I have used my Epiphone Valve Jr for this, but I’ll mod that one for pure guitar use rather than guitar/bass use. This amp can be modified into many uses, but my primary goal was to make a low-watt bass amp for practice and recording. The circuit between the volume/tone controls and the output transformer is pretty similar to the Mullard 5-10. Negative feedback from the 16 ohm tap through an RC network into the cathode of the second EF86 stage. Signal path: Left machine/right machine/jack inputs -> first EF86 as triode stage -> line input -> tone/volume controls -> second EF86 as pentode stage -> direct-coupled ECC83 LTP phase inverter -> cathode-biased EL84 output tubes -> ultra-linear output transformer -> speaker outputs (taps measured to ~6 and ~16 ohms). Screwdriver trim pots on the left side for adjusting DC for left and right machine photocell pickups. Speaker output and power input on the rear right modular socket. Volume control, tone switches, speaker output jack and meter/switch for checking tubes and output voltage on the front. Input jack on the left side and terminal inputs for left machine, right machine and line on the rear left modular socket. Two EL84 power tubes, two EF86 and one ECC83 in the preamp. Six-pin modular sockets on the left and right rear edges, probably for easy amp swapping. No brand/model name on the amp itself, but saw that name on other movie projector equipment in that attic. The guts before I started working on it.īuilt by Hans H. I brought it back to my work headquarter and removed the top cover, found a pen and paper and started tracing and sketching the circuit. He told me it had been in use for the last time in the early 80s. I met the guy in charge of the technicalities of the house and asked if I could have this amp I was free to grab it. I was back at that community house in early February on another sound engineer job. I’ve been thinking of this amp since, wondering what kind of amp this could be modified into. It was quickly inspected before I nicked some of its tubes and put it back where I found it. Power and signal cables on side terminals were cut. Seemed like it belonged to a movie projector system, probably built in the 1960s. About a year ago, on a sound engineer job at a community house, I came across an old tube amplifier in the attic.
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