Thanks for the update. The RM-9 is a great amp. Since you have the MkI version down the road you might consider sending it to Roger to be upgraded to MkII.
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The Marantz amp has earded its rightful historical appreciation and is a true collector item.
However if judging strictly on sonic merit the RM-9 is better sounding(as you discovered) due to better passive parts(Marantz has very good transformers). The RM-9 given your description very likely has a well designed and stout power supply. A 'good' tube power amp will provide the full realistic tone,timbre and natural color of instruments but avoid the overly warm lush and excess flab and sweetning. Seperation and clarity will be first rate without smearing and congestion. I find bass produced by the better built tube amplifiers to be most natural and honest without artificial 'slam' and dryness.The texture and nuance just sounds right.Testing different tubes could possibly improve the sound further.
I`m a huge jazz fan and can relate to your taste and happiness when it just sounds right.In my case simply upgrading my 300b tube (Shuguang Black Treasure to the Takatsuki-TA)my SET amp went from very very good to sublime music reproduction.
09-04-12: Clio09ach, I see Clio09 got here before me!! ;-)
With no disrespect to Clio09, IMO do *NOT* make the mistake of upgrading the Mk1 to Mk2. My friend had the Mk1 & after several years his curiosity got the better of him & he sent it in for an upgrade to Mk2 & that was a mistake, he admitted. The sweetness of the amp was gone in Mk2. The Mk2 had a much bolder, powerful sound & the delicacy of the Mk1 version was gone. This was bad news for my friend & he ended up selling the RM9. I listened to his system with the RM9 Mk1 & the RM9 Mk2 & I concured with him - the RM9 Mk1 was a much better tube amp. And, Mk1 version was powerful enough to drive his PBN Montana speakers.
This should explain the differences in the various versions of the RM-9. Second post is from Roger:
Coupling capacitors were not replaced, nor do I feel these would make a difference in Roger's circuit. In addition, to me the sound did not change all that much between the versions. That said I feel the RM-10 MkII is an overall better amp than either the MkI or MkII version of the RM-9 if you can live with 35 watts.
Thanks very much Pehare. Yes, Roger has been extremely nice and helpful. I only wish I could get him to explain everything he knows to me, but that might be a long phone call.
I believe it has the original tubes and the transconductance on my TV-7 is 39-41 for all 8 tubes! I also got a set of RAM KT-88s but haven't tried them.
I probably will upgrade to a MK-II at one point, after I've gotten extremely familiar with the Mk-I. Roger said he'd just sell me the parts and let me install them. That way I can switch back if I want.