JCM 800 mod in magazine
TanaLeaf9
gain, distortion, etc., essentially by adding an extra 12AX7 tube. (This is in
a mag which features an interview with Eddie Van Halen by Dweezil Zappa, in
case anybody recognizes the issue.) I showed it to an engineer tech friend of
mine, who expressed some concerns (which were over my head) about this
particular mod.
Has anybody tried it? Can anyone give us any pointers on the ins & outs of
adding a preamp tube like this to this model?
For that matter, which is better -- a JCM 800 modded with an additional 12AX7,
or a JCM 900? (I'm in the used market, and wondering how best to invest my
limited capital!)
John Huff
On this subject, what are main differences between the 800 models?
I played through one recently that was amazing, just wanted a bit more
gain but I don't dig pedal dist unless it is a strict fuzz or
overdrive/boost. This one looked to not have EL-34's-would an EL34 800
break up quicker and still have a big, punchy bottem end whack like
this one?
Also, what is it about 800 series that is responsible for the fatness,
punch and overall balls missing from newer series Marshalls?
Daniel
Admiral Ballsy
Bruce Egnater wrote that article, it was Guitar Player magazine. It also had
mods for Fenders that added a switching pot for trem intensity and a pot for
NFB.
Bruce's mod was for the 2203/2204 amps, and it works OK on the pre-'84 models
(with the flying-lead PCB), but is prone to oscillation on the later design.
Problem is , you gotta drill a hole, mount the tube, etc., and then you're
only using half of it. I get plenty of gain out of these amps without adding
anything active, the second tube stage is full of untapped potential.
AB
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ehemin...@my-dejanews.com
joh...@ix.netcom.com(John Huff) wrote:
>
>
> On this subject, what are main differences between the 800 models?
> I played through one recently that was amazing, just wanted a bit more
> gain but I don't dig pedal dist unless it is a strict fuzz or
> overdrive/boost. This one looked to not have EL-34's-would an EL34 800
> break up quicker and still have a big, punchy bottem end whack like
> this one?
I think there's basically 3 models in the high power lineup, a no master
volume, a master volume, and a single input # w/ footswitchable distortion and
reverb.
> Also, what is it about 800 series that is responsible for the fatness,
> punch and overall balls missing from newer series Marshalls?
>
> Daniel
>
-----------== Posted via Deja News, The Discussion Network ==----------
ClanWidRiv
circuits (in general) save for different output+pwr. transformers on the
earlier+later JCM2204s and slightly different filtering on the later JCM. Also,
the old 2204 has a lower B+(around 385v), while the early/later JCM 2204s have
around 440v. Also the later JCM2204 has a pot-mounted PCB and a different
circuit layout.
re: the GP mag. mod (by Bruce Egnater)
There's no way to be sure how someone else will hear something, but if you're
going to try it(and assuming you know how), make sure you take ALL the
parts(wire, resistors, caps) off non-destructively (i.e., just don't clip parts
off) so you can de-mod the circuit to exactly the way it was just in case you
don't like it. This may take more time and be more of a hassle, but what
happens if you clip off a component in a way where the leads are too short to
put it back on, and then you find out you don't like the mod? Also, the exact
same component may not be in production any more and extremely difficult or
impossible to obtain.
Also, make sure the new 12AX7 1/2 stage is FAR away (as Eganter says to do)
and twist the filament wires to the added stage tightly and route it(and
everything else) neatly. This is to prevent unwanted hum/cct.
interactions(freak out noises, etc.).
As to the techs concerns, I'd like to hear what they were exactly(in case I
missed something). I don't think the added heater current(.15A) would be a
prob. (the later 2205/2210 appear to use the same power transformers but use
one more preamp tube). Possibly faster tube wear out? Could be a price you have
to pay for driving the tubes harder and getting more distortion.
Dai Hirokawa
Tonefactor
>punch and overall balls missing from newer series Marshalls?
>
>
Bigger transformers.
Tonefactor
>gain, distortion, etc., essentially by adding an extra 12AX7 tube.
Why hack up a perfectly good JCM-800? Just put a Tube Screamer in front of it
for the same effect. Chances are, the mod will sound like shit anyway.
pfris...@mindspring.com
> a mag which features an interview with Eddie Van Halen by Dweezil Zappa, in
> case anybody recognizes the issue.) I showed it to an engineer tech friend of
> mine, who expressed some concerns (which were over my head) about this
> particular mod.
>
> Has anybody tried it? Can anyone give us any pointers on the ins & outs of
> adding a preamp tube like this to this model?
>
> For that matter, which is better -- a JCM 800 modded with an additional 12AX7,
> or a JCM 900? (I'm in the used market, and wondering how best to invest my
> limited capital!)
>
>
That was a mod done by Bruce Egnater. If you have any questions about it,
you can contact him at BEgn...@aol.com. I know this is a very intense mod,
which involves punching holes in the chasis (not for the weak hearted). IMHO
a JCM 800 will always sound better. Before you go chopping it up for the sake
of greater gain, try some pedals ( tube screamer, graphic EQ, KLON, etc.)
