Can anybody confirm the input capacitance of the MM Phono stage of this pre-amp?
It’s not listed in the specs section of the service manual. The circuit diagram shows a 56pF capacitor to ground on the input stage but this sounds very low as I understand most phono stages are somewhere around 150-300 pF.
Does the input transistor contribute to extra capacitance in addition to the 56 pF in circuit? How much?
My phono cartridge specifies ideal capacitance of 400 pF, and allowing for typical 150 pF in the cabling, I need about 250 pF in the pre-amp.
It’s not listed in the specs section of the service manual. The circuit diagram shows a 56pF capacitor to ground on the input stage but this sounds very low as I understand most phono stages are somewhere around 150-300 pF.
Does the input transistor contribute to extra capacitance in addition to the 56 pF in circuit? How much?
My phono cartridge specifies ideal capacitance of 400 pF, and allowing for typical 150 pF in the cabling, I need about 250 pF in the pre-amp.
Some phono cartridges require a lot less to make a flat(tish) curve.
I would say, that 56pF (or even 47pF) sunds just about right.
If your preamp doesn´t have additional, selectable load capacitance switch on the "Phono-input", then just
try the 250pF instead. Be prepared, that if you change your cartridge, you might have to (again) reduce the value.
I would say, that 56pF (or even 47pF) sunds just about right.
If your preamp doesn´t have additional, selectable load capacitance switch on the "Phono-input", then just
try the 250pF instead. Be prepared, that if you change your cartridge, you might have to (again) reduce the value.
The input JFET adds very little capacitance. The gate-source capacitance is reduced to nearly zero by negative feedback.
Ed
I would advise against such approach - the cartridge is such a weak signal generator that the cable should be kept as short as possible.
It is easier to get a good phono stage than to get another good and likeable cartridge to match existing one
Having taken a look at the schematics - yes 56pF it is and in most of my amplifiers I have used 150 or 220 pF as starting value.
Just solder a capacitor in parallel with the existing one below the board and listen to the possible change in sound.
AT-VM95E is only up to 22kHz with just 20dB channel separation. Not my preference.
https://www.audio-technica.com/en-eu/cartridges/line-series/at-vm95-series/at-vm95e