Hello Zen Mod. Better to guess than not, and corner the candidate. The circuit in red stays working as the front end like that in the SONY Amp V2. However, the new difference is the circuit in blue which maybe the following power output stage like that in Mr. Pass's Invention on Constant Current Constant Voltage HiFi amp which had used BJTs.
1. The input is a pair of complementary SITs each idling at 0.3-0.5A
2. SITs maybe cascoded like the FE of VFET2.
3.The SITs are loaded with power resistors [to the power rails like in F5] and thus drive 2 banks of complementary multiple Mosfets; which maybe idling low or high.
4. The Mosfets are the contributors to brute power, and the SITs imbibe the subjective delicacy of triodes to this ensemble.
5. Thus get super powerful complementary SITs.
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Any of the following
1) cascode input for more power
2) folded cascode input
3) symetrical double differential input
4) something like BA3
5) something like sony vfet pt2 front end
6) schade feedback on output
7) something like ZenMod suggested
8) combination of any of the above
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If I already had an F5 and wanted to improve on it (more likely just wanted to make a change for the fun of it), what would I change ?
more power - done already with F5 Turbo.
less distortion without more feedback - 'better' devices, load-line cancellation ?, more complex front-end with local feedback ?
more distortion - less symmetry - dissimilar output devices (e.g. one of them a SIT) ?
more power - done already with F5 Turbo.
less distortion without more feedback - 'better' devices, load-line cancellation ?, more complex front-end with local feedback ?
more distortion - less symmetry - dissimilar output devices (e.g. one of them a SIT) ?
My version of F5 has more 2nd harmonic, more current capability, and less parts. I try to use KISS wherever possible.
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LATFET - lower Gm, lower input capacitance which is more linear than vertical fets, negative temp coefficient at 150mA - 200mA, different biasing voltages than vertical fets, more expensive
Vertical FET - higher Gm, higher input capacitance which is more non-linear, positive temp coefficient until high currents (10A or so), cheaper, better availability
I would add that the temperature coefficent is virtually zero ie goes from slightly negative to slightly positive but is very close to zero at nearly all bias levels we are interested in (ie don't thermally run away above 200mA)
Which I have found means you can easily run them without degeneration even with multiple pairs (provided you match them), which is not easily achieved with most other mosfets.
Makes it easy for dumbies (like me) to make very simple circuits using them, no fancy biasing circuitry required.
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