Another Simple RIAA preamp ?

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Hi there.

I was recently browsing some old AA & AudioXpress issues, when I came upon the schematic of a RIAA preamp in the readers' mail. I reproduce it here (hope there's no copyright infringement). It is authored by Mr Eddy Folkers, and was apparently publicated in "Hifi News & Record Review, Sept. 1984" by M.J. Hawksford (the same Hawksford as the "cascode" one ?). It is mentionned that the two input transistors should have low gain (typ. 100), beta matched, and the four other BJTs should have a beta > 300.

Just wanted to know what you guys think of it, or if someone has already built it, or listening impressions form anyone ?
 

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On first glance, is this MM or MC? The input impedance is pretty low and the rec for using low beta makes it sound like the input current noise does not matter. In fact the input impedance looks like around 400 Ohms or so. Bipolars right on the input are bad for RFI and the huge electrolytics there might not please some people.
 
scott wurcer said:
On first glance, is this MM or MC? The input impedance is pretty low and the rec for using low beta makes it sound like the input current noise does not matter. In fact the input impedance looks like around 400 Ohms or so. Bipolars right on the input are bad for RFI and the huge electrolytics there might not please some people.

Well, quick sims showed a rough 50dB gain @ 1kHz. So should be MM. But I agree that the input impedance is low, < 1kOhms with most of the BJT models I used for my sims. RIAA response is rather good (see pic). Dunno about PSRR, or how the whole thing could be improved. Will surely tried to breadboard one to "see" how it measures and sounds...
BTW, thanks all for your enlightening comments.
 

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