This four-channel beast is a hybrid valve PA amp, built by a bloke named Jim Farrington in NSW sometime in the late sixties or maybe seventies. From what I can tell, they mostly stayed local to where he lived, and you don’t see many pop up anywhere. I picked this up on eBay, and it was sent from his hometown.
Looking at the few photos on Ozvalve Amps, it seems he used the same head and chassis for most builds, swapping out the control panel and designing amps to suit whatever job it was for.
There’s no schematics around, and I’m not about to trace the whole thing — there’s just too much going on. I might figure out the reverb section though, and maybe keep that as is.
VINTAGE FARRINGTON PA AMPLIFIER
SPECS
It's going to be a little vague at this stage, and might stay this way.
- 4 x solid-state preamps: bass, treble, level, reverb. Hi and lo impedance inputs
- Master volume, reverb and tone controls (bass, treble)
- The modulation indicator lamp is not related to signal modulation or trem of any kind
- Reverb: valve driven, Hammond / Gibbs 1122 tank. 6BM8 to drive it
- 4 x EL34 fixed bias output stage
- I'm guessing some kind of 12AX7 based phase inverter
- A&R transformers
- Solid-state rectifier
- Line output from the speaker terminals
PLANS
The plan is to rebuild it, swapping some of the solid-state preamps for valve ones, but I’ll probably keep one solid-state channel just to hang on to a bit of its history.
Channel one: Guitar effect, probably a boost
Channel two: Solid state
Channel three: Fedner preamp with bass and treble controls
Channel four: Pentode channel of some description
Master tone controls to be removed. I'm guessing this amp will need to keep the master volume, as it has a reasonable amount of output power
As each channel has two input jacks, I'm considering a modular approach, with an in and out for each channel.
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