Inductors in Aleph 30 PSU

Hello Freddie,
I've tried to put 2mH/1ohm inductors in my Aleph 5 PSU, the capacitors were 22000uF and 2x22000uFfor each rail, so I made a C-L-C filter.
It seems to work well, but my Aleph have a current ratio, between the (un)costant generator and the output current of 0.5 (50%): in this case, the amplifier works always in single-ended mode, and the current generator, the upper side of the amp - never shuts off.
In a different way, it seems to me, the original Aleph.

Tortello
 
Freddie,
As with capacitors, bigger is better in this application. The main thing will be to keep the DC resistance as low as possible--meaning heavier gauge wire. Yes, you can wind your own inductors, although for some reason many people seem reluctant to do so. Since we're dealing with DC here instead of AC (as in a speaker crossover), you can use iron core inductors with a clear conscience.
Tortello,
I'm not sure if I understood your post correctly, but the Aleph 5 is supposed to operate in single-ended mode all the time. The presence (or lack) of an inductor in the power supply will not change that.

Grey
 
Hi Grey,
As I could see, the Aleph 5 has a linear "true single-ended" behaviour up to some power, depending on the load impedance; beyond there is a "quasi-single ended" behaviour, with a partial shuting off of the current generator: the output waveform, however, is a perfect sinewave, due to the negative feedback action, that accordingly corrects the "active" side ( the lower stack of Mosfets).
The Aleph 5 can deliver 90W into 4 ohms, that should not be possible with a biasing current less than 2 amps, also with the employment of the PL patent #5,710,522.
This can also be seen by a little step of the THD vs. output power, at about 20W into 8 ohms and 10W into 4 ohms, as I could see from an official PassLabs sheet.
The best way to obtain a true single-ended operation, is to impose the current modulation of the unconstant generator and the "active" side equal, or to the half of the output current (that is the same thing) as reported in the PL patent, by a convenient value for R21 (in the A5 schematic): the output power into low impedance loads however decreases, due to the current limit of the circuit.
I prefer this way, so I increased the biased current to 3 amps, to partially compensate the drive capability into heavy loads.

Tortello

[Edited by tortello on 09-13-2001 at 11:13 AM]
 
hifi,

I don't know the exact price of the caps. But a friend of mine bought two 600VA 2*18V toriod transformers, and fifty 10000uF 35V caps for 1393:- SEK for me at Elfa (Elfa personal rabatt). But I can't order more parts from him now, since he isn't working there anymore. But It was quite cheap. The parts would have costed me 2600:- if I bought them myself.

Have you got the IRFP9610 yet?

/Freddie

[Edited by Freddie on 09-13-2001 at 04:22 AM]