John Curl's Blowtorch preamplifier part II

[john curl]

Not good, is it?

[john curl]

DF96, it is a little more complicated than this simple example, but the principle is correct. Balance is useful and 'necessary' in the CTC Blowtorch.

[Steve Eddy]

Originally Posted by john curl

Enid Lumley... yadda yadda yadda

Why don't you address the point of my post, John, instead of wandering off on some obfuscation?

She had 'golden ears' too...

Any charlatan can have "golden ears," because they never have to actually demonstrate their claimed abilities.

se

[DF96]

If you need balance, why not insist on it by having suitable supply arrangements? It seems perverse to design a circuit which requires exactly balanced supply rails, then run it from a PSU which is guaranteed to provide unbalanced supply rails unless the circuit draws exactly balanced currents. I assume you felt there was a good reason to do it this way.

[hitsware]

Originally Posted by DF96

If you need balance, why not insist on it by having suitable supply arrangements? It seems perverse to design a circuit which requires exactly balanced supply rails, then run it from a PSU which is guaranteed to provide unbalanced supply rails unless the circuit draws exactly balanced currents. I assume you felt there was a good reason to do it this way.

I think he mentioned not having ground attached to the xfmr as the reason.

[Wavebourn]

Originally Posted by hitsware

I think he mentioned not having ground attached to the xfmr as the reason.

It is attached, actually. But attachment is modulated with 120 times per second speed. It is the matter of preference.

[vacuphile]

Originally Posted by john curl

Let's talk about 'balance'.

With the power supply I am working on which has < 1mOhm @1500 Hz,the difference by closing the switch would be something like 2,2 uV. At DC it would be much less, but have no way to reliably measure.

Problems are lay out and higher frequencies. You can make supply with extremely low output impedance, much lower than realistic pcb-traces would add.

So that also means: where would you connect that LED, to see what the effect on the voltage at different points would be?

vac

[Wavebourn]

Originally Posted by cliffforrest

Why?

This is not the issue, and you know it!

The LED can run between the + and - rails directly, (series 5K or 2 series 2k5 if you have doubts about Thevanin!)

But you know all of that.

Also light can go on front panel through transparent plastic stick (to avoid "out of Faraday cage" effect)

[john curl]

Good Idea Wavebourn, but is the plastic stick also conductive enough to be an RF barrier?

[john curl]

Things sort of got quiet when I brought up the 'balance' example. Any questions?