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In the Forum: Analog Playback
In the Thread: The last phonocorrector: “End of Life" Phonostage
Post Subject: Of mosfets, caps and distortion.Posted by Brian Clark on: 6/4/2008
 Romy the Cat wrote:
Brian, and how do you find your MOSFET behaves compare the 12AX7-based cathode follower?

Romy, I have yet to try. Only got them on recommendation very recently. They're cheap enough to try in a B9A plug-in without altering anything in the circuit, though perhaps a good idea to add a carbon comp resistor on the gate. I'll try and find one of those plugs in the garage and give it a go.

I have 5-6 different versions of silver-mica though and I prefer air caps. I do not know what Dima tried. He has the same corrector with Ocean State’s air caps only in place of the first 12AXy he uses Russian nuvistors

Yes but you can't use an air-cap as a coupler in that circuit. The SSGs are a whole lot cheaper than VenHaus's V-Caps.

I do not think that 834P circuit is designed for any specific distortions.

Whereas I do. deParavicini's worked on designs in Japan over several years and became familiar with the  research going on there in the Seventies which culminated in identifying the HD decay-spectrum as a key indicator for "musicality". I.e. a monotonically decreasing level as order increased such that each HD  component masked the following component. This occurs naturally in a single triode operating under normal conditions. When I simulated the 834P circuit two things were obvious - the level of THD was high but the aforesaid decay spectrum approximated that of a single triode valve.

For what it's worth and acknowledging it is part of a bigger picture of course.


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