The JBL Model 4430 Studio Monitor

I bought a used pair of these fine speakers in 2002.

The 4430 studio monitors were built from 1981 to 1999. Driver configuration has changed slightly during this period:

The Lansing Heritage website has more information on the 4430 and its drivers.

My 4430 pair dated from the early eighties and uses a pair of Alnico 2421A mid drivers. Even as the efficiency is quite high (93 dB/W/m) the 4430 is quite difficult to drive in the lower bass region. At least for tube equipment. You need a decent damping factor to drive the heavy bass cone of the 2235H (155 gr.) in a controlled manner.

A single-ended, no-feedback 300B is rather not capable of doing that. I have tried other push-pull tube amplifiers but in the end only the Hafler 9505 Transnova MOSFET power amplifier was successful in controlling the 2235H and at the same time providing many of the virtues of SET amplifiers. The Transnova circuit is a configuration where the power MOSFETs are providing voltage gain and power amplification at the same time. You can find more information on the Hafler 9505 including schematic on Hifiengine.

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