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A catalog of headphone amplifier circuits.

Posted 19th May 2013 at 10:45 AM by rjm
Updated 21st May 2013 at 12:12 AM by rjm

Lots of circuits out there, but most are variations of a small set of archetypes. Let's see if I can put together a list:

1. Dedicated headphone amplifier IC. e.g.(lme49860)

2. Battery powered, single stage, generic audio op amp. The ever-popular mint tin cmoy.

3. Op amp + buffer (complementary transistor pair, diamond buffer, unity gain op amp, etc, in either integrated or discrete package.)
a. closed loop connection or "compound amplifier" configuration as developed by Walt Jung.
b. open loop, two stage circuit, e.g. nwavguy o2 and my sapphire amp.

4. simple 2 or 3 transistor "introduction to electronics"-style amplifier

5. The "little big amp", a scaled back version of a transistor or vacuum tube power amplifier design. (Zen, DoZ, transformer coupled SET amps)

6. The power follower. Single-ended MOSFET or BJT, with or without CCS load, voltage amplifier front end, etc. I'll lump in mu-follower & SRPP designs in here too. Szekeres amp, etc etc.

That, I think, covers 95% of the DIY scene at least. Less popular, but still interesting, options include,

7 The Marsh Headphone Amplifier is unusual enough to warrant special mention. The Audio Technica AT HA-2002 belongs in the same box. Both are small transistor amplifiers, but specifically designed for headphones rather than a scaled down power amp. The 47 labs 0247 is also a dedicated headphone amp circuit, which was scaled up to become the 0347 power amp!

Anything significant I missed?
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