50 Watt 2500 SL-X and 100 Watt 2100 SL-X amplifier formats;
Extra ECC83 [12AX7] valve in the pre-amp;
Switchable master volumes;
4 band EQ;
Pre-amp volume control and a Gain sensitivity;
Switchable high and low output;
Valve failure LEDs „
* Prices may differ from that shown
I own a JCM 900 High Gain Master Volume 50 watt combo amplifier that was purchased for me way back in 1991 for my 18th Birthday.
I remember the price was £349, which was pretty reasonable for a brand new 50 watt, twin speaker, valve amplifier at the time.
I remember thinking all my Christmases had come at once when I got this amplifier! It sounded so much better than anything I had used before and made me feel like a bit of a pro player. Not that I was!
The combo is quite compact, and contains twin 12 inch Celestion G12-75T speakers. The speakers are set immediately next to each other in the combo to keep the width of the enclosure to a minimum.
The cabinet of the amplifier is constructed from wood, possibly ply or particle board, and covered with a thick black vinyl covering which is tough enough to stand most bumps and knocks. The front of the combo has a black speaker grill cloth, with a large white Marshall logo glued to it.
This amplifier is powered by valves. It contains two EL34 valves to control the power output of the amp, and 3 ECC83 valves to control the preamp. The amplifier is rated at 50 watts, and although this amp is not as loud as some 50 watters I have heard, it is certainly loud enough for a rock band rehearsal or gig.
The control panel on the front is set out as follows:
Preamp volume control
Gain volume control
Master volume control A
Master volume control B
Treble EQ control
Middle EQ control
Bass EQ control
Presence EQ socket
Volume A/B switch
The back of the amplifier contains the following:
HI/LOW output switch
Effects Send socket
Effects Return socket
DI Output (Recording compensated) socket
DI Output (Normal) socket
Twin Speaker Output sockets
Power lead input socket
This amplifier contains two separate Master Volume controls which allow you to dial in one set volume for your normal sound, and then switch to a second volume control for quieter or louder parts. In my experience, most people tended to use this second volume feature as boost for guitar solos.
Another useful feature is the HI/LOW output switch on the back of the combo. This allows you to switch from 50 watt, HI to 25 watt, LOW power in order to reduce the overall volume of the amp. This is useful for quieter bands, or studio recording where you may wish to have a bit less volume, but still have the amp turned up quite loud. It is common knowledge that all valve amplifiers sound better when they are running close to full volume!
The sound of the JCM900 series caused quite a bit of debate when they were released. Although they won many admirers with amateur and professional guitar players alike, they also attracted a fair amount of criticism from some Marshall fans.
Well it was due to the rather processed nature of the sound. The JCM800 series, which preceded the JCM900, featured a number of amplifiers that some consider to be among the best Marshall ever produced. They had a fairly raw sound to them, with a great deal of the classic Marshall high end bite. The JCM900s however removed quite a lot of the rawer sound and made it much smoother and processed, more in keeping with the trend for guitar sounds at the end of the 1980s and into the early 1990s.
This smoother sound suited some players, but caused other players to level criticism at the JCM900s and claim they would be sticking with the earlier Marshall amps. This is a stigma that has stuck to some degree. On the second hand market, the JCM800 series regularly fetch higher prices than JCM900s.
My personal view is that both the JCM800 and JCM900 series sound very good. It is more down to personal preference for guitar sounds, and the type of music you play as to which series you prefer.
Anyway, as said above the JCM900 is all about producing smooth, slightly processed sounds.
The pre-amp and gain controls on this combo allow you to dial in clean sounds to all out distortion. It must be said that this amp does not have a great deal of headroom for clean sounds, it is more suited to distortion sounds. You can achieve a clean sound by setting the Gain control to 0 and the Pre-amp control to about 2. However, the more you turn up the Master Volume, the more the sound goes from clean to crunch! If you’re after an amp that does clean and loud, you’d be better off with something like a Fender amplifier.
However, if you like your guitar sounds to be distorted, this is definitely the sort of amplifier you would like! Pushing the Pre-amp control above 5 gives you the beginnings of distortion, a crunchy sound that is suited for blues and classic rock. Pushing the Pre-amp control up further and bringing in the Gain control allows you to dial in some very distorted sounds, suited to heavy rock and metal styles.
The distortion on the amplifier is very smooth, the EQ controls allow you to add a bit of extra treble, middle or bass, but the change is not that drastic. In some respects this amp could use a little more bite to it. When playing in a band, some of the guitar tends to get lost as it fails to cut through quite as much as you might like. Of course there are ways around this such as pushing the Master Volume up further, or getting an extra speaker cabinet in order to spread the sound out a bit further and allow you to compete with the other instruments better.
The combo has a useful effects loop included which allows you to wire up a series of effects foot pedals to your amp. The loop works pretty well and also features a mix control to allow you to alter the level of the loop depending on what sort of effect you are putting through it.
The DI outputs on the back allow you to send the sound of the amplifier to another source such as a mixing desk, or another amplifier. These are quite useful, although it has to be said that the recording compensated DI output tends to push out quite a harsh sound that isn’t that well suited for recording, as I’ve discovered in the past! Much better to just stick a microphone in front of the amp turned up loud to get the sound you are after!
In terms of reliability, in keeping with most valve Marshall amplifiers, these things are pretty much bomb-proof! They should give years and years of service without breaking down on you.
Overall then, I think the sound of this combo is very good. It can still compete with most modern combos in terms of the amount of distortion in can produce. It is also quite a flexible package with the effects loop, master volume switching and power output switching.
These combos represent very good value for money on the second hand market, so my advice would be to try one out. If you like the sound, go for it!
Thanks for reading!