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-   -   Interesting norwegian RIAA amp (http://www.diyaudio.com/forums/analogue-source/9725-interesting-norwegian-riaa-amp.html)

peranders 10th January 2003 04:52 PM

Interesting norwegian RIAA amp
 
http://home.no.net/andiha/articles/a...afig/riaa1.gif

Interesting RIAA amp with descrete design and DC-servo.

analog_sa 10th January 2003 05:13 PM

The riaa network appears to be fed by the current mirrors (transconductance amp). Is it possible to calculate the driving impedance with sufficient accuracy?

cheers

peter

Cobra2 10th January 2003 06:02 PM

And there is more...
 
here..:
http://home.no.net/andiha/articles/audio/index.htm

ArneK

peranders 11th January 2003 06:14 AM

Quote:

Originally posted by analog_sa
The riaa network appears to be fed by the current mirrors (transconductance amp). Is it possible to calculate the driving impedance with sufficient accuracy?
It's not kind of taste of driving RIAA networks but I think that the output impedance is rather "resistive" in the audio band, therefore the gain wil be predictable.

It's also not my kind of taste to have parameters that give varying results. The gain (I suspect) will differ between different amps because the transistor parameters will variate.

analog_sa 11th January 2003 06:31 AM

Peranders

I was not worried about the gain but rather about RIAA accuracy. Don't you need to know very accurately the driving impedance in this configuration? There doesn't seem to be a resistor between the transconductance amps and the 'passive' RIAA.



cheers

peter

peranders 11th January 2003 08:32 AM

Quote:

Originally posted by analog_sa
Peranders

I was not worried about the gain but rather about RIAA accuracy. Don't you need to know very accurately the driving impedance in this configuration? There doesn't seem to be a resistor between the transconductance amps and the 'passive' RIAA.

The "resistor" is the output impedance and the gain will variate but, not the much the RIAA curve looks, just a little maybe.

analog_sa 11th January 2003 10:58 AM

It's obvious the output impedance is the 'resistor'. But how do you calculate its value without knowing the current gain of the transistors? That's why normally there is a resistor with value a lot higher than the preceding stage output impedance. Is this circuit supposed to be tuned to the selection of active devices?

peter

peranders 11th January 2003 01:30 PM

When I've taken a closer look I believe that the DC-gain is (R23/R17)/2, quite predictable.

halojoy 11th January 2003 09:10 PM

Andiha homepage
 
2 Attachment(s)
Quote:

Originally posted by peranders
When I've taken a closer look I believe that the DC-gain is (R23/R17)/2, quite predictable.
If I was to judge by the formulas at Andiha Homepage Andiha Audio
I would say he probably knows what he is doing.

This page for example, makes me ;) DIZZY ;) just by a quick glance:

The Complete Amplifier

And this is what he is talking about
a typical voltage feedback operational amplifier


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