software

I have tried 7 or 8 JCM 800/JMP MV single channel heads and they all sounded like Marshalls, the JCM 800's being brighter and have more gain than the JMP's. But 2 of the later 80's JCM 800s sounded grainier and thinner, they didnt really punch like the earlier JCM 800's. Recently i was told that for the most part this is because Marshall in the later 80's started to use lower power filtering and removed a pair of the metal power quot;cansquot; from there amps. Does Marshall still do this with there amps? What about other cheaper, mass-produced amp makers like Peavey, Fender, Crate, or even Mesa? Do they still use this cut cutting method?

Thanks

I do remember reading something recently about Marshall reducing the number of power filtering caps somewhere along the JCM800 line, but don't remember the details, or where I read it. Some help I am, huh?

Less power filtering would not really reduce the power level, but it might make an amp SOUND less powerful. Perhaps a thinner sound, less low end, not as much WOMP! on the transients.

Whatever it was I read, it had ways of telling (from the front, I think) which amps were which. Search here, also Ampage.com, maybe 18WAtt.com.

The JMP and JCM MV heads are my favorite Marshalls, they're what I grew up on. Find one in good shape, then tweak to taste.

Anyone know?

i have a feeling it has to do with the transformers

Yes the filtering keeps the amp from running out of juice so to speak.
The less filtering well result in a weaker sound, plus the transformers are not as powerful as they where on the old Plexi's, I seem to recall.


Originally Posted by Maximusgordon 2.0Anyone know?

Yes , I do..will have to get back to you a little later....(sorry, walking out the door to go do something!)

Jeff Seal

I know for a fact that the older Marshalls with 4 LCR (big blue cap cans) sounded smoother and better than the ones with 2, like all newer ones have. That goes for JMP's and JCM 800's. I don't know if it made them lower in volume, but it made the gain sweeter and less harsh.

1 of the biggest cost cutting measures that most of the big manufacturers seem to use is on transformers these days. Bound to make a difference to the sound, also not as robust as the mil spec 1's.

Yup...cans...transformers...and later 800 series had diode (ss) clipping. All resultiing in poorer quality sound.

Best thing in the world to do if you have one of those latter 800s (or a current reissue series amp, or 900 or 2000 series) is send them to a guy like Jeff Seal or Trace at Voodoo. They can work wonders.

Check out voodoo's quot;deluxequot; mods HERE

Some discussion on Transformers HERE

and some info on PLexi's HERE

I don't think early/later determines whether an 800 has diode clipping. The dual-channel JCM800's had diode clipping, the single-channel JCM800's never had diode.

Regarding transformers: 100-watt JCM800's always had first-rate transformers. Most 50 watt 2204 amps have a cheapy output transformer. One of the best upgrades you can make is to replace the OT in a 2204 with a really good aftermarket replacement.

Well that helps some, thanks. But does anyone know what amps and/or companies that have started using less than 4 caps and lower filtering? Im sure Jeff Seal knows, i can wait...

Bump!!!

The number of caps used in the filter supply section can be quite decieving, Although the 800 ch. switching Marshalls were not what you were inquiring about, they are probably the best example to use here. There are three distinct variations and the number of filter caps are different for each one....

1. Early ones had 6 LCR caps...like Super Leads and most early MV JMP's
2. Next ones had 5 LCR caps
3. Later versions had only 3 LCR caps, but they quot;twicequot; the reserve power than any earlier one's....doesn't make sense does it?

The Marshalls that have the quot;4 packquot; of filter caps next to the trannies are actually running them in series.....when this is done the capacitance rating is cut in half, while the voltage rating is doubled. When they are run in parallel the capacitance is summed, and the voltage rating remains the same.

So, Marshall Super Lead plate reserve supply is (50 50uf = 100uf/500v for one cap) two 100uf caps running in series = 50uf/1000v

The later 800's (including the single channel) plate reserve is simply one 100uf/500v which is twice as much capacitance.

The same setup is replicated after the choke....
Running in series allows the caps to work in a much lower voltage range as opposed to continously subjecting one cap to 486v, while it's max is only 500v! This contributes greatly to the lifespan of the cap, but at the cost of quot;reservequot; or quot;on demandquot; current. Of course, both designs have proven themselves very reliable.

