didn't think of doing that and will not
every mosfet is having some minimal rail voltage , when intrinsic capacitances are becoming at least a little more linear/ less hungry
say that 30V is lowest practical rail voltage for this one
for lower voltages, I'll have Plethora of Pinjatas amp - same (this) FE, output parts and bias mechanismus as B. M25 R.2
so, as always, plenty to choose from , no need for too much of compromises
every mosfet is having some minimal rail voltage , when intrinsic capacitances are becoming at least a little more linear/ less hungry
say that 30V is lowest practical rail voltage for this one
for lower voltages, I'll have Plethora of Pinjatas amp - same (this) FE, output parts and bias mechanismus as B. M25 R.2
so, as always, plenty to choose from , no need for too much of compromises
As ZM said in post #1, optos are for over current protection at 10A. The bias is the lt3092 but it’s holding some tricky current sources above and below the input network to bias the outputs. Looks like they would offer very high impedance, so maybe that helps with the stability. That is my question.
I'll address tech. questions little later, after doing some chores ........... having 17yrs young She around is endless source of fun...... I'm doing all the things my Father certainly didn't 
now, only to quote my self :
now just report about today's visit to my Official Second Set of Ears
it's bloody jolly good
did I said Spooky?
whatever of nasty demanding but divine music we did throw on it, it came with ease
nuff said, it did pass (almost as Pass made it 
), now I can freely dissmantle N channel mosfets and mount THF51 instead
tomorrow or day after, you can expect report and results
another instance of All the Glory, or Major Flop
if you don't hear anything from me in 3 days, Flop it is
now, only to quote my self :
OK1-OK2-TH1 .......... 10A limiting circuit, Savior of Our Souls, blatantly stolen from Pa
now just report about today's visit to my Official Second Set of Ears
it's bloody jolly good
did I said Spooky?
whatever of nasty demanding but divine music we did throw on it, it came with ease
nuff said, it did pass (almost as Pass made it
), now I can freely dissmantle N channel mosfets and mount THF51 insteadtomorrow or day after, you can expect report and results
another instance of All the Glory, or Major Flop
if you don't hear anything from me in 3 days, Flop it is
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How much happy-ness for BFR are you using? 22R or 510R? Probably a good idea for future builders to use pin headers to find happy place somewhere between 22R and 510R.
17 year old riding Ducati with you? You are blessed ZM. By that age they want to have endless source of fun ... with their friends all the time
I'm certainly living different life with my children than my parents did with me but my life is vastly different from what my parents lived and for that I am eternally grateful to them.
17 year old riding Ducati with you? You are blessed ZM. By that age they want to have endless source of fun ... with their friends all the time
I'm certainly living different life with my children than my parents did with me but my life is vastly different from what my parents lived and for that I am eternally grateful to them.
Twitchie ....... it seems I'm cursed of not having much time this year to give to my 2-wheeled pets ....... even weather wasn't exactly helping (sissy excuse)
reason is that I had too much fun with recent and upcoming amps, so didn't felt need for fueled meditation...... frankly, there is no difference in brain speed - me being in my workshop, or being on bike ...... even if there is obvious difference in Butt moving speed
regarding sonic impressions... I just replied to grataku in PM, and realized it's worth pasting here (besides some other things, he asked for comparison between LuDEF and this amp):
I did wrote something , but didn't referenced to recent amps
LuDEF, even having insane low THD - for amp without NFB, is still having sonic footprint - xformer nature (which I like) and evident 2nd harmonic dominance
Babelfish XA252 - it is exactly as PL XA25 is described in (better) Audiopholl periodicals - invisible
practically - I'm finding it as counterpart to what is Iron Pumpkin for preamps
though - one fact is extremely important - due to careful nurture of having dominant 2nd (doesn't matter how low) it is not sounding sterile
all that set for minimal THD/max OLG , BFR resistor value of 22R
reason is that I had too much fun with recent and upcoming amps, so didn't felt need for fueled meditation...... frankly, there is no difference in brain speed - me being in my workshop, or being on bike ...... even if there is obvious difference in Butt moving speed
regarding sonic impressions... I just replied to grataku in PM, and realized it's worth pasting here (besides some other things, he asked for comparison between LuDEF and this amp):
I did wrote something , but didn't referenced to recent amps
LuDEF, even having insane low THD - for amp without NFB, is still having sonic footprint - xformer nature (which I like) and evident 2nd harmonic dominance
Babelfish XA252 - it is exactly as PL XA25 is described in (better) Audiopholl periodicals - invisible
practically - I'm finding it as counterpart to what is Iron Pumpkin for preamps
though - one fact is extremely important - due to careful nurture of having dominant 2nd (doesn't matter how low) it is not sounding sterile
all that set for minimal THD/max OLG , BFR resistor value of 22R
Hi ZM,
Nice work
Question, where is your output bias thermal stability coming from? I needed thermistors on my non-optical bias to keep it from running away.
Thanks
let me know if pic is worth less than 1000 ....... JFets
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let me know if pic is worth less than 1000 ....... JFets
good, now even I understood how it works!
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let me know if pic is worth less than 1000 ....... JFets
Hi ZM,
So, from your picture, you are saying that the programmed constant current sources remove the drift in the bias voltage, with voltage sagging, and the bias drift from the outputs heating up is just handled by the thermal mass of the output heatsinks. So if you want it stable you had better use big heat sinks or the bias will go up as it heats up. Correct?
With SissySIT R.3/M25 R.2, no worries as it’s tracked by the optos?
Thanks
you got it wrong
stare at pic some more
there is servo function in that, fully working, no need for aux gimmicks as NTCs and whatnot ...... and heatsink must be adequate, but not as biasing helper
current mirror is having programmed current at one side, while other side of current mirror is increasing or decreasing own current, so that voltage sags stays constant
current of "working" side of CM is changed simply by effect of changing voltage between rail and base, while emiter resistor is not changing ........ so effect must be change of current though part
contrary to that, reference halves of CM are having everything constant - both current through them, same as constant voltage between bases and rails
stare at pic some more
there is servo function in that, fully working, no need for aux gimmicks as NTCs and whatnot ...... and heatsink must be adequate, but not as biasing helper
current mirror is having programmed current at one side, while other side of current mirror is increasing or decreasing own current, so that voltage sags stays constant
current of "working" side of CM is changed simply by effect of changing voltage between rail and base, while emiter resistor is not changing ........ so effect must be change of current though part
contrary to that, reference halves of CM are having everything constant - both current through them, same as constant voltage between bases and rails