Few different ways, but you need to define what you want to do:
1. Sending unit to ARC
2. DIY... Normally Audio Research tech specialists are capable to give you information where you need to look for failures and sell you necessary parts so you can replace them yourself. I can also help ID-ing bad components and other DIY guidance.
3. Local repair specialist if available.
What you're describing is common problem in built-in stages that pick up the noise from line componets due to their very high sensitivity OR have a bad tube.
1. Before examining circuit components, I would HIGHLY recommend inspecting the solder joints around all RCA plugs inside the preamp box.
2. Try to replace phonostage tubes(ARC definitely will help you ID them if you can't) that are in most cases inexpensive or buy inexpensive ones first to test if the problem dissapears.
3. If the problem still there, you'll have to examine PCB solder joints and circuit components mainly ones that isolate ground and power supply(see DIY).
1. Sending unit to ARC
2. DIY... Normally Audio Research tech specialists are capable to give you information where you need to look for failures and sell you necessary parts so you can replace them yourself. I can also help ID-ing bad components and other DIY guidance.
3. Local repair specialist if available.
What you're describing is common problem in built-in stages that pick up the noise from line componets due to their very high sensitivity OR have a bad tube.
1. Before examining circuit components, I would HIGHLY recommend inspecting the solder joints around all RCA plugs inside the preamp box.
2. Try to replace phonostage tubes(ARC definitely will help you ID them if you can't) that are in most cases inexpensive or buy inexpensive ones first to test if the problem dissapears.
3. If the problem still there, you'll have to examine PCB solder joints and circuit components mainly ones that isolate ground and power supply(see DIY).