John Curl's Blowtorch preamplifier part II

[Steve Eddy]

Originally Posted by dimitri

Here it is
Steve:

Thanks.

Sorry. It saved out with a capital S on Simon and when I put up the URL here, I used lower case.

It's fixed so it can be grabbed from either URL.

se

[john curl]

Thanks Dimitri, my Microsoft Word won't open it for some reason.

[Joshua_G]

Originally Posted by john curl

Thanks Dimitri, my Microsoft Word won't open it for some reason.

Download the newest version from Microsoft.

[PMA]

I do not understand why resistor 'distortion' of some -145dB 2nd or 3rd harmonic matters, though active element distortion of -40dB (tube) is just fine. This (-145dB 3rd) is hardly a case of any sound difference.

[simon7000]

Originally Posted by scott wurcer

No, I was having drinks with Kirkland and the guys from ESS in Los Alos.

The distortion will increase at lower frequency because of less thermal averaging. I repeat a good thermal model and separation of real voltage coefficient from the thermal effects would be very useful.

Do you have a good thermal model! ? Right now is just play time. My feel says tinker around until something pops out at you.

I suspect that I am not finding any unexpected voltage discontinuity effects.


Pavel,

The 145db decreases as you go down in frequency. I am now using 333 hz as my test frequency.

The hearing threshold is around -10db at 3khz. Un-equalized music has about 10db more energy at 300 compared to 3k so there should be at least a 20db compensation factor for a 9th harmonic under those conditions. Some folks even put a 10-20 db boost on the low end!

My design goal as mentioned before is 160 db for the entire system. I would like individual components to be better than that.

[john curl]

Simon, I think that IF you really approached thermal problems from a transient point of view, you would find much more of a problem than by measuring with continuous tones.

[PMA]

Simon -

masking, and usable instantaneous dynamic.
Maybe you might like to follow John's advice.

Regards,

[PHEONIX]

My design goal as mentioned before is 160 db for the entire system. I would like individual components to be better than that.[/QUOTE]

Hello Simon,

What happens when you put a couple of resistors in series, the THD must obviously be reduced. This surely must be a solution to this problem.

I respect your high standards for THD performance.

Regards
Arthur

[goran7]

Resistor for audio equipment - US Patent 6317024 Description

[john curl]

It is interesting that putting the resistors in series would potentially reduce the distortion.