Understood, and learning much. So that is really the main source of my problems, as I have the 330k there! So 330k would be 1.65 according to your explanation. (I am fortunate ZM is not local or I suppose the bamboo stick would be felt!). So that explains all of the issues. I will swap out ( I must have lost the 120k and is probably why the 330k went in there) and check again before proceeding.
Thank you for your help and patience!
Thank you for your help and patience!
Concerning nature of this and your other square law amps, I developed a question. I suppose real Papa XA 252 is also real square law amp? which of the current line up of Pass Labs amps are Square law devices? I would think all current ones? Some of the older reviews showed rows of source resistors, wondering when change came.
I need to move to next square law amp with "regular" mosfets. Then I can see how much of this amps excellent sound is coming from pucks, and how much is square law. Have a feeling that square law is mostly responsible...
Thanks for any info,
Russellc
I need to move to next square law amp with "regular" mosfets. Then I can see how much of this amps excellent sound is coming from pucks, and how much is square law. Have a feeling that square law is mostly responsible...
Thanks for any info,
Russellc
Did someone answered to this question? I am also interested about this information. What would be the max Idss for these jfets do use in Babelfish XA252 mosfet version?
Can I replace BD139/BD140 with Toshiba TTA004B/TTC004B? Are there also other parts that I can substitute with a Toshiba parts?
What is the difference between Babelfish XA252 mosfet and SET version besides some extra small parts?
My speakers are 8 ohm 88db.
I have 500VA transformer 4x18VAC. Can I use it to build Babelfish XA252 mosfet version? Ideal would be 2x28VAC and 600VA? What is the max rail voltage to go with this mosfet version? If I go for 500VA 2x36VAC and using cap multipler or SLB smooth like butter to drop some voltages is this then doable?
Is 4U/400 case ok for that if I use my transformer 500VA, 4x18VAC? If I go for higer voltage rails then will be 4U/500 case be also OK?
5U/400 case is really Fugly!
I am sorry for so many questions.
so, it seems you did pony up substantial amount of greenies, needed to build this amp, without actually proper reading thread from start
it is, from the start of thread, well clear established that PL XA25 is more than inspiration for this one, and even if not carbon copy, at least current limiting protection is blatantly copied from original
so, yes, PL XA25 is pure Square Law OS amp
judging by latest Papa's writings, his definition of SL includes not just OS totally without degeneration, but also OS having some mild degeneration, in form of source resistors up to some value of his arbitrage
As I'm just ZM, even if Mighty, that arbitrage is out of my area of knowledge, so as is the case with other areas where I'm Chicken, I can call SL OS only ones without any source resistance
by that criteria and to my knowledge, only PL XA25 is having pure SL OS, of all PL and FW products
2pcs of 2SK2145BL are biased with dedicated CCS, where current is programmed as 0V65/120R; so Idss is not critical at all, my eye is on preferred/minimal xconductance of (any) combo used
dunno what's "JFE2140" ?
pretty much anything can be replaced with appropriately chosen part; for bipolars - voltage, current and Hfe are factors you need to look at; though, each change demands proper battery of tests, mainly to determine that circuit as a whole is still stable without oscillation tendency
I wrote some and certainly did post all graphs for all 3 iterations of amp; if you ask more specific question, instead "what's difference between these two shades of same color", I can try to reply
short and bitter - no go for XA252 with that voltage; 18Vac is too low, 36Vac is too high - perfectly doable but some resistor values needs changing, some bjts replaced with higher voltage ones, and certainly 5U/500 as must
btw - as you're asking for some sort of minimized XA252 - that Donut is perfect for almost Dual Mono (dedicated set of secondaries per each channel) for Plethora of Pinjatas ......... which is nothing more and nothing less than Mini XA252
and perfect in 4U/400 Modu
https://www.diyaudio.com/community/threads/plethora-of-pinjatas-set-p-amp-s.386912/
Oh, I read the xa 252 thread many times, also reading other info, 6moons and so forth. I suspect "magic" I wonder about is mainly due to SL.
I think pucks can really put the beans out, but main magic is SL. Looking at many amp reviews, I kept seeing all those source resistors, leaving me to wonder which others are square law. Maybe I'm wrong, but i'm thinking SL is largest contributor to the big, transparent and powerful sound coming from this amp!
