The input devices are "standard" 2sk170 and 2sj74 JFETs. My use of cascoding is to reduce higher order harmonic distortions due to the Early effect and device capacitances, not to increase power. Cascoding greatly reduces the negative effects of the gate-to-drain capacitances of the drive MOSFETs (those receiving inputs from the transformer secondaries), allowing the use of VFETs that ordinarily would not be considered. The power dissipation of the drive MOSFETs is low: set by the cascode voltage and the idle current. The cascode MOSFETs dissipate most of the class-A idle power. I am using FQA28N15 and FQA36P15 MOSFETS for both purposes. There might be good reasons to consider BJT devices for the cascodes.
You don't need the P-channel in an F6...
But yes, the P-channel compliment is the 12P20, which buzzforb also has lots of.
(I wholeheartedly recommend his Fets - they are genuine, matched, and very reasonably priced.)
Does anyone have Spice models for 16N25 and 12P20? I would like to run some simulations for them.
Glad you have a a prototype schematic and a name.If you get it hot enough you can use it as an incinerator.
I guess I am not familiar with the Threshold designs. Do you have a relevant pointer?
Has anyone else notices that Papa appears to be using single-turn trimmers in the F6 bias circuits shown in the 6moons article: 6moons audio reviews: FirstWatt F6. Is there a good reason not to use multi-turn trimmer pots?
Papa is having them a ton of each value , and he's turning them personally
multiturns are for sissies ........ as ZM
and , yes - cascoding is from Treshold dayz
look at pic , and use PAT2PDF - Free PDF copies of patents: Download and print!
you can look also http://www.diyaudio.com/forums/pass...published-amplifier-circuits-nelson-pass.html and also http://www.diyaudio.com/forums/pass-labs/198589-papas-pubs.html
multiturns are for sissies ........ as ZM
and , yes - cascoding is from Treshold dayz
look at pic , and use PAT2PDF - Free PDF copies of patents: Download and print!
you can look also http://www.diyaudio.com/forums/pass...published-amplifier-circuits-nelson-pass.html and also http://www.diyaudio.com/forums/pass-labs/198589-papas-pubs.html
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