Bought two JCM800's on a whim.

[guitarman967]

I picked up a first year 1981 JCM 800 2203 with low serial number and an 88' 2204 with the horizontal inputs.
They were both waaay too cheap to pass up, especially the 81

Heard lot's of hype over the years about different 800 versions. Kind of piqued my interest.
I'll review both and when I get the 88' in.

I might not touch the 81' since I heard the circuit is the same as the 70's JMP's but might mod the 88 out slightly if it needs a little tweaking.
Any advise of good mods for these amps?
Heard clipping the bright cap is essential?

 

[Ventura]

Nice catch. Clean 'em up, get all the knobs to work without scratching, new glass, rebias, and then decide which you wanna mod up.

That's a killer score, if you're into Marshalls

 

[Kapo_Polenton]

Do not go crazy on ripping these things apart. A few small tweaks and they will be rocking. My 6550 82 JCM800 with vertical inputs was raspy and tight sounding.. I did the following mods in addition to resistor piggy back mod to get the amp to run off EL34/KT77's. Here are the mods and i guarantee you will dig it. Just the right amount and a tad from a boost gets you everywhere else you want to go:

- Leave V1A cathode resistor -10k stock. ( with a 4.7k is a common gain mod but gets too fizzy for me and takes away from the raw lower gain tones of the amp) and bypassed it with a .1uF Sozo.

- Bypass V2A cathode resistor( 820r) with a .68uF cap. ( I used sozo again I like their tonal qualities)

- Drop the 100k NFB resistor down by piggy backing a 47k over top to bring it down in around 51-53k depending on drift. (loosened it up a tad but not in a bad way.. made it more forgiving)

With EL34's it should make you very happy. Just a few tiny tweaks , a V1 preamp tube you like, and your hands do the rest. Goes from lower gain crunch to more detailed higher gain. I still boost slightly for leads. That's the way I likes it and you prob will too. You could pay hundreds for such and such mod or just make a few swaps and be happy with what you have. In most cases people with these expensive modded amps still end up modding further or using an OD to tighten and defizz.

 

[mchn13]

If you turn the pre all the way up, it takes the bright cap out of the circuit from the way i understand it. I just run the treb real low on mine, as i like the gain around 6 or 7, then boost it.
Ive got an 800 and a jmp, the 800 being a horizontal input 2203, and i wouldnt mod either one. Just get em up to spec imo.

 

[Kapo_Polenton]

Don't cut that bright cap.. just turn it up. The cap gives you the cut and captain crunch in your cereal! If anything decrease the value but i mostly always liked it stock.

I'll also tell you that for everyone who does a big mod on one of these, there seem to be 2 people who said they ended up preferring theirs stock and with a boost.

 

[blackba]

Looking forward to the review of both. I know its a 50Watt versus a 100Watt, but I am interested to see the comparison between the two.

As far as the bright cap, you can always just pull one lead and then resolder it if you don't like it. I wish all bright caps in amp were switchable, some amps have that feature, others don't.

 

[guitarman967]

Do not go crazy on ripping these things apart. A few small tweaks and they will be rocking. My 6550 82 JCM800 with vertical inputs was raspy and tight sounding.. I did the following mods in addition to resistor piggy back mod to get the amp to run off EL34/KT77's. Here are the mods and i guarantee you will dig it. Just the right amount and a tad from a boost gets you everywhere else you want to go:

- Leave V1A cathode resistor -10k stock. ( with a 4.7k is a common gain mod but gets too fizzy for me and takes away from the raw lower gain tones of the amp) and bypassed it with a .1uF Sozo.

- Bypass V2A cathode resistor( 820r) with a .68uF cap. ( I used sozo again I like their tonal qualities)

- Drop the 100k NFB resistor down by piggy backing a 47k over top to bring it down in around 51-53k depending on drift. (loosened it up a tad but not in a bad way.. made it more forgiving)

With EL34's it should make you very happy. Just a few tiny tweaks , a V1 preamp tube you like, and your hands do the rest. Goes from lower gain crunch to more detailed higher gain. I still boost slightly for leads. That's the way I likes it and you prob will too. You could pay hundreds for such and such mod or just make a few swaps and be happy with what you have. In most cases people with these expensive modded amps still end up modding further or using an OD to tighten and defizz.

Its awesome to get advice from peeps that know whats up! Thanks to everyone.
Now, in this instance, what exactly do these small tweaks accomplish?

