John Curl's Blowtorch preamplifier part II

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#95,402
Alexandre said:
More from Bruno (Ed Simon will appreciate):

"The funny thing about ohm's law is that there are no resistors that follow it exactly. Every resistor data sheet gives an indication of the extent in which it deviates. If this info is not stated it just means that it's missing 🙂"

Source:
The G word: Demo project - A balanced volume controller | EDN
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Does he mean that resistance changes with current that changes temperature? Still, the laws is applicable to the actual resistance, not the marked value! 😀
 
#95,409
DPH said:
I'd say it was more of a joke that a resistor isn't a pure, immutable unit of resistance. But in any case, Ohms law is safe, the details and complexity lies elsewhere (as Scott says "resistance is a dependent variable").
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The mercury column standard was maintained until the 1948 General Conference on Weights and Measures, at which the ohm was redefined in absolute terms instead of as an artifact standard.
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#95,410
jan.didden said:
You can do that but it will again negate one important advantage of this setup, namely that the tracking of the two channels when changing volume is almost perfect.
Jan
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Channel tracking depends upon how well the two individual pots on the same shaft are matched in terms of their resistance ratio at each angular position of the shaft. Channel imbalance larger than 1dB is quite possible with normal quality pots.
This subject was discussed in the BPBP thread:
BPPBP - Bruno Putzey's Purist Balanced Preamp (well a balanced volume control really)

Regards,
Braca
 
#95,411
John,
Hate to interrupt all the other thread deviations with audio. Is it your opinion that the Vendetta phono preamp is better than the Constellation Orion? It would seems the Orion has more developed jfet regulators ( more parallel devices) with fet preregulators, a more advanced servo circuit and quieter raw supply - R core transformer, fast/soft recovery diodes etc.
The front end topology seems a more refined version (balanced now) of the Vedettas single ended front end, same for the second stage as well. Or is the unavailability of the Vendetta's 2sk147/2sj72 devices forcing the use of more paralleled 170/74 to be used to get the noise down a drawback in your experience.
 
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#95,415
DPH said:
John, you're right, I haven't kept up with "high end" audio too much at all. There's only so many variations of a Lin-based opamp-on-steroids that I can take before it all looks the same. Yes, class-D has been around for a long time, but this is one place where we're seeing the greatest improvements in design (that might have a positive effect audibly).

As far as any innovation in the world of Bybees, a "new" material based on junk science and measured to have essentially no effect is still junk science measured to have essentially no effect. (The essentially based on whatever resistor thingamagig there was/is going around, which obviously behaves like a resistor. I've forgotten the details).

Plenty to be learned in making speakers work better, especially in the rooms they occupy (and oftentimes smashed up against walls to satisfy the spouse, etc), but that's hardly another Lin-based opamp-on-steroids.
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Wtf. You know JC has posted a measured difference with Bybees. It was just deemed irrelevent since it took exceptional equipment to measure the itty bitty change, but it was there.
 
#95,416
Destroyer OS said:
Wtf. You know JC has posted a measured difference with Bybees. It was just deemed irrelevent since it took exceptional equipment to measure the itty bitty change, but it was there.
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You should review the conversations around those plots, no annotations and no way to to determine what was shown. The exceptional equipment was mostly nonsense and no information regarding even what was measured to facilitate corroborating experiments. There's nothing more there than brilliant pebbles, CD de-magnetizers, or the little stickers for your 8-legs.

Folks just can't get over that these things are just at worst fraud and at best a delusion.
 
#95,418
scott wurcer said:
You should review the conversations around those plots, no annotations and no way to to determine what was shown. The exceptional equipment was mostly nonsense and no information regarding even what was measured to facilitate corroborating experiments. There's nothing more there than brilliant pebbles, CD de-magnetizers, or the little stickers for your 8-legs.

Folks just can't get over that these things are just at worst fraud and at best a delusion.
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Jesus, I didn't realize we need peer reviewed studies around here. You can hear them anyways. It takes nothing more than average hearing to clearly hear the difference. Although it is laughable to try them inline with the speakers because .5r (two bybees) will affect the QES a bit.

Daniel I apologize I am not sure how many tens of thousands of posts back it is. I should have book marked it. JC probably has it saved.
 
#95,419
It's all good -- don't worry.

As far as needing peer review, to a degree, yes. It can be informal. We're not talking full blown studies and such (I'm an academic so I'm not asking for a "good" publication-quality document), but if you're going to make exceptional claims, and then don't back it up in a way that has a chance of being replicated, these assertions become very very problematic.
 
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