OK, here goes,
Jon L brought up some very good points so let me address them:
1. Why use electrolytic caps for input coupling. Even if it's blackgates, I would much prefer a quality film cap.
It's a question of cost and space. The Blackgates are very good sounding caps, and they are small and not too expensive. When I was doing Sonic Impact mods, the size and cost of the best input caps could both be double that of the amp! I chose the Blackgate E-caps for the good performance versus size and price. They are also race car red.
Some listeners prefer the Blackgates to metalized caps. Film-foil is the best way to go sonically, and I use them often in upgrades. They are
not cheap*.
2. Cheap Panasonic caps on the board. Suggestion: go the whole 9 yard and get Blackgate standard or better.
Why disrespect the Panasonics? They are inexpensive, but not "cheap." I am very pleased with them in power supplies. The Tripath is a switching amp that kicks a
lot of RF noise back into the power supply rails.
No other cap I've tried is as effective as the Panasonic FM series at reducing this RF noise. The only caps that come close are Blackgate. I've tried many different types and brands. Electrolytics, ceramics, metalized foil, film-foil, tantalum, polyester, etc.
The results are easy to see on the oscilloscope. The Panasonic FM caps reduce switching noise better than any other cap I've tested. That's why I like them. Placed at strategic points on the board, they reduce power supply noise by as much as 75%.
3. For PS caps, I would prefer to see something like Rubycon Z series instead.
See above.
4. Noble pot. Either get rid of vol control or use those Ebay/Hong Kong ladder attentuators at least. Maybe even the TKD carbon film pots.
The volume control is there for those who wish to use the amp sans preamp. There is a version without pot. As for the Noble, it is of very nice quality and tracks well. No pot can match the definition of a good stepped attenuator, but at what cost? Adding a stepped attenuator would add
at least $150 to the cost of the amp. That jumps the price by about 35% just for that one item.
5. There's no specifics/pictures of the PS. It just mentions battery vs. linear PS option.
The PSU is nothing fancy or high tech. Just a good solid 3pin 3A regulator in a low noise configuration. The amp will never draw much more than 1.5 amps before it runs into clipping - So 100% headroom.
What makes this power supply so good is the massive amount of high quality capacitance used - Nichicon "Gold Tune" designed for audio power supplies.
I love massive power supplies; they give an amp a real sense of power and stability. A strong power supply will provide great dynamics, bass slam, good driver control and a stable stereo image. All good things in an amp.
Give us a plain, ugly, cheap case with thoughtfully executed board/parts, and I'll sign up for one.
That is something I just can not do. There is no way I'm going to spend the enormous amount of time, money and energy it takes to make one of these amps and put it in an ugly plastic box. That is for the DIY crowd. I've build stuff like that for myself, but not to sell. The case and knobs
are expensive, the knobs cost about as much as the case. But if you want an amp that sounds this good, why not have it look and feel good too? That’s part of the enjoyment, no? Anyhow, a cheaper case wouldn't knock that much off the price; you still have to pay for all the labor and R&D.
So the choices I've made are all for a reason, a very good reason to me. I hope that this long post has helped to shed some light on those choices. There are other choices and design factor that I did not go into, but all are thought through and tested.
Hope that helps.
In the future I may build an "OctoLux" amp with no holds barred, price no object. But who the heck would buy one?
* I would like to use the AudioCap Thetas on the inputs, but they are almost impossible to get at the moment. My source tells me that the military is buying them all.
