Here’s a spreadsheet I built for calculating RIAA values in two stage tube phono preamps. When comparing results to other published designs using the same filter network, everything looks correct (within a few percent due to estimation of Rp). I used this sheet for El Matématico.
If you want to estimate values for something like a CCS loaded stage, you can set Rload on the appropriate stage to 1M or thereabouts. If you’re looking at using a cascode, mu follower, SRPP, etc 1st stage, you’ll need to make sure the Zout figure the sheet uses (cell I6) reflects the Zout of the topology because it is used to calculate R1. Same thing goes for cell I3 (Miller capacitance of 2nd stage) if you use a gain stage after the filter that affects this (cascode, grounded grid, etc).
Go build a phono preamp!
wauwatosa tube factory 
Hi. I have had a play with the calculator and I think I have got the hang of it. Is there any way to validate the error against the RIAA target values?
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Glad you found it useful!
If I were to validate on paper, I’d use Excel to calculate gain for the target and chosen values at the corner frequencies and compare. In fact, that would be a good thing to add to this worksheet and I’ll try to find some time to do so.
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