OTL TUBE HEADPHONE AMP
The driving force behind this project was the desire to listen to my mp3 player in comfort with a set
of headphones instead of the earbuds. Besides the benefit of a good set of headphones is the
addition of a crossover network which blends both channels and allows a more realistic and enjoyable
listening experience. The inspiration and basic design for this project came from
HEADWIZE
an excellent site with many good projects.
The amplifier schematic is from the
TOP-LEVEL OTL TUBE HEADPHONE AMPLIFIER
project and was designed by Andrea Ciuffoli . I made a couple minor changes to suite my needs such as a 6SL7 at the input with 220k plate resistors and cathode bypass caps for the additional gain required by my
mp3 player and a 220 ohm cathode resistor for the E182CC to reduce current draw and allow the use of
a smaller 60ma power transformer, this does reduce overall gain some but I needed the smaller
transformer to fit in a 4" x 8" chassis.
The power supply is adopted from the
OTL TUBE HEADPHONE AMPLIFIER
project by Kurt Strain; but I am using a CLC filter instead of a CRC filter and the 2 channels are not isolated.
The crossover network is borrowed from
An Enhanced-Bass Natural Crossfeed Filter by Jan Meier and is an excellent addition.
I find the amp a pleasure to listen to and a worthwhile project. This was a tight build and you have to
prepare your layout very carefully to fit everything in a 4" x 8" chassis. What would I do different? Well I would
do a couple things different; I would eliminate the volume control, use a 12AX7 in the preamp for a little
more gain and I would use a 100ma power transformer to allow the use of a 68 ohm cathode resistor for
the E182CC as the original designer intended.