Impedance ratio and T-amps

[Sasquatch]

I have been registered with this forum for a while but have only started posting in the last couple of weeks, so forgive me for just jumping into the discussion.

I love the sound of tube amps and bought the Tripath SI on a whim based on the laudatory reviews. I thought the sound was clear and far better than solid state, but thin and without good bass. Being a tweaker, I immediately removed the circuit board from the case and installed it in a different chassis with bigger and more adequate input caps, a switching power supply to provide adequate current, and high quality bypass caps. I added a 50,000 mike Sprague reservoir cap that can run the amp alone for .5-1.0 sec for slam. The sound was better but still a little thin in the midrange. FTR, I like a big, fleshed out "organic" sound with good dynamics.

After looking at the schematic (and confirming this on a multimeter), I realized that the amp has a 20K input impedance but has a 50K (in my case 100k) pot in front of it. Thus, voltage distortion should be unacceptable by common design standards.The optimal impedance ratio ought to be better than 1:10 (first to second stage). So, I built a resistor loaded tube buffer after the pot and before the amp. This is a stupid amount of circuitry in front of that little circuit board. Nonetheless, the sound was superb--better than any tube amp I have built. This has been the greatest pleasure I have had in audio. The true measure of great audio is whether your shoulders slump within 5 seconds of listening. Nothing else matters. If you don't relax, it's not good. This configuration does it with only the slightest hint of improvement needed (nothing's ever perfect)

Well, after looking over reviews of these amps, I noticed a pattern. People who don't like the amp usually don't report having preamps. People who love the amp, do. They turn the volume control to max and then use their preamp to control the volume. This means that they have supplied the board with a good impedance ratio.

I submit that the major factor in the appreciation of this wonderful chip is the impedance ratio driving the chip itself. And adding some tube distortion may help matters.