Combo amp question

[Ant1981]

My JCM 800 4210 two channel combo sounds so bright and brittle, is this just a trait of the JCM 800 two channels? It's a 1x12"

I personally prefer to use a JCM 900 head with a closed back 2x12 or 4x12, could this be why the combo sounds so bright to me as its an open back?

[Gex]

Yup.

Closed backs are alot bassier, tighter on the low end, thicker.


Open backs are brighter and better for cleaner tones.

I used to have a JCM 800 4210 (I think) 1x12 combo, and sitting next to it with it cranked was PAINFUL.

I got a cab, and things started sounding ALOT better.

[Ant1981]

It even sounds awful and bright on clean too.

[jakenold]

I would seriously not recommend a Marshall to you.

The JCM900 and JCM2000s's (and afaik the 800's too) have a sillicon-diode clippingcircuit in their preamp-sections - in other words, the amps are part solidstate!

As Gex has written above me, if you like the sound but want to add more low-end, a closed-back extension cabinet is the way to go. As to which speakers, I would recommend ones with big magnets like the Celestion 75's. 85's and 120watters - the Vintage 30's are better for their mids.

I hope this will help you!

[Praetorian]

Dude most amps these days have a solid state power supply. Mesa rectifiers are only called rectifiers because they still use rectifier tubes in their power supply.

[Gex]

Originally Posted by Praetorian

Dude most amps these days have a solid state power supply. Mesa rectifiers are only called rectifiers because they still use rectifier tubes in their power supply.

Dude thats not what he's talking about. Your right about the Mesa part, they are unique in that they have a switch on the back that can switch between SS to tube Rectifiers. (for those who are curious: SS rectifiers are "faster" so notes will be tighter and there wont be any sag (or. .latency) between the picked note and the note that jumps out of the amp. Tube rectos will make the amp sag a little, having a little bit slower response, giving it the vibe of an old vintage tube amp. Its so that the Metal fans that need a quick, tight attack can have that, and vintage tone fans can have that authentic vintage tube sag.)


But he's talking about clipping diodes (what most distortion pedals use to create distortion) in the PREAMP, so you have tubes creating the basis of the overdrive, but you have a solidstate circuit in the preamp squeezing extra gain from the preamp. Its a quick, cheap, and easy way to get high gain from a tube amp, but for a price: It sounds cheap, like you're running a distoriton pedal, which is essentially whats happening, but its hard-wired and unseperable from the preamp.

End result: a squealy, clippy, harsh, thin, compressed tone.



I dont think thats the problem here. Try unplugging the speaker in the combo and hooking it up to the cabinet instead.

[Praetorian]

hmm, yeah, that's not characteristic of any higher end Marshall I've ever used (let's not bring up the JCM2000), it probably is just the speaker.

[Ant1981]

Most amps would you beleive it have some degree of diode clipping in these days. And to be honest, you won't notice it. All people seem to do is talk about it cos they saw someone else talk about it, you can't notice it.

Most amps have diode rectifiers and not a valve rectifier for clipping the top end of the sinewave.

[rgr]

Originally Posted by Ant1981

Most amps would you beleive it have some degree of diode clipping in these days. And to be honest, you won't notice it. All people seem to do is talk about it cos they saw someone else talk about it, you can't notice it.

Most amps have diode rectifiers and not a valve rectifier for clipping the top end of the sinewave.

2 different things, rectifiers don't "clip the sine wave", they change the AC from the wall outlet to DC that the tubes can use, so they are part of the power supply. The reason tube rectifiers sound softer (mostly at high volumes) is that they can't react to the changing power needs as quickly as ss rectifiers.

The diode clipping in alot of amps (not most however) now days from a diode clipper circuit in the preamp, pretty much like having a built-in distortion pedal. The Jubilee series Marshalls and the 900s have this, with the possible exception of the SL-X. I don't think the 2000s have diode clipping, but not totally sure.

[Ant1981]

From the description on harmony central, my amp should sound sweet, it sounds crap at the moment, i'm sure i've used better sounding combos, maybe it needs a re valve?

[Drew]

Originally Posted by Ant1981

From the description on harmony central, my amp should sound sweet, it sounds crap at the moment, i'm sure i've used better sounding combos, maybe it needs a re valve?

Honestly, between trusting your ears and trusting Harmony Central, I'd trust your ears.

That said, a fresh set of tubes is always a good idea on a stock marshall. What's in there now, and how long have they been there? If the poweramp tubes are more than a year old and have been getting frequent use, you're probably due for a new set.

Personally, I have yet to find an amp that sounds worse with JJ's in them than without - worth a try. The high gain preamp set in my Nomad actually warmed up and "enriched" the lower gain ranges of the gain knob, so that might be a good starting point - talk to Bob at www.eurotubes.com for a starter.

[rgr]

Have you tried disconnecting the internal speaker and running a cabinet with the amp? That will tell you if it is because it is a combo or if it is the amp. 800s are great sounding amps, but they are getting a little old so they may need a little work to get them sounding like they should. Or, maybe it's just not the amp for you, I'm not really much of a combo guy, I like heads and cabs.