Its been about a week, so as good a time as any to share my impressions.
I really, really like Scryer.
Words that come to mind are clarity, sweet, full, dynamic, magic. Its got the grunt and fullness in the bottom half that I would expect from a SE common source amp. And its tremendously lucid, like I would expect from a follower. Really quiet, so the sense of dynamics and space between notes is excellent. Its got the SIT magic going.
For me, Scryer satisfies the itch to listen to a common drain SIT amp, as well as the urge to swap in a lush, common source SIT amp.
I really, really like Scryer.
Words that come to mind are clarity, sweet, full, dynamic, magic. Its got the grunt and fullness in the bottom half that I would expect from a SE common source amp. And its tremendously lucid, like I would expect from a follower. Really quiet, so the sense of dynamics and space between notes is excellent. Its got the SIT magic going.
For me, Scryer satisfies the itch to listen to a common drain SIT amp, as well as the urge to swap in a lush, common source SIT amp.
Ready to tempt the magic smoke!
I swapped out my F5 boards from that chassis (I have an upgrade path for them anyway with Toshiba output pairs) and reused that power supply. It’s a MicroAudio SMPS with extra caps at the output.
To confirm, it looks like from ZM’s development of this amp that the Iq can be measured at the big resistors next t9 the positive rail. Is this correct?
Do trim pots need to be started at one end or the other? Or, is midpoint ok to start? Similar process back and forth like setting bias and offset on the F5?
[Edit: I’m studying SissySIT R3 thread on this…]
Thanks for your support for this
[Sorry about the match, ZM]
I swapped out my F5 boards from that chassis (I have an upgrade path for them anyway with Toshiba output pairs) and reused that power supply. It’s a MicroAudio SMPS with extra caps at the output.
To confirm, it looks like from ZM’s development of this amp that the Iq can be measured at the big resistors next t9 the positive rail. Is this correct?
Do trim pots need to be started at one end or the other? Or, is midpoint ok to start? Similar process back and forth like setting bias and offset on the F5?
[Edit: I’m studying SissySIT R3 thread on this…]
Thanks for your support for this
[Sorry about the match, ZM]
Attachments
yes, 1A5 initially
when both Iq and DC Offset are in ballpark, fine tune both in temp equilibrium ( not that it matter much, but procedure yadayada)
1A6 to 1A8, whatever makes you happy
1A6*0R11=176mV
when both Iq and DC Offset are in ballpark, fine tune both in temp equilibrium ( not that it matter much, but procedure yadayada)
1A6 to 1A8, whatever makes you happy
1A6*0R11=176mV
Darn. One side adjusted fine. The second channel only reads 3.5mV across the resistor for the full travel of the trim pot. Big sink is cold. Little sinks are slightly warm. All sinks on the working channel are appropriately warm. Bias trimpot works as expected.
What would cause there to be no Iq? Backward trimpot? I hope not a dead SIT…
What are some test points I can measure for context? I can get to the SIT and big mosfet pins easily.
What would cause there to be no Iq? Backward trimpot? I hope not a dead SIT…
What are some test points I can measure for context? I can get to the SIT and big mosfet pins easily.
Last edited:
sorry, no time now, outa town
will reply in evening
check that you have 1V2 across R122
diodes orientation etc.
will reply in evening
check that you have 1V2 across R122
diodes orientation etc.
Thanks, no worries. I’m heading out of town for a couple days, too. Will revisit the errant channel on Monday.
1.186V across R222. Orientation of all diodes, caps, and transistors look correct.
1.186V across R222. Orientation of all diodes, caps, and transistors look correct.
I have numbers of SITs, THF-51s, 2SK180.
(No, not for OPLDF.) 😉
I'm quite sympathised with this Scryer.
I think I need one set. Or two.
Is it possible to drive a stereo Scryer in balanced-bridged mode?
Then I definitely must have two pairs.
There is only one thing, there are too much parts in it.
This is a real parts graveyard.
It is too complicated. (For me, of course.)
And how tolerate this thing, if I overbias it?
Say, something Iq 3A with +/- 30VDC power supply.
You know me, I'm a wacky FAB, my F6 sings quite O.K. with above parameters.
If I'm right, it means, those poor IRFP064n FETs in my F6 dissipating almost 100W heat, per piece.
Meanwhile heatsink temperature climbed up above water boiling point.
So I'm afraid, one piece IRFP9140 in Scryer will burn immediately in similar conditions.
Is it possible to parallel some of them?
Anyway, Plot's build is quite fugly.
And lastly, if I build it, will it tell me the winning lottery numbers?
