wakibaki
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Voltage sources are all 1.5V.
w
Voltage sources are all 1.5V.
w
The swings you are seeing there, ~150V pk-pk, are using 2N3904 transistor model throughout. The simulator doesn't care that 2N3904 blows up, it doesn't tell me that, just carries on regardless.
When I put in TIP50 + 2N2222, things get much worse. Swing falls to +/-90V, THD goes way up. I increased the drive to 2.5V pk-pk and moved the quiescent voltage to ~180V (you can see the increasing assymmetry, with compression of the sinewave on the negative half of the cycle), to get 211V pk-pk out at ~5.5% THD.
Things are slightly better when output is taken from the bottom of R3 & R4, drive must be increased again (to ~2.7V pk-pk) to get 211V pk-pk out, but THD is better at ~4.5%.
I tried to attach the schematic so you can run the simulation yourself, both as a .txt file and as a .zip, but the forum is not cooperating.
I am not entirely happy with the circuit, I don't feel I understand what is going on in it. I don't like having two current sources feeding a current sink. This means that the circuit is very tightly balanced with just the base currents of the LTP making up any difference in current, and the quiescent point setting is very critical. I can't help but feel that it will not be very stable with temperature.
I was a programmer and then an FPGA designer, I came to discrete audio design via software radio, RF design and only latterly IC audio design. Since ill-health forced my retirement this has been a good way to stay out of trouble, but you will get better advice from some of these guys who have been doing it longer than I.
w
Tried a lot of variations on this. I found the spice model for IXCP10M90S (strictly speaking a regulator) is just a MOSFET.
These are far from elegant, require a second PSU, but interesting nevertheless.
This is nice and symmetrical with an ideal CCS...
...but even with a cascode it's deteriorated a bit.
What can we try to improve things a bit? Here's what we can get with the IXCP10M90 with CCS loads...
At 80Vpk-pk, 0.25% THD
40Vpk-pk, 0.117%
Now with the DN2540, 170Vpk-pk, 0.07% THD
These are all just simulations, I've got no reason to build any of them. Kept me out of trouble for a couple of hours tho'...
w
I made R10, R11, 20k, R5 300, D1 1.5V but emitter of Q8, Q9 is ~1.7V.
Can you give me some spot voltages?
w
I thought the Broskie tube cad articles were clear on the "SRPP derived" impedance multiplier concept
I have 1.3mA in R9 and 3.9mA in R13, but emitter of Q8 is still only ~2V. Can you see what the problem is?
w