JCM900 combos any good?

rico

After a few pints of ale I've been browsing the usual places and my gas for a JCM800 4010 isn't really going away but the lack of amps for sale is leading me to look at JCM900 models. 

Are they any good?

cheers!

Voxman

For reasons I've never really understood, the JCM900 tends to get a bad press in some quarters.  It was designed to give more distortion with an edgier flavour than a JCM800, but I think its much maligned and more than a one trick pony.  Its cleans are pretty decent by Marshall standards, and it can deliver some nice warm lower crunch tones as well as all out balls.  I actually quite like them.  

I would add though that the one I played most recently had EL84 tubes instead of the stock 5188's which I think makes it sound way better & much more punchy & defined.   

timmysoft

They get a lot of internet hate but I think they're great. The 50w dual reverb 2x12 is ny favourite.

good cleans and decent drive, I've had loads of them and never suffered any reliability issues. 

Tim

TTBZ

I haven't played the combo but the dual reverb head is one of the worst sounding amps I've used. It's a fizzy, buzzy mess.

ICBM

They're OK - better than the JCM2000s. The reason they get a bad press is that they're essentially hybrid amps and that they aren't quite as well-made as the 800s.

The Dual Reverb is much more of a hybrid than the High-Gain Master Volume. Whether it matters is a different question...

The build quality isn't too bad, although the pots are notoriously poor and there are a couple of other minor issues, but they don't have any really serious problems that are hard to fix.

The ones that came stock with 5881s - there were a few years in the 90s when good EL34s were hard to get, in the quantities Marshall use - are easy to convert to EL34s and worth doing.

monquixote

I played in a band with a guy who had the 2x12 combo (don't know exact model).

It was pretty good  if not spectacular and seemed reliable.

CHRISB50

I used to have a dual reverb head and loved it!

smigeon

I used to have the dual reverb 50 watt 2x12 combo. For me, the dirty channel was pretty good. Nice and edgy and agressive. Good for rocky stuff and punk. I wasn't such a fan of the clean channel as some of the earlier posters, but then I am more of a Fender fan in that regard. The shared EQ (if I'm remembering right) also didn't help in getting both a good distorted sound and a good clean sound. But a perfectly good amp that I'd still be happy using for rocky/punky sorts of application.

SimonC

Do double check the pots if you're buying one, though.
The crackling and popping from mine drove me crazy, nothing I tried seemed to fully cure it either.

ICBM

SimonC said:

Do double check the pots if you're buying one, though.
The crackling and popping from mine drove me crazy, nothing I tried seemed to fully cure it either.

Replacing the pots is the only way.

The stock ones have a very annoying taper usually, too - most noticeable on the gain and volume where they do nothing from 0 to 2 and then suddenly kick in. Unfortunately you're limited to using a similar type due to the way the PCB is mounted using them, although you can get better-quality ones.

Guitar_Slinger

I've got a 50w 1x12 Hi Gain Dial Reverb.  Bought because it's easy to get in n' out of gigs or rehearsal, to play rock covers with the Marshall sound. And because I couldn't find a black 2554 combo that wasn't silly money. Does all that perfectly for me and can switch to 25w.

Mine's a 1993 model, with EL34s and after being gigged a few times and rehearsed a lot I had it serviced by Marshall and got all the pots replaced because one went a bit funny and I went for the lot.  There might have been the taper thing between 0-2 that @ICBM mentioned but the, I only bought it to play loud in a rock band so that doesn't bother me.

The only time it sounded bad was when I put it through a rehearsal room 4x12 once, but it was fine once I switched back to the internal speaker.  I used it regularly from about 2009 to 2012 and it didn't let me down.

Guitar_Slinger

BTW, I played a LP through it and still have the amp, but aren't in a band ATM because of work/family commitments. Can't see myself selling it TBH, it's too handy have around for when you need it.

Haych

ICBM said:

They're OK - better than the JCM2000s. The reason they get a bad press is that they're essentially hybrid amps and that they aren't quite as well-made as the 800s.

The Dual Reverb is much more of a hybrid than the High-Gain Master Volume. Whether it matters is a different question...

The build quality isn't too bad, although the pots are notoriously poor and there are a couple of other minor issues, but they don't have any really serious problems that are hard to fix.

The ones that came stock with 5881s - there were a few years in the 90s when good EL34s were hard to get, in the quantities Marshall use - are easy to convert to EL34s and worth doing.

@ICBM forgive my ignorance but could you elaborate a bit further on the hybrid statement please? In what way are they hybrid? Is some part of the signal path solid state, is that what you meant, or have I misunderstood?

When you say they're better than JCM2000 does that apply to both TSL and DSL flavours? I always thought the DSL was a decent amp (not played one but am interested in having one, hence why I ask) by all reviews I've heard/read. 

As the OP I wanted something other than a JCM900 but am thinking of settling for one as what I really want (4140) hardly ever come up for sale, and when they do it's always at a time when I'm broke. 

Thanks in advance. 

ICBM

Haych said:

@ICBM forgive my ignorance but could you elaborate a bit further on the hybrid statement please? In what way are they hybrid? Is some part of the signal path solid state, is that what you meant, or have I misunderstood?

No, you haven't misunderstood .

They are hybrid amps in that some parts are solid-state, mostly IC (integrated circuit).

The circuit stages are as follows -

High Gain Master Volume: valve 1a > gain control > valve 1b > sensitivity control > solid-state diode clipping > valve 2a > valve 2b > tone stack > IC loop driver > FX loop > IC loop recovery > IC switchable master volume controls > valve 3a/b (phase inverter and presence control) > power valves.

