phono stage with different replay equalization?

[hesener]

Hi,
there is a new japanese phono stage (Zanden Model 1200 Mk2, check out www.zandenaudio.com) that features three different settings for the replay equalization: RIAA, DECCA, COLUMBIA.

I was thinking to build a phono stage along the lines of attached schematic found here (passive RIAA equalization), and was wondering who could help me with finding out the time constants for these different settings, and modify the schematic to accomodate them.......

thanks a lot

 

[Robert McLean]

Try this link for a start. It is not tube based, but it does have a chart of various curves and the frequencies of the poles and zeros.

http://www.rfwilmut.clara.net/repro78/repro.html#eq

Convert frequency to time constant as follows

T = 1/(2 * pi * F )
and
RC = T.

How to pick R and C and what to do next depends on the circuit.

I know I have a link here somewhere to a tube based phono amp that has 3 or 4 curves selected by a switch, which will be of a lot more practical help than what I have given here, but I just havent found it yet.

 

[hesener]

thanks a lot! that is very helpful.

this danish guy actually has a preamp with quite a number of settings, and explains all the time constants used by various companies on his website.

appreciate your help....
alfred

 

[dreamth]

Found this old thread and thinking of reviving it as it's the professional approach over fixed riaa.You might like a different approach first used by EMT, a variable tune riaa network. R23 and R25 are actually forming a 470 ohm wirewound potentiometer. Its effect is more like a Presence pot.It was built and verified and works great. with higher impedance networks you might need a cer-met lower noise potentiometer.

 

[6A3sUMMER]

If you do not have any of those old recordings from Many Decades ago,
then the different equalizations are pointless.

Decades ago, they all settled on RIAA.
All the 33 LP recordings I have from all over the world say RIAA.
I started purchasing them in 1970, when I got a turntable.

Of course, you can use the different equalizations as a sort of 'tone control'.

 

[richardr]

I think that it goes further back

All my records from the 1960's are RIAA including the mono. I have never owned a record other than a 1940's 10" of Enrico Caruso that was not RIAA. I think that you are preparing for a recording that you won't own. The Shellac recordings at 78rpm will not work with Decca or Columbia as each record company had their own equalization before RIAA.