Yes, sure, but at 9.6v the diode voltage drop may need consideration. I used doublers quite often, especially at high voltages and lowish current, or if i had to stack caps and/or diodes because of voltage limitations anyway. I also used multistage multipliers as crude, but almost lossless constant current sources for feeding shuntregulators by adjusting the capacitances connected between the ~ inputs
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Since I probably will need to elevate the 9,6V winding at some level above ground to avoid hum problems, it might become messy to use it as a source for a negative rail at the same time.
I've been peeking a bit at the RCA 50W amplifier with nested feedback. Perhaps a similar input/driver could be made with 2* PCF80 per channel, using the triodes for input and concertina duty and the pentodes as balanced drivers with local feedback loops from the output tube plates to both driver plates and driver cathodes. More complex than the stuff I usually build, but food for thought:
I've been peeking a bit at the RCA 50W amplifier with nested feedback. Perhaps a similar input/driver could be made with 2* PCF80 per channel, using the triodes for input and concertina duty and the pentodes as balanced drivers with local feedback loops from the output tube plates to both driver plates and driver cathodes. More complex than the stuff I usually build, but food for thought:
In reality I can just add various junkbox transformers until I have all the voltages I need, I'm just brainstorming for some more or less creative and elegant ideas here
It would be nice to use those PCF80s I have, in one way or another. Using the pentode sections as a long tailed pair input stage with a bit of Schade feedback as in Pete Milletts Engineer's Amp would be another option.
It would be nice to use those PCF80s I have, in one way or another. Using the pentode sections as a long tailed pair input stage with a bit of Schade feedback as in Pete Milletts Engineer's Amp would be another option.
Fuling, Been collecting parts to do a SET 813 amp. Would you consider moving those OPT's that you have along?"it genuinely scared me to death"
I know the feeling... Years ago I spent big money on parts for a GM70/813 SET project that never happened, the 1500VCT power transformer had the same vibe as a loaded gun...
Kodabmx, Do you think if you used 2 per channel ,and interleaved them as you suggest, the Antek's OPT's performance could be improved?You'll find the LF is trash unless you use two interleaved, but I think I mentioned that
Keep in mind that silicon steel has a lowish permeability at low excitation levels, so that an LCR meter will likely read on the low side - a better idea would be to hit the primaries with a few 10s of volts using a variac, and measure the resulting excitation current. I have a variable frequency sine source at work used for evaluating power supplies, and I use that with an output at 300 Hz to make sure that there are no LF bandwidth problems. That way, I can look at the primary inductance and turns ratio of a given transformer.
Disregard this post. Not even possible with the winding and tap scheme of the Anteks.
Even though I'm in the middle of a high-profile, big budget DHP PP project I can't stop thinking about those big toroids from page 1 in this thread. As mentioned earlier I found another big toroid with a 230V secondary with taps for 75, 130, 165 and 190V (IIRC), quite suitable for a low-ish voltage, high current B+ PSU that should fit any tube that would match those output transformers. It also has a 9,6V 60VA winding that is tempting to use for heating tubes, although the current rating is a bit low for a quad of big sweep tubes or an octet of smaller ones. Dropping 3,3V @ 5-6A across a resistor wouldn't feel like good engineering either.
Another thought: As I'm already working on a nice PP triode amp, why not build something freakier with the toroids just for fun? A pair of PL81 (small 8W sweep tube with a top cap and Noval socket) can deliver around 20W into a 2k p-p load, probably more if I ignore some ratings a bit. A quad of PY88 dampers (also Novals with top caps) could serve as rectifiers in a hybrid Graetz bridge and all the heaters could be connected in series and fed from the B+ supply.
With a healthy dose of CFB in the output stage and some global NFB it might at least sound like a decent SS amp...
Another thought: As I'm already working on a nice PP triode amp, why not build something freakier with the toroids just for fun? A pair of PL81 (small 8W sweep tube with a top cap and Noval socket) can deliver around 20W into a 2k p-p load, probably more if I ignore some ratings a bit. A quad of PY88 dampers (also Novals with top caps) could serve as rectifiers in a hybrid Graetz bridge and all the heaters could be connected in series and fed from the B+ supply.
With a healthy dose of CFB in the output stage and some global NFB it might at least sound like a decent SS amp...
Fuling,
Your Post # 162
Danger . . .
That is ready for the electrolytic capacitors to short, open, or Explode!
There are two electrolytic capacitors that have the + end of the cap connected to Both an Anode, And a Cathode.
That means the capacitors will be reverse biased 1/2 of the time.
You will need to use non-electrolytic capacitors.
Your Post # 162
Danger . . .
That is ready for the electrolytic capacitors to short, open, or Explode!
There are two electrolytic capacitors that have the + end of the cap connected to Both an Anode, And a Cathode.
That means the capacitors will be reverse biased 1/2 of the time.
You will need to use non-electrolytic capacitors.
6A3sUMMER: That schematic is just something I "borrowed" from Tubecad as an example. I agree that it does look a bit suspicious. If I decide to build something like that I'll probably use large film caps.
By the way, I just ordered a dozen PL81 (21A6) pentodes and a quad of PY88 (26AE3) dampers. They're cheap and I needed to order some surplus carbon comp resistors and other stuff from that dealer anyway. My boss asked me if I can work night shift for a couple of months after the vacation, and as I work in a mechanical workshop it means I'll have plenty of time to build something funky with those big toroids.
By the way, I just ordered a dozen PL81 (21A6) pentodes and a quad of PY88 (26AE3) dampers. They're cheap and I needed to order some surplus carbon comp resistors and other stuff from that dealer anyway. My boss asked me if I can work night shift for a couple of months after the vacation, and as I work in a mechanical workshop it means I'll have plenty of time to build something funky with those big toroids.