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Picked up a Vacuum Tube Audio SP9 tube preamp today. Replaced the JJ tubes (sounded terrible) with 2 Telefunkens and 2 NOS JAN sylvanias, all four of them 12AX7's.
What a difference it made with my MC40's. These Altec's never sounded so good.
Pictures at this thread.
Vacuum Tube Audio SP9 Preamp, Any good? | Audiokarma Home Audio Stereo Discussion Forums
I'm grinning.
BillWojo
That volume control action when switching sources is just too cool for school!
GeeDeeEmm
It is, the first time a did it I was surprised to see the knob rotate all the way down and than climb back up to where it was set. I'm sure it's done to mute the relays changing state and causing popping in the speakers.
I need to start looking for some 12AX7 tubes to roll through this, it seems very responsive to changes. I certainly like the way it sounds, more detail and things like a Hammond tube organ sound real, the upper octaves seem to have a bit of sparkle to them. Overall I'm very pleased.
BillWojo
You should spend a bit of time reading Joe's Tube Lore on the 12ax7. I have found his impressions to be quite in line with what I have heard on the limited number of tubes I have rolled. I ended up with the Sylvania 5751 triple mica grey plate on my amp - an absolutely stunning tube, and hands above the competitors for my application. The black plate variant was also very nice, but just a bit more lean. Sometimes it depends on the other tubes, and what flavour they lend to the amp, and how you need to compensate to get where you want to go. Of course, there are people that do not hear a difference. I think that until your system gets to a certain level, maybe it is hard to hear the difference (other component deffiencies get in the way).
regards -- Roger