Tubes for Modulus 3A

I took delivery of a used Modulus 3a today. I have a Modulus 3 which will go to my second system upstairs. I am not happy with the sound of this preamp, it sounds a bit thin, not much bass. I replaced the tubes with new Sovtek 6922's, but I am still not there yet.

I don't want NOS tubes and want to keep the price low and I also don't want tubes that will die in a few months. Recommendations please? I want more bass!!!
Have you tried using the tubes from your 3? What result?
I didn't try the tubes from my other preamp as I had already installed it in my office system. The sound seems to be getting better as the tubes break in, There is definitely more detail than my Modulus 3 had and the bass is tight, but not full. Rest of the system is Classe 15 (175wpc) amp, Vandersteen 2ce signature speakers, Raysonic 168 cd player, Marantz 8001 sacd player, Magnum Dynalab tuner. All cables and speaker wire are MIT Terminator 2, and power cords and conditioning is courtesy of Shunyata.
Have you tried a pair of Mullards? Though a little pricey there are bargains around. The Modulus pieces are hard on tubes from what I read.
Tungsram 6922s are cool!!!
That's one tube I NEVER skimp on. Manufacturers used the 6922 because of its quality compared to a 12ax7 and such. Good 6922 can make or break a system. You don't need to break the bank but $100 pair is well worth it, amperex, mullard or such. I actually like Golden Dragons if you can find them.
Keep in mind that 6922's will last up to 10,000 hours. Much longer than other types.
I previously owned a Modulus 3. The prior owner inserted a brand new quad of National 6922 tubes. I got less than 300 hours out of the new tubes. They became microphonic. I sold the preamp and the buyer tested the tubes and confirmed they were spent. I think AI recommends Russian tubes which are known to endure inspite being run at the limit. There's no reason for a preamp (properly designed) to cook tubes this way. Not meaning to put down your choice of preamp - they do sound nice. I just could not see retubing yearly. Mullards or Amperex may sound nice but probably will not last long in these preamps. A costly affair over time.
Here are the ones that Kevin Deal recommends from Upscale Audio. He has never steered me wrong over many years and many many tubes:
Like it or not you have to use rugged tubes in the AI. Unfortunately most of these are threadbare Sovtek types, including 6h23's (which I use in my ARC SP10 because like the AI it also requires rugged tubes). You might try some EH6922's. They have very different tonal balance than the Sovteks and might work in the AI. Since I believe these were the tubes which were OEM with Raysonic's you might just have some on hand to try.

How I solved my problems with the sound of 6h23's in my ARC was to find my 'warmth' in my phono cartridges, or tubes in DAC's or CDP's. For example with your stuff I'd try some EH6922's in the AI and some JJ/Tesla 6922's in my Raysonic. I'm familar with the sound of JJ's in the Raysonic (128) and they can sound quite lush. That Raysonic might just be the source of the warmth your system needs.

Funny you mention this as that is exactly what I was planning on. Yesterday, I ordered the JJ6922 tubes from The Tube Store and when they arrive, I will put the EH6922 tubes from my Raysonic into the Modulus 3a and the JJ's will go into the Raysonic. I think it will be the best of both worlds. Although the EH6922 tubes sound good in the Raysonic, I think the JJ's will give me the exact sound I am looking for.

I will report back once the switches are made and the new tubes have broken in.
I use cryo'ed 6H23-EB's with Herbie Tube Dampers in my AI Mod3b. I also use 3 cones (points down) for isolation.

what is the difference between the 3a and 3b? There is no mention of the 3b on AI website.
The differnce between a 3a and 3b is about 12 months of wait time. All joking aside Art made severial refinements (I would need to review the manual) but I was never able to pin him down. That being said it's a great unit.

Sorry I can't be of more help.
Art Ferris called me this evening regarding a post I made about my secondary preamp the Modulus 3 (origional) I have a problem with one channel in the phono section and we had a great chat. He said their web site will be updated before the end of the year and that he is making the 3b now and it has much more refinements than the 3a. He did tell me to be careful regarding the EH6322 tubes as the newer ones are junk, perform poorly and microphonic as hell.

He really made my day!

You should get your tubes from him... more often than not it is better IMO to go to the manufacturer.

I have owned a Modulus 3A for many years. I breathed new life into my unit by replacing the 400V 100UF electrolytic capacitors with new ones; same brand and value.
One of the electrolytics is too difficult to replace, I left it in. I found room to replace one of them with a Jantzen cross cap metallized polypropelene 100UF 400V capacitor.
I believe this will solve your problem. As for the tubes, the 3A does not give any great response to expensive tubes.
Apparently, my experience with tube rolling in the M3A is the exception to those previously stated. I've owned the M3 and M3A preamps for about 13 years and only replaced the tubes once in order to gain more midrange warmth and detail. Our local electronics wizard suggested Amperex Bugle Boys. If memory serves they were about $100 each. No question they improved this preamp one to two orders of magnitude. The entire soundstage was much bigger, warmer and more detailed. Mr. Electronics wizard went on to say Russian tubes were designed for industrial use and while they are well-made and typically have long life, they are not intended for audio applications and their sonic characteristics are inferior. I have used tube amps and preamps for almost twenty years and must say the AI equipment is among the most reliable of the various tube equipment I’ve owned: BAT, Beard and Herron.