Our singer's birthday last night. Some friends of ours played the bulk of the night but we used their gear to play half a dozen songs. So I got to use a Marshall SLX half stack. I decided to set it up pretty much how I did the 900 - take the treble and presence right down and bring a bit of it back to hit the sweet spot. Very different sounding amp to the 900, it seems to be aimed at guys that like a scoop in the mids which personally I don't. I was playing a bit louder than I usually do as it was a large pub.
Got an okay sound and went into our first song and the sound disappeared completely. It did not cut it in the mix at all mainly because of the weak mids. My mate Dave, owner of the amp, tweaked it while I was playing and got it sounding better but he also had to turn it up a lot more to get it to cut through. As far as I know the SLX is all tube whereas the 900 uses diodes in the gain circuit but I much preferred the sound of the 900. The 900 had much stronger mids and a lovely grainy quality to the overdrive that was absent in the SLX.
Still, it's fun to try different gear.
The SL-X is mostly valve and doesn't use diode clipping, however given that it has a preamp topology like many great high gain amps it doesn't sound the best. There are some odd choices in there for frequency filtering and the tone stack does next to nothing to help you out. It's not a tone stack with typical marshall values around it. Also, the master volume switching is done using solid state, so after the tone controls (which are late in the preamp) the signal needs to be dropped so it doesn't fry the opamps, then later on its switching opamps that drive the phase inverter, which is valve again. The don't sound the best, but their rep is that they are the best of the 900's. Probably easier to work on them and mod them than the rest of the 900's too.
The JCM900 4100 dual reverb is a hybrid amp. It's not just that the clipping is done with diodes (like the friedman/jose/cameron mods) its that most of the preamp is solid state. The tone controls that you can tweak are driven by a valve gain stage and cathode follower (one whole valve) the tonal impact of which is debatable, by which i mean may be it would be better to have the valve at the first stage and the tone stack driven by opamps, but there are a couple of opamp gain stages your signal goes through before it gets to that point. There is a single valve gain stage which give you a "presence" control in the preamp (I think), and the other valve is the phase inverter. The first couple of gain stages are opamps, the FX loop send and return stages are opamps, the reverb driver and recovery stages are opamps and the master vol switching is opamp.
