John Curl's Blowtorch preamplifier part II

[Esperado]

32 bits with dithering seems satisfactory, on a theoretical
point of view ?

[PMA]

Real world would be no better than 20 bits.

[Esperado]

Yes, let say 24+ 8bits (60db) of volume control = 32.

[1audio]

A good digital volume implementation is not simple and then it needs to have the post ADC gain optimized to ensure you are not running at too much attenuation on the digital side. Dithering the attenuated output is important.

In a system environment it can be a good solution but with individual components will run a high risk of getting the gain structure non optimal. The Berkeley Alpha dac is a good volume implementation but really needs a separate preamp on the output to get the gains aligned in many cases.

[BV]

Sorry, but this is IMO very "suboptimal" solution.

[Esperado]

Originally Posted by BV

Sorry, but this is IMO very "suboptimal" solution.

Oh, really ?

[Max Headroom]

Originally Posted by john curl

Depends on the cap quality Gootee.

Yes.
I have replaced many leaky pot and switch electrolytic coupling caps.
The symptoms are a scratching noise when the pot is moved, and a thump or scratching when switches are operated or rocked.

Dan.

[fas42]

Originally Posted by Esperado

As i use mainly Digital sources, my next solution for volume control will be exclusively in the digital domain. And i will add a ADC to deal with my analog sources.
JC will kill-me

Good move ... you won't be sorry, Christophe. My first CD player was the top Yamaha of the time, used an analogue volume out. Gave me hints of what was possible, but then started playing up, tracking problems. Dealer exchanged for the new model top unit, which used digital volume. This is when I started making real progress, and the breakthrough occurred ...

Frank

[fas42]

Originally Posted by 1audio

A good digital volume implementation is not simple and then it needs to have the post ADC gain optimized to ensure you are not running at too much attenuation on the digital side. Dithering the attenuated output is important.

Why? If totally in digital it works like charm, my still working 27 year old Yamaha beats the pants off nearly all digital plus analogue I've heard over the years. You just have to chuck the preamp ... sorry, John!

Frank

[kgrlee]

Originally Posted by john curl

This pot was in a JC-2 preamp a few months old, at best. It was a MANUFACTURING DEFECT and it was UNIVERSIAL .... loadsa good stuff ....

JC, thank you for these pearls of wisdom from the Jurassic days when you diidn't shy from getting your hands dirty with stinkin' measurements.

IIRC, you mentioned a wire wound pot which was your reference standard before Blowtorch.

Could you reprise your thoughts on these and explain how Blowtorch achieves its exemplary performance c/f supa dup wirewound?

You also hint at having done trials with some evil digitally volume controls eg PGAxxxx. Could you summarize your findings including any measurements you made? As these do not appear in any of your product, it won't matter if us Unwashed Masses misinterpret your measurements.