On other hand, If all the other Pass amps are "regular" source resistor types, and no rush to introduce assorted SL Pass Lab amps, I will have to rethink.
As soon as I can build POP or M25 I will have my confirmation. Anyway, this (XA-252) is best one I've built thus far. It rocks beyond expectations!
Russellc
I think pucks can really put the beans out, but main magic is SL. Looking at many amp reviews, I kept seeing all those source resistors, leaving me to wonder which others are square law. Maybe I'm wrong, but i'm thinking SL is largest contributor to the big, transparent and powerful sound coming from this amp!
On other hand, If all the other Pass amps are "regular" source resistor types, and no rush to introduce assorted SL Pass Lab amps, I will have to rethink.
As soon as I can build POP or M25 I will have my confirmation. Anyway, this (XA-252) is best one I've built thus far. It rocks beyond expectations!
Russellc
I may be off, but it seems Nelson was hitting around this with F5 turbo's diode set up. less resistance as heat climbs, giving "turbo" effect. Controlling bias with no resistors like with this amp is the bees kneesso, it seems you did pony up substantial amount of greenies, needed to build this amp, without actually proper reading thread from start
it is, from the start of thread, well clear established that PL XA25 is more than inspiration for this one, and even if not carbon copy, at least current limiting protection is blatantly copied from original
so, yes, PL XA25 is pure Square Law OS amp
judging by latest Papa's writings, his definition of SL includes not just OS totally without degeneration, but also OS having some mild degeneration, in form of source resistors up to some value of his arbitrage
As I'm just ZM, even if Mighty, that arbitrage is out of my area of knowledge, so as is the case with other areas where I'm Chicken, I can call SL OS only ones without any source resistance
by that criteria and to my knowledge, only PL XA25 is having pure SL OS, of all PL and FW products
^ Well he looked familiar... but no, I can't think I've ever watched it.
Did he build single ended tube amplifiers? Big 300B? If not, no, then no clue.
I live safely behind The Orange Curtain. We don't have bearded, hairy guys, with Bose 901s at home, going around with a single action revolver.... that's LA and SF.
Did he build single ended tube amplifiers? Big 300B? If not, no, then no clue.
I live safely behind The Orange Curtain. We don't have bearded, hairy guys, with Bose 901s at home, going around with a single action revolver.... that's LA and SF.
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Well, things as Zardoz are absolutely necessary part of education for any A Class amplifying aficionado
Without proper context, one can't value his Fetish(es) appropriately
So, that explains how it is possible that you're having so much gear originating from darker side of Proud Albion ........
^Ay! "Albion"? I just googled that... England? I thought it was a vacuum cleaner brand from Yugoslavia ( The Albion 600 Sport Abarth Vacuum Machine, deLuxe ).
You mean that State Of The Art mechanical device rotating most perfectly using torque transfer by a petroleum derived BELT?
That's Scottish, not English!
Gotta say, you've taking this thread beyond Monty Python.
Now, stop playing with old, weird movies and beget the 100 wpc, negative 2nd harmonic rich Biggvs Dickvs SIT! Make sure to put some 16V diodes this time.
You mean that State Of The Art mechanical device rotating most perfectly using torque transfer by a petroleum derived BELT?
That's Scottish, not English!
Gotta say, you've taking this thread beyond Monty Python.
Now, stop playing with old, weird movies and beget the 100 wpc, negative 2nd harmonic rich Biggvs Dickvs SIT! Make sure to put some 16V diodes this time.
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naah
better to, according to your practice, you buy for cheap, second hand, proper NAIM amp, which needs special cables to sound (meeh) which then really begz to have additional auxiliary PSU, which then needs special cable in between, and both needing special mains cables, then you need special preamp of same brand, needing special interconnects, but also needing auxiliary additional PSU........
all that to sound (meeh)
which is all proper, to everyone is so easy to lost direction in that superfine Proud Albion Fog
better to, according to your practice, you buy for cheap, second hand, proper NAIM amp, which needs special cables to sound (meeh) which then really begz to have additional auxiliary PSU, which then needs special cable in between, and both needing special mains cables, then you need special preamp of same brand, needing special interconnects, but also needing auxiliary additional PSU........
all that to sound (meeh)
which is all proper, to everyone is so easy to lost direction in that superfine Proud Albion Fog