Marshall Studio 900 Review

Replicating the experience and sound of the 900s—the 50- and 100-watt, trouser-leg-flapping monsters from the golden age of grunge and metal—with a 20-watt output stage isn’t easy. As with the previous Studio models, one key to success is the use of large 5881 tubes, but in a cathode-biased output stage driven by lower plate voltages than in the big-bottle amps of old. Along with the ability to retain the beefy, full-throated sound of the originals, this approach yields longer life from tubes that are built to withstand much harder use. And, since the output stage is cathode-biased, a tube change means simply popping in a new pair of 5881s and off you go, with no re-biasing necessary.

Marshall aficionados will note that the JCM900 series amps were originally made with EL34 output tubes, and later 6L6s (which are direct substitutions for the 5881s used here). It was also fixed-bias rather than cathode-biased in both cases. In a circuit like this, though, the high-gain tone is driven much more by the preamp circuit, which is built around two 12AX7 tubes (plus another in the phase inverter). The Studio version also uses diode clipping to increase saturation levels in the style of the high-gain stage in the original 900 Series.