Have you guys been studying George's (tubelab) and Smoking-Amp's work on the UNSET thread? They have figured out a better Schade version. Basically, put an FET source-follower in the cathode of the pentode and drive the gate of the FET with the input signal. The pentode then gets the Schade treatment and you pull the output from the anode. Producing some fantastic triode curves. I wonder if the bright minds here can build an all-FET version of it.
Here's the meat of it:
G2 using MOSFET ultralinear feed
Here's the meat of it:
G2 using MOSFET ultralinear feed
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1995 also an interesting option
p.856-859
https://worldradiohistory.com/UK/Wireless-World/90s/Wireless-World-1995-10-S-OCR.pdf
Presenting the L'BAF2015 - No SIT's? No problem
Didn't know where else to stick this one, seems like a good place. Essentially the BAF2015 circuit with a choke load instead. I had to add the source resistor, otherwise the bias ran a bit wild, I believe OllBoll(sp?) predicted this in Ben's orig SIT thread where I initially posted the idea. Similar performance to the original circuit, a bit smoother with the choke load. 30.5VDC rails, 26.5Vds biased @4A. I used the venerable 193V, but decided on the 195T10, more bias sounds better. Currently waiting on some big honking 200mH@10A chokes. Anyway, for those that cannot get their hand on some SIT's, don't pass this one up. A few add-ons, J113 buffer lifted from Ben Mah's original common source SIT amp thread, arduino controlled soft start. And surprisingly, with wires strewn about with little care, absolutely silent. Sounds too good to finish the case!!(lazy)
enjoy!
John
Didn't know where else to stick this one, seems like a good place. Essentially the BAF2015 circuit with a choke load instead. I had to add the source resistor, otherwise the bias ran a bit wild, I believe OllBoll(sp?) predicted this in Ben's orig SIT thread where I initially posted the idea. Similar performance to the original circuit, a bit smoother with the choke load. 30.5VDC rails, 26.5Vds biased @4A. I used the venerable 193V, but decided on the 195T10, more bias sounds better. Currently waiting on some big honking 200mH@10A chokes. Anyway, for those that cannot get their hand on some SIT's, don't pass this one up. A few add-ons, J113 buffer lifted from Ben Mah's original common source SIT amp thread, arduino controlled soft start. And surprisingly, with wires strewn about with little care, absolutely silent. Sounds too good to finish the case!!(lazy)
enjoy!
John
Attachments
if you want xerox copy of Papa's Schade effect, move big cap (C1, negative end) to source of MOS
there are the ways for biasing that beast without introducing source resistor, but there must be a line, preventing me of messing in every Gulyás
Thanks guys! Of course many thanks to Nelson, MR, Ben, Zen, and many others. I purchased a truckload way back of Solen S102.2 coils before prices went wild. At roughly 224W of dissipation, they barely get warm after about 8hrs...build it big. same for the heatsinks; hands on indefinitely.
ZM - yes, this was mentioned in another thread, when I initially posted the idea, but I wasn't sure how to handle that, I'll have to re-visit this....in the mean-time, sounds too good to mess with it
ZM - yes, this was mentioned in another thread, when I initially posted the idea, but I wasn't sure how to handle that, I'll have to re-visit this....in the mean-time, sounds too good to mess with it
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biasing will stay the same, while modulation of mosfet will be referenced to its Source, not GND
as is , you introduced source resistor to help you in DC domain (Iq stability) but you also introduce local degeneration, thus changing transfer characteristic as Papa prescribed
how to do that - easy - just reconnect neg side of C1 to Source
as is , you introduced source resistor to help you in DC domain (Iq stability) but you also introduce local degeneration, thus changing transfer characteristic as Papa prescribed
how to do that - easy - just reconnect neg side of C1 to Source
Schade,it can
though, problem lies where your bias generator is referenced
as you draw it, with presumption that biasing circuit is referenced to GND (as in your present build), that's recipe for BigBadaBoom ......... or music interrupted with silence, in best case
second thing (second, but not less important) - for follower duty, you're expecting helluva swing that puny input xformer must endure
no go
if you want Schade, see (still need confirmation) preliminary Lazy Singing Bush schematic - it is xformerless with reason
at least I believe that I posted Schade Mos iteration
though, problem lies where your bias generator is referenced
as you draw it, with presumption that biasing circuit is referenced to GND (as in your present build), that's recipe for BigBadaBoom ......... or music interrupted with silence, in best case
second thing (second, but not less important) - for follower duty, you're expecting helluva swing that puny input xformer must endure
no go
if you want Schade, see (still need confirmation) preliminary Lazy Singing Bush schematic - it is xformerless with reason
at least I believe that I posted Schade Mos iteration
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