https://www.diyaudio.com/community/threads/ez-dump-dump-your-current-without-really-trying.263065/page-10

The opamps could be any reasonable FET types: even a TLO71 or similar should work.
U1: LF356 is better, LT1056 should be even better (no, it oscillates, LF is the best)

U2: less demanding: TL071, TL081, LF411

Q7/Q8 should be in thermal contact with drivers or main heatsink.
Not a must, but good to have.

The input should have the standard DC blocking cap + the HF filter, like the circlophone, or any normal amp.

1k  R3 - 6 should be 1W
R28 - 29 (zener resistors) 0.5W - 1W
R24 (zobel) 1W
Also 5k1 resistors could be 0.5W in the next build


supply transistors: 2N5551/2N5401

shifting transistors: BC237/337
drivers: NTE373/374 (or KSC2690/KSA1220, or TTC/TTA004, or MJE340/350)
output: MJ21194/21193

L1: 3u3: 22 turns of wire 1mm (18 AWG), on 14mm AA battery
L1: 2 layers:  24 turns of wire 18 AWG (12 turns per layer) on 10mm AAA battery


All small caps ( <= 1uF) can be ceramic X7R
Zeners can be 250mW

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For floating op-amp:
To mitigate the issue, guarding can (and should) be used: it would connect to Vee or Vcc of the opamp.
The auxiliary inputs can be disabled, but in a non-intrusive manner.
The exact method depends on the opamp type.
Balance pins could be shorted with a cap (to avoid disturbing the DC),
and this will eliminate most of the differential perturbations in an "agnostic" way:
a LF411, LF356, LT1056, TLO71 can be treated in the same way.

10nF (2 caps per chip, e.g. from from pin1 to vcc, and from pin5 to vcc)

LF356:  +  Vcc   (pins 1 and 5)
LT1056: +  Vcc   (pins 1 and 5)

LF411:  -  Vee
TLO71:  -  Vee   (pins 1 and 5)
TL081:  -  Vee   (pins 1 and 5)

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1k resistors need to be 2W (not just 1W), they run really hot (approx 100 C)