Audible Illusions Modulus 3A noise

I recently purchased a used Rogue 99 Super Magnum with phono stage. When I hooked it up I could hear static noise/hissing which was not acceptable. Before I did anything I replaced all of the tubes which were tested for shorts, Gm, and noise. These were purchased at a premium (only a few dollars more than standard retail). After warming up for 30 minutes I placed my ears next to a speaker and turned up the gain and volume to max. I couldn't hear a thing. Then I brought in my wife who has incredibly sensitive ears and asked her if she could hear any hissing, humming, buzzing etc. NOPE!!! I had the preamp connected to an Accuphase A-36 power amp and then to Fritz Carrera speakers. My signals input to the preamp were a Yamaha CD-S2000 and Thorens TD-1601 with Ortofon Cadenza Blue cartridge. That system as assembled is very quiet now.  

That sounds like a bad tube. You can try cleaning the sockets and pins  first tho.

If you plan to keep your AI in stock form, I suggest only using Russian tubes, Sovtek or the 1975 Voskhod 6N23P.

Do NOT try any others especially not an NOS type tube.

I've been repairing and referbishing AIs for around 15yrs.

Feel free to email; hope I've helped.

Purchase tubes from a reliable seller it will be cheaper and the tubes will be just fine. Personally I'd go for NOS or good older pulls over current production 6922s. JAN/Phillips 6922's are typically a solid value. AI preamps have a ton of gain so they can really magnify a noisy tube make sure you get whatever you buy tested for noise.

@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. 

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.

@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.

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.

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... 

@carlsbad2 , the preamps are not mass produced as the company is extremely small.  The wait time is usually 6 months or more.  I believe Art Ferris is either retired or semi retired.  

I have owned 3 AI tube preamps since 1994.   I had the original Modulus 3, the 3A, and the 3B. None of them gave me tube noise or hiss.  The key is to get your tubes directly from AI,  or find matched sets of 6H23NEB tubes for the preamp, they are very rugged and quiet   You may find them at the Tube Store or from Upscale   Your noise will disappear like magic, poof  

6922's can be very noisy.  I have had good luck with a lot of the older tubes.  I don't use the term NOS because they are almost non existant.  what most sell as NOS is just a used tube that tests well.  which is really all you need.

I haven't had much luck with the new production inexpensive tubes. 

I don't know that pre, and in that price range is is likely mass produced PCB based, but assuming it doen't have design or build problems, tubes can be found that are dead quiet. 

Good luck,

Jerry

It is used 

Best advice is buy a replacement tube from a dealer that tests for shorts, Gm, and noise. It's only a few bucks more per tube. 

If it uses 6922 like most of their gear does then i would suggest Gold Lion 6922 phono pre grade.  6922 are hit or miss.   The NOS are rare and expensive and honestly many are strong "pulls" from 1960s and 70s lab and medical equipment. It was used in test equipment before audio and many "NOS" are just nos testing used tubes.    Don't waste  money on those .

JJ tubes are good, like others the 6922 is hit or miss. Best to buy screened for noise also.    I had a CJ preamp that was tough on tubes and only two types lasted.   Gold Lion 6922 gold pin and genuine Volkshod Rocket label from the mid 70s.  I have a pair of those in my DAC and they are great if you can find them.   Still I would recommend new GL for that pre.   

Is it new or used?