertised as a metal amp. Adrian is one guy that knows what he’s doing and I wish he’d make more Orange Marshall’s lol.

[@HeadfirstAmps]

Our Alta has the brightness baked in!

[@danz4904]

I prefer to have the bright cap removed. It opens up a lot of great blues & rock sounds at lower preamp gain levels. With the bright cap in you're missing out on some great tonal range.

[@HeadfirstAmps]

That’s true, however it’s not the sound of Marshall fuelled rock n roll. Bright caps are switchable in my own designs for the best of both.

[@Burkhimself]

Jason, where is the best spot to put a clipping diode (and what type) that can “clean up” the best with a guitar’s volume ? Really curious….

[@HeadfirstAmps]

Jose style is after the cathode follower and before the tone stack, I have other videos that detail this

[@qua7771]

I put a 220k resistor in series with my bright caps.

[@HeadfirstAmps]

Great idea

[@geezberry8889]

plate snubber might be stock. the whole amp might be stock. i wouldn't touch anything. voltages all great. I'd advise the owner to use an eq pedal to dial out his ice pick

[@HeadfirstAmps]

Yes, I think that 27pF snubber is factory!

[@vox1966]

Leave it alone it’s not supposed to to sound like doom music get a orange amp with vintage 30s you will have nothing but bass I own a 1978 it’s the kind of music back then

[@batpigguitar]

Hey I remember that axe.

[@HeadfirstAmps]

I always forget how great it sounds! Need to play it more.

[@batpigguitar]

@@HeadfirstAmps yeah I miss that one.

[@johnhudak3829]

You know, it also doesn't hurt that you can absolutely play your friggin' ass off, brother. So. . .that might be contributing to the amp sounding good. 😃

[@HeadfirstAmps]

Haha, thank you!

[@coalfacechris1336]

Leave it be....

[@nickm.9474]

Just turn it up! Doesn’t that take the bright cap out of the equation some what.

[@HeadfirstAmps]

If the gain pot is on 10, yes it does….but then it gets too flubby and bloated in the front end. The bright cap is there by design for a reason.

[@wesleyc.4937]

Maybe he'd rather play footsie with his pedal board.

[@digitalchris6681]

Large bright caps rule. It's what makes Marshalls sound.... well, Marshally. I even modded my JTM45 from 100pf to the full 4700.

[@HeadfirstAmps]

Legend! That’s awesome.

[@digitalchris6681]

@@HeadfirstAmps actually - just thought: I know the 2203 spec has a 1000pf but when I was tweaking my amp I found that 1000pf was too bright - it needed the full 4700 (super lead, 1987x etc) which let through more mids. So there's a suggestion to your client: don't remove the cap but actually increase it ! Or.... buy a decent attenuator and TURN IT UP !

[@acepalacio8223]

SLP to my ears