so, let's see did ZM had a brainfart (quite possible) when I wrote "CW +Iq"
problem with me is that I hate CW and CCW designations, constantly making errors with that, used to trust only in DMM screen when setting things
anyway, more current through precision CCS means more voltage between output gates, means more Iq
as covered with value of resistors and tripot in precision CCS, minimal Iq is not going to be 0A, but something substantially smaller than final, but still not zero
ok, check
LM334 calculus for Iq is basically Vref/Rset (simplified), meaning that when trimpot is on max value, then Iq is minimal
now, if we take a look at Daughterboard pcb, where we can check resistance of trimpot ........ it is practically the same as you did it .... see enclosed pic I just made
does it mean that I ooked up with CW+Iq note, can't check in this moment because I'm not in workshop and I can't really decipher it from trimpot orientation ( never learned how damn things are oriented)
now, all values are set for usual range of Ugs voltages of both IRFP9140 mosfet in negative rail and for nominal SIT candidates in upper rail; as my test did show, 2SK2087C and THF51 are having comparative Ugs voltages
OK,see schm, originally posted in #109 https://www.diyaudio.com/community/...o-sissysit-42-as-a-cradle.387767/post-7256125
if you have proper original value of level shifter resistor of 120R, change it to 150R or 180R (that will push SIT gate closer to Mosfet gate, thus decreasing Iq), and I believe it'll be settable
all you need then ( counting on previously set input buffer and closed jumper) is to set output DC offset with P103
when you set everything , I'll ask you to measure gate voltages of IRFP, IRF, and THF - all 3 ref. to speaker output node
problem with me is that I hate CW and CCW designations, constantly making errors with that, used to trust only in DMM screen when setting things
anyway, more current through precision CCS means more voltage between output gates, means more Iq
as covered with value of resistors and tripot in precision CCS, minimal Iq is not going to be 0A, but something substantially smaller than final, but still not zero
ok, check
LM334 calculus for Iq is basically Vref/Rset (simplified), meaning that when trimpot is on max value, then Iq is minimal
now, if we take a look at Daughterboard pcb, where we can check resistance of trimpot ........ it is practically the same as you did it .... see enclosed pic I just made
does it mean that I ooked up with CW+Iq note, can't check in this moment because I'm not in workshop and I can't really decipher it from trimpot orientation ( never learned how damn things are oriented)
now, all values are set for usual range of Ugs voltages of both IRFP9140 mosfet in negative rail and for nominal SIT candidates in upper rail; as my test did show, 2SK2087C and THF51 are having comparative Ugs voltages
OK,see schm, originally posted in #109 https://www.diyaudio.com/community/...o-sissysit-42-as-a-cradle.387767/post-7256125
if you have proper original value of level shifter resistor of 120R, change it to 150R or 180R (that will push SIT gate closer to Mosfet gate, thus decreasing Iq), and I believe it'll be settable
all you need then ( counting on previously set input buffer and closed jumper) is to set output DC offset with P103
when you set everything , I'll ask you to measure gate voltages of IRFP, IRF, and THF - all 3 ref. to speaker output node
Attachments
CCS pot
CCW = Low Iq = High R
CW = High Iq = Low R
That’s clear to me now.
I swapped in a 150R level shift. Pot at minimum. Current too high. Forget exact value. Swap 180R and lowest I can go is 2A2
Other channel with 120R, lowest Iq is 2A4
Should I increase Level shift some more? 220r? Parallel the 1k smd resistor somehow? Or short it and crank 1k pot up to 900r or so?
CCW = Low Iq = High R
CW = High Iq = Low R
That’s clear to me now.
I swapped in a 150R level shift. Pot at minimum. Current too high. Forget exact value. Swap 180R and lowest I can go is 2A2
Other channel with 120R, lowest Iq is 2A4
Should I increase Level shift some more? 220r? Parallel the 1k smd resistor somehow? Or short it and crank 1k pot up to 900r or so?
The amp is cooking. I had 220R level shift resistors and biased to 1A8 / 0V offset. After cooking for 90 minutes the bias crept up to 2A0x and 1A9x. I coudn't get back down to 1A8 with pot at minimum, so I put in 240R resistors and adjusted them to get 1A8 / 0V offset. Now I'm cooking some more.
