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12AX7 tubes for Music Reference RM-10

I looking to replace the 12AX7 tubes in RM-10 amp. Looking at the manual it says something about "V1" being grade AB and "V2" being BA. Below is a quote from them:
" Note that V1 is a RAM grade AB (section 1 selected for low noise) and V2 is grade BA (section 2 low noise). It is essential to have a grade A section as the first amplifier to achieve the very low noise of which the RM-10 is capable."
The question is: do I need some type of special 12AX7 tube? Do they have to be matched? Balanced? etc...
Any feedback will be greatly appreciated, thanks in adavance to everyone.
jmcp60
14 responses Add your response
magnumpi205
504 posts
 
Roger from Music Reference is Roger from Ramlabs. Seems like the right person to call.
clio09
3,355 posts
 
Yes they have to be matched. The plates should be matched between the tubes in the method specified by RAM, AB for V1 and BA for B2, meaning the outer plates of each tube and the inner plates of each tube.

Best to get the tubes from Roger. I use the stock tubes as supplied by RAM and they are very quiet. The sound is also more than acceptable. I believe Roger can supply some nice Sylvania NOS 12AX7 tubes in addition to the stock Yugo tubes.
gmuffley
132 posts
 
Jim McShane can offer matched, low-noise tubes at a very attractive cost.
mt10425
1,138 posts
 
I'm very happy with the 12ax7 tubes I just got from Jim McShane.
pubul57
3,712 posts
 
The tubes are not special, the way they are measured and matched by Roger is, and they happen to be very good tubes, the Eis that is. That being said, I suspect you would do fine with a set of tubes matched by Jim McShane, or Andy at Vintage Tube Services for NOS. I stick with Roger's tubes because nobody matches better, and he voiced the amp around his tube - keeps tube neurosis from setting in:)
pubul57
3,712 posts
 
Anthony, is Roger only using 1/2 of the tubes? The A half?
gmuffley
132 posts
 
Both halves of the tube are used. One section is a grounded grid voltage gain section and the other is used as a concertina phase splitter.
graywulf's avatar
graywulf
10 posts
 
If you know someone with an Avo or a Hickock? problem solved they can check valves to check the sections match for mu and ma ...
gmuffley
132 posts
 
Both halves of the tube are used. One section is a grounded grid voltage gain section and the other is used as a concertina phase splitter.

Sorry. I meant to say grounded cathode--not grounded grid.
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tonykay
1,301 posts
 
I really like the sound of tubes but after reading this
thread, I think it sounds too complicated to buy used tube
gear. Thanks for stemming my tube neurosis even before it
gets started.
pubul57
3,712 posts
 
TOnykay, you don't have to make the amp, just listen to them, should not be too complicated and you just might find it is well worth the effort to cross the line into tube territory.
hifigeek1
770 posts
 
I have an AVO tube tester in my shop if you need to check some tubes. I've also had very good luck with JJ E83CC/12AX7 tubes if you were looking for a particular brand of tube.
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tonykay
1,301 posts
 
I decided to try tubes in a small way. I boughta tube-driven Stax headphone system. Yes, I like it a lot. So, my
next step will be to buy a McIntosh 275 MkV. If it sounds as good as the Stax, I'll be a convert.
jaffeassc
166 posts
 
I ran the RM10’s in mono block for a few years. I tried several 12 AX7’s during that time. While the stock tubes (EI) are quite good, I found that a good pair of NOS Amperex, to my ears, was a significant improvement. I bought mine from Andy.
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