John Curl's Blowtorch preamplifier

[john curl]

I don't think everything always has to be 'voiced' by ear, but it can help, sometimes. For many years, I relied on measurements, both normal and exotic, and still did pretty well. Then I built a power amp that my associates found wanting, subjectively, yet it measured very well. I learned then, that measurements are not everything. I have found that it is avoiding certain passive parts is what makes the most difference, for my designs.

[PHEONIX]

Originally posted by john curl
I don't think everything always has to be 'voiced' by ear, but it can help, sometimes. For many years, I relied on measurements, both normal and exotic, and still did pretty well. Then I built a power amp that my associates found wanting, subjectively, yet it measured very well. I learned then, that measurements are not everything. I have found that it is avoiding certain passive parts is what makes the most difference, for my designs.

Hello John,

With things that I build I have found that unless you use a proper full range monitoring speaker which is set up properly that you are waisting your time when it comes to evaluation. By proper full range monitor I mean a minimum of a 3 way speaker, bass driver , mid range and tweeter, anything less than this is not good enough for evaluating a product that needs to sound good on most systems. I dont think that two way speakers cut the mustard for evaluation purposes, and its very easy to be fooled into thinking your product sounds good only to find it does not translate the same way into other peoples systems.

With full range speakers you can here things that you cannot possible here on a two way speaker , because it is more revealing.

By the way I agree with you on the impact that passives have on the sound of amplifiers.

Regards
Arthur

[john curl]

I use my WATT 1's with a sub. It is VERY revealing. Too much for some.

[PMA]

I would like to know what kind (technology, manufacturer) of Re emitter resistors in power output stages are recommended (0.1R - 0.22R values). IMO they make a big difference. Their inductance contributes to stability/instability in a high degree, as well as PCB tracks to/from them.

[x-pro]

Originally posted by PMA
I would like to know what kind (technology, manufacturer) of Re emitter resistors in power output stages are recommended (0.1R - 0.22R values). IMO they make a big difference. Their inductance contributes to stability/instability in a high degree, as well as PCB tracks to/from them.

I did measure some power resistors in the past - many have very measurable distortion at 1 A current level (0.01-0.1%). I don't have results now - perhaps one day I will repeat my experiment.

Alex

[analog_sa]

Originally posted by PMA
I would like to know what kind (technology, manufacturer) of Re emitter resistors in power output stages are recommended (0.1R - 0.22R values). IMO they make a big difference. Their inductance contributes to stability/instability in a high degree, as well as PCB tracks to/from them.

I have always had best results with non-inductive diy wirewounds using nice copper wire.

[PMA]

Originally posted by x-pro


I did measure some power resistors in the past -

Me too

[PMA]

...

[janneman]

Originally posted by PMA
...

PMA,

These *may* be interesting curves, but I have no idea what it is, how it is measured, etc, so at this point it isn't very usefull.

Jan Didden

[AndrewT]

is that overshoot due to self inductance of a spiral wound resistor? Would wirewound and metal film be equivalent in this case?

Would carbon film also have some self inductance if spiral cut?