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Audio Research SP5 issues

rudedogg

rudedogg

AK Member
Subscriber
Hey all. I have an old Audio Research SP5 solid state preamp. It works very well for 1/2 hour. Then once warmed up it has a “snap, crackle, pop, like a failing transistor. Being this preamp has the dreaded gain modules, i fear it is a door stop. The noise is in the right channel only, but is present in all input selections, and appears regardless of volume and balance positions. The power supply seems stable, i see no DC spikes while it occurs. Sooo i think it is the right module failing. They do get pretty warm. Any chance somebody has actually fixed one? Or developed a workaround?
Thanks!
 
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I followed @ConradH updates to an sp4 and thought it was ok. I've since sent it down the road. I've not seen a sp5.

If I didn't like it I was going to install my own hafler dh-101 line level boards with the taa updates. I stuffed a board but never installed it.

No idea how to fix that potted gain module in your sp5.
 

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not having any familiarity with these, is it possible to swap the modules channel to channel to see if the problem moves? That would at least confirm where the problem is, if not what it is.
 
gadget73 said:
not having any familiarity with these, is it possible to swap the modules channel to channel to see if the problem moves? That would at least confirm where the problem is, if not what it is.
Click to expand...
I will have to look at pinout. But i bet it is the same… and a good diagnostic tool
 
did some poking, seems like these are more or less like an op amp, but made of discreet components and all potted in a plastic blob so as to make it unserviceable? Sounds fun. It borders on heretical but I might be tempted to just make up a perf board that brings all of the connections to a DIP8 socket and use some decent but available op-amp.
 
Yeah they're dying for sure. I have schematics for AM 1, 2, and 6, but not the others.
I'm also not smart enough to design something that would work based on the original schematic. Bummer, the units are built well.
 
Those are the previous poster’s bay offerings of some of the NLA devices he has designed and had built making them available to others.

I don’t know and you can see ivandezande can’t confirm that these would work.


Someone should be able to measure a working SP with these modules and get basic operational information to be able to replace the modules with something.
 
hey blue, the diyaudio link conrad shared hinted the modules are a unity gain buffer. gadget's suggestion to use an opamp would be a great idea.

no idea if this will work or if I even comprehended the diyaudio thread. plus it will take time.
 
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