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tomtt 28th October 2006 01:49 AM

design and personality
 
one of my fav post-

does not matter, what you know, or if you can really Hear-

http://www.audioasylum.com/forums/tu...ges/93457.html

i know this guy is a borderline genius, and has an ear,

yet as a doctor, his 'bedside manor' well...




lol

this parts not a joke-

http://www.audioasylum.com/forums/tu...ges/93307.html

jlsem 28th October 2006 02:58 PM

Do you know Jeff Medwin? Last I heard he lives in KC as well. Maybe you could pay him a visit and report back whether he is on to something.

John

SY 28th October 2006 03:36 PM

Or just on something.

rdf 28th October 2006 04:15 PM

That, and maybe on to something. PSUD sims surprisingly show low DCR has merit, though not with the tiny caps he recommends in the final stages.

tomtt 28th October 2006 07:56 PM

Quote:

Originally posted by rdf
That, and maybe on to something. PSUD sims surprisingly show low DCR has merit, though not with the tiny caps he recommends in the final stages.

low dcr, separate supply for each stage, separate supply

for G2, use a variac to start and maintain voltage.

The Truly Hardcore know this stuff,

not often seen here, sadly-

http://www.audioasylum.com/forums/tu...ges/93307.html

parts-


smaller caps charge / discharge much

quicker than the large values.



http://www.audioasylum.com/forums/tu...ges/93318.html


power xformer-

http://www.skycraftsurplus.com/index...ROD&ProdID=367


i've known him about 10 years.

rdf 28th October 2006 08:20 PM

Quote:

Originally posted by tomtt

smaller caps charge / discharge much

quicker than the large values.


True, however according to the sims at the expense of power supply ringing and increased ripple. Where the trade-off lies depends on circuit topology and building one, which I haven't done the latter yet so can't confirm. Seems promising though.

BTW, Hammond makes a little open frame choke - the 159Y, 0.6H @ 0.75 amp, 11 ohms - which goes for about $23. Double the inductance for just one extra ohm.

Edit: Have you tried low DCR?

tomtt 28th October 2006 10:59 PM

2 Attachment(s)
sadly no...

jlsem 29th October 2006 01:18 AM

I read a few of his posts and he certainly has a few problems understanding basic power supply design nomenclature. He calls his power supplies LC because the first component is a choke. But it has too small an inductance to act as a proper choke-input and is really nothing more than a low-value resistor with some inductance. His power supplies would have even less series resistance if he simply left the the first choke out. I personally like power supplies with optimum inductance values AND very low DCR.

I would think that G2 loads are quite small and a choke with an inductance of ca. 100 Hy is necessary to achieve a genuine choke input power supply and all of the benefits it entails.

John

sorenj07 29th October 2006 02:05 AM

Quote:

Originally posted by tomtt
sadly no...

what is that thing?

ray_moth 29th October 2006 03:09 AM

Jeff gets carried away sometimes. He believes he's found the only true path to power supply design and cannot bear to think that there could possibly be another way to success. He feels that those who don't follow his path are lost sheep and it is his mission to save them.

Jeff admits that he doesn't have the knowledge to support his design with engineering/mathematical explanations but holds that, since it works, there is no need to do so. He tends to get angry with people who demand theoretical proof. He counters such demands by saying that "The proof of the pudding is in the eating." The fact that very few AA inmates actually disagree with the fundamental principle of low DCR is masked by the furore and the ensuing arguments that Jeff stirs up.

Low DCR has always been at the heart of Jeff's approach but this business of low inductance and low value capacitors is quite recent. It seems to have originated from his friend and mentor Dennis Fraker, who posted often on AA, under Jeff's name, a few months ago. However, Dennis seemed to have been focusing only on his 2A3 SE amplifier and what worked best for that, rather than the broader picture.

Good layout was a key point in Dennis's approach and few would probably argue with that, if it had been put in a reasonable way; however, Dennis's patronising attitude caused many inmates to rail against him.

Both Jeff and Dennis managed to make themselves unpopular in AA. Jeff is still there but his posts are fewer and lower key. Dennis is gone from AA.

Quote:

I would think that G2 loads are quite small and a choke with an inductance of ca. 100 Hy is necessary to achieve a genuine choke input power supply and all of the benefits it entails.
I would think 5 Hy would be enough for most puposes. BTW, Jeff always despised voltage regulation for screen supplies, claiming that he had a lot of experience with it and had never found one that was free from noise. He stated that the screen is very sensitive to a noisy supply.


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