looking for null circuit

[danielwritesbac]

Originally posted by ide2003
hi there danielwritesbac, appreciated your tips.

will check mine, schem. attached, I use 50k pot, C1=2.2u, R1=1k, R2=20k in that order.. is this the culprit of 'big' dc-offset?

thanks
TPS

Yes it is.
You can change R2 to 10k and then you can measure lower dc offset as the result. This may change the capacitor size needed at C1.

Tip:
Imagine. . . the pot needs protected from DC entrance, which can come from a buffer, preamp, or source.
Imagine. . . a future buffer/pre project. Have a look at some examples and see how they will connect to your amplifier.

EDIT: I will conduct an experiment today with both feedback and input load as 10k. Also, I'll set "nfb seeks ground" the same value as "input series" resistor. This is the way of a balanced amplifier; however, there's an additional step that I either don't know or can't remember.

[danielwritesbac]

Originally posted by danielwritesbac
EDIT: I will conduct an experiment today with both feedback and input load as 10k. Also, I'll set "nfb seeks ground" the same value as "input series" resistor. This is the way of a balanced amplifier; however, there's an additional step that I either don't know or can't remember.

WOW!!!
The analog meter didn't budge on its most sensitive setting. Normally, it'll show about 45mv on my amps.
The digital meter on its "200m" scale read 00.1. My fingers could get it to read 08.2, so, apparently my body makes more dc offset than this amplifier. It could be paralleled without the typical heat penalty.
I had to use a smaller-than-usual gain setting because there was too much.
The bass is nice!

[ide2003]

Originally posted by danielwritesbac


WOW!!!
The analog meter didn't budge on its most sensitive setting. Normally, it'll show about 45mv on my amps.
The digital meter on its "200m" scale read 00.1. My fingers could get it to read 08.2, so, apparently my body makes more dc offset than this amplifier. It could be paralleled without the typical heat penalty.
I had to use a smaller-than-usual gain setting because there was too much.
The bass is nice!

men!. you're fast!..thanks, so many to try..so little time..


TPS

don't quite understand this, danielwritesbac, a schematic is great thanks b4

EDIT: I will conduct an experiment today with both feedback and input load as 10k. Also, I'll set "nfb seeks ground" the same value as "input series" resistor. This is the way of a balanced amplifier; however, there's an additional step that I either don't know or can't remember.

[AndrewT]

and you know what

I'll set "nfb seeks ground"

means.

[ide2003]

Originally posted by AndrewT
and you know what means.

nice that you come-by AndrewT, you know, this EE talks that keeping me going gaa-gaa all the time..I can read the schem, can solder, do a nice mech job..but gave up on these..

TPS

[AndrewT]

we've all given up trying to persuade Daniel to use the conventional language that we can all understand.

[danielwritesbac]

Originally posted by AndrewT
we've all given up trying to persuade Daniel to use the conventional language that we can all understand.

I forgot how to call "sides" of a voltage divider. Low leg? High leg?
Sorry about that.

Since this isn't using a DC null circuit, and so its off topic, I moved the discussion of my experiment (soon to list a schematic) over to: 10k nfb and 10k input impedance. Anyone tried it?

[ratza]

Originally posted by danielwritesbac


I forgot how to call "sides" of a voltage divider. Low leg? High leg?

Sorry about that.

How about in and out?