Heres a spinoff that sings well at high bias. As indicated by PauloPT in 2012 the sound was really nice at 200mA
These two designs allow this type of output stage to compete at an equal footing with the other types of output stages whether EFIIs, CFP, CFP+EF. Rugged Sanken Darlington's with 200mA bias should get you there
The frequency response as well as 20kHz square wave follows, pretty decent for this category of amplifiers
The posts in 201,202,204 do not have adequate compensation. Chasing lower THD values necessitates adjustment of compensation lest the amplifier suffer from ghost sporadic oscillations that have given some ultra low THD amplifiers a bad rap. Posts 206 and 207 are stable and have acceptable compensation and are suitable mods , however the sound characteristic may be different from the original.
There are many schools of though when it comes to amplifier design
BJT class AB amplifier Design rules(non ultra low distortion)
1. Voltage controlled BJTs dont need cascoding
2. All switching stages to be driven by a class A driver
3. For linear amplifier degenerate LTP or control pair.
4. LTP can be used without cascode
5. Pick suitable compensation scheme where necessary
BJT class AB amplifier Design rules(non ultra low distortion)
1. Voltage controlled BJTs dont need cascoding
2. All switching stages to be driven by a class A driver
3. For linear amplifier degenerate LTP or control pair.
4. LTP can be used without cascode
5. Pick suitable compensation scheme where necessary
One can settle for posts 1,206,207 and 210 depending on ones sound signature taste. The THD utopia promised by 207 needs to be evaluated without bias, while the principles of 210 also need to be evaluated without bias. Whether you prefer a laid back sound or a forward sound will also dictate your choice. However these designs lean towards a warm sound.
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The diyaudio community is a small community and most diyers already have too many amplifiers. Social media is also much more lucrative and entertaining than a specialist forum, however am still looking for one or more free spirits that may exist and ready to give the community AB tests for posts 207 and 210. What the brain does with what hits the ear drum is still a gray area. Open micro research is also fun. Raise your hand and let me know whether your doing your own board or would like me to volunteer layouts.
Raj here is a suggested CFP solution for those that prefer that kinda sound. Its been many years since I chatted with Rod Elliot many years back. Many thanks to the many veterans we exchanged ideas with about the 1DIFFQC amp and other amps including Nelson Pass and Douglas Self.
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The quasi complementary design in post 207 has a slew rate of 15V/us, while the CFP in post 213 has a slew rate of 10V/us, while the latest version of SYMEF does 25V/us,1DIFFET also does 25V/us
0.032670%, 10kHz THD CFP 4ohm post 213
0.021259%, 10kHz THD Quasi 4ohm post 207
However its good to note that spatial cues are between 500Hz to 1500Hz, making the midrange a very important driver, usually this frequency range is handled by a single driver
0.021259%, 10kHz THD Quasi 4ohm post 207
However its good to note that spatial cues are between 500Hz to 1500Hz, making the midrange a very important driver, usually this frequency range is handled by a single driver