I am modifying an Alembic F2B/Fender Blackface preamp section to sound more like a blue line SVT. I am pretty much just re-biasing like the the SVT (220k anode/ 3.3k unbypassed cathode) instead of the typical Fender bias (100k anode/1.5k bypassed cathode).
I have noticed in doing so I have lost a lot of top end and have narrowed it down to the tone stack. The only thing that could have changed pre tone stack that could have effected tone would be the output impedance has gone from 39k (bypassed cathode) to 142k (unbypassed cathode).
So my question is, what effect on the tone stack does the output impedance have? None of the equations for figuring out response of the FMV tone stack take the previous stages output impedance into consideration. The tone stack also has an RC pre-emphasis circuit after it for a switchable treble boost. Could this be a possible cause of the the loss of top end (due to the impedance change)?
I have noticed in doing so I have lost a lot of top end and have narrowed it down to the tone stack. The only thing that could have changed pre tone stack that could have effected tone would be the output impedance has gone from 39k (bypassed cathode) to 142k (unbypassed cathode).
So my question is, what effect on the tone stack does the output impedance have? None of the equations for figuring out response of the FMV tone stack take the previous stages output impedance into consideration. The tone stack also has an RC pre-emphasis circuit after it for a switchable treble boost. Could this be a possible cause of the the loss of top end (due to the impedance change)?
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