Schematic Help - Phono Preamp Capacitance

[Canticleer]

Hi,

I'm new to this forum and I'd like to ask for some help concerning my Audio-Technica LP120X.

I own a Denon PMA-800ne amp with build-in preamp for MM and MC cartridges. Now I'de like to figure out what the preamp capacitance is, to see if it meets the recommended load capacitance of my AT-VM95E cartridge (100-200pF).

I found a Schematic of the Denon online but it doesn't make me any wiser.

I wonder if someone would be so kind to have a look at it and see if they can find out what the capacitance is.

The schematic can be fount here: Link

Thank you very much.

 

[Mr Boochie]

My guess is 150 pico-farad & 110-ohm (total) for the MC section. 150 pico-farad & 47,110-ohms (total) for the MM section. See blue arrows and slide switch position.

 

[rothwellaudio]

It looks to me like 347pF for MC and 197pF for MM, barring the effects of Miller capacitance, stray capacitance, feedback etc.

 

[sregor]

It looks to me like 347pF for MC and 197pF for MM, barring the effects of Miller capacitance, stray capacitance, feedback etc.

+1

 

[Canticleer]

150 pico-farad & 47,110-ohms (total) for the MM section.

197pF for MM

Thank you all for the effort and your replies. When adding the capacitance of the internal wiring of the LP120X and the RCA cable it seems hard to meet the recommended load capacitance of 100-200pF, in both cases. I guess the total will then be somewhere around +300pF. The LP120X doesn’t sound bad though, with the Denon PMA-800.

 

[patient_ot]

It looks to me like 347pF for MC and 197pF for MM, barring the effects of Miller capacitance, stray capacitance, feedback etc.

I think you are correct but would you mind highlighting or naming the capacitors on the schematic for us. I'm curious why Boochie came up with a different result.

 

[rothwellaudio]

I think you are correct but would you mind highlighting or naming the capacitors on the schematic for us. I'm curious why Boochie came up with a different result.

At the extreme left of the diagram appears to be C603, 47pF, which is always in circuit as an RF filter. Then C605 (150pF) is always in circuit too.
C647 (150pF) is in circuit in MC mode but is effectively out of circuit in MM mode.

 

[Mr Boochie]

You guys sure the components left of C647 and C648 isn't part of the RIAA circuit?

 

[rothwellaudio]

You guys sure the components left of C647 and C648 isn't part of the RIAA circuit?

The RIAA eq is formed by C617, C619, C621 and R621, R623. You need to see the full diagram to see those.
The components to the left of C647 are for RF filtering.