Donuts are rotated to "null point" and tightened up. Bottom cover & feet are installed. This one will be on big speakers soon!
You asked for some measurements. After adjustment and with the heatsinks warm - here are the voltages measured from SPK+ to the measurement points:
Left channel:
SIT Gate: 3V4
IRFP9140 Gate 4V4
IRF510 Gate: 5V55
Right channel:
SIT Gate: 3V4
IRFP9140 Gate 4V4
IRF510 Gate: 5V57
In comparing the bias mechanismus between the original Rev 1 SissySIT and this 42 version I can see the offset is much more rock solid. It doesn't dance around. Nice work!!!
And of course - let’s not forget some porn
Donuts are rotated to "null point" and tightened up. Bottom cover & feet are installed. This one will be on big speakers soon!
You asked for some measurements. After adjustment and with the heatsinks warm - here are the voltages measured from SPK+ to the measurement points:
Left channel:
SIT Gate: 3V4
IRFP9140 Gate 4V4
IRF510 Gate: 5V55
Right channel:
SIT Gate: 3V4
IRFP9140 Gate 4V4
IRF510 Gate: 5V57
In comparing the bias mechanismus between the original Rev 1 SissySIT and this 42 version I can see the offset is much more rock solid. It doesn't dance around. Nice work!!!
And of course - let’s not forget some porn
Attachments
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Would it be possible to date the schematics? I noticed the component names changed! I thought I lost my mind.
Whatever is left of it, that is.
if you have precision CCS integrated on main pcb, schm from post #1 is what you need
if you have precision CCS on Daughterboard (so blank space on main pcb with funny rectangle), last bling schm is what you need ( also noted in post #1)
if you don't have any of these, print whichever one you want (or both) and make a nice poster for your workspace
if you have precision CCS on Daughterboard (so blank space on main pcb with funny rectangle), last bling schm is what you need ( also noted in post #1)
if you don't have any of these, print whichever one you want (or both) and make a nice poster for your workspace
Ay! I was looking at the old schematic... trying to figure out what that level shifter resistor and associated diode do (R129, ZD101) when I realized that the latest schematic has different numbers from the previous one.... but they are both 42.
Newer one.
You know, I don't listen nor measure, I just print the schematics and staple them in my listening room.... I need to learn to read music.
Besides, I'm not a degenerate, so I want my amps to be without degeneration.... Mon Dieu!
It seems to me like you need some real tight tolerances for the SiT and associated Mosfet to make these amps a manufacturing possibility. I don't think FW could go into manufacturing by tuning each individually.
I hear it sounds spectacular... I can't wait. Might be the reason to get rid of the Maggies and just run the Audio Notes? To be honest, I haven't powered the A2/Maggies for five weeks now.... been listening to the F4/Audio Notes.... they sound REALLY good. As I noted, the 42s with the Tonkin SiTs sound like "The King Of Amps"...
Thanks.
Now, can we run them bridged like the F4?
Newer one.
You know, I don't listen nor measure, I just print the schematics and staple them in my listening room.... I need to learn to read music.
Besides, I'm not a degenerate, so I want my amps to be without degeneration.... Mon Dieu!
It seems to me like you need some real tight tolerances for the SiT and associated Mosfet to make these amps a manufacturing possibility. I don't think FW could go into manufacturing by tuning each individually.
I hear it sounds spectacular... I can't wait. Might be the reason to get rid of the Maggies and just run the Audio Notes? To be honest, I haven't powered the A2/Maggies for five weeks now.... been listening to the F4/Audio Notes.... they sound REALLY good. As I noted, the 42s with the Tonkin SiTs sound like "The King Of Amps"...
Thanks.
Now, can we run them bridged like the F4?
