This must be an older amp because it has no:
1. output cross coupling
2. "Baker" anti-saturation clamp diode on the VAS (nor any Darlington)
3. LTP degeneration
4. Current mirror
5. LTP CCS
The -42V supply drops near to the main rail voltage before the VAS, so I think the intent is to avoid supply ripple on the Miller cap and improve the PSRR, not to extend the output swing. And the separate VAS supply may not droop under load with the main supply. The positive VAS CCS supply is actually dropped below the main supply rail. This could actually be deliberate if it avoids saturating the output transistors to avoid the delay coming out of saturation, given the lack of cross coupling. It would be interesting to experiment with this amplifier to see if the ~missing modern features improve the amp or not. For example, using a current mirror without LTP degeneration can be too much gain causing instability, without increasing the miller cap compensation.
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