Preamp Experiences with Atma-sphere Amps

I've used a Conrad Johnson ACT2 with both the M-60s and the MA-1s - both of those the mk.III versions. Though the cabling was limited to single-ended RCA, with 3 meter ICs the CJ had a good grip on the amps. Its a preamp flush with virtues and they and all that wonderful OTL transparency came through in spades.

However, in my opinion - and not to put too fine a point on it - there is a really obvious synergistic choice for your situation and that is the MP-1. I cannot think of another sub-$20k preamp I'd pick ahead of it to drive the M-60s.

Tim

I use a Shunyata Helix Python on my MP-1, with that plugged into a Hydra V-Ray, and Shunyata Helix Taipans on MA-1 amps.

Significant improvement came with insertion of NOS 6SN7s in the line stage and NOS 12AT7s in the phono section of the MP-1. Likewise for NOS 6SN7s in the MA-1s. The Atma's are as sensitive (if not moreso) to tube selection as any gear I've owned and in my system swapping out some of the stock Chinese 6SN7s paid big dividends. (But neither PCs or tubes told just how good are the Atma-Sphere electronics until I added several Real Traps in my room.)

I take tube choices and power cords as largely a matter of personal taste. Mine include a Sylvania GTA or RCA GTB driver in the MA-1 along with Sylvania and Ken-Rad VT231s. Likewise in the MP-1, strategic placement of a single Ken-Rad or Raytheon VT231 in each channel of the line stage improved both the top-end air and sweetness of orchestral and other acoustic recordings, along with lower register tautness and timbre. Discussion of phono stage 12AT7s in the MP-1 probably warrant their own thread, but to drop a few names: Seimens, Sylvania and Mullard.

Pubul57 - how do you find the MP-3 compared with the Joule?

Tim

Here is some of what I've learned about tubes in the MP-1 Mark III:

As you stand facing the MP-1 with its cover off, the 6SN7 tube closest to the front panel in each channel has the most sonic influence on the linestage.

The three 12AT7s aligned in a row toward the left rear of each channel have the most influence on phono stage sonics.

The pair of 6SN7s in each channel that line up behind the tube closest to the front panel are particularly sensitive to noise and unmatched sections. As the MP-1 is a fully balanced design, closely matched sections *within* a tube are v. important for all its tubes.

Tube dampers really help on tubes you want to insure are the quietest. 'Herbies' are easily the best I've tried. In each channel I use 3 in the line stage and 3 in the phono section. At first you may think you've lost some sparkle, but give 'em time and you may find as I did that you've lost some distortion and gained a bit more timbral rightness and quiet.

With 10 6SN7s in the MP-1 and 5 in each channel of the MA-1s, I would have few spares if I used 20 tubes from my NOS stock to fill every socket. In my opinion the 6SN7s in the amps have more influence than all but the one in the MP-1 that I identified above, so I replace all in the MA-1s, and just the one in each channel of the MP-1. Today I'm using '40's black glass Ken-Rad VT-231s in the MP-1.

I appreciate Ralph's comments about the difficulty of finding decent 12AT7s for the phono stage, however it can be done. There I'm using late '60's Siemens-Halske triple mica E81CC tubes in the three critical spots with a Brimar filling out the fourth. I've also had good luck with the Sylvania Gold Brand 6201 sold by Kevin Deal, but the Siemens are really special.

YMMV.

Tim