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John Curl's Blowtorch preamplifier part II
John Curl's Blowtorch preamplifier part II
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Old 4th December 2012, 06:57 PM   #30821
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by Kindhornman View Post
Mr. Wurcer,
Sounds formal doesn't it.... What determines when one of these opamps or even a discrete device is discontinued? Are we bound by the same rules that are applying to computer CPU speeds and the every increasing speeds of logic circuits or is there something else that determines the lifespan of one of these devices? If a device is meeting the purpose that it is designed for what changes are driving the obsolescence of what seem like perfectly capable devices. I only ask you because you seem to be intimately involved in their design.
When sales decline far enough, certainly when there is a long period with no new designs you issue a last time buy notice. We have BTW sold designs to outside companies that have small but steady sales, there is still one running from 1968.
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Old 4th December 2012, 07:01 PM   #30822
Kindhornman is offline Kindhornman  United States
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Scott,
Just so I am following you here. When you sell a design to a company does that mean that they produce the part themselves or do you continue on an exclusive basis to produce the device for that customer?
 
Old 4th December 2012, 07:14 PM   #30823
pooge is offline pooge  United States
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Originally Posted by jneutron View Post
Make what good?
I'd center the Z to minimize the difference in the delay.
jn
Center it how? Between minimum and peak load impedance?
 
Old 4th December 2012, 07:22 PM   #30824
scott wurcer is offline scott wurcer  United States
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Quote:
Originally Posted by Kindhornman View Post
Scott,
Just so I am following you here. When you sell a design to a company does that mean that they produce the part themselves or do you continue on an exclusive basis to produce the device for that customer?
No we just enable someone else make it and sell it. It's pretty rare. In the case of say the AD844 who would bother, it really is about no more complicated than the simplified schematic and no one has an exclusive right to that topolgy.
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Old 4th December 2012, 07:23 PM   #30825
john curl is offline john curl  United States
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Try parallel strands of #22, like the rest of us. '-)
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Old 4th December 2012, 07:25 PM   #30826
Esperado is offline Esperado  France
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Originally Posted by pooge View Post
So would the easy solution be the Mogami wire with 8 ohm impedance as shown in Nelson's article, perhaps terminated as also shown in article? Seems easier and more "attractive" than dressing 8 pairs of CAT5/6 cable, even though only subtle changes, sometimes, were heard between the various cables.
The purpose was to have an economic shieded cable, on one side, and it was question of 3 cat 6 for 8 ohms.(each one composed of 100/4 = 25 ohms).
One thing witch has not been mentioned is, if the lengths of the paralleled cables are a little different, reflexions can be a little more randomized.
 
Old 4th December 2012, 07:35 PM   #30827
jneutron is offline jneutron  United States
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Originally Posted by Kindhornman View Post
JN,
While using four pairs of #18 would you do anything fancy here? What I mean by that would you braid the wires a la Kimber cable and his interwoven stranding or just forget it and run everything in parallel?
Cut them to the same length. If you twist them to different pitches, they'll act like a cat5/6 cable..totally independent fieldwise. If you don't twist them, keeping them apart half an inch or so would be enough to prevent coupling.

A really good braid might actually be worse than random bunching if you keep the conductors flat.

Quote:
Originally Posted by pooge View Post
Center it how? Between minimum and peak load impedance?
Yup. It doesn't have to be to four digits, I'd just try to keep the cable z within an order of magnitude of the lowest..splitting the diff is probably good enough.

It might even pay to get as close to 1Khz speaker z as possible..I think that's where we work the best.

Don't forget...this delay stuff may or may not make a darn bit of audible difference. The actual existence of delays due to line load mismatch doesn't prove audibility.


jn
 
Old 4th December 2012, 07:50 PM   #30828
pooge is offline pooge  United States
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Originally Posted by jneutron View Post
It might even pay to get as close to 1Khz speaker z as possible..I think that's where we work the best.

Don't forget...this delay stuff may or may not make a darn bit of audible difference. The actual existence of delays due to line load mismatch doesn't prove audibility.
jn
Yes, audibility is in question, but if the physics are good and the implementation is not hard or expensive, why not? I have some Mogami cable I've never used because of the high capacitance issue. At the time I bought it years ago, I thought it would help shield against RF entrance to the amp via the speaker wire. Now trying to re-evaluate its use. I presume an RF termination a la the Pass article would help.
 
Old 4th December 2012, 08:31 PM   #30829
jneutron is offline jneutron  United States
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Originally Posted by Esperado View Post
One thing witch has not been mentioned is, if the lengths of the paralleled cables are a little different, reflexions can be a little more randomized.
Small changes won't make much difference to reflections. If the resistance is significantly different, current imbalance would trash the lowering of inductance.

jn
 
Old 4th December 2012, 08:40 PM   #30830
Esperado is offline Esperado  France
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Originally Posted by jneutron View Post
Small changes won't make much difference to reflections. If the resistance is significantly different, current imbalance would trash the lowering of inductance.
You are right, my mystake. I forget the speed of the light, so used to deal with the sound's one :-)
 

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