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|14th March 2017, 04:03 PM||#1|
Join Date: Sep 2016
Please criticize my PSUD simulation
Hi, i need your help to interpret PSUD simulation.
So, the power supply will power 4 x kt88 biased at 55-60ma, and 3 x 12au7 on the driver board. B+ will be ~480V to the plates and ~370 to the driver board.
First simulation is with soft start off, the second with soft start on, and the third, zoom on the current change.
If i take the RMS values for the 2 current taps, the voltage is about right.
The psu doesn't seam to ring or overshot, or at least i think so from what i'm seeing.
How do i interpret the current sink curve? Should the recovery be faster or between some values? Would the power supply recover fast enough on transients ? Or would it sag ?
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|14th March 2017, 10:29 PM||#2|
The three little hardly matter.
The 5V3 Peak Current rating is EXceeded at start-up, and also at Full Power. This makes sense. One rectifier can power two power tubes. Here you have four. The 1->2 ratio is not exact, of course; but four 6550 can suck a LOT of current, and few twin-rects can stand the load.
Sunn 2000s is a four-6550 amp with hollow rectification:
> 4 x kt88 biased at 55-60ma
So 230mA idle.... what is the FULL Power demand? Possibly 400mA-500mA.
Did you see Rating Chart III in the 5V3 data?
For 425Vrms per plate they want you to use around 48 Ohms in series. Your 38r in PT is not enough. In PSUD I have to add another 69 Ohms to stop PSUD warnings. (PSUD may be more exact than old GE hand-approximations.)
Also note that 5V3 page 5 does not show any 425Vrms above 390mA output.
In normal hi-fi use, FULL power never happens long enough to sag a 200+uFd cap. But full sine power is a common test for power supply sag and possible amplifier distress.
With added 69 Ohms, 454V at idle but 367V at full power (500mA). That's significant sag. A 4X6550 amp in unclipped speech/music may be fine. In "heavy" duty such as PA, I would want less sag.
With 2,000PIV 2A sand diodes and no added R, I like 550V idle and 500V full power much better. There may be glass rectifiers of this size.
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