John Curl's Blowtorch preamplifier part II

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The VAC/VSA ? or the now merged Endeavor/Audio Alchemy? (VSA absorbed Endeavor)

I don't have the guide handy, but here's a photo if that helps with ID.
 

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ES,
I do understand that we can't correct for uncontrollable un-damped mechanical resonances, that is an argument I have had enough times, so we are on the same page on that condition. All of these conditions are a major reason I have chosen to go with a lower efficiency design with more linear conditions of the under-hung long gap length device design, all of the problems excepting impedance rise with coil heating are much easier to control and create a much more linear device. Amplifier power is cheap in reality vs non linearity of most equal or overhung designs.
 
I don't have the guide handy, but here's a photo if that helps with ID.

Yes, that's the VSA/VAC (VSA= Von Schweikert Audio).

I thought it was the room with the best speakers of those downstairs, in the big dollar category, but was thoroughly not impressed. Which is funny because I like MSB's DAC. To me the VAC was the let down in the room that just wouldn't let anything spectacular happen.

I noticed the room treatment, it's probably why the sound-stage had some real depth.
 
I have once tested maybe 80 or 100 devices and they were nearly all 12-13 mA, very few outliers by more than 2 mA when I wanted some high Idss ones.

It goes without saying that they were not that consistent when I needed similar ones for a differential amplifier.

Fet-aided op amp:
<http://www.analog.com/library/analogdialogue/archives/47-10/discrete_amplifier.pdf >

regards, Gerhard
Vielen Dank! Yes that was what I rather hoped, that the end points were as usual quite far out on the tails of the distribution. And fortunately in this case I am not trying to select for differential pairs.
 
ES,
I do understand that we can't correct for uncontrollable un-damped mechanical resonances, that is an argument I have had enough times, so we are on the same page on that condition. All of these conditions are a major reason I have chosen to go with a lower efficiency design with more linear conditions of the under-hung long gap length device design, all of the problems excepting impedance rise with coil heating are much easier to control and create a much more linear device. Amplifier power is cheap in reality vs non linearity of most equal or overhung designs.

Ferro-Fluid!
 
Ferro-Fluid!

If you want to discuss the effects of long and lossy transmission lines and their effect on stadium speakers, then do so, get to the point.

For long lines typical of a stadium build, the t-line settling time impact on transient signal distortions can be rather large. Specifically, in the band directly above the minima. As well the cable's total resistance.

It's folly to expect a twisted pair of any gauge to drive an impedance that varies from one to two orders of magnitude below the cable's LC impedance. Inclusion of the large resistance of the cable means the settling times will require a calendar to measure.

If you want to maintain copper weight, just go with a 4 pair multiconductor in place of a single twisted pair, do what the cat5 cable guys play with..but with a much more honkin equiv gauge.

Just add a zobel at the speaker, I'm not sure the series resistor maintains stability.

If you REALLY want to bring something new and great to the table, measure the step settling time at your next stadium gig with the longest runs. Put a 1, 2, 5, 10, 20, 50, and 100 ohm load at the far end, and put a step function in at the amp side. Measure the current at the amp end, show us measurements of how long a step settles to 95% final value for the same cable but different load impedances. THAT would be of interest to all. That would demonstrate very clearly what you have to content with in your work. And, it would show the way for better wiring in your jobs.

edit: then, demo a 4 twisted pair cable of equiv gauge paralleled up at the same length, show the huge effect it will have on the settling time of the 10, 20, and 50 ohm loads.

John
 
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Ragnarok

By the way, somewhat off topic: be sure to read the review of the Schiit Audio Ragnarok in the May 2016 Stereophile. JA has a very hard time making measurements owing to the errrr interesting application of a microcontroller to determine output stage bias.
 
I'd outgrown the show by then, but Clarabell was the last clown I didn't find scary.

That clown gave me nightmares. And I remember having a dream where Howdy Doody's strings were cut by a big pair of scissors and he lay, collapsed and helpless, sprawled on the stage, his head twisted sideways, eyes staring off blankly into space.

My mother told me to stick to Captain Kangaroo.
 
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