JCM800 Build Questions

[azrael]

I'm looking to either build or modify a JCM800 for myself.

Now, I can't seem to find a 2204 at a decent price...so it's looking like I might as well build a brand new one.

I was wondering if you all could weigh in my build plan?

Essentially, since I am building it, I would like this amp to be the best it can. I was planning on buying a kit from Ceriatone, but I am thinking of changing some of the parts. In particular, the transformers and the choke.
So...

- Are Zoso caps a good idea here? Will they make a noticeable difference when they break in?
- What kind of resistors come in Ceriatone kits? If they are carbon comp, do these make a difference in the circuit? If not, would metal gilm or something serve me better, due to the better tolerances?
- Are the Silver Mica caps here better than the original circuit's ceramic caps?
- Any other tips or anything I should know?

I suppose the biggest point to make here is that I am not trying to build an accurate replica. I am trying to build a clone that performs/sounds great.

[paulster]

Depending on where you're located have you costed up getting a Metroamp kit (including their superb transformers) versus the Ceriatone and then having to source good transformers yourself?

Sozo caps work really well in Marshall builds, although in this instance you're probably better off with the Sozo Mustard Standard rather than the Mustard Vintage for a JCM800 as recommended by John at Sozo for their wider frequency response, and also because it'll save you some money.

Ceriatone supply carbon film resistors which are perfectly fine for the 800, as it still isn't too high a gain amp. They were already over carbon comps when the 800s where originally released. Personally I like the Beyschlag non-inductive MF resistors as they are dead quiet and don't have that 'metallic' quality that some other brands can impart. PRP GP1 resistors (see West Labs) are really nice too, although I've not used them in a JCM800 build, only other Marshall-style builds.

Trannies though. Get good trannies, especially the OT, as this is the single most important component and the costliest to get wrong.

[azrael]

Never knew Metro did kits, but unfortunately, I'd much rather have the 2204 than the 2203. I'm in California, FWIW.

Hmm...Those MF resistors would reduce noise? That's definitely something I'd file under "works better" for myself, haha.



What kind of transformers should I be looking for?

I'm a college student, so I can't totally break the bank on them, but I'd still like something a good step up from the Ceriatone, and maybe even from the originals.

[M Fowler]

Metro has great kits with instructions and help to boot.

Triode also has a JCM800 kit without chassis for $349. But you would then need to use an available layout/schematic and get a chassis such as the JCM800 blank chassis from Turretboards.com

Mark

[jaysg]

I suggest contacting Brian Wallace (Marstrans) for info on transformers. His pieces are very nice and well worth it.

Here's my 2p worth. I own an '83 2204. I replaced the OT with a Plexi style OT and it made a greater difference than I expected. You need to figure out whether you want a dead nuts on stock sounding amp or something a bit different. The stock OT creates a much treblier amp than a Plexi OT does. I prefer what I've done to mine, but you may not.

[edit to answer question below]I used an Obsolete Electronics OT. They're not made anymore. I think Joe Pampel(Speedracer) decided it was more effort than he wanted to expend for a bit of money on the side.

[azrael]

Metro has great kits with instructions and help to boot.

Triode also has a JCM800 kit without chassis for $349. But you would then need to use an available layout/schematic and get a chassis such as the JCM800 blank chassis from Turretboards.com

Mark

That's not too bad, I can always get the chassis + cabinet from Ceriatone, and use their layout.

Are their transformers good?

I suggest contacting Brian Wallace (Marstrans) for info on transformers. His pieces are very nice and well worth it.

Here's my 2p worth. I own an '83 2204. I replaced the OT with a Plexi style OT and it made a greater difference than I expected. You need to figure out whether you want a dead nuts on stock sounding amp or something a bit different. The stock OT creates a much treblier amp than a Plexi OT does. I prefer what I've done to mine, but you may not.

Well, i plan to rectify the overly trebley response of the JCM800 with a few mods, most noticeably, that bright cap it has.

What OT did you use?
I assume Brian is a user on here?
EDIT: Did a quick google search, found him.

[paulster]

I'll add that I also used a plexi OT (Metroamp) in a build of mine that's switchable between 1959 and 2203 and I really like the results. That iron really seems to suit a JCM800 style amp.

Brian Wallace supplies great transformers, so he's definitely worth a look.

I've never tried Nik's, although he's a great guy to deal with.

[azrael]

Brian Wallace's transformers are very well priced, it seems, as well.

If he thinks I can get where I wanna go with one of those, I definitely check it out. Thanks for the heads up on his stuff!

[John_P_WI]

Just my 2 cents....

I as well as others have used Antique Electronics transformers from Magnetic Components or Marvel. I believe Triode sells one very similar. They are both Triodes and Antiques "house brand". There is a guy gldtp99 who has some "mule" clips of his amps using these. Do a search.

A Hammond 272 JX will give gobs of power, 425 v on the plates (no bias tap though).

My advice on the pre amp, use a good jcm topology like Bruce Egnater's TOL design, or his class build amp. The biggest problem I have had with the JCM's is the inconsistant tone as the MV is swept. This can be solved by adding a 150k series resistance to the mv wiper, or using a boot strapped master ala KOC. Also mind your grounds to quiet things.

I also like depth mods to thicken things up.

Good luck,

John

[selloutrr]

can't find one for a decent price??? I find them for $6-800 all the time on craiglist you are into a build for at least that and no assurance it'll work. just get a used one and mod it. IMHO any amp under $2000 is not worth the time to clone.

[azrael]

I don't want to pay more than 700 for one. People are trying to sell them for 1200, because of the reissues.

The lowest I've found was the two channel version with reverb, for 650. Don't really want that one.

Part of this is because I want to create something that's better than what I can buy out there.

[M Fowler]

Appears to be Chicago Magnetics.

I fail to understand why not encourage some one to build their own amp?

Sure I buy amps but I also enjoy building them and most of the time I can build one cheaper than buying it I just watch my parts scrounging closely. Buy in quanity to keep my inventory of parts on hand as well. Minimal shipping costs that way.

[selloutrr]

Nothing wrong with building amps its fun! it just seems pointless on a mass produced amplifier that can be purchased for cheap with less effort then digging for parts. by the time you add parts and shipping you have bought a pre made amplifier. save yourself the time get a working one mod it if you want. personally and this is only my opinion, no need to attack... for all the amps in the world the JCM800 was just at the right place at the right time but tonally is painful to listen to. If you really just want to build an amplifier for the sake of building an amp. build a modern vintage tone monster and be happy! if you really want a marshall just buy one.

[Structo]

The problem with buying any of the more modern amps is the use of pcb's and ribbon cables, which make modding them difficult.
It can be done but it is so much easier to build on a turret or eyelet board the sub different parts in and out to see what it does to the tone.

You should certainly be able to build one cheaper than most boutique companies charge for their take on a circuit.

But, if and when I build a Marshall clone, it will be with a Metro kit.
I have hung around their forum and the kits are very well received with good parts available.

When building from scratch you have to understand the multiple shipping charges from vendors can often nudge the price way up.
Especially on the heavier items like the transformers.

I suppose if you take a long range approach and slowly gather your parts you could make it less painful on the wallet, but dang, those metro kits look pretty darn good and you can get the Sozo caps too.

[selloutrr]

I'm with you about the PCB except clones hold no value unless sold to a fellow cloner but on the market they are pennies on the dollar. at least a name brand can move for close to what you buy it for used. unless this is the amp you want to grow old with....