I recently ordered a quad of RAM matched Russian EL84 tubes and had to report on what I heard last night.
To back up just a minute I recently rebuilt my already modified version of the Dynaco ST35 amp. Rather than the traditional 12DW7 driver tube I'm using a RAM tested 5751 for voltage gain of both channels followed by a 12AX7 or 12AU7 phase splitter for both channels. Eventually I want to rewire the latter for a 6CG7. You know... for fun.
I modeled my rebuild as a cross between Roger's amps and the classic Dynaco ST70. I think it turned out pretty good-looking.
Anyway, after living with a set of "matched" tubes from another vendor and having at least 2 of them start squealing on me at warm up I was ready to see if Roger's tubes would work better.
And holy crap do they! The first thing I noticed thankfully was that everything was dead quiet on start up. I set the bias and played some music at low volume for a couple of hours to let them warm up for a while. Eventually I was able to sit down and listen and I noticed something was wrong right off the bat. I had a feeling one of my speakers was out of phase and sure enough I found that was the case. After fixing the speaker connection I sat down again and was impressed by the clarity I was hearing but now felt the need to adjust my speakers a bit. Once I got them into a better position I sat down again and listened.
The most obvious difference was depth. Some recordings shifted back a good 5-6 feet behind the speakers! Detail was excellent and the dynamic range seemed better than ever. I'm amazed at the difference a properly matched set of tubes can make in this little amp! I was enjoying it so much I passed out in my seat! I have a pair of modified Dynaco Mark IV's I've been trying to sell but now I think I may retube them first and see if they may be worth hanging on to.
Highly recommended!
