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Consider PSUD 2 and mikeyb's supply







Dave,

I am applying a conventional PSUD2 step test, using the two 10 HY 150 Ohm chokes in mikeyb's example. I mated his "L-Critical" filter to a One Electron BFT power transformer, which mikeyb has told me he uses on his 300B amp. That "BFT" has a lower DCR than most conventional and traditional power transformers.

The PSUD screen shot shown (below mikeybs'), is what I have done with a modern supply, for the last two years.

The current-step, in both simulations, induces a current change from 60 mA. to 69 mA. (15%) occurring at 4.1 seconds, in both simulations. We are viewing a 900 mS. "window" in each simulation. Same time scale.

Lets compare results.

With the 10 HY 150 Ohm chokes, the wave form is fully settled and "clean" in 450 mS. The voltage drop is about 3.65 VDC with a 9 mA. change in current (the 15% step).

With the modern supply, below the first simulation, using a typical power transformer I use, or, one that can be obtained from Hammond (newest 2010 300 series PTs) we have these results.

In the same current-step, the modern supply is fully recovered in about 52 mS., about nine times faster. Also, the same 9 mA. current step causes about a 2.25 VDC drop in voltage, after cleanly settling.

This means the 10 HY 150 Ohm choke supply has a dynamic Z of 3.65 VDC divided by 0.009 A. or 405 Ohms. The modern supply has a voltage drop to a 9 mA. current change of about 2.25 VDC, when fully settled. 2.25 VDC drop divided by 0.009 A., is 250 Ohms of Dynamic Z. (Ohm's Law.)

Which supply dynamic Z would will power a 2A3 or a 300B better my friends, (any friends?) 250 Ohms or 405 Ohms?

One other important factor. In John Swenson's chronological compilations, he goes to great trouble to measure music to find the needed time for a supply to settle, so that it can keep the music intact, not "sagging" repeatedly (and additively) on music transients, due to the power supply filter to the finals. His conclusion was that 50 mS. was needed.

What supply would you think will do best, based on John Swenson's music measurements, one that settles cleanly in 52 mS. OR, one that takes 450 mS. to settle cleanly.

Oh, Oh, Oh, I better discuss the obvious ripple to the 2A3 finals in the lower simulation. Worry not!! The modern supply has about what??? 300 mVAC on it. No problem at all with a SE amp, and the step down output transformer.

Drummerwill has posted up here to Slo n'low that his modern power supply "reference" amp is very quiet. Forum member "rage" has also made similar posts, after A-Bing, versus three commercial amps (with traditional power supply filters), on 104 dB speakers, his amp was quieter. Both these Forum members were using things I supplied, steel chassis, proper spacing of components, and "magnetic parts" I designed.

Cheers,

Jeff Medwin, audio amateur, ...and let the flames begin.


Edits: 08/24/12 08/24/12 08/25/12 08/25/12 08/25/12 08/25/12
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