Hi abrazif,
I have just received an AR P35 and fortunately it is working. The internals look as close to a prototype product as you are ever likely to see so I am pleasantly surprised it sounds so good. I have not found a service manual or schematics for this amp, could you try again to upload for the benefit of the wider DIY audio community and help to keep these amps running.
I have just received an AR P35 and fortunately it is working. The internals look as close to a prototype product as you are ever likely to see so I am pleasantly surprised it sounds so good. I have not found a service manual or schematics for this amp, could you try again to upload for the benefit of the wider DIY audio community and help to keep these amps running.
I actually worked on these when I was just starting my career in electronics. Yep the internals were a bit, errrr, rough and ready! It was fun working with Stan Curtis and I certainly learned a lot at the time. The AR version was basically just a re-branded Cambridge version. I don't recall anything electrical that changed. I seem to recall AR were twitchy about the wooden end cheeks and they had to be treated with fire retardant.
The circuitry/build was certainly a good candidate for tweaking. It was definitely built as cheaply as possible inside but quite a bit spent on the case and turned ally knobs. The offset center source select annoyed me enormously! The PSU components were pretty well specified.
The phono stage was pretty elaborate for the time. Single rail 30V supply, multiple regulator stages (simple transistor regs not IC's). Passive phono EQ inbetween gain stages. Preamp was basic op-amp stage. Power amps pretty standard class A/B.
I'd do basic tests on phono and main PCB's and then they would be assembled into case. Another electrical quick test by me, put headphones on and turn the toroidal Tx for minimum noise via phono stage then Stan would do a full spec test using his fancy Audio Precision (I think) gear.
Generally it was pretty reliable at the time. I think the phono stage regulators could have done with a bit more power headroom.
It's been nostalgic seeing the photo's of it on here. Just realised it was well over thirty years now!
The circuitry/build was certainly a good candidate for tweaking. It was definitely built as cheaply as possible inside but quite a bit spent on the case and turned ally knobs. The offset center source select annoyed me enormously! The PSU components were pretty well specified.
The phono stage was pretty elaborate for the time. Single rail 30V supply, multiple regulator stages (simple transistor regs not IC's). Passive phono EQ inbetween gain stages. Preamp was basic op-amp stage. Power amps pretty standard class A/B.
I'd do basic tests on phono and main PCB's and then they would be assembled into case. Another electrical quick test by me, put headphones on and turn the toroidal Tx for minimum noise via phono stage then Stan would do a full spec test using his fancy Audio Precision (I think) gear.
Generally it was pretty reliable at the time. I think the phono stage regulators could have done with a bit more power headroom.
It's been nostalgic seeing the photo's of it on here. Just realised it was well over thirty years now!
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