I'm interested in RIAA preamps design

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#141
Hans Polak said:
You can simply extract the R&L values from the models at DC.
Be aware however that not all manufacturers use the same way of specifying, some specify the figures at a certain frequency, which of course does not give the same values as at DC.
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Thanks Hans. I'd figured this out. The missing ingredient is the recommended C. After some searching I've got 100-200p for DL109. But I still don't have a recommended C for DL107 ... though it's probably the same.
Leoniv said:
You are right, an electric model is enough to obtain a difference. But still the easiest way is to measure the frequency response of the cartridge with a load of 150 kOhm using a test LP.
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Even in this august company, not everyone has a test LP and even then, there are arguments over which ones are pukka.

The best guide to what works is the maker's recommendations. We sorta know this for 47k & 100+pF cos that's what most MM cartridges were designed for.
 
#142
@marcel, thx for explaining, but we shouldn't worry about a few tenth of a dB difference in this specific case, because with both graphs it's obvious that without any further correction this substitute for the Riaa 75usec pole is not the way to go for this V15 III cartridge.
Damped loading may only be beneficial in very special cases.

Hans
 
#144
I think 100+pF means > 100 pF, and 275 pF > 100 pF.

If you want a moving-magnet preamplifier to work well with the vast majority of cartridges, you have to make the input capacitance selectable. Hence the DIP switches and capacitor bank at the input of the preamplifier that was the original subject of this thread.

Screenshot_20250421-134117~2.png
 
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#145
andyr said:
Early Japanese MMs were designed for 100K - not 47K.
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Many 60s & early 70s British preamps had 68K.

I think it was SHURE around the time of V15-II that prompted 'standardisation'. V15-III needed 47K & 450p to achieve its VERY flat response to 20kHz
andyr said:
And the specs for my Stanton WOS CS100 say 47K ... and 275pF.
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Have you got a 'nominal' L & R for the CS100? I'm actually after the spec for Stanton 880/1 which I think CS100 is based.
 
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#147
MarcelvdG said:
If you want a moving-magnet preamplifier to work well with the vast majority of cartridges, you have to make the input capacitance selectable.
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Absoloootely! 👍

MarcelvdG said:
Hence the DIP switches and capacitor bank at the input of the preamplifier that was the original subject of this thread.
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I suggest a far more flexible - and simpler - arrangement is to provide one or two parallel pairs of input RCA sockets ... into which 'R-loaded' and 'C-loaded' plugs can be inserted.

That's what I do, anyway. 🙂
 
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