Half bridge + transformer. Input please?
Gregg
I just posted a circuit on alt.binaries.schematics.electronic.
Doing my usual "What If....." with Spice, here is a modification of a
circuit I found on the Jensen Transformer site. Have you had any
experience with a totem- transformer output like this? If so, How'd it
go?
It would be interesting to see what CFB could do to this one. I tried
to configure the program to accept CFB calculations, but it "just
canna do it captn'".
The Spice output transformer is configured thusly:
Pri Turns: 10,000
Pri Res: 2.5k
Leak Ind: 1 mH
Sec Turns: 4000
Sec Res: 250 ohms
Leak Ind: 100 uH
Z-ratio: 6.25:1
(optimum found between 4:1 and 10:1 in 0.25 increments)
Cathode resistor is unbypassed on 12AX7 for near-unity gain buffer
response. Bypassing increases gain significantly. With 100uF, maximum
output can be realized with a few tens of mV, with crappy bottom end
(20-100 Hz is pthhhhhbt).
Drive at 20V pk-pk is chosen for maximum allowable THD 2.5%.
NFB resistor values chosen for minimum distortion while retaining 10%
FB.
The 600 ohm resistor simulates a terminated 600 ohm line.
If a 6SN7, 6CG7, 12AU7 is used instead of a 6DJ8, the transformers
Z-ratio must be increased to 16:1 to have the optimum output. This
results in a THD of 8% with the same level of drive and about 1/2 the
output voltage.
Thanks,
--
Gregg