Well, it looks a litlle like an N.P. design, a little but not much. It's 3 stage, with a diff amp input w/tiny IRF FETs, the same FETs as VAS but, cascoded in the VAS, and an F4 looking output with .56 ohm Rs. Kinda BA-2 looking circuit I guess. Extra biasing and shut down and safety stuff. Wimpy PSU with 1 12,kuF cap. Output bias is aB, (maybe 60mA/FET Iq w/3Pr.). They say it gets warm??? I don't think so. They atribute that to classA? Nota! But it is good for bass. I use it with a(1) JBL2226 in a open baffle U box. I would by another but the Nedymium(SP) magnet thing made 'em go from $330. to $500. I'll think about it sumore...
O.K. Back to the regularly scheduled pgm... What about the 085??? I think I can put together a test circuit of the SRP type... I want to drive some resistive looking ribbon tweeters??? 6 ohm??? high output Z should not bother me right? but the sweet sounding Mu follower i might like. I'm deaf in 1 ear and can't hear outa the other. I've loved ribbons ever since I could hear! I'll invite friends over...
I hope, with hope being the key word, to be listening to r085 version of F2 tonight. Got ALeph CCS and SRPP in the queue. Absolutely swamped with fet distribution. I need to ask Nelson for a better version of the R085 curves. Need more V and I on the graph. I gotta here OB, although i dont currently have tthe room for it. THe F5T will be doing my down low duties in active setup. Multi output version has such great control. THis is part of my search for top side amp. Got some ADC interstage for F6 attempt with R085. since F6 doubles gain, should allow for low Rs and feedback.
Hey, buzzforb, As long as no ones complaining about OT stuff. Am I on your list some where fore FETs? I just think I'm getting lost in all this F5X and FET GB stuff... I'm just wondering if I'll get a PM sometime. I can wait, but, I don't want to find out in the end I was looking at the wrong list or something??? 
I have a print out of the list which breaks it down into pages. I am doing them a page at a time. Somehow the list got sorted alphabetically, so the people who signed up first are not necessarily at the top of the list. Good news is that i believe you are on the second page, which i am about to start. Shhould get an email tomorrow about details.
PKI put a SS fet into the ACA amp. He should be able to give you a good idea of possible sound of SS fets in this style amp. It has been a long time since i built it. As I remember, it was very nice, but not enough power, so it didnt stay long. I am a transformer Ho now. Naked F4 will probably be only amp I have that is not transformer based. I will see if M2 clone can unseat the Funny^6. I heard the Funny, I stopped looking. I am now just working on variations of the idea including a preamp.
Some idea tossing:
I think I understand the concept that the mu follower resistor network between the lower drain and upper source will work like the PLH-pot, going form push-pull to pure CS I have some questions about how this would be realized in practice with 2 R085 or similar depletion mode parts:
Would it really be as simple to do as the first schematic? Or do we need a cap and a resistor network from top/middle of network to the gate as per The Valve Wizard -Mu Follower
Or would the answer be: We use the cap to allow the AC signal to pass fiddle the pot to bias the top R085?
I think I understand the concept that the mu follower resistor network between the lower drain and upper source will work like the PLH-pot, going form push-pull to pure CS I have some questions about how this would be realized in practice with 2 R085 or similar depletion mode parts:
Would it really be as simple to do as the first schematic? Or do we need a cap and a resistor network from top/middle of network to the gate as per The Valve Wizard -Mu Follower
Or would the answer be: We use the cap to allow the AC signal to pass fiddle the pot to bias the top R085?
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Cool, lets see if I understand it now: the zen pot over the resistors ensure that we don't need to move the output in the resistor network but can instead fiddle with the pot. If we don't want the pot we would connect the cap at the output and then move the output up and down instead, but a pot is of course easier if we want to trim back and forth.
If we turn it to the bottom the top R085 acts as a CCS, if we turn it to the top it will be quasi push pull and something in the middle is probably our goal where Nelson liked 2/3.
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yup
you can put another 100R pot in parallel to existing one , and connect 10K resistor to wiper - handy for biasing that SJDP
first one is so called Zen Amount Pot
second one can be called ZZZZing Amount Pot , or AntiKlunk Amount Pot , or !Knulk Amount Pot
!Knulk being 1/Klunk!
you can put another 100R pot in parallel to existing one , and connect 10K resistor to wiper - handy for biasing that SJDP
first one is so called Zen Amount Pot
second one can be called ZZZZing Amount Pot , or AntiKlunk Amount Pot , or !Knulk Amount Pot
!Knulk being 1/Klunk!
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Re-done after initial obvious dumbness:
When we are at it what if we do something crazy? If I've understood correctly inductors as they make awesome and efficient current sources so can we make an inductor loaded mu follower? The idea would be to get mu follower distortion cancellation with an inductor efficient CCS.
The question is just if the cap in parallel with with the inductor will defeat the efficiency increasing properties of the inductor making it into just a big and expensive resistor =)
When we are at it what if we do something crazy? If I've understood correctly inductors as they make awesome and efficient current sources so can we make an inductor loaded mu follower? The idea would be to get mu follower distortion cancellation with an inductor efficient CCS.
The question is just if the cap in parallel with with the inductor will defeat the efficiency increasing properties of the inductor making it into just a big and expensive resistor =)
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