This is always subjective, what kind of sound are you going for?
hope this helps,
Paul Frischmann
TimTube
In article <78q8i8$je2$1...@nnrp1.dejanews.com>, Admiral Ballsy
<admiral...@hotmail.com> writes:
>
>In article <19990128004310...@ng-ce1.aol.com>,
> tana...@aol.com (TanaLeaf9) wrote:
>> I have this old guitar mag that details a mod to a JCM 800 to give it more
>> gain, distortion, etc., essentially by adding an extra 12AX7 tube. (This
>is
>in
>> a mag which features an interview with Eddie Van Halen by Dweezil Zappa, in
>> case anybody recognizes the issue.) I showed it to an engineer tech friend
>of
>> mine, who expressed some concerns (which were over my head) about this
>> particular mod.
>>
>> Has anybody tried it? Can anyone give us any pointers on the ins & outs of
>> adding a preamp tube like this to this model?
>>
>> For that matter, which is better -- a JCM 800 modded with an additional
>12AX7,
>> or a JCM 900? (I'm in the used market, and wondering how best to invest my
>> limited capital!)
>>
>>
>
>Bruce Egnater wrote that article, it was Guitar Player magazine. It also had
>mods for Fenders that added a switching pot for trem intensity and a pot for
>NFB.
>
>Bruce's mod was for the 2203/2204 amps, and it works OK on the pre-'84 models
>(with the flying-lead PCB), but is prone to oscillation on the later design.
>
>Problem is , you gotta drill a hole, mount the tube, etc., and then you're
>only using half of it. I get plenty of gain out of these amps without
adding
>anything active, the second tube stage is full of untapped potential.
>
>AB
I did this mod for a metal guy who requested it, he liked it very much....I
thought it was painfully harsh and abrasive....Guess I'm not a metal guy. I
ran into Bruce one day and told him I'd done his mod, he asked almost in
astonishment, "And you liked it?". I guess Bruce does not give away the good
stuff.
Tim
A great amp can make a lousy guitar sound great.
A lousy amp will make a great guitar sound lousy.
SLaPCaTT
I have that Mod on my Marshall, in fact Bruce Egnater did mine, it's called
the "Modzilla" and I will say that my Marshall screams like it never did before
I love it and it's footswitchable. I have the mod on file and I could scan it
and send it to ya'
Bob
O'Connor
>
> In article <19990128004310...@ng-ce1.aol.com>,
> tana...@aol.com (TanaLeaf9) wrote:
> > I have this old guitar mag that details a mod to a JCM 800 to give it more
> > gain, distortion, etc., essentially by adding an extra 12AX7 tube. (This is
> in
> > a mag which features an interview with Eddie Van Halen by Dweezil Zappa, in
> > case anybody recognizes the issue.) I showed it to an engineer tech friend of
> > mine, who expressed some concerns (which were over my head) about this
> > particular mod.
> >
> > Has anybody tried it? Can anyone give us any pointers on the ins & outs of
> > adding a preamp tube like this to this model?
> >
> > For that matter, which is better -- a JCM 800 modded with an additional 12AX7,
> > or a JCM 900? (I'm in the used market, and wondering how best to invest my
> > limited capital!)
> >
> >
>
> Bruce Egnater wrote that article, it was Guitar Player magazine. It also had
> mods for Fenders that added a switching pot for trem intensity and a pot for
> NFB.
>
> Bruce's mod was for the 2203/2204 amps, and it works OK on the pre-'84 models
> (with the flying-lead PCB), but is prone to oscillation on the later design.
>
> Problem is , you gotta drill a hole, mount the tube, etc., and then you're
> only using half of it. I get plenty of gain out of these amps without adding
> anything active, the second tube stage is full of untapped potential.
If you REALLY need a lot more gain than even the modified second stage
can provide, or, if you just want that same sound but a bit smoother,
then you can convert the cathode follower that drives the EQ into a
voltage amp, too. You might have to shift some leads around and add a
cap and two resistors, but you can get the four-stage sound without
punching any holes.
Have fun
Kevin O'Connor
O'Connor
> (with the flying-lead PCB), but is prone to oscillation on the later design.
>
> Problem is , you gotta drill a hole, mount the tube, etc., and then you're
> only using half of it. I get plenty of gain out of these amps without adding
> anything active, the second tube stage is full of untapped potential.
If you want to get even more gain than the modified second stage
provides, or, you want to get that same level of distortion but
smoother, then you can rewire the cathode follower that drives the EQ as
a gain stage. You have to add two resistors and a cap or two, and move a
few leads.
js...@pe.net
current if this is what the worry is.
xman
I've played ones that sound great and ones that sound like crap so shop
around. I would probably take a good-sounding 800 over a 900 but some may
disagree.
TanaLeaf9 <tana...@aol.com> wrote in article
<19990128004310...@ng-ce1.aol.com>...