Audible Illusions Modulus 3A noise

Kevin,

Since your preamplifier is used you really don't know how many hours are on the tube set. AI preamplifiers are notoriously hard on tubes and sensitive to tubes that do not have a low noise floor. I would second @stereo5's advice and contact Upscale Audio regarding what replacement tubes would be recommended. For what it's worth, owner of several AI preamplifiers over the years and many tubes purchased from both Upscale Audio and The Tube Store... 

Have you tried switching the line stage tubes, left for right? If the noise moves with the tube swap it is the tube, if the noise remains in the same channel, after the swap, then the issue is the preamp. Best of luck.

@viridian I am going to try this, the procedure is outlined in the manual I have.  I just think that these electro-harmonix tubes that were in it represent a low cost alternative that perhaps just don't work very well.

Anyone have experience purchasing tubes from AI?  I see you can purchase from their website.

I have purchased tubes from AI. Rather expensive, IMHO. Agree with stereo5, who clearly has purchased tubes from AI as well, as long as the tubes are determined to be the issue.

@tubegb  

“AI preamplifiers are notoriously hard on tubes and sensitive to tubes that do not have a low noise floor.”

Your statement is grossly incorrect. Here is an L3A that is literally on more than it is off. Thousands of hours of usage on the tubes. No noise. Plus the unit was purchased used so who knows how many hours were on the tubes beforehand. 
 

One issue that occurred was a noise similar to a bad tube noise. The fixes, yes plural, was a cheater plug on my mono amps. Also one set of my RCA cables allowed noise into the preamp. Replaced that cables, dead quiet.