John Curl's Blowtorch preamplifier part II - Page 3820 - diyAudio
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Old 15th April 2013, 03:27 PM   #38191
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Quote:
Originally Posted by vacuphile View Post
I was reading Lipshitz's 1985 AES-paper "stereo microphone techniques: are the purists wrong". At the end he mentions as a fundamental flaw of stereo that:

-quo-
Consider equal in-phase signals at the loudspeakers, as would
be produced by a center-front source. At the listener's head the sound
pressure is up by a factor of two (6 dB) by scalar addition but the
sound velocity is up by only 3 dB (a factor of_sqrt(2)=1/sqrt(2)+1/sqrt(2)) by
vector addition if the loudspeakers subtend a 90 angle at the listener.
There is thus a 3 dB deficit.

-unquo-
What an odd thing for him to say. Terribly incorrect, but really odd. The sound velocity is not higher. The waves pass in the night, so to speak, at levels which humans can survive.

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Originally Posted by vacuphile View Post
but wouldn't sound waves also combine to create new virtual sound sources, combining their momentums?
I believe that requires non linearity in the medium..Isn't that how that two U/S wave virtual source thingy works?

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Originally Posted by vacuphile View Post
I hope this learned gathering has clues.
That is an entirely different and somewhat off topic question..

I can only speak for myself.. I am clueless..

jn

Last edited by jneutron; 15th April 2013 at 03:51 PM.
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Old 15th April 2013, 03:29 PM   #38192
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Originally Posted by john curl View Post
However, these relays are not quite as good a solution for OUR personal needs, when we strove to make the BEST product possible, rather than a practical product. And to this day, I stand behind this 'solution', although it is difficult to recommend it to anyone else.
Great. And I've never criticized your choice of Shallco switches.

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While I must admit that Bob's selection of a 4 section switch seems 'extreme', it is actually consistent with his switch and pot layout philosophy.
But it's not "extreme" in the sense of going the extra extra mile to achieve some greater performance benefit. It's utterly nonsensical and actually a step backwards in terms of performance benefits. I think Bob may have been laboring under the common mistaken "audiophile" notion that the "ideal" balanced configuration should have the inverting and non-inverting sides completely separate from one another as if they were separate channels like left and right.

I've seen this a number of times in the marketing literature for "high end" components. "Completely separate signal paths for balanced operation!"

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That is: All switches and pots are firmly mounted to the FRONT face of the enclosure. No false front panels, no extra supports necessary for mounting the switches, the pots and selector switch mounted in the same plane for easier connection.
Forcing you into a rats nest wiring job that can only diminish performance.

I liked Bob. He was quite a character. But the internal layout of the Blowtorch should have been left to someone else.

se
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Old 15th April 2013, 03:38 PM   #38193
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Originally Posted by john curl View Post
JNeutron, Do you know the specific differences between Vfets, lateral mosfets, vertical mosfets, Hitachi pinout, Harris IR equivalent mosfets, IR mosfets, and SUPERTEX T0-220 complementary mosfets (not made anymore)? IF not, then please withdraw from the controversy.

For everyone else: JUST the mention of the word: VFET shows that Scott is completely in the dark about the design parameters, as there are NO VFETS in a JC-80. Only, Supertex TO-220 mosfets that are difficult to substitute with anything else.

The schematic shows VN01/VP01 and you initialed it and sent it to me. I can only find that part number listed as Verticle DMOS FET.
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Old 15th April 2013, 03:38 PM   #38194
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Originally Posted by john curl View Post
JNeutron, Do you know the specific differences between Vfets, lateral mosfets, vertical mosfets, Hitachi pinout, Harris IR equivalent mosfets, IR mosfets, and SUPERTEX T0-220 complementary mosfets (not made anymore)? IF not, then please withdraw from the controversy.
You mean, other than working as an electrical test engineer for a manufacturer of V fets?? Or, having been in the position of taking every semiconductor type known to man at the time including ALL manufacturer's fets, performing a 200 to 400X visual inspection of the chips in a waffle pack, bonding the die to a gold plated TO-3 header, wirebonding via either U/S or T/C bonding using 1, 2, 5, 15, and 20 mil wirebond, and then subjecting the packaged device to testing to determine if the parts meet the manufacturer's specifications?

I know far more about the devices than you could ever hope to even understand, but I am willing to teach you if you were to ask questions. So I guess the answer is....YES, I do.

ALAS....that was not what Scott was talking about. The question was regarding the collective discussion about substitute parts.

So stop blathering. Instead of trying so desperately to find any opportunity to attack others, read more carefully please.

jn

Last edited by jneutron; 15th April 2013 at 03:41 PM.
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Old 15th April 2013, 03:39 PM   #38195
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Oh well just another attempt to discuss an actual JC circuit.
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Old 15th April 2013, 03:42 PM   #38196
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Originally Posted by scott wurcer View Post
Oh well just another attempt to discuss an actual JC circuit.
sigh.. you tried.

jn
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Old 15th April 2013, 03:57 PM   #38197
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Originally Posted by john curl View Post
Only, Supertex TO-220 mosfets that are difficult to substitute with anything else.
The TO220 parts are history but the dies live on in TO92 and SOT-89 packages http://www.supertex.com/pdf/misc/p_e..._SG_device.pdf . Supertex was never very successful with high power parts. I always understood them to be vertical DMOS parts. I am still using them in new designs and current products e.g.: P-9 .
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Old 15th April 2013, 04:22 PM   #38198
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Originally Posted by elektroj View Post
Steve Eddy, you're very shortsighted.

Just think for a minute about the following factors from the equipment manufacturer perspective:

1. Parts availability (in stock/custom order/lead times)
2. Price break (1/10/25 pcs.)
3. All possible combinations that you might need to cover requirements of your potential customers.
4. If you decide to go with two slightly different parts, but do not know how many units will be built with one part and how many with the other, how many of each part do you stock? If you buy both parts in enough quantity, you end up spending more money, not less.
And so on.

P.S. Actually, I'm wondering how many of the posters here do really make their living by serving the so called "High-End" customers.
Wow! you have my world nailed
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Old 15th April 2013, 04:32 PM   #38199
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JN, a VFET is not necessarily a VERTICAL FET. It is an early power jfet that was made by NEC, Sony, and Yamaha, for example. It is a DEPLETION MODE device and it was discontinued, because it was too difficult to get a suitable yield. It is also sometimes called a Static Induction Transistor.
The power devices used in the JC-80 are called VMOS, because they are a vertical MOS structure, with ENHANCEMENT instead of DEPLETION as the fundamental property of the device. They cannot be easily interchanged.

Last edited by john curl; 15th April 2013 at 04:49 PM.
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Old 15th April 2013, 04:40 PM   #38200
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Scott, your attempted insertion of this schematic at this time was inappropriate. It would have answered nothing and would not have contributed to further understanding of the questions recently posed. Secondly, you didn't appear to 'understand' the schematic details to do anything but confuse the situation, just like Demian just did by implying that a TO-92 part could easily replace a T0-220 part, even though the die inside are the same.
That is something that JN might do, Demain! After all, with a 45 degree spread angle of heat flow, anything should be possible! I maintain that only liquid Freon would do the job properly, and maybe not well enough, given the plastic thermal resistance. '-)
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