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RE: Audio research preamp broken

Posted by fredtr (A) on September 30, 2020 at 10:59:49

In Reply to: Audio research preamp broken posted by tunenut on September 28, 2020 at 17:40:48:

I have a couple of older ARC preamps, an SP3 and SP11. I like working on equipment so when I have had problems with these I repair and update them myself. I haven't seen a problem that matched yours, but the SP11 did have a PS problem that caused the lights to do unusual things, and no sound. It was just a capacitor, cheap, quick fix. I didn't post this because of that, it is to pass along the impressions I have of the ARC equipment, which is excellent design, build quality and components. I doubt you will ever have to replace the coupling capacitors, about the only thing that I have seen age in mine are the tubes and electrolytic capacitors.

The schematics are very good, and my experience is that the equipment has been very easy to repair. ARC uses currently produced tubes, the SP11 uses 6922/6DJ8's and I would not use the currently produced 6922's that ARC will try to sell you. I found the Philips and other older tubes sound better. I have a friend that has a pile of these from old oscilloscopes and I'm sure there are other sources of inexpensive good sounding 6922's. Sorry I couldn't find the reference 1 at the ARC schematics download site to see what tubes and FET's it uses, and to guess at the source of your problem. I can see the other Reference preamps, is it also known under a different name?

So if cost is your concern, either ARC authorized repair, of anyone else that does electronic repair, but tell them what you want done. First the repair, which most likely will be inexpensive and then discuss with them replacing any electrolytics, I just measure ESR to decide what to replace if any. And for tubes, buy some, replace them yourself and listen.

I have had very few problems with these older ARC preamps. I did do a lot of experimentation on the SP3 to see what changes did what, meaning I would change something and then listen. I'm mentioning this because I would not be concerned that this will be the first of many fixes. Get fixed what is wrong, and do a bit of updates if needed and you should be fine for a long time.

I mention this from time to time. I go to hamfest's mainly for the entertainment factor. These are almost all old nerd's that like working on equipment and know electronics. Many of these guys would diagnose and fix your preamp for almost nothing.

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