Referring to the circuit in post #2, I found that the bias current stability with line voltage fluctuations and PSSR in general is improved by replacing the 10K resistor between the V+ rail and the optocoupler collector with a current source. I used a 2.7mA current regulating diode: Semitec E-272 (Mouser 954-E-272). The same CCS can be accomplished with a JFET having a high enough Vds max plus a suitable source resistor to obtain a current around 2.7mA.
yes, plenty of ways to guild it ...... I did tried CCS solution there, but in overall scheme decided that (this way) I have little more flexibility regarding tweaking Iq of Mu half, same as better behavior of output node potential , of amp as a whole, when rail fluctuating up or down, due to change in mains
as always, final solutions are, in a way, more group of compromises than group of solutions; I'm often finding that, in some later revision, I'm sometimes choosing different set of compromises...... but lately I'm not coming back so much as I did it before
in any case , Singing Bush isn't exactly carved in Stone ........ it's more Prairie phenomena
🙂
as always, final solutions are, in a way, more group of compromises than group of solutions; I'm often finding that, in some later revision, I'm sometimes choosing different set of compromises...... but lately I'm not coming back so much as I did it before
in any case , Singing Bush isn't exactly carved in Stone ........ it's more Prairie phenomena
🙂
ZM:
Your distortion spectra look excellent.
Do you have any measurements of PPR (the pullup/pulldown ratio = pullup AC current divided by pulldown AC current)? In my mu-follower equations PPR is an essential parameter. The current gain (beta) of the mu-follower is:
I will post my 2SK182ES 2A5 measurements with the mu-follower as a CCS. PPR=0, beta=1.
Your distortion spectra look excellent.
Do you have any measurements of PPR (the pullup/pulldown ratio = pullup AC current divided by pulldown AC current)? In my mu-follower equations PPR is an essential parameter. The current gain (beta) of the mu-follower is:
- beta = 1+PPR
- PPR = Rmu*gme
I will post my 2SK182ES 2A5 measurements with the mu-follower as a CCS. PPR=0, beta=1.
I didn't made these measurements ...... started with ballpark values , then tried (everything) up and down from that, while observing THD Spectra;
as you certainly know it - having Math is one approach , and having 90% of Math is equally good as having 10% of Math ....... so I simply avoided that approach, chosing direct experiment rather than one founded on Math ; I tried thinking that way , but unpredictability of SIT transfer characteristics got better of me
besides, one thing I did learn from Pa - you always must leave enough time for some Wine and Guilty Pleasures 🙂
- that's why I'm following your last thread with great interest - extremely fine when someone chewed it for ya ....... but somehow I'm always short of grasping it all
as you certainly know it - having Math is one approach , and having 90% of Math is equally good as having 10% of Math ....... so I simply avoided that approach, chosing direct experiment rather than one founded on Math ; I tried thinking that way , but unpredictability of SIT transfer characteristics got better of me
besides, one thing I did learn from Pa - you always must leave enough time for some Wine and Guilty Pleasures 🙂
- that's why I'm following your last thread with great interest - extremely fine when someone chewed it for ya
....... but somehow I'm always short of grasping it all"in any case , Singing Bush isn't exactly carved in Stone ........ it's more Prairie phenomena "
Love the analolgy 😀😀
Love the analolgy 😀😀
Look Ma, with no hands!!!!!
after being Customized for 40 days or so, I found them on Porch today
who sez that Postmen are insisting on signatures these days .......
(if nothing else, that's confirmation that my PO is working locally, sort of ...)
so, finally , pair of Biguns, sent by my own Bob's Your Uncle, Mr. Bubba Cyclotron Flocchini
who knows, maybe one of these days I'll have enough Vis Vitalis to try them, as comparison with already tried pair
be well, stay safe!!
after being Customized for 40 days or so, I found them on Porch today
who sez that Postmen are insisting on signatures these days .......
(if nothing else, that's confirmation that my PO is working locally, sort of ...)
so, finally , pair of Biguns, sent by my own Bob's Your Uncle, Mr. Bubba Cyclotron Flocchini
who knows, maybe one of these days I'll have enough Vis Vitalis to try them, as comparison with already tried pair
be well, stay safe!!
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good thing with that yes signature-no signature procedure is - I didn't paid any Customs Fee
ook!
ook!
"Along with LOR, Castaneda was required 70's reading!"
Tolkien and Castaneda classics - interesting to re-read after "maturing"
Tolkien and Castaneda classics - interesting to re-read after "maturing"
Russel, if you already didn't - for that level of insanity (put there '' '' ) , find documentary of never made Jodorowsky's Dune
things described in Castaneda's books are ...... well, not for screen
🙂
things described in Castaneda's books are ...... well, not for screen
🙂
I see 6 fewer SITs left in the wild.
Supply and demand is understood but then why are 300B tubes so damn expensive? Maybe one day I will be able to trade some Tokin VFETs for a nice pair of Elrogs? 😀
I posted some more 2SK182ES mu-follower measurements today, starting with post #98, showing similar spectra. The load line plots on the FrankenTracker curves might also be interesting:
SIT measurements, Mu Follower, and amplifier build
SIT measurements, Mu Follower, and amplifier build