Amp/Preamp Asylum

Posted by Bambi B (A) on September 27, 2009 at 07:20:57

In Reply to: RE: 12at7 tube for C-J PV-3? posted by popsy on September 26, 2009 at 23:30:07

popsy,


Though I used a PV-10 a while and have followed Conrad-Johnson gear, I'd never heard of the Conrad-Johnson PV-3, and I'm sorry to have missed these. The PV-3's a cutie- reminding me a bit of my late 50's EICO HF-14, a compact integrated that makes 12W mono from 3-12AX7's and 2-EL84's- simple and direct. The PV-3 actually has only half the number of controls of the HF-14 and two fewer tubes. And, as well, like EICO, the PV3 was available as a kit . -I suppose if an EICO and a Dynaco PAS3 had a child in 1982, it would have been a PV-3. Cute as a puppy and what a lot of fun for $300:

http://www.conradjohnson.com/It_just_sounds_right/a-PV3.html

The tube diagram shows the 3-12AX7's and the 12AT7 at the right rear of the box.

As for the right 12AT7 for the PV-3, the first thing is to learn what the 12AT7 does. It's not clear how much sonic effect it imparts. I have three pieces of gear in which the 12AT7 is part of the power supply and has no discernible effect on the sound. However, in a Peavey VMP-2 microphone preamplifier (6-12AX7, 2-12AT7), the 12AT7's have a substantial effect.

I mention this difference as the care necessary in shopping, and the price of 12AT7's varies substantially. There's no need to watch Ebay Germany for two months to buy the perfect Valvo Hamburg blue label, triple mica 6201 for $150 when a tested NOS GE "Five Star", triple mica 6201- is $15 and could be in your PV-3 three days from now,..

My suggestions:

If the 12AT7 affects the sound: 1. Siemens triple mica E81CC. This is a very energetic tube that I use in sleepy vintage gear to wake it up a bit. Punchy and clean sound with a nice, transparent bass. Very quiet. I use this one in all the McIntosh 12AT7 spots.

If the 12AT7 doesn't affect the sound: GE "Five Star", triple mica 6201, RCA "Command" black plate 6201, or Tung Sol 6201. Any of these if in good nick will deliver the electrons properly a long while and are still delightfully inexpensive. The Tung Sol seems especially nicely made.

Either way, buy tested NOS and with reasonably close triode sections just to be sure- again we don't know how the 12AT7 is working in the circuit.

Happy hunting!

By the way, what are the other pieces of the PV-3 system? What do you listen to?

-

Cheers,

Bambi B

[ > Using 8 -12AT7s in 6 pieces of gear: Audio Research SP8-1, Audio Research SP10 -1, Audio Research D115-1, McIntosh MX110-2, McIntosh MR67 -1, Peavey VMP-2 -2, ]

• http://www.conradjohnson.com/It_just_sounds_right/a-PV3.html   (Open in New Window)