phono stage building blocks...

[kevinkr]

Will corroborate SYs comments on both books - well worth the price of admission.

I wrote a program 27yrs ago based on Liphshitz that calculates the values of all of the passive components in a single stage network knowing source and load impedances, and I use it to this day. (Based on algebraic equations derived from s plane parameters. I no longer remember how I figured it out.. LOL) As expected it is quite accurate and zero fuss, the accuracy of the network synthesized can easily be verified in any version of spice or built and tested with the same results. Today there are on line calculators that do exactly the same thing and provide the same results.

 

[andyr]

If any have a good resource for understanding the mathematics of the RIAA curve, please post them here. I'll look into them further.

Here is a great article on RIAA by Simon Shilton:

Phono Stage Design

You can tweak Simon's circuit by including "Allen Wright's 50KHz boost" if you want - it's simply a low-value resistor in series with C2. And although the article is on a valve site, you can use ss gain stages before and after the passive RIAA equalisation, if you want. (I used JFETs.)


Andy

 

[DF96]

Here is a great article on RIAA by Simon Shilton:

Phono Stage Design

Useful for those new to the subject; not great - no new insights. (He needs to learn to spell!)

He says

Suffice to say that it would also have been much better if E24/E48/E96 values had been around when it was finalised, as it is you end up having to make non-standard values to get an accurate response.

I hope he is not suggesting that the RIAA curve should have been chosen with preferred component values in mind, as this would tie people to using one network only (and x10, x0.1 etc. in impedance derived from it).

 

[piano3]

Yes, it is a pretty basic article. The author brings up the issue of absolute phase; I have never been able to understand why this might be important. I would expect any precision filter to contain a mess of series and parallel resistors and I personally am happy if the capacitors can be massaged to preferred values. Also this business of an additional sub-sonic filter at 20 Hz; couldn't this cause phase shift problems within the audio band? Better to sort it out mechanically.

 

[DF96]

A subsonic filter will cause phase shifts within the audio band. How audible this will be depends on many things, such as speaker, room, ears etc.