 

[guitarman967]

Looking forward to the review of both. I know its a 50Watt versus a 100Watt, but I am interested to see the comparison between the two.

As far as the bright cap, you can always just pull one lead and then resolder it if you don't like it. I wish all bright caps in amp were switchable, some amps have that feature, others don't.

I agree with that. Im not a fan of amps that are too bright. I hear it as harshness.
I did some mods recently to a few soldanos. I thought lifting the leg of a bright cap on the preamp potentiometer ala warren haynes would do the trick on a single channel hot rod but it didnt. The mids just ended up getting blurry. No cut or definition. So, thats fresh in my mind with these amps....
I might only find the soldanos a little bright because i run the gain at 3-4. Ive found that setting to be the perfect amount for classic sounds and i can roll off gtr vol. For some clean action.
I intend on using the 800 in a similar fashion. Just enough gain to get the job done. I have plenty of other amps that do high gain well.

 

[Kapo_Polenton]

The mods I suggested bring more definition/mids/gain. The negative feedback resistor value swap might also lower the gain some but it just has more mojo and playability. Nothing extensive or crazy, just small tweaks that i learned from people here or at metro forum. Very common starting points for more extensive mods. Bright cap is up to you what you want to do with it but you might need it if ever you turn those bad boys up! (lol like you will ever need to play above 4 on those damn things, they are loud as f-ck) ..

 

[guitarman967]

The mods I suggested bring more definition/mids/gain. The negative feedback resistor value swap might also lower the gain some but it just has more mojo and playability. Nothing extensive or crazy, just small tweaks that i learned from people here or at metro forum. Very common starting points for more extensive mods. Bright cap is up to you what you want to do with it but you might need it if ever you turn those bad boys up! (lol like you will ever need to play above 4 on those damn things, they are loud as f-ck) ..

Does clipping the bright cap neuter the amp in your opinion? Does the amp get warmer with volume?

 

[Nodnarb25]

I've owned both. Congrats on your purchases!!!

My 2204 from 1981 needed no mods and sounded great "as is". But, I sold it. Doh!

My 2203 was a reissue from the mid 2000's and was just hurtful and loud. The tone was just "flat", for lack of a better term. It would have been a fine candidate to send to Voodoo (or your favorite mod squad) for a tone upgrade. But, I sold it too.

If I could do it over, I would keep the better sounding one stock and mod one. Have fun!

 

[guitarman967]

I've owned both. Congrats on your purchases!!!

My 2204 from 1981 needed no mods and sounded great "as is". But, I sold it. Doh!

My 2203 was a reissue from the mid 2000's and was just hurtful and loud. The tone was just "flat", for lack of a better term. It would have been a fine candidate to send to Voodoo (or your favorite mod squad) for a tone upgrade. But, I sold it too.

If I could do it over, I would keep the better sounding one stock and mod one. Have fun!

Awesome, thanks
Ever played a JMP 2203/2204? Wondering how close the tone of the early 800's really are.

 

[mchn13]

I've owned both. Congrats on your purchases!!!

My 2204 from 1981 needed no mods and sounded great "as is". But, I sold it. Doh!

My 2203 was a reissue from the mid 2000's and was just hurtful and loud. The tone was just "flat", for lack of a better term. It would have been a fine candidate to send to Voodoo (or your favorite mod squad) for a tone upgrade. But, I sold it too.

If I could do it over, I would keep the better sounding one stock and mod one. Have fun!

Awesome, thanks
Ever played a JMP 2203/2204? Wondering how close the tone of the early 800's really are.

I have an 86 jcm, and a 77 jmp, and theyre super close to me. The jmp seems a little sweeter in the high end, but then again i have two different tubes in the power sections... I actually have kt88's in the jmp.

 

[Kapo_Polenton]

Does clipping the bright cap neuter the amp in your opinion? Does the amp get warmer with volume?

Doesn't neuter it, doesn't even change the quality of the distortion that much either.. it just darkens it somewhat and cuts out a bit of the bite. At the end of the day, snip one end of that cap and give her a go! Very quickly you will be able to decide.

 

[Nodnarb25]

I did have a JMP 1987. It was marginally cool. I don't miss that one much. I think the hard reality about vintage Marshalls is that they are very "hit and miss" on sounding good. Each one I owned I retubed and recapped. They were in good service, but some just were very un-inspiring.

That's why my main "Marshall" is a Voodoo amp now. It delivers on the promise of what a Marshall is supposed to sound like.

