Re: Low THD transformer circuit



Robert Baer wrote:

Eeyore wrote:
Robert Baer wrote:
Eeyore wrote:
martin griffith wrote:
Eeyore <rabbitsfriendsandrelations@xxxxxxxxxxx> wrote:
John Larkin wrote:
martin griffith<mart_in_medina@xxxxxxxxxxx> wrote:

Just found this
http://www.pat2pdf.org/patents/pat4614914.pdf
It's how Audio Percision let very low thd from transformers

Why not load the transformer secondary into a summing point

How about the real load ?

and drive
the primary through a resistor, or from a current source? That would
keep the core at nearly zero flux.

I'm not clear how you can have near zero flux though.

Graham

I've seen it done on Quad amps, apparently even with ferrite
transformers for the input stage. The Beeb had a go at it as well,
sorry no URLs


There's this little equation that says E = -N.dthi/dt though !

No flux means no voltage.

Graham

Yep!
And an (ideal) op-amp works with zero voltage difference at the
input, where zero input times infinite gain gives exactly what was
needed at the output.


That's a very silly reply.

Graham


We were speaking of "ideal"; in practice the input is equal to the
output divided by the open-loop gain.
So an error voltage (input) of a microvolt, times a gain of a million
gives one volt drive for the feedback (and load).
Thus even a modest open-loop gainof a million, one gets reasonably
close to the ideal.

You won't find gains of 1/2 million at moderate audio frequencies.

More like a few thousand.

Graham


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Relevant Pages

  • Re: Low THD transformer circuit
    ... It's how Audio Percision let very low thd from transformers ... Why not load the transformer secondary into a summing point ... I'm not clear how you can have near zero flux though. ... output divided by the open-loop gain. ...
    (sci.electronics.design)
  • Re: Low THD transformer circuit
    ... It's how Audio Percision let very low thd from transformers ... Why not load the transformer secondary into a summing point ... I'm not clear how you can have near zero flux though. ... output divided by the open-loop gain. ...
    (sci.electronics.design)
  • Re: Low THD transformer circuit
    ... It's how Audio Percision let very low thd from transformers ... Why not load the transformer secondary into a summing point ... I'm not clear how you can have near zero flux though. ... And an op-amp works with zero voltage difference at the ...
    (sci.electronics.design)
  • Re: Low THD transformer circuit
    ... It's how Audio Percision let very low thd from transformers ... No flux means no voltage. ... output divided by the open-loop gain. ... So an error voltage of a microvolt, times a gain of a million gives one volt drive for the feedback (and load). ...
    (sci.electronics.design)
  • Re: Low THD transformer circuit
    ... It's how Audio Percision let very low thd from transformers ... Why not load the transformer secondary into a summing point ... I'm not clear how you can have near zero flux though. ... And an op-amp works with zero voltage difference at the input, where zero input times infinite gain gives exactly what was needed at the output. ...
    (sci.electronics.design)