RIAA amp using shunt feedback

Hi,

Figures without the spectrum mean nothing.

The whiter shunt spectrum can have lower figures
than the pinker series spectrum but in reality have
no real advantage other than paper specifications,
and likely some real distortion disadvantages.

rgds, sreten.
You are right, how the noise sounds, how disturbing it feels, depends on spectral
densities in the frequency line. If one frequency is dominant (e.g. 100Hz), that is bad.
Anyway, typically, one figure, namely SNR, is used as a measure of noisiness.
E.g. SNR: ≥85dB(A) (in Yaqin MS-22B which I own).
In my amp the noise sounds sort of dark, no single frequency being prominent.
 
I just went to Keith Snook's site and this seems to work.
~ Scanned and cleaned up Wireless World Articles ~
only for short time (I try it the day before yesterday).
Try this link
www.keith-snook.info/wireless-world-magazine/wireless-world-articles.html+&cd=1&hl=de&ct=clnk&gl=de]~ Scanned and cleaned up Wireless World Articles ~[/url]
for the line-up of this articels.
Or search on webarchive:
http://web.archive.org/web/20140215...s-world-magazine/wireless-world-articles.html
Scroll down for pdf download to this article:
Wireless World Aug 1977 Distortion in low–noise amplifiers ~ Eric F. Taylor
Maybe one of the members can save all articles. After short time all guys, which want to have it, must pay therefore - so I think - go to
https://en.wikipedia.org/wiki/DataXu
I have find out this solution to find as follow:
the URL
http_www.keith-snook.info/wireless-world-magazine/wireless-world-articles_html
I do acquiesced in the "GOOGLE" search field and open the cache-version (this option you will find when you click on the green arrow) or in the webarchive (http://archive.org/web/) - which also provide the wanted article overview, but only for a short time - so I think.
 
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I do not think having ever read comments or experiences about Eric F. Taylor's phono preamp where the non-inteverting input of the circuit is connected to ground. It combines the advantages of low noise and low common mode distortion. The signal input is floating. It was described in a fairly known article : Eric F. Taylor 'Distorsion in low noise amplifiers' Electronics World August 1977, page 56.
Which commercial available phono RIAA preamp uses this circuit topology ?
thank you for advices.
 
Thank you, Eric, for your comment. I am so much in love with shunt feedback concept that
I cannot accept series feedback buffer preceding my RIAA stage, “sorry”! And besides,
adding more SS-staff (ss=solid state) to signal path is always bad for the sound.
So, why I still think that the feedback chain in this stage is not loading the op amp?
It’s because the current running in it is the same as the current running in the input
resistor. So it is produced by the cartridge coil, not by the op amp and, in fact, op amps
output voltage is produced by this current. This is a bit mystical, but it all stems from the
fact that if op amps output is not saturated, then, because of large voltage gain, its input
lines can be seen as being shorted or, in fact, having so called offset voltage (little mV-voltage)
between them - and from the assumption that there is no current running in these lines
(no voltage, no current!). If op amps input stage is made using FETs, this assumption is well
justified because of the very low bias currents. Well, maybe you knew all this.
And once again: I’ve been listening to that 47k input resistor noise daily and I can assure that it is
not disturbing at all. The only sound heard when the needle is running in empty grooves is
the noise produced by the record surface. It covers the amp noise totally. So, why not opt
for shunt feedback configuration if it sounds better.
Anyway, in theory, it should…
I have been asking the same question for decades.
Unfortunately, the SNR of the RIAA preamp device alone is considered by most people to be the most important parameter.
OTOH one always has the additional record surface noise while each listening session.
I don't understand until now, why a very high value of SNR is really important on a phono preamplifier (it's not a microphone preamplifier without record surface noise !!).
 
Hi DF96…again.
You are right, input current bypasses the first op amp in the series configuration too
and in fact it goes straight back to the cartridge trough that 47K resistor!
But the real beauty of the shunt feedback configuration is that the op amp’s input lines
are tightly grounded (minus line virtually grounded) all the time and in that sense
you can say that the op amp stays out of the picture
. But of course it must output the
current that is needed to push the signal forward and in that sense it is very much present.
Series feedback configuration suffers from the fact those input lines are both
“reading” the voltage in the 47K resistor (i.e. voltage coming from the cartridge) which
produces common mode distortion with inferior transient handling.

…Regards MK.
Under
Musical Fidelity A1 › Technical
and in the attached file you will find an approach from Tim de Paravicini (developer also for EAR).
The input resistor was replaced by a a transconductance amplifier stage (T16, voltage in, current out).
What about this ?

Which commercial available phono RIAA preamp uses this circuit topology ?
thank you for advices.
any news ?
 

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