Discussion about the headphone interface on the 6AW8 PC Speaker amp
got me to thinking so I whipped up a little OTL circuit, just for
headphones, using the 6CY7 (essentially a 'half power' 6EM7)..
Why? Well, when researching the series resistor thing I noticed a lot
of the so called 'tube' headphone amps have solid state outputs and a
lot of the all tube ones couldn't drive 32 ohm headphones very well..
The 6CY7 should take care of both those issues, and with the IEC
specified 120 ohm source impedance
Schematic and pics of the breadboard (I only did one channel) are up
on my site http://flipperhome.dyndns.org
It's not really fleshed out more than needed to breadboard and see the
circuit work, but that it did.
There's plenty of room for tweaking it. Spice indicated excellent open
loop performance, in case that's what floats your boat, but I wrapped
13dB around it anyway for the exercise. And there's room for a bit
more gain since, for the sake of simplicity, I didn't bypass the gain
triode Rk.
I figured some might get a few laughs at my sloppy breadboard so I
included a pic of it for your amusement.
|