Having said all this, more quot;reservequot; power doesn't actually equate to quot;betterquot; and does have an impact on tone as the supply is quot;depletedquot; when cranked...this is more commonly referred to as quot;sagquot; (as GJ discovered... ) but it does increase the quot;abilityquot; of an amp to be louder before breakup.....

Most current production amps fall into two categories:

Those designed to please the most people possible, at an affordable price (which usually does equate to less power) which lends itself to smaller trannies (as pointed out earlier) and quite a few other quot;compromisesquot;...simple economics.

And those that are considered quot;boutiquequot; and carry higher prices to reflect better quality......(my personal quot;dream ampquot; design would retail for over five figures, which would make it quot;commercially unviablequot;... which would explain why it's a quot;dream ampquot; and not currently on the market!)...

The trend towards less power adds to the quot;declinequot; of megawatt amps, but introduces the element of quot;reliabilityquot;....

Ex.- My personal Marshall is capable of delivering 186 watts!, since I honestly only use maybe 50 watts max at a gig, it would stand to reason the amp as a whole would be much more reliable than using a 18 watt amp pushing all 18 watts night after night!

Hope it helped......

Jeff Seal

Like the guy above said it's all about the caps, or so I would think. I know that in headphone amplifiers (and speaker amplifiers) if you have bigger caps there'll be more bass and it'll sound quot;more powerfulquot;, so the same should go for guitar amplifiers (they're just amps with pre-amps built-in) so yeah, take out those POS caps from those marshalls and put in some high-quality audiophile-grade caps (which aren't expensive, actually...contrary to popular opinion)...


Originally Posted by Jeff SealThe number of caps used in the filter supply section can be quite decieving, Although the 800 ch. switching Marshalls were not what you were inquiring about, they are probably the best example to use here. There are three distinct variations and the number of filter caps are different for each one....

1. Early ones had 6 LCR caps...like Super Leads and most early MV JMP's
2. Next ones had 5 LCR caps
3. Later versions had only 3 LCR caps, but they quot;twicequot; the reserve power than any earlier one's....doesn't make sense does it?

The Marshalls that have the quot;4 packquot; of filter caps next to the trannies are actually running them in series.....when this is done the capacitance rating is cut in half, while the voltage rating is doubled. When they are run in parallel the capacitance is summed, and the voltage rating remains the same.

So, Marshall Super Lead plate reserve supply is (50 50uf = 100uf/500v for one cap) two 100uf caps running in series = 50uf/1000v

The later 800's (including the single channel) plate reserve is simply one 100uf/500v which is twice as much capacitance.

The same setup is replicated after the choke....
Running in series allows the caps to work in a much lower voltage range as opposed to continously subjecting one cap to 486v, while it's max is only 500v! This contributes greatly to the lifespan of the cap, but at the cost of quot;reservequot; or quot;on demandquot; current. Of course, both designs have proven themselves very reliable.

Having said all this, more quot;reservequot; power doesn't actually equate to quot;betterquot; and does have an impact on tone as the supply is quot;depletedquot; when cranked...this is more commonly referred to as quot;sagquot; (as GJ discovered... ) but it does increase the quot;abilityquot; of an amp to be louder before breakup.....

Most current production amps fall into two categories:

Those designed to please the most people possible, at an affordable price (which usually does equate to less power) which lends itself to smaller trannies (as pointed out earlier) and quite a few other quot;compromisesquot;...simple economics.

And those that are considered quot;boutiquequot; and carry higher prices to reflect better quality......(my personal quot;dream ampquot; design would retail for over five figures, which would make it quot;commercially unviablequot;... which would explain why it's a quot;dream ampquot; and not currently on the market!)...

The trend towards less power adds to the quot;declinequot; of megawatt amps, but introduces the element of quot;reliabilityquot;....

Ex.- My personal Marshall is capable of delivering 186 watts!, since I honestly only use maybe 50 watts max at a gig, it would stand to reason the amp as a whole would be much more reliable than using a 18 watt amp pushing all 18 watts night after night!

Hope it helped......

Jeff SealThanks a lot for the response, that does help. What about the higher end mass-produced amps, like Mesa Boogie, Rivera, and Krank etc.? Dont know how much experience you have with those amps, but if you know...