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you can bridge anything, even bridges, but you really need to be decisive and informed, to do that
point is - in 99% of cases, when you bridge "regular" amp, you get nulling of all even harmonics in THD Spectra, in other words - welcome details and enormous space, byebye vividity and immediacy (which is somewhat more thing of even harmonics being dominant in THD Spectra)
so, (42) being really special amp, tech. vise - DEF OS best working while still in A Class dominion and best to avoid wandering in B Class dominion
that saying - if DEF stage is nicely working with 8R load (and whatever happens with nominal 8R load) , when you bridge it, each half of bridged amp is now seeing half of load, not particularly best scenario
remember - (42) is small amp, and in case you need bigger amp - best to leave alone small amps aside and build proper bigger amp
for instance - if 15-18W@8R of (42) isn't enough, there is Babelfish XA252 - be it SIT iteration (say 35W@8R) or Schade or full MOS (50W@8R) ........ and that speaking only of my amps, without even looking directly in Papastable
I mean, I made so much different ones lately that even I am mostly lost (imagine how Pa is feeling, after all these years), while I'm slightly feeling hysteric just looking on pile of pcbs of things to come, and not even counting on things still being only in my comp folders
ook, I'm still young, and retirement will never come
edit: bridging ......... something similar as (42) while not DEF OS - see https://www.diyaudio.com/community/threads/the-marriage.390965/
OS Square Law, able to hop through KlunK! with ease, while KlunK! point being extremely high
say that (of my complete amps, Boo & Pooh linked above really being just OS-es nested) proper candidates for bridging are all from list having straight complementary output, pretty much all MOS and just one bipolar (Il Penitente)
point is - in 99% of cases, when you bridge "regular" amp, you get nulling of all even harmonics in THD Spectra, in other words - welcome details and enormous space, byebye vividity and immediacy (which is somewhat more thing of even harmonics being dominant in THD Spectra)
so, (42) being really special amp, tech. vise - DEF OS best working while still in A Class dominion and best to avoid wandering in B Class dominion
that saying - if DEF stage is nicely working with 8R load (and whatever happens with nominal 8R load) , when you bridge it, each half of bridged amp is now seeing half of load, not particularly best scenario
remember - (42) is small amp, and in case you need bigger amp - best to leave alone small amps aside and build proper bigger amp
for instance - if 15-18W@8R of (42) isn't enough, there is Babelfish XA252 - be it SIT iteration (say 35W@8R) or Schade or full MOS (50W@8R) ........ and that speaking only of my amps, without even looking directly in Papastable
I mean, I made so much different ones lately that even I am mostly lost (imagine how Pa is feeling, after all these years), while I'm slightly feeling hysteric just looking on pile of pcbs of things to come, and not even counting on things still being only in my comp folders
ook, I'm still young, and retirement will never come
edit: bridging ......... something similar as (42) while not DEF OS - see https://www.diyaudio.com/community/threads/the-marriage.390965/
OS Square Law, able to hop through KlunK! with ease, while KlunK! point being extremely high
say that (of my complete amps, Boo & Pooh linked above really being just OS-es nested) proper candidates for bridging are all from list having straight complementary output, pretty much all MOS and just one bipolar (Il Penitente)
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The XA252 SIT is definitely on the radar... don't get my going on the SET version... but I wonder if I'll need as I'm planning to do bridged F4s to power the Maggies.
And the Audio Notes are singing with a single F4... I figure the SissySIT 42s will make them sing even better... Maybe I just need something that puts out 20 wpc and something that puts out 200 wpc.... I do have the F5 and A5s for the in between but I'm not using them... also got other amps... not using them either.
Retirement? Well, I'm working for my stereo right now. The idea is to retire while you're young enough to enjoy it.
Besides, I told my kids I want to be buried with my turntable, a preamp, an amp and speakers... my son asked if a picture of the stereo would suffice... So I better have time to enjoy the stereo while my hearing is good.
With my luck, I might end up wearing a Bose Hearing Aid.
Speaking of amps... is there some list in DIYAudio about all of these amps? I mean, there's like a TON of AMPS in here. Hmm... maybe I should not ask?
And the Audio Notes are singing with a single F4... I figure the SissySIT 42s will make them sing even better... Maybe I just need something that puts out 20 wpc and something that puts out 200 wpc.... I do have the F5 and A5s for the in between but I'm not using them... also got other amps... not using them either.
Retirement? Well, I'm working for my stereo right now. The idea is to retire while you're young enough to enjoy it.
Besides, I told my kids I want to be buried with my turntable, a preamp, an amp and speakers... my son asked if a picture of the stereo would suffice... So I better have time to enjoy the stereo while my hearing is good.
With my luck, I might end up wearing a Bose Hearing Aid.
Speaking of amps... is there some list in DIYAudio about all of these amps? I mean, there's like a TON of AMPS in here. Hmm... maybe I should not ask?
