SissySIT R.3

Jump to Latest
#621
Zen Mod said:
no need for testing, except if you want to test them for (potential) buzz under load

if you confirm around 18Vac no load, do not worry , you'll end where is needed
Click to expand...
So the transformer I was planning to use is a little high, measured 20.3V unloaded.

I found an alternative I had in the garage, its a little lower at 19.3V unloaded. Supposed to be 35V center tapped. 8A output and I have two of them so I can still go dual mono PS. So planning to use these, figuring the extra volt will be ok.

Randy
 
#623
I second TungstenAudio's opinion that 20.3V unloaded is fine. I run my SissySIT on dual mono nominal 20V AC transformers. With the wall voltage at my place being mostly around 225-230V AC, that comes out as rail voltages of +/- 25V DC. Works perfectly.
(You need to use capacitors rated for at least 35V in the PSU).

Regards, Claas
 
#624
few volts up can't harm anything

sole thing to take care of is dissipation of puny IRFP down (45 to 50W with exquisite cooling arrangement)

btw. I did tried IXYS puck in that position ........ no pluses ...... THD figures are even slightly higher than with IRFP9140

that would require more complexity in circuit ...... solving drive of puck gate with brute force ...... and only then comparing with existing SissySIT

I mean, why bother ...... there is Babelfish XA252 SIT made, addressed all of that
 
#625
I got my heatsinks separated from the case yesterday. Drilling and tapping M4 holes today.

I also ordered longer M4 bolts, as the 8mm just made it through the SIT and ceramic heat pad (I was lucky enough to get a few sets of SIT sized 2mm aluminum ceramic pads, with the grommets in a group buy)

I did notice that the 5mm standoffs, from the deluxe accessory kit work perfect to incorporate the MOFSET, so all set there.

I decided to populate my amp boards with the smaller FASTON tabs, during the case rewire, in case I end up moving the boards into my monoblock cases, displacing the M2x boards.

Happy to be moving along. I appreciate seeing the creative work going into the published amps here, thanks guys. It’s an inspiration.
 
#626
That was a bit fiddly but the PCB is installed - one more check and I can start setting up the first channel.

l4pTNpX.jpg
 
  • Like
Reactions: Monk55
#628
if arranged properly, no big deal

serviceability (tweaks as first on my mind, hopefully not repairs...... maybe even more thinking about recapping in 15yrs) is always first/unconscious thing - result of eons I spent in repairing biz

in many cases (arrangements) it is just matter of leaving 2" longer wires (than absolutely necessary).... so pcbs can be lifted and rotated for necessary work

in that context, nautibuoy did it pretty well
 
#629
Yay! First channel set up and playing music! 🍾☺️

I'm only using my mobile phone as a source and a bare test/sacrificial speaker so far but it sounds nice and clean sounding if a little quiet - I guess it needs a bit more drive on the input.

Set up was easy thanks to the instructions in post #1.

I won't push my luck so I think I'll leave it there and get some fresh air for now.

Thanks Zen Mod.

BTW. I'm not expecting to need to recap the thing unless medicine works out how to get me recapped first!
 
Last edited:
#633
ggetzoff said:
Choky,

I mean the interstage transformer (600/600). Half or quarter watt?
Click to expand...
no GG

there is no Watt in signal xformer

as written on schmtc- take any of these:
Edcor PC 600:600
Jensen JT-123-LPCH
Cinemag CMOQ-4LPC
Cinemag CMOQ-4HPC

Edcor is ridiculously cheap, Papa's find and reason that he's laughing every time when he remember getting to them, in first place
Cinemag ( any of two) is my pref.
 
You must log in or register to reply here.
Top Bottom