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Please criticize my PSUD simulation
Please criticize my PSUD simulation
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Old 14th March 2017, 04:03 PM   #1
franciscano is offline franciscano  Romania
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Default 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 ?

Thanks

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Old 14th March 2017, 10:29 PM   #2
PRR is offline PRR  United States
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Please criticize my PSUD simulation
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:
http://el34world.com/charts/Schemati...Sunn_2000s.pdf
Two GZ34.

> 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?
http://www.mif.pg.gda.pl/homepages/f.../093/5/5V3.pdf
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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