M19H Headphone Amplifier
I have been working on a new headphone Amplifier which is finally ready - in stock & priced at $600.
Additionally as it includes RCA line outputs, it can also function as a basic preamp.
Power supply - I have gone totally overboard here as in my opinion the power supply has a major effect on the sound quality. Power diodes are a special low radiated noise, very soft recovery types.
Main filter capacitance is a massive 40,000uf using the Nichicon "Gold Tune" KG series, designed specifically for high grade audio equipment.
Internal regulators are low noise fast transient response Linear Technology devices. These are the same series regulator as the one the Kraftwerk PSU uses.
Amplification is composite design using a LME49600 diamond buffer running in class A coupled to a Muses J-FET operational amp, which also designed specifically for use in audio. At $18 each they cost significantly more than most op-amps.
Gain can be switched between 2x or 6x to cover low or high impedance headphones. RCA sockets are Switchcraft & gold plated.
Power input is from a dual output 9v + 9v external transformer.
The volume control is a plastic film unit so should have long life.
Relay muting so the unit won't produce any turn on/off pops.
Input impedance is 20k so a nice easy load.
Audio bandwidth is very high & distortion extremely low.
I will post some tech results shortly.
Note! not suitable to drive headphones with an impedance of less than thirty ohms.
However I am working on an alternate version which will suit very low impedance headphones.