RE: Concerning EQ for older records.

Posted by 13D3Tube (A) on October 28, 2008 at 05:20:18

In Reply to: RE: Concerning EQ for older records. posted by cactuscowboy@bresnan.net on October 15, 2008 at 22:35:30:

I have just acquired a Bugle Pre to which I am going to add a variable treble turn over facility, as Cactuscowboy seems to have done.
I am not interested in using 78s, so I will be using just four treble turnover frequency points that are equivalent to Attenuation levels at 10kHz, as follows: ffrr 3K (-11db), AES, EMI, Mercury etc 2K5 (-12db), NAB and Collumbia 1K6(-16db), RIAA 2k122 (-13.75db).

I will not change the bass turnover point, but keep it at 500.

The most useful indications, I found at
http://www.smartdev.com/RIAA.html
Gary Gallo here gives the correspondences between treble turnover and treble attenuation at 10kHz.
and at
http://www.shellac.org/wams/wequal.html
where you can find which record companies used which curve and at what date.

Of course, as I am implementing this on a Bugle Pre, it was useful to have the calculator on the Hagerman site,
http://www.hagtech.com/equalization.html
This allowed me to work out that only one resistor needs to vary: the one at Rc in the RIAA circuit shown on the Hagerman equalization calculator page, but you must take account of the fact that Rc is in parallel with the 47k loading resistor.
In the Bugle pre the two resistors that must be replaced by the switchable Rc resistors are R25 and R7 in the Bugle circuit, shown at
http://www.hagtech.com/bugle.html

I will use a DACT 4 pole 5 position switch to create my variable treble turnover.

I assume that Cactuscowboy implemented a similar variable equalization
switch.
This is an excellent circuit to experiment with; and I will use it alongside my usual valve preamp, with either a Denon 103 for stereo, or a ClÃ©ment canteleverless cartridge, or a Denon 102 for mono.

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Follow Ups Full Thread

Topic - Concerning EQ for older records. - M3 lover 17:55:57 10/15/08 (9)

the cheap way - mothra 14:10:15 10/16/08 (0)

RE: Concerning EQ for older records. - Tom B. 12:00:30 10/16/08 (2)

More history and an opinion. - M3 lover 13:14:22 10/16/08 (0)

This is what I used to use... - Crazy Dave 12:55:14 10/16/08 (0)

Nice post, with some good info and links. - JimK 08:28:09 10/16/08 (0)

Playing non-RIAA LPs on an RIAA only system usually results in reduced treble, too much bass and a muddy sound. - richardz 04:49:45 10/16/08 (0)

RE: Concerning EQ for older records. - welly 00:58:02 10/16/08 (1)

Graham Slee also has a good FAQ on EQ curves - sjg 04:06:19 10/16/08 (0)

RE: Concerning EQ for older records. - cactuscowboy@bresnan.net 22:35:30 10/15/08 (0)

RE: Concerning EQ for older records. - 13D3Tube 10/28/0805:20:18 10/28/08 (0)

Follow Ups

RE: Concerning EQ for older records. - 13D3Tube 10/28/0805:20:18 10/28/08 (0)

RE: Concerning EQ for older records.

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