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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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Tubes Asylum Questions about tubes and gear that glows. FAQ |
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In Reply to: reactance of output capacitor on riaa eq component value posted by Kevin Elliott on December 7, 2000 at 17:29:53:
Hi Kevein -You obviously have more training than myself - I think just the generator Z of the driving stage (one for 'lumped passive RIAA' phono EQ) is important and that the cap's reactance is a minor contributor to the network's response above a certain frequency - especially as there is an effective 'boost' by the preamp to compensate for cutting the bass weak with the RIAA standard. Sometimes I see the coupling cap chosen to get some rolloff in the warp region which may not be a bad idea - also - theres the old argument that 'absolute accuracy' may not mean much due to the recording/cutting process.
ECAP would allow you to model the preamp - probably with fair accuracy if you get decent inputs for mu and gm for the tubes using characteristics at the operating points for determination of the values. (use the FET model with rp across the plate and cathode equivalents) - I guess a test would be to model the phono stage (easy)and daisy cahin it into a model of an "InverseRIAA" network - any deviation from a stright line should tell the error.
I bet you got a good sounding phono stage - the 6DJ8 sounded good in mu-foloweres, cascodes, etc.
best wishes
Freddy
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Follow Ups
- Reactance of output capacitor - I think its 'trivial' - Ecap the preamp then model response thru an inverse RIAA model - freddyi 17:52:48 12/07/00 (3)
- Re: Reactance of output capacitor - I think its 'trivial' - Ecap the preamp then model response thru an inverse RIAA model - Kevin Elliott 18:05:11 12/07/00 (2)
- Re: Reactance of output capacitor - I think its 'trivial' - Ecap the preamp then model response thru an inverse RIAA model - steve 21:40:57 12/08/00 (1)
- Re: Reactance of output capacitor - I think its 'trivial' - Ecap the preamp then model response thru an inverse RIAA model - Kevin Elliott 08:41:10 12/11/00 (0)
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