Can someone recommend replacement tubes for my MFA MAGUS A2 Preamplifier please?

I suggest calling Andy at Vintage Tube Services for NOS tubes.

Plenty of current production tube sellers including:
Tubedepot.com
thetubestore.com

Below is some information that might help other who want to offer their advice. There is also a FAQ on tubes at audioasylum.com

 Classic MFA Magus A2 preamp designed by Bruce Moore. Has outboard power supply, 2 12ax7s for phono and a 12au7 and 6DJ8.

Thank you JPerry. I did reach out to the Tube Depot who were very patient and helpful. I ordered 2 of the Tungsol 12AX7 as a start and I’ll see how they help. 

I've been there with other equipment.

problem must be isolated before jumping to new tubes.

problem in both channels?

what channel?  first move tubes 1 at a time l to r, see if problem moves to other side. If not, switch another one.

cables? anything new?

rare, but something in speaker crossover could be amiss, do you have small speakers to hook up just to prove the problem persists with any speaker?

Here's a suggestion: call Scott Frankland (the F in MFA) and ask him directly. I spoke with him yesterday about my Magus preamp and he is very helpful. His number is (408) 926-6731.