I am simulating this kind here:http://www.diyaudio.com/forums/solid-state/182492-exotic-classa-amplifier-never-seen-before.html
May be help.
It is hard to say, but the sound just only like class A. Better driving method will sounded better. ClassA only make it easier to removes output distortions. without difficult EC.
What is the serial number for your SE-A1? Mine is A11097, I believe there was possibly only about a hundred made which makes sense given their price in 1977!
I was very lucky to buy an SE-A1 this year, its a 100V AC input but has been working fine on the step down transformer I bought for it, though under very heavy use the lamps dim on the VU display so I suspect its struggling at high demand! Time to upgrade the transformer supply
I too have had it go into protection mode once but I don't think this was an issue with the amp, more too much input and the amp protects itself and the speakers, thankfully!
The sound from it is incredibly detailed, I was initially reserved about how good a 30 year old amp could be with technology moving on etc, how wrong I was after hearing the first piece of music through it. It kicks my £3k Sony DA9000ES in to touch and that was very highly reviewed.
I need to try and find a schematic for someone I know who has a broken one, can anyone help?
Unfortunately there are no schematics, you will have to reverse engineer it. There is a shop in Europe that has just done a huge rebuild on an A1 and A2, I'll try and did out the link for you as it looks like a huge job.
I repaired my A1 a couple of years ago but it took weeks and a lot of head scratching to sort. Turned out to be a dry solder joint on a signal diode, caused the low 5v rail bias to go from 7.5a up to 15a! Which then took out the fuses. But just simply getting through the layers of PCB's to get to the fuses is a timely job! Good luck and I hope the customer had deep pockets!
I repaired my A1 a couple of years ago but it took weeks and a lot of head scratching to sort. Turned out to be a dry solder joint on a signal diode, caused the low 5v rail bias to go from 7.5a up to 15a! Which then took out the fuses. But just simply getting through the layers of PCB's to get to the fuses is a timely job! Good luck and I hope the customer had deep pockets!
According to the customer, this pair of amp/preamp is working, but it needs to be refreshed. Mainly, I am trying to find a comprehensive list of the electrolytic capacitors used, to facilitate ordering new parts for a recap. There are probably a couple hundred capacitors in there. I prefer to avoid taking the whole thing apart to catalog every cap and have it sit, disassembled for a week or two as parts orders process. And with something this heavy, I would hope to be as prepared ahead of time as I can!
Here you go, this is a very interesting read with some great photos showing the enormous complexity of both the A1 and A2....good luck and keep us updated with how you get along with it!
https://www.facebook.com/media/set/?set=a.893980034012162.1073741875.550271421716360&type=3
https://www.facebook.com/media/set/?set=a.893980034012162.1073741875.550271421716360&type=3
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