On the SLX head version the solid-state diode clipping is replaced by an extra dual valve stage.

Dual Reverb: clean channel - IC-based overdrive circuit using 2 IC stages with diodes in a feedback loop, 'Tube Screamer type'; boost channel - IC-based distortion circuit using 4 IC gain stages with diodes clipping to ground, 'DS-1 type' > valve 1a > valve 1b > tone stack > IC loop driver > FX loop > IC loop recovery > valve 2a (gain stage and presence control) > IC reverb drive and recovery > valve 2b > IC switchable master volume controls > valve 3a/b (phase inverter) > power valves.

So as you should be able to see, the Dual Reverb is a very good definition of a true hybrid amp, with alternating valve and solid-state stages throughout. The main overdrive/distortion circuits are more or less pedals built into the front end of the amp (slightly different in detail, but they work in the same way). The Master Volume models are less so, although it's only the SL-X which does not use solid-state gain or clipping - but is still not strictly all-valve, since the FX loop and MV stages are IC.

The odd position of the presence control in the Dual Reverb may also help to explain its rather flat dynamics, since it's a preamp control rather than a power amp control on this model.

Haych said:

When you say they're better than JCM2000 does that apply to both TSL and DSL flavours? I always thought the DSL was a decent amp (not played one but am interested in having one, hence why I ask) by all reviews I've heard/read. 

The DSL does sound better, but they share the same build quality and reliability problems - the DSL50, DSL100 and TSL100 (and TSL122 combo) use the same main PCB which is where most of the problems are. The TSL60 is different and equally bad but in different places… but sounds even worse! The DSL201 and 401 combos aren't quite as bad - they still do have well-known problems though, and the 201 has a tendency to blow output transformers.

Hope that isn't too much jargon!

Haych

Thanks @ICBM, very useful stuff there and no not too much jargon. 

Wasnt the jubilee similar though? Thought that had some kind of diode clipping, and they're meant to be Marshall holy grail?

ICBM

Haych said:

Wasnt the jubilee similar though? Thought that had some kind of diode clipping, and they're meant to be Marshall holy grail?

Yes, they use diode clipping - in both lead and rhythm clip modes, although not clean rhythm - but unlike the JCM900s, the actual gain is all valve so it's more debatable as to whether they're a hybrid. Unlike the 900s, the FX loop is extremely poor exactly because it's not properly buffered with an IC...

I'm not quite sure why they're regarded as the 'holy grail' - they're probably the last really well-made Marshalls (apart from the reissues) but I've always found them a bit buzzy.

siraxeman

I had a 4502 Dual Reverb combo (2x12) for about 10 yrs....it wasn't bad. That said I did mostly use the clean channel + pedals back in those days. I remember one time when I watched another guitarist who asked if he could use my amp...and he was using the dirt channel and out in the audience I actually was quite impressed and thought it sounded great! I always felt it was very easy to make it sound quite harsh sounding. Anyway I sold that when I got a DSL50 head and 1960AV cab...and I thought that was better all round in terms of sound - cleaner more sparkly cleans and smoother distortion on the dirt channel. That got sold eventually and I now have a DSL50 combo...which I still love. I did for a short time buy another JCM900 4502 combo as I saw it going for £150 in Crack Converters in town...so I bought it with full intentions of flogging it on...which I did - for £400. But I did keep it for a couple of months first and to this day I've no idea why but it did sound miles better on the dirt channel for some unknown (to me) reason. Maybe the previous owner had done a mod on it..I'm only guessing. Maybe it was biased better I really don't know but it sounded like a different amp to the one I had for 10yrs. Both were running EL34s to.

rico

@ICBM thank you for the wealth of information.  Just to be an awkward sod, how does the JCM800 combo line up fit in here? I'm trying to narrow down some choices between the 800 or 900 combo or the mini jubilee. Currently have a DSL401 which is about 12 years old and completely stock apart from the bridge rectifier which went pop. Thanks!

ICBM

There are two types of JCM800s - the plain single-channel Master Volume, and the Split Channel & Reverb models - which came in 50W 1x12" and 2x12", and 100W 2x12".

The MVs are the same as the classic JMP ones and are all-valve, but the Split-Channels are more complex and use diode clipping. There are also three distinct versions of the Split-Channels, but they look identical from the outside and are hard to tell apart despite sounding (the first version particularly) quite different. They have quite a dated, 80s rather than 'classic Marshall' sound though so you may not be interested anyway!

Like the heads, the last 100W MV models also have a slightly different circuit layout with 'horizontal' rather than 'vertical' input jacks and don't sound quite the same. Confusingly the 50s also changed the jacks, but not the circuit...

Voxman

The JCM800s don't have the distortion levels you might think and most often when people rave about JCM800 tone they are usually referring to a modded amp or with a tubescreamer or sd1 or treble boost or combination run through the front end.  In fact the JCM800s claim to fame is how well it took boost or distortion pedals.

ICBM

Agreed - a JCM800 MV model doesn't have more gain than about enough for a crunch rhythm sound. You need a pedal for anything approaching modern lead gain levels. All the classic dirt pedals work well, although I think the SD-1 is the best.

The later two versions of the Split-Channel amps have a bit more, as do the Jubilees, but even at the time they were thought of as 'not enough' - one of the selling points of the JCM900s were that they were the first Marshalls that had enough gain as stock and didn't need modding or running with a pedal in front. (Cynics would say that's because it was inside the amp!)