Most of the Marshall predecessors were tube amplifiers.
That means, the signal has been amplified by tubes in the preamp as well as in the power amp – without any transistors.
The most famous models were the Marshall JTM45 and the JCM800.
When the JCM900 has been put on the market in the 1990s, some guitarists were pretty disappointed because the distortion of this model was created through transistors and diodes.
Those who called themselves the “true” guitarists refused to use the JCM900 – and some still do so today.
The reason why Marshall used transistors for the JCM900 was quite simple: guitarists all over the world longed for more distortion than the well-known models were able to offer.
The JCM800 maybe was and still is the most famous tube metal amps of those days.
But in the end the JCM800 does not create as much gain as you would expect him to do- especially the non-master volume version.
Besides you will have to turn up the volume of the JCM800 until you get the striking tube distortion.
This is why almost every guitarist who owns a JCM800 (or also the JTM45) uses a distortion pedal to as a booster.
Mostly this is a Tubescreamer or some kind of fuzz or treble booster.
One thing you should keep in mind: A distortion pedal uses a transistor and diode clipping.
The JCM900 is nothing more than a combination of a tube amp with a complete tube power amp and a preamp with a transistor distortion.
The Guv`nor and the Bluesbreaker are only two proofs for Marshalls competence in creating outstanding distortion pedals.
The JCM900 is one of the few amps that even at low volume sound pretty good.
Famous users of the JCM900
There are numerous guitarists who used and still use a JCM900: Billy Howerdel (A Perfect Circle), Jeff Beck, Josh Homme (Queens of the Stone Age), Billy Joe (Green Day), Noel Gallagher (Oasis), Dave Navarro, Ace Frehley (Kiss), and many more.
And there are also some guitarists with a legendary sound although they are using a tube amp with integrated transistors.
The Marshall Silver Jubilee also has a transistor preamp and is used by Slash, John Frusciante and Joe Bonamassa. So, it cannot be that bad.
In my honest opinion, the JCM900 has been put on the market far too early.
Or, that the pioneers are always having a harder time.
Today, guitarists use completely digital solutions (AxeFX, Line6) and swear on their tube-like sound.
The JCM900 is hardly underrated and therefore the prices of used versions are pretty low. So maybe it is about time to try it out before this amp too becomes an expensive collector`s item.
And if you definitely don’t like the sound at all, you can plug a separate preamp into integrated effect loop to use a cheap true Marshall tube power amp.