Let me chime in here since I built the preamp we're talking about...
First off, thanks to Happy Rabbit for posting this up! I'm really glad you like the preamp. And thanks to everyone else for your thoughts. Here's a few of mine..
Yes, the ECC99 has a sweet sound but still remains accurate to the signal. I too use it as a driver tube for the 66 series power amps. The only problem is that there is no tube rolling since only one manufacturer produces this tube. Kind of a blessing in disguise; much work was put into operating points for the common cathode stages for lowest distortion. The tubes are matched for their gain and distortion characteristics and rolling in another tube would throw that off. They should last a good long time so frequent replacement will not be necessary.
The Alpha pot mentioned is the balance pot and not directly in the signal path. It bridges the L & R channels with the wiper to ground (shunt mode), and has a 10K resistor padding it on both sides (this way the balance works about 6dB in either direction, enough to compensate for most recordings). Sure I could throw a $10.00 Clarostat in here but it wouldn't make any difference and the Alpha pots have a nice 'feel' when rotated.
The ALPS pot: not super expensive like a switched attenuator but these have to be built to a price point after all. I'm sure that if I threw a $300.00 part in here it would increase the transparency somewhat but the cost increase would be exponential. Even though they are built to order and the sales are direct, small runs of parts and casework are very expensive and it all adds up (even shipping containers and packing is surprisingly expensive).
The electrolytics mentioned are PSU bypass caps; a 100uf bypassed by a 10uf bypassed by a .47ur poly. Each and every plate has it's own trio of bypass caps. The electrolytics are the Nichicon low impedance line and they were selected by ear for the best overall sound.
The main (outboard) regulated power supply uses Cornell Dublier and Nichicon caps.
Every product is a sum of it's parts, it's true. All my products are prototyped trying select different parts and the final configuration is chosen to maintain the ESA house sound. I have had some clients request other parts be used in certain areas and I will honor that request as long is the part fits and it doesn't throw off the overall sound of the unit. It retails for $3850.00 and is hand built, point to point. This preamp performs very well as you can see from Happy Rabbits' description above. That it can replace a well regarded passive unit says something!
-Kevin
