SissySIT

[Zen Mod]

Opening new thread , to make things easier to follow and comment .

Everything started with collective brainstorming in Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans thread , and resulting prototype posted in #618 , Most Greedy Boy, of them all... or (there is no) DEFiSIT of Papa's Koans

Tnx to all Greedy Boyz involved ........

as I wrote , SissySIT ( in fist time called SUFI-SIT , but then I realized that too much seriousness is ..... too serious ) is practically THF51-S Tokin SIT nested in Babelfish M25 circuit (even pcb) , with necessary change in some parts values .

so , schm and last/final pcb iteration are these :

(observe that I finally decided to match my pcbs to DiyAudio UMS ...... taking in account Jason's and 6L6's stance - better keeping things less complicated , than asking for few more taps in existing UMS..... so , besides SissySIT being Sissy , ZM is Mighty Sissy , doing things to save Greedy Boyz from some drilling/tapping efforts)

[Zen Mod]

few general notes:

- yes , it is Poor Man's iteration of SIT-3
-yes, same pcb for Babelfish M25 and SissySIT , skipping/adding few parts for each and using few different parts values for each
-yes,you can choose what to use in circuit - Edcor, Jensen , or Cinemag ; see complicated xformer area - footprint/pads included for all 3 of them

now , to keep this post more interested , placed few pics of my dear T-Bed (from previous thread) :

[Zen Mod]

to quote myself , it was little trouble , who could expect that ........ sims aren't so precise regarding biasing network resistor values (few important factors missing in models , most important of them being gate leakage current)

so , had to heavily alter some resistor values - against values predicted by dummy sims made by even dumber operator , but solved it

I'm pretty satisfied , THF51-S not exactly being PapaSIT (read - made for sissy audio purposes) , but real tough welding drek

intended PSU is classic FW format - Donut with 2x18Vac secondaries , usually resulting in some 22V5dc rails (use CRC in filtering bank)

Iq , say between 1A8 and 2A

actual conditions in T-Bed are 25Vdc rails and Iq of 2A

due to damn big THF case , even 0.1mm thick mica is good enough for THF case being just slightly warmer than metal beneath it

so , 1W measurements (EMU1212 , DIY interface box , ARTA) are :

(FW SIT-3 , as reference , having approx. 0.15% 1W/4R and 0.21% 1W/8R)

[Zen Mod]

10W at 4R and 8R

SIT-3 , 0.6%/4R and 1%/8R

[Tea-Bag]

Originally Posted by Zen Mod

I'm pretty satisfied , THF51-S not exactly being PapaSIT (read - made for sissy audio purposes) , but real tough welding drek

Sound resemble DefeSIT aka SIT-3? I assume it does not sounds like M2.

[Zen Mod]

FW SIT-3 declared as 18W/8R and 30W /4R

having THD of , say, 2% at 18W/8R and 2.3%/4R

from some reason (excitement , what else) , I forgot to measure at 30W/4R .... so including what I have - 18W/8R and 16.5W/4R ..... was probably shooting for same amount of THD

disclaimer - these mesaurements made with additional 6db autoformer in-between EMU and amp; it's probably adding some THD of it's own , but who cares

edit: Tea- will answer that later , with more info

[Zen Mod]

you can see from my measurements vs. SIT-3 data - difference between PapaSIT and THF51-S nature ........ SIT-3 is characteristically having lesser THD on 4R load , while THF is having lesser on lesser (8R) load ; as I see it - result of PapaSIT being developed for lower rails voltage/higher current (pretty much FW form factor/audio usage) , while Tokin Biggie being ... what it is - shaker table/industrial workhorse

final graphs, Freq. response at 4 and 8R load , 1W

[Zen Mod]

now, Tea asked for comparison with little jewel (little just in physical size , not in sound ) DEFiSIT ....... for my ears , and for my regular sets of second ears .... same magic is there ; speed , details , authority .....

maybe I can say that SissySIT is somewhat Berserked DEFiSIT , and note that all comparisons are made between properly made DEFiSIT (dual mono and whatnot, with Cinemags on input) , while SIssySIT is still "just" T-Bed iteration - with crappy PSU common for both channels , ubercrappy powerwiring and Edcors on input

as illustration , set of measurements of my dear DEFiSIT ......

[Zen Mod]

few pics of SissySIT in action , in my workshop

[Zen Mod]

while I'm still on the Mountain , not yet arrived at peak with my fave concrete pole , to sit on , both amps are at my friend's ...... he's regular user of my Babelfish J2 , so to paraphrase his words :

-same sound character
-same musicality
-in this phase -old PSU caps , Edcor instead of Cinemag, common PSU , lousy wiring - little rougher than DEFiSIT
-space , resolution ........ everything as per wish

comparison with Babelfish J2 ...... higher level of resemblance to tube sound , but most important difference is in details presentation.... BJ2 is presenting details as is , direct to head , whily SissySIT is more subtle .... same as difference in sound presentation of Benz Micro LPS and Ortofon SPU Royal cartridges ... both worth having and enjoying