I picked this up on a whim. It’s the rarer EL34 version of the already hard to find SL/X model so I couldn’t resist it. I was expecting it to be fun, and I hoped it would be better than the ordinary JCM900 (which I think is the worst amp Marshall have produced). Got it home two hours ago, plugged it in to a Greenback-loaded cab, and… Wow is all I can say! What a massively underrated amp. I’d like to clarify my position here – I’ve owned three Anniversaries which were my main amps for around 7 or 8 years, I’ve owned a 2204, a 2466 Vintage Modern, and I recently had a JVM410 HJS for a few months. Like most of us I’ve played through countless DSLs, TSLs, 2205s, 2210s, 4100s and 4500s in rehearsal rooms and as rented/borrowed gear. Suffice it to say I’m a big Marshall fanatic, but recently I was ready to write them off. It seems to me like there’s lots to recommend their more recent amps – and let’s face it if you want the Marshall feel, you need a Marshall. But in my opinion, apart from the Satriani head, they haven’t got an amp COMPLETELY RIGHT since the 2555.

Marshall JCM900 SL-X chassis
Marshall JCM900 SL-X chassis

Well that’s what I thought until today. This amp is just awesome! The only thing it has in common with the 4100s and 4500s is the look. The tone is CLASSIC. Rich, aggressive, bright, visceral, touch sensitive, real Marshall stuff. I’ve been researching these and what piqued my interest is they use essentially the JCM800 power stage and yet have none of the diode clipping of other Marshalls from the era. The way it works – I think – is that the Preamp Volume knob controls the gain of the first stage, and the Gain Sensitivity controls the gain of the second stage. But the way it actually works is this: Preamp volume gives you gain at all frequencies (and gets muddy as you turn it past halfway) and Gain Sensitivity gives you gain at high frequencies (and yes it gets thin at very high settings). So in other words, these two work like frequency-selective gain controls – or like mixing the normal and bright channel on a Plexi. Except this has more preamp gain than I would ever use – more in fact than the Vintage Modern in HDR and that’s saying something… With the controls near the bottom I get a stock 70s type of response. It’s rich, touch sensitive and bloomy. Great for pop, classic rock and very sensitive to pickup selection and volume pot manipulation. Probably not quite as addictive as the real thing but this is proper classic Marshall stuff.

Marshall JCM900 SL-X rear view
Marshall JCM900 SL-X – rear view

With both controls at around halfway I get a JCM800 fit to burst. Sure it’s not quite the real thing – but it’s ballsy, in your face, bright as HELL (in a good way) and the bottom end is rich and visceral. Like an 800, there isn’t truckloads of bottom end, but what bottom there is feels GOOD. With the Gain Sensitivity would up higher than this, I get early EVH for days. The bottom end is loose(ish) but still big, the top absolutely burns, and it’s got that slight shrillness on the thin strings but it isn’t thin. I’m absolutely over the moon with this amp. I’ve spent a lot of time with the 4500 in the past, and this is completely different. I find the 4500 and 4100 thin, ratty and inorganic, and I spend most of my time on the gain channel wondering why my bottom end went. In my opinion, this amp is the real deal. Try one if you haven’t already and think about picking one up before they go the way of the Jubilee – that’s my humble advice. Just to make the deal even sweeter, the seller revalved it with all JJs, biased it and it’s been played four times since. Maaaarghhh so happy with this deal!