[rlw3]

has anyone used other tubes besides the kt88s and 6bq7s? what differences did you hear? i understand 6550s are hard-they were in my rm9. thanks

[Ericus Rex]

I'm not sure you can use other tubes in the RM 200.  I think it's been optimized for KT88 only.  The RM 9 can use several tube types.  I doubt the RM200 can.  Give Roger a call.

[bullwnkl999]

Per Roger's okay, I used JJ E34Ls in my RM-200 for about 4 months, but you have to make sure the bias isn't too high.  Ultimately I found the sound a bit soft and less focused.  I went back to my RAM KT-88s and there I have stayed, with the 1-ohm taps on my 98dB sensitive speakers.

[rlw3]

thank you all for your interest. If you have not done so i would recommend that you read Roger's remarks in maunufacturers reply to the Stereophile rm-200 review. he clearly states the various possibilities for tube rolling. i think changing power tubes is well known, but i was hoping someone might have used some of the substitutes for the small 6bq7s

[Roger A. Modjeski]

You can use almost any dual triode with the same popular 9AJ pinout and 6 volt heater. Try the 6FQ7/6CG7/6GU7 series for a larger tube.

There's a whole bunch of other 6BQ7 equilavents whose letters are:  AQ,BZ,BK,BS,FW,JK,KN,FW. 

FYI, in the American tube numbering system the first number is the heater voltage, the last number is the number of elements plus or minus 1. Therefore a double triode usually ends in 7 without an internal shield and 8 with. But the rule bends a bit and even though a 6BQ7 has a shield they don't count it. The above list will end in 7 or 8 and any letters following such as "A" can be ignored.

Keep in mind the bias of the driver affects the bias setting of the outputs so be sure to start low and bring it up to 35 mV (my new favorite setting). We can provide ones selected for low offset (to get the bias values equal within a channel) and low hum. If you are rolling from your stach or ebay keep in mind you may find a small percentage that work out well.

Like the RM-9 almost any output tube can be used with varying results... of course. You wont hurt anything. The power with EL34s is 80 watts because thats a pentode as opposed to a beam tetrode. I am very happy with the Genelex KT-88 reissue and several of the currently available 6550s. These can be seen and priced at tubeaudiostore.com

The Genelex is the current winner hands down. One of my dealers is putting them in everything. His last order was 100 pcs.

[richidoo]

I have heard RM9 mk2 with RAM matched el34s, ARC matched SED 6550 and Gold Lion KT88. The KT88 sounded best. Nice tube.