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In Reply to: RE: Summertime Blahs posted by drlowmu on July 19, 2014 at 07:06:20
I've been working to get this puppy in a proper chassis for a while...busted up my shoulder and all effort has stalled. The prototype achieved some pleasant results after much tweeking...
Went down the CF rabbit hole with some success...ultimately distortion levels resulting from pumping up the input voltage will be the killer.
Need to finish the build and start listening again...
Winter will be here soon enough...we'll start slinging solder again...
Stuben
Follow Ups:
Stuben
I went that route long time ago.
It was interesting but not my cup of tea.
Fast, articulate and very clear sounding.
Reminds me of a good PP amp.
I fell in love with the SE sound though.
Good Luck Though
DanL
Totally agree concerning DHT performance compared to tricking Pentodes into somewhat DHT performance...My listening amp will probably always be a DHT amp. Getting different sounds from Pentodes however has been fun..
Thanks...If I can't get what I want from the CF amp, a 2a3 scheme is already in the works. This is DIY...
Loads of fun
Stuben
Cool post. Tell me, have you PSUD2 simulated that supply with a step test of current? Three L/Cs in series to the Finals is inherently unstable and, if the values are not carefully chosen, it can ring like crazy, which we want to avoid. I was lazy and did not simulate it yet.
Jeff .
Jeff,
Thanks, I'm the lazy one...I have neglected to run the latest PS arrangement.... Will consider...
I have always considered transient pulls of current due to frequency induced load chances, and have been working under the premise that Chokes, when sized correctly for critical Inductance, provides "a Resistance to change in current" or simply put a "Surge"...
I also understand that an amplifier builders ultimate goal should be to provide amplification with no color. A wire with gain...
I will certainly get around to building a PS inspired by your posts.
Stuben
Steuben,
Awfully even-handed and a very nice response. Good attitude !!
If you want to use me to bounce ideas off of, please just contact me by private email. I have put in literally hundreds of hours on PSUD2 analysis, and may be able to assist you some.
Jeff
My post was a bit broken ..."the chokes resistance to current change" should be related to the chokes ability to filter AC through the production of CEMF and the "Surge" comment really describes the chokes ability hold energy while the rectifier is not conducting...I get in a hurry and forget everything I might have known...
I can run the calcs on my own...it's always nice to bounce stuff off the other inmates...although that was not my intent...just providing a short break from the blahs... ;> )
What are your thoughts on an amps ability to provide current upon frequency induced load changes...?? This subject has always fascinated me.
Stuben
Stock ( top ) versus a very quick suggestion ( bottom ).FILTER TO FINALS : Smoother settle below, quicker total recovery ( 200 mS versus 500 mS ) at the expense of higher Z, which can be ameliorated with lower DCR audio magnetics, 20 Ohms and less.
The G2 and front end supply will "see" the odd settling of the Finals, in the top simulation, and that is not good. I guessed at DCR values, used what is typical in both simulations.
Jeff Medwin
Edits: 07/20/14 07/20/14
Higher 'Z' ? I had no idea you could measure impedence on PSUD2 . At what frequency was this measurement taken ? ...and what was the actual impedence ?Al
Edits: 07/20/14
Hi Al,Follow this. In the top simulation, the voltage dropped on the current step, from about 286.88 VDC to a settled VDC of about 283.00, a 3.88 VDC drop.
In the bottom simulation, the voltage dropped on the current step from about 344.70 to about 334.01 VDC, a 10.69 VDC drop.
In each case, the current change was 14 mA. or .014 A.
Ohms Law, Voltage over current equals resistance.
3.88 VDC divided by .014 A. is 277 Ohms.
10.69 VDC divided by .014 A. is 763 Ohms.
277 Ohms versus 763 Ohms. This math, Ohm's Law, can be applied to any current step in PSUD2.
Are we two now on the same page ? Hope so.
One other point I'd like to make. Over the last couple of years, I have changed my priorities on Power Supplies and PSUD2. I no longer believe that the "lowest Z" is the best sounding supply. If that were the case, everything I built would have a solid state rectifier, yet I LIKE the sound of directly heated vacuum tube rectifiers over Crees, etc. and I will use vacuum rectifiers with no cathodes, despite their higher Z. I prefer the sound of ONE dual rectifier tube, and will not parallel tubes in my DC circuits any more. I also have greatly relaxed my desire for the fastest settling supply, like under 50 mS as per John Swenson. This under 50 mS comes at a price, of an overshooting, sometimes ragged step response. In 2014, I look to have a SMOOTH step response as one of several simultaneously combined priorites, so I have veered from the writings of Hasquin and Swenson, and am pleased to do things now as "I" like to do them, despite "theory ". Dealer's choice !! Live, listen and learn.
Regards,
Jeff Medwin
Edits: 07/20/14 07/20/14 07/20/14
That is not impedence . What you describe is a phenomenon unique to PSUD , it does not happen in a real amplifier . You are describing the settling time of the simulation .
I don't see Hasquin or Swenson here much any more . I think you've scared them off ;)
Al
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