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Proton AA-1150 Power Amp distortion fixed!

Rick Sykora

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#1
I have had this for a while now (decades actually) and has performed well for me (it has dual mono construction and that is REAL glass across the front!)...
proton amp.jpg

Except every now and then I would hear "distortion" during some piano passages on Dire Strait's Love Over Gold. I took it to my (otherwise very competent) local repair shop (twice) only to have the owner swear there was no problem with it (twice). So, the challenge was on and, after some internet searching, found something that suggested the output protection relay contacts were dirty. Sure enough, I cleaned the contacts and all was good again. :)

Recently was considering putting it up for sale and did not want new owner to have any issues. So, started looking for some replacement relays. The originals are Sanyou SRU-S-124D 24Vdc. Talked to my tech and he suggested Newark. Tried the site and did not find. Then called Newark and got crappy service and almost gave up. I then found a cross reference online and a NTE R46-5D12-24 relay was suggested. The specs looked very close and the leads had the correct spacing too. Wholesale Electronics had them for $3.50 each and so I ordered. After a bit of careful unsoldering, the new relays are in and work great!

As I am sure there are some other Proton AA-1150 owners out there (along with the more powerful D1200 that probably used the same output relays), thought I would share. Mine is not currently for sale, but my repair tech wants it badly so will likely trade-in when he gets something I want.
 

Angsty

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#2
The Proton AA-1150 was/is a beautiful amp. I owned one for about 10 years, but I sold it to get a Bryston. The reduction in noise and distortion was substantial when driving difficult speaker loads. No regrets with that choice, but now I’m wondering if it was a design issue or a maintenance issue.
 
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