Re: It's back!!!

Posted by Lynn Olson (M) on December 17, 2001 at 03:33:47

In Reply to: Re: It's back!!! posted by Gary P on December 16, 2001 at 22:02:32:

I was kind of weirded out by the requirement for the pentode CCS to have a floating heater that tracked the cathode, until I saw your recommendation for a dual-bobbin heater suppler. Ah-hah, I thought, it all comes clear now!

Back when I lived in Portland, Matt Kamna did a lot of measurements of primary-to-secondary and secondary-to-secondary interwinding capacitance. Matt was the one that mentioned that electrostatic screening would reduce this capacitance by ten to fifty times ... no small improvement, and the decrease in HF response of the power transformation is an additional bonus. He also made the dismaying discovery that the distortion on his AC power lines was 5%, not including HF switching grunge from the neighbor's microwave ovens, TV, computer, etc. etc. Any clever techniques to decrease HF noise from the supply is always welcome!

I have occasionally considered an outboard power supply for the iron-enriched Aurora, but the awkwardness of sending the live filament/cathode return for the 300B's several feet and back, not to mention the contact corrosion of the umbilical connector, deterred me from taking it any further. The dual-bobbin filament opens in interesting option: the filament transformer could reside in the main (audio) chassis, with magnetic screening of course, while the really heavy and EMI-emitting B+ supply could be outboard. RG-6 transmitter coax might be a good way to transport the B+ and ground between the two chassis.

Still curious about the very crude expedient of adding a substantial wirewound resistor in series with a plate choke ... this would give at least a few K isolation between the main audio circuit and the inevitable capacitive strays of the choke. From the point of view of load phase angle, the series R would keep the plate load from being purely reactive at the ends of the audio spectrum. This isn't very attractive for the final stage, I admit, but dropping 200~300 volts in the driver or input stage would work OK, and I think the driver at least would appreciate not seeing a dead short at 1 MHz.

Compared to the refinement of your latest hybrid CCS, the Aurora looks like Fred Flintstone designed it. It's awaiting a pile of Mikey-chokes to arrive at John Tucker's place, and once they arrive, it'll get bench-tested and the value of parafeed caps optimized. The requirement for coupling caps is what led to the research on the problems of DA and DF in caps, not to mention the dismaying self-microphonics of these guys. I still like Teflon best, but 5uF Teflons are rare animals indeed.

Latest Aurora (Open in New Window)

This post is made possible by the generous support of people like you and our sponsors:

Follow Ups Full Thread

Topic - Less noise, less emotions, what happened!!??? - Gary P 11:39:04 12/14/01 (25)

It's back!!! - Gary P 16:05:52 12/15/01 (10)

Re: It's back!!! - eagle1 06:17:15 12/16/01 (0)

Re: It's back!!! - Lynn Olson 01:57:12 12/16/01 (6)

Re: It's back!!! - Gary P 08:50:05 12/16/01 (5)

Re: It's back!!! - Lynn Olson 19:01:09 12/16/01 (4)

Re: It's back!!! - Gary P 22:02:32 12/16/01 (3)

Re: It's back!!! - Lynn Olson 03:33:47 12/17/01 (2)

Re: It's back!!! - Gary P 06:50:40 12/17/01 (1)

We have to quit meeting like this, people will talk - Lynn Olson 22:51:49 12/17/01 (0)

Re: It's back!!! - Eli Duttman 17:34:34 12/15/01 (1)

Re: It's back!!! - Gary P 19:42:00 12/15/01 (0)

noise = infinte information? - lk4200 15:46:20 12/15/01 (0)

Less Parts,more emotions??? Interested in JFet CCS. - -3db 15:37:46 12/15/01 (1)

Re: Less Parts,more emotions??? Interested in JFet CCS. - Gary P 15:46:35 12/15/01 (0)

Same here :-) - PÃ¤r 10:06:53 12/15/01 (0)

Re: Less noise, less emotions, what happened!!??? - eagle1 07:10:04 12/15/01 (0)

Re: Less noise, less emotions, what happened!!??? - Lynn Olson 03:57:41 12/15/01 (0)

Less noise, less emotions, Argh! - VoltSecond 21:29:28 12/14/01 (0)

Re: Less noise, less emotions, what happened!!??? - Kurt Strain 17:35:12 12/14/01 (1)

Re: Less noise, less emotions, what happened!!??? - Gary P 18:25:45 12/14/01 (0)

Re: Less noise, less emotions, what happened!!??? - gdahl 15:31:40 12/14/01 (2)

Re: Less noise, less emotions, what happened!!??? - electron_luv 23:17:24 12/14/01 (0)

Re: Less noise, less emotions, what happened!!??? - Gary P 18:40:19 12/14/01 (0)

Digital source? - DrM 12:47:02 12/14/01 (1)

Re: Digital source? - Gary P 18:11:56 12/14/01 (0)

Follow Ups

Re: It's back!!! - Lynn Olson 03:33:47 12/17/01 (2)

Re: It's back!!! - Gary P 06:50:40 12/17/01 (1)

We have to quit meeting like this, people will talk - Lynn Olson 22:51:49 12/17/01 (0)

You can not post to an archived thread.