James B Lansing SA-600 AMP/Kenwood combo sale. (FREE SHIPPING)

RARE James B. Lansing Sound JBL SA600 Integrated Power Amplifier.. Condition is "Used" AS IS. Shipped with USPS Priority Mail FREE to the buyer.

It was recently tuned up and serviced after being discovered. Can supply documentation from the shop that serviced and cleaned it. The unit works perfectly, 100% original  :) This is a really cool, rare pice from the early days of JBL. Restored, pristine units can commonly go for 4k.

Buyer will receive the Kenwood unit as well.

Feel free to email questions. Rare find, add it to your collection NOW!

****In the mid 1960’s, most engineers were still working with tubes with low loop gains and were not equipped to deal with the high loop gains that multi-stage solid state amplifiers offered. However, the SA-600 designer, Bart Locanthi, had cut his teeth on military guidance systems in the 1950’s – the heyday of the analog computer – and would have been, as I have remarked elsewhere on this site, highly cognisant of things like slew rate, slewing distortion, loop gain, phase margin, overshoot and so forth.  Unusually for the time, the front end diff pair (Q7 & Q8)  is degenerated and loop compensation provided by an 82 Ohm and 150 pF resistor across their collectors along with a 220 Ohm and 75pF network from the VAS output to ground.  It operates in inverting mode, which has been tried on numerous commercial amplifiers over the years (the modern take on this is that non-inverting mode offers advantages with respect to noise performance).  This design delivered 30 Watts RMS per channel, which was more than enough for the efficient loudspeakers of the day, and quite in line with the general power levels on offer from tube based gear.