Considering the age I'm sure it has been mentioned, and this is exactly why I'm making a new post concerning it. The list on headwize looks interesting and like it covers all the various directions one wants an amp to take. The thing about this amp by Kevin Gilmore that stands out is a seeming realization of a lot of factors other amp designs miss, the points questioned in a minute. First though, if it is already considered crap compared to something else I can make, or if you are all sure I will run into annoying problems like sourcing the random old FETs, stop me now...
So, how important are these points he outlines as the basis of this design?
- Capacitors in the audio signal path are BAD. Even the best silver-mica or poly caps exhibit non-linearities at low voltage levels. Capacitors belong in power supply sections and nowhere else. Capacitors used to compensate an amplifer generally mean that the amplifier is otherwise unstable, with poles in the right half plane and is therefore a bad design.
- Ultra high open loop gain: REAL, REAL BAD!!! That basically means anything with an opamp in it. Opamp circuits with open loop gains of 10,000 or more require large amounts of feedback to make them usable. While this reduces THD, the intermodulation products, and especially the transient intermodulation products are much higher than they should be.
I like the idea of no caps as they would seem to remove certain "useless" things that others will consider essential to the music, or alter it in a strange way. The attitude to opamps I also understand as being these bleep-blorp fake audio pumpers instead of something that simply takes what comes in and makes it louder. Not that I know anything about electronics except interpreting some datasheet parameters and making circuits from schems.
I know I will have difficulty getting these transistors (or will I in a relatively large electronics store these days?) If so, link or suggest a revised version of this circuit that is up-to-date but retains these qualities that make it seem great, or suggest alternatives to the transistors or what values I need to compare to determine myself whether a different part is suitable.
I will probably make this in balanced mode (no problem recabling the future headphone with 4 conductor) and will run MS1i's or AD700. I think I'll end up DIYing a DAC in the same enclosure for a complete solution.
Should I scrap this for difficulty, rather suggest to me a recent amp that follows these design rules if they're actually important?
