The vintage Vox AC10 & AC15 all have the same phase inverter and output stage, with some very minor variations. Popping these in as a reference for myself - yes, I have simplified some things / made generalisations. If you're interested in ACs in general - https://www.voxac30.org.uk/.
POWER SUPPLY
- Power transformer secondaries: 300-0-300, 120mA
- Rectifier: EZ81, 320V DC output
- Filtering: 16uf - 8H - 16uf (mostly)
- Phase inverter: usually 22k, 8uf. Sometimes 47k
- Preamp: As above
POWER AMP / OT
- 8k primary, 8 & 15ohm secondaries
- EL84 Plates: ~305 - 310V
- Cathode bias resistor: 130ohms, 5-8w
- Cathode bypass: 50uf
- Plate and screen resistors: either one or the other, never both - 100 ohm
- Grid stopper: Usually 1k5, 10k on the 1959 AC15
- Grid leak: 220k
- Coupling caps from phase inverter: 47n/50n on AC10. Mix of 50n & 10n on AC15
- Cut: 5n & A250k (10n on AC15 1960)
Expect about 10v on the cathode.
PHASE INVERTER
Vintage Vox amps have two channels, each using a side of the phase inverter as an input. For a single channel amp, the unused input of the phase inverter must be grounded with a capacitor - 47n - 100n.
- Classic long-tail pair, ECC83
- 100k plate resistors
- Coupling caps to EL84s: 47n/50n on AC10. Mix of 50n & 10n on AC15
- 1meg, 1k2, 47k combo for grids / cathode (sometimes 1k)
- Coupling cap on input: 10n & 100n
- Volume pots from previous stage: A500k
VOX AC/10 OS/008 1960
VOX AC-10 NO. V-1-3
VOX AC/15 NO. 2 OS/005 1959
VOX AC15 NO. 3 OA/031 1960
VOX AC-15 NO. V-1-5
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