Marshall jcm 900 100w high gain head: questions

darcym

I've never seen the "high gain" version of a JCM 900, what's the deal with this, I mean it's obvious by the name, but how much more gain, is it good gain, or fizz, all preamp ? does it clean up well with the gain down (not talking fender cleans)

It's detailed as having reverb on each channel optional, is this digital reverb ?

Is the 100w usable or will this thing sound good at lower volumes, or does it need to be cranked/attenuated ?

never seen one before, so lots of questions

Drew_TNBD

They sound like Marshalls. The one I borrowed for a good time had been modded quite a bit, but I really liked it. It stood up well against more expensive amps like my Fryette and the DSL100. 

ICBM

That's the standard Dual Reverb model - they were all called 'High Gain'. The gain goes to 20 .

The reverb is solid-state-driven spring. Actually the whole amp is a hybrid - a mixed solid-state (both IC gain and diode clipping) and valve preamp, and a valve power amp. Most of the distortion comes from the solid state.

The clean channel will go to completely clean - they're actually quite clear and bright. By the same token the distortion channel in particular is a bit buzzy though, until they're really cranked up. They still sound OK at lower volume, although there is usually a noticeable step in the volume control where they go from off to fairly loud (due to poor quality pots), so very low volume can be tricky.

There's also a Low Power mode which runs the power valves in triode rather than pentode, which gives about half the power and a smoother, duller tone. You can also very easily turn off one pair of the power valves by taking out one of the valve fail fuses, so you can get it down as low as 25W in Low Power mode if you want.

Build quality is OK rather than great. Apart from the pots, there are a few other problems, although they seem a bit better than the DSL/TSLs.

Not a terrible amp, but definitely a 'modern' Marshall rather than a 'classic' one.

darcym

Super info, thank you

ThePrettyDamned

@icbm isn't one of the jcm900s actually all valve? Or is that Internet foolhardyness? I've heard people claim the hybridness makes them sound like a ds-1, which is absolutely rubbish, they sound pretty good!

I think I'm thinking of the sl-x. I very nearly owned one, thought it sounded really nice and had tons of gain but sounded good at lower classic metal and punk levels too.

ICBM

The SL-X is *nearly* all-valve, and the bits that aren't probably don't matter too much - the FX send/return stages (although they're always in the signal path) and the MV switching (also in the audio path), which are both ICs. This replaced the earlier 'High Gain Master Volume MkIII' model which uses a diode clipping network instead of the fourth preamp valve in the SL-X, but still uses no ICs to generate distortion.

The Dual Reverbs are the more truly hybrid ones. The circuit on the distortion channel is loosely similar to a DS-1, yes - the clean channel is more like a Tube Screamer. That doesn't mean they sound exactly like either of these pedals though! But don't write off the DS-1 anyway, Satriani apparently got all his distortion with a DS-1 through the clean channel of a Marshall Anniversary…

ThePrettyDamned

ICBM said:

The SL-X is *nearly* all-valve, and the bits that aren't probably don't matter too much - the FX send/return stages (although they're always in the signal path) and the MV switching (also in the audio path), which are both ICs. This replaced the earlier 'High Gain Master Volume MkIII' model which uses a diode clipping network instead of the fourth preamp valve in the SL-X, but still uses no ICs to generate distortion.

The Dual Reverbs are the more truly hybrid ones. The circuit on the distortion channel is loosely similar to a DS-1, yes - the clean channel is more like a Tube Screamer. That doesn't mean they sound exactly like either of these pedals though! But don't write off the DS-1 anyway, Satriani apparently got all his distortion with a DS-1 through the clean channel of a Marshall Anniversary…

Oh I actually like the DS-1! Like, once I've found the right spot for the tone control, which takes a few minutes... 

I really liked the SL-X I heard, not tried the other JCM900s.  Interesting about the hybridness of them, it's quite cool really.  Internet wisdom says they do everything badly because of that  

ICBM

ThePrettyDamned said:

Interesting about the hybridness of them, it's quite cool really.  Internet wisdom says they do everything badly because of that  

And yet internet wisdom is quite happy with the Jubilee, which uses diode clipping for both distortion modes - although it doesn't use ICs in the signal path.

ThePrettyDamned

ICBM said:

ThePrettyDamned said:

Interesting about the hybridness of them, it's quite cool really.  Internet wisdom says they do everything badly because of that  

And yet internet wisdom is quite happy with the Jubilee, which uses diode clipping for both distortion modes - although it doesn't use ICs in the signal path.

Yeah man, pretty weird. 

I think it largely boils down to "DID MY FAVOURITE PLAYER USE ONE? IF SO YAAAAAY IT'S REALLY GOOD"

samzadgan

My last amp was the high gain master volume...it was really good. From what i understood it was similar to jcm800 with additional gain knob. The additional gain knob enabled the diode clipping, but if you turned if all the way off the diode clipping was no longer part of the circuit.

I used it clean and it was a fantastic pedal platform...i probably would have kept it had it not been for the super bass.