Or for this extra function, I will need a Crystal Ball as well?
Many thanks in advance, My Mightiness!
Gyuri
(No, not for OPLDF.) 😉
I'm quite sympathised with this Scryer.
I think I need one set. Or two.
Is it possible to drive a stereo Scryer in balanced-bridged mode?
Then I definitely must have two pairs.
There is only one thing, there are too much parts in it.
This is a real parts graveyard.
It is too complicated. (For me, of course.)
And how tolerate this thing, if I overbias it?
Say, something Iq 3A with +/- 30VDC power supply.
You know me, I'm a wacky FAB, my F6 sings quite O.K. with above parameters.
If I'm right, it means, those poor IRFP064n FETs in my F6 dissipating almost 100W heat, per piece.
Meanwhile heatsink temperature climbed up above water boiling point.
So I'm afraid, one piece IRFP9140 in Scryer will burn immediately in similar conditions.
Is it possible to parallel some of them?
Anyway, Plot's build is quite fugly.
And lastly, if I build it, will it tell me the winning lottery numbers?
Or for this extra function, I will need a Crystal Ball as well?
Many thanks in advance, My Mightiness!
Gyuri
My Wakoo Neighbor 
yes, it is possible to drive Scryer in balanced - bridged ........ same as it is possible for myriad of amps, you can bridge them and bridge them till the end of world, and achieve even SPL needed for concerts of the plutonium rock band Disaster Area
now, number of parts .........
as I did show in threa dopening, Papa's F8 is having common source JFet stage + common source JFet stage ; first one loaded with resistor, second one loaded with Mu follower
Scrywer is having common source JFet stage + common emmiter BJT sstage + DEF stage; first one loaded with resistor, second one loaded with CCS
so, in principle, Scryer having just half stage more, by Papa's cheating way of explaining things - follower stage count as half active stage
everything else is there just for giggles, to amuse ZM's amusement senses
I could make just slightly changed F8, having few parts more, call it Babelfish F8 and be done ........ but that could be just "DIY F8", not something which I can name properly
I did explain all segments of schmtc in first pages of thread - everything can be simplified, if you want to do - just strip it chunk by chunk, and you'll end with F8
This way, I'm not having input nor output cap; Iq is damn stable in wast region of rail changes ( either mains fluctuation of some monkey doing gimmicks with Variac button) and temperature - practically same cold to hot
DC Offset also nice, even if just slightly better behaving than slide of output node in original
etcyadayada
if you want something simpler, bridged, yet possible to get (variable) flavor of artificial SITness or even real SITness - see here: https://www.diyaudio.com/community/threads/the-marriage.390965/
yes, it is possible to drive Scryer in balanced - bridged ........ same as it is possible for myriad of amps, you can bridge them and bridge them till the end of world, and achieve even SPL needed for concerts of the plutonium rock band Disaster Area
now, number of parts .........
as I did show in threa dopening, Papa's F8 is having common source JFet stage + common source JFet stage ; first one loaded with resistor, second one loaded with Mu follower
Scrywer is having common source JFet stage + common emmiter BJT sstage + DEF stage; first one loaded with resistor, second one loaded with CCS
so, in principle, Scryer having just half stage more, by Papa's cheating way of explaining things - follower stage count as half active stage
everything else is there just for giggles, to amuse ZM's amusement senses
I could make just slightly changed F8, having few parts more, call it Babelfish F8 and be done ........ but that could be just "DIY F8", not something which I can name properly
I did explain all segments of schmtc in first pages of thread - everything can be simplified, if you want to do - just strip it chunk by chunk, and you'll end with F8
This way, I'm not having input nor output cap; Iq is damn stable in wast region of rail changes ( either mains fluctuation of some monkey doing gimmicks with Variac button) and temperature - practically same cold to hot
DC Offset also nice, even if just slightly better behaving than slide of output node in original
etcyadayada
if you want something simpler, bridged, yet possible to get (variable) flavor of artificial SITness or even real SITness - see here: https://www.diyaudio.com/community/threads/the-marriage.390965/
Pictures!
I discovered a loose strand of wire (tiny!) on the board when I got it out. That could be one possible culprit.
I touched up one suspect solder pad for the 0R resistor (it wasn’t bad, but what the heck).
What about the little heatsink touching R135? Could that be a problem?
Let me know if you see anything awry!
I discovered a loose strand of wire (tiny!) on the board when I got it out. That could be one possible culprit.
I touched up one suspect solder pad for the 0R resistor (it wasn’t bad, but what the heck).
What about the little heatsink touching R135? Could that be a problem?
Let me know if you see anything awry!
