Hi,

I would like to build my first (but not terrible) headphone amp from spare parts.

So instead of just randomly picking one of the transistors and building a class-A circuit with a resistor as the constant-current-source, I would like to ask you for advice:

- The pre-amp will be a DIY Pass B1 (unity gain), so I'm not sure if the amp needs voltage gain or if a simple follower would be enough.

- I have no idea which of the transistors (see below) are suitable for building a decent quality headphone amp.

My headphones are:

- Sennheiser HD570 64 Ohm, 102dB@1V, max 100mW

- Sennheiser HD280 64 Ohm, 102dB@1V, max 500mW

- Etymotic HF2 16 Ohm, 105 dB@0.1V, max 120dB

Parts:

- a spare case

- a transformer 2x 0-12 Volts, 0.66 Amps each

- possibly different wall warts

- rectifiers, voltage regulators, ...

and of course some resistors and capacitors.

I would appreciate any suggestions of simple circuits using these components.

Luda

I would like to build my first (but not terrible) headphone amp from spare parts.

So instead of just randomly picking one of the transistors and building a class-A circuit with a resistor as the constant-current-source, I would like to ask you for advice:

- The pre-amp will be a DIY Pass B1 (unity gain), so I'm not sure if the amp needs voltage gain or if a simple follower would be enough.

- I have no idea which of the transistors (see below) are suitable for building a decent quality headphone amp.

My headphones are:

- Sennheiser HD570 64 Ohm, 102dB@1V, max 100mW

- Sennheiser HD280 64 Ohm, 102dB@1V, max 500mW

- Etymotic HF2 16 Ohm, 105 dB@0.1V, max 120dB

Parts:

- a spare case

- a transformer 2x 0-12 Volts, 0.66 Amps each

- possibly different wall warts

- rectifiers, voltage regulators, ...

HTML:

```
FET U Drain-Source U Gate-Source U Gate-Drain I Drain I Gate P total
5 BS250KL P-FET -45 V +-20 V 0.18 A 0.83 W
6 ZVP3310A P-FET -100 V +-20 V -0,14 A 0.33 W
20 BS170 N-FET +60 V +-20 V 0.5 A 0.35 W
11 IRFP044N N-FET +55 V +-20 V 53 A
3 IRFP044N (salvaged)
8 2SJ74 P-(J)FET +25 V 0.012 A -0.01 A
20 2SK170 N-(J)FET +40 V -40V Ic = 0.02 A? 0.01 A 0.4 W
8 2SK170 GR(F)
Bipolar U CBO U CEO U EB I C
10 BD135 NPN +45 V +45 V +5 V 1.5 A
9 ZTX 450 NPN +60 V +45 V +5 V 1 A
```

and of course some resistors and capacitors.

I would appreciate any suggestions of simple circuits using these components.

Luda

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