[sdiy] Headphone amps using op-amps

Oren Leavitt obl64 at ix.netcom.com
Wed Dec 12 21:08:27 CET 2012

On 12/12/2012 12:22 PM, John Speth wrote:
>> If I'm driving a pair of cheap headphones from a standard op-amp (I've
> got a
>> TL072, a MC1458 or a LF353 available - you don't get much more 'bog
> standard'
>> than that lot) is there anything special I need to do?
> Great question!  I suppose the answer lies in how do we design an
> inexpensive circuit that can reliably drive a low impedance inductive load
> with reasonable sonic fidelity.

It's basically an impedance matching issue - I've gotten good listening 
volume just putting a small 1 kOhm / 8 Ohm audio output transformer 
between op-amp output and speaker.
A better way is to boost the drive current with an added complimentary 
pair of transistors at the output. There are many examples in op amp app 
notes and data sheets.

- Oren

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