John Curl's Blowtorch preamplifier part II

[Waly]

Originally Posted by simon7000

As shown in the attached measurement of a higher wattage resistor at 50 mW

Where did you find these high power resistors with -100dB 3rd harmonic distortion @1Khz and 50mV dissipation? Brand, series?

I'll take a couple, these may be valuable collector items.

[john curl]

There is no 'magic' just physics, at a level that most here do not appreciate.

[gpapag]

Originally Posted by simon7000

Pavel…
To me the interesting issue was the use of a low wattage, low quality resistor in the feedback loop. I suspect that is actually the dominant distortion source. So if you like to brighten up your recordings with more distortion, chip amps are more than adequate to give you that result.
ES

Originally Posted by simon7000

George,
The point was that the IC had less distortion than the feedback resistor. So the amplifier was was good enough or in other words not the limiting factor.
ES

Ed
If the feedback resistor was your worry, why you framed the chip amps?
It is an external component.
Don’t discrete amps have such a resistor too?
Wouldn’t it produce equal distortion there?

I’ll have a couple of drinks because in sober state I see these two posts not matching.
I wish to see them matching .

George

PS. Ironically, Scott was the first one here to target inappropriate low wattage feedback resistors

[Esperado]

Originally Posted by fas42

Christophe, we are essentially coming from the same direction,

I hope so, fas42. Just i try to keep a scientific attitude. The first time , long time ago, i had heard of those rumors of the improvements given by some cones under power amps, i had done the following to figure out: Record the output of my amp, powered, both with no signal and with 1000Hz, and made big shocks on the amp. Of course, nothing ! I had not buy any of the golden plated cones. But i had take big cares to rigidify and dump my enclosure's walls the best i could and to isolate my CD transport from vibrations.
In the same spirit, i do not buy "Audiophile" cables. But i changed all the RCAs i could for mini XLRs, and added ferrite coil on all my cords.

[Esperado]

Originally Posted by john curl

There is no 'magic' just physics, at a level that most here do not appreciate.

Can-you justify by any measurement the advantage (on a sonic point of view) of your Blowtorch chassis, machined from plain unobatnium ?

[john curl]

Just aircraft grade aluminum.

[morinix]

Originally Posted by john curl

There is no 'magic' just physics, at a level that most here do not appreciate.

I maintain that it is the art of science.

[simon7000]

George

I read those as saying the same thing! Pass the Ouzo. The civilized way to settle a non-dispute.

ES

[fas42]

Originally Posted by Esperado

Record the output of my amp, powered, both with no signal and with 1000Hz, and made big shocks on the amp. Of course, nothing ! I had not buy any of the golden plated cones. But i had take big cares to rigidify and dump my enclosure's walls the best i could and to isolate my CD transport from vibrations.
In the same spirit, i do not buy "Audiophile" cables. But i changed all the RCAs i could for mini XLRs, and added ferrite coil on all my cords.

Yes, you are coming from a similar angle: the fact you ditched the RCAs, added ferrites, tells me you can hear these distortion artifacts.

The trouble with the amplifier test you tried is that you expected to register an instantaneous difference. In general, it doesn't work this way, many of the issues take time to build up, the sound begins to degrade in a subtle manner over a period of time -- just like what happens if you rely on RCAs.

With the amplifier test, what I would have done is feed it an IM test signal, of high complexity if possible, and recorded the distortion spectrum over a period of time, every half hour or so. With, and without the footers. My assertion would be that you would be able to see changes in that spectrum occurring, if there was "something in it".

Frank

[Telstar]

Chip amps have poor CMRR. The quality i.e. of the feedback resistor matters in discrete designs too, but less.
Do chip amps sound bad? no, some are quite good, mostly thanks to the very short signal, and to good behaviour at HF (unlike class d).

Originally Posted by john curl

There is no 'magic' just physics, at a level that most here do not appreciate.

Or they have no idea how to measure. (Me neither but I'd like to learn)