 

[guitarman967]

This is the '81 2203. Seller's pic. Gonna take some of my own.
This amp sounds insane!
No mods, straight in. Its odd, through all my amp whoring, this is probably the amp I've been looking for all along. It has the perfect amount of gain for me.
I roll back for cleans.
Maxon 808 in front to really push it into high gain territory for leads or some heavier riffing
I've always overlooked the 800 series.. Man, I was wrong about them though. This is by far the best Marshall I've played.
I'm wondering how the '88 2204 I've got coming in will compare.
I really do like this amp stock tho.. I've never played an early 800 before this one and I don't specifically remember what I didnt like about the later models I played. I think they just had a harsh sound that didnt sit right with me.. this things sounds anything but harsh though. Real smooth sounding especially with a single coil but still has that Marshall "cut".

The feel of this amp is really what sets it apart from other "Marshall" type amps. It's tight in the lows but it's not stiff to play like my Soldano's. Now, I love my Soldano's but they definitely make you work for it.

The only thing I might do to this thing is add an FX loop. Someone already drilled the holes. They removed it at some point tho.
Can someone with experience in that dept. please point me in the right direction? Obviously no tone loss would be the main consideration here..

 

[Norton666]

This is the '81 2203. Seller's pic. Gonna take some of my own.
This amp sounds insane!
No mods, straight in. Its odd, through all my amp whoring, this is probably the amp I've been looking for all along. It has the perfect amount of gain for me.
I roll back for cleans.
Maxon 808 in front to really push it into high gain territory for leads or some heavier riffing
I've always overlooked the 800 series.. Man, I was wrong about them though. This is by far the best Marshall I've played.
I'm wondering how the '88 2204 I've got coming in will compare.
I really do like this amp stock tho.. I've never played an early 800 before this one and I don't specifically remember what I didnt like about the later models I played. I think they just had a harsh sound that didnt sit right with me.. this things sounds anything but harsh though. Real smooth sounding especially with a single coil but still has that Marshall "cut".

The feel of this amp is really what sets it apart from other "Marshall" type amps. It's tight in the lows but it's not stiff to play like my Soldano's. Now, I love my Soldano's but they definitely make you work for it.

The only thing I might do to this thing is add an FX loop. Someone already drilled the holes. They removed it at some point tho.
Can someone with experience in that dept. please point me in the right direction? Obviously no tone loss would be the main consideration here..

In my experience , rock players tend to agree with this statement. Lots of tone chasing and all along , its right under their nose. Same can be said about metal players with the 5150 IMO .

 

[Nilo]

This one seems to work just fine. It's what i built in my 2204 but with a few changes to run it on a 12ax7 instead and also make the loop accept pedals way better. It's always going to be picky about what you put in the loop though since its a serial one.
The Strymons work great, the Mad professor Deep Blue Delay aswell.

http://www.blueguitar.org/new/schem/mis ... x_loop.gif

to run it of a 12ax7 and make it accept stompboxes better (other than just running line level FX) just change the two resistors on the cathode of the first triode. Change the 560R for a 1,5k and the 22k for 100k.

Also, place it before your master volume or the master will act as another send level. So, you go tonestack > loop send stage > loop return stage> Master volume.

And it is wise to make it true bypass using a DPDT mini switch.

Good luck!

[EDIT:] Just fixed my writing a little bit. The time in sweden is 02:40 a night and to not wake anyone up the lights are out and i can't really see my keyboard.

 

[Kapo_Polenton]

Metro loop.. I had installed a Granger loop at first and it was horrid. Got a metro loop used and it is awesome. Keeps my tone in tact.

About it sounding so good, you might want to have a look under the hood. If someone drilled holes for a loop, they might also have tweaked a few components including bright cap. Take a look.

 

[Nilo]

Metro loop.. I had installed a Granger loop at first and it was horrid. Got a metro loop used and it is awesome. Keeps my tone in tact.

About it sounding so good, you might want to have a look under the hood. If someone drilled holes for a loop, they might also have tweaked a few components including bright cap. Take a look.

How's the metro loop as far as headroom goes?
What I mean is that some solid state loops have a very loop headroom and it isn't possible to use a boost in the loop to raise the volume without having the SS loop distorting and thus sounding really shitty. The Marshall RI loop does this and some other SS loops I've tried.

The one I suggested is a tube buffered loop and has great headroom.