now you (we) are going to even more appreciate each of 250pcs of SIT-3 , knowing that every one is unique
Indeed. Getting parts that work is already hard enough, and then one
presumably needs to tweak things so the final amps are consistent.
This is one heck of a difficult amp to put in production.
Thanks guys.
Looks like I should head over to the fish market.
Dennis,
Please know that I do things in a very limited and subjective manner. In other words, not so organized.
You see that random THF-51 acquisition is risky for DEFiSIT, except for the forced bias circuit.
@ Mighty Man
What I cheked is below and I forgot what condition I did. Maybe one of 28V 2A / 31V 2A / 32V 3A. I was dreaming of big tower amp driving my Dynaudio.
But you can see the Vgs are not so jumpy, but too low.
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@ Dennis
well , I believe things are much easier as I made them .... even if THF I've put in two channels are just similar (not identical) , and those pentodes down (IRFP9240) are even less similar , I didn't found some difference in THD measurements of two channels
however , I'm much often Plonker than Genius ...... even if Papa insist calling me that
(now I just need to remember how exactly is he calling me - Genius or Plonker)
well , I believe things are much easier as I made them .... even if THF I've put in two channels are just similar (not identical) , and those pentodes down (IRFP9240) are even less similar , I didn't found some difference in THD measurements of two channels
however , I'm much often Plonker than Genius ...... even if Papa insist calling me that
(now I just need to remember how exactly is he calling me - Genius or Plonker)
Dennis,
Please know that I do things in a very limited and subjective manner. In other words, not so organized.
You see that random THF-51 acquisition is risky for DEFiSIT, except for the forced bias circuit.
@ Mighty Man
What I cheked is below and I forgot what condition I did. Maybe one of 28V 2A / 31V 2A / 32V 3A. I was dreaming of big tower amp driving my Dynaudio.
But you can see the Vgs are not so jumpy, but too low.
counting on fact that all 3 tables were made with same goal in mind , we can count on fact that thety're comparable
from that I can see that 2SK182S is having too big Ugs ...folding on other side of IRFP9240 Ugs , so wee need to fill gap between sources , to have gates in same point
while with 2SK180 - I see Ugs is even smaller than THF , so opto bjt will have even more space to be put in
from that point of view , SissySIT is most probablydoable with 2SK180 , while possible difference in sound vs. THF iteration , I can't predict ...... probably not much , but that only real test can show us
I would just throw in, and say to myself this is good enough.
Because with my rule DEFiSIT is good enough. More than that is... Greedy Boys.
OK ZM, here goes the random pics.
2SK82-IRFP9240 with 0.6 ohms Source R
2SK82-IRFP9240 with no Source R CCS from 12V batteries to the 100 ohms gate resistor
THF-51S-IRFP9240, same as above
THF-51S-IRFP9240 with CCS from regulated supplies to the 100 ohms gate resistor - hum
THF-51S-IRFP9240 with separate bias from regulated supply to the 100 ohms gate resistor - still hum
The SIT-3 serving my curiosity
Chassis .... dear old F2 (hardcore porn right?)
YBA slaughtered into KORG B1. This YBA circuit is just ridiculous and I punished ..
2SK82-IRFP9240 with 0.6 ohms Source R
2SK82-IRFP9240 with no Source R CCS from 12V batteries to the 100 ohms gate resistor
THF-51S-IRFP9240, same as above
THF-51S-IRFP9240 with CCS from regulated supplies to the 100 ohms gate resistor - hum
THF-51S-IRFP9240 with separate bias from regulated supply to the 100 ohms gate resistor - still hum
The SIT-3 serving my curiosity
Chassis .... dear old F2 (hardcore porn right?)
YBA slaughtered into KORG B1. This YBA circuit is just ridiculous and I punished ..
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Using an F2 as a chassis is ultra hard core.
Good stuff Chul.
Dennis
This does not mean F2 is not good enough. This F2 is my DIY friend's and he got a brain stroke and impaired. His only joy is listening to music and he wishs to have a listen to SIT. Initial plan was only replacing one FET but ended up like this. This ia no offense to the F2 I hope.
did you tried adding it up , having output from P source ?
as I said :
as I said :
I had a dream ............ no , wrong start
I had a big dilemma last night - trying to nest THF51-S in SEF amp concept , where upper part is having source resistors and optocoupler (biasing main device ) is fed on them ........ or to nest it in Babelfish M25 concept , so no source resistors and where optocoupler is fed from Hall current sensing chips in rails
first one is having lesser THD , accordining to sims ;
second one is having greater THD, again according to sims , but higher level of purity , rawness , call it whatever you want ..... sans source resistors it is closer to Papa's most wakoo one - DEFiSIT amp
so , this morning decided to try it thrown in Babelfish M25 cradle ......