Babelfish M25, SissySIT - general building tips and tricks

[August]

Still getting better and will need to sleep soon. Will probably need to run in some more. Compared to premium ACA first impression somehow softer, less harsh (because of zero feedback?) more dark background. I am struggling a bit here, have some weird tinnitus symptoms since a few days, hope they will pass.

Getting more dynamic, keep turning the volume further down, now getting better idea of IP signal energy preservation that you mentioned which is much more apparent with this amp (more iron, duh). I have Cinemags in. Using 6V output of DAC so IP can be on moderate gain.

 

[Zen Mod]

no porn, no glory

but, when you get your beauty sleep

 

[August]

Iron pumpkin with SissySIT together, maybe later will have some engraving done and front LED possibly. Thinking about Pumpkin remote/screen upgrade possibly.

 

[August]

Or does porn always include exposed parts?

 

[Zen Mod]

well, nobody will object if you post inside porn

happy with sound?

Sissy will need some time to burn in ........though, I'm sure that you already have a glimpse of future full Nirvana

 

[cwlo]

I just completed mono block Sissy's R.3. They sound great! I do have one question/issue, in that one of them has a turn-off noise. Not a thump but a "Ziiiip" sound. Bias and offset are dialed in nicely. I swapped out the cap bank for another one and the sound persisted on turn-off. Any direction on what else to check? Thx, Chris

 

[Zen Mod]

frankly, no clue, none of mine having that

inspect all wiring and components yadayada

if there is no other shenanigans and Ziiiiiiiiiiiiiiip isn't powerful, feel free to ignore it and take as something funny

amp with personality, quirky one

 

[tamra]

I've got a pair of SIT, existing!
I have M25 r.2 pcb so I can change into sissy sit r.3 right?

 

[Zen Mod]

Unfortunately - not

first iteration of SissySIT was having pcb unified with M25

next revisions are having separate pcbs for two amps

M25 R.2 is having source follower/level shifter on negative rail (most likely my inertia, detail inherited from Old Soul, that one being predecessor in time, to M25 R.2), while for SissySIT you need the same (level shifter) on positive rail, where SIT is situated


anyhow - I'm finding both of these amps worth building ........

regarding SissySIT, last blingie is SissySIT (42)

having it all - not just accommodated footprint for 2SK2087C too, but also biasing mechanism changed to Current mirrors approach, and also fully DC connected all the way, from input to output

 

[tamra]

Thank you ZM.
I will build one more amp 😸

 

[Dudeisms]

Have a DC problem with my Sissysit. Was listening last night and just by dumb luck I put my hand on the sissysit. The left rear heatsink was cold, everything else warm as usual which I thought was odd. Decided to measure the speaker terminals and I have got readings of 11 to 13 V dc 😳

 

[sp33ls]

Uh oh, that's some notable 0Hz. Sounds like you caught it before any damage could be done to your speaks?

Which SissySIT revision did you build? I added some Neurochrome Guardians in my R.3 -- not because I don't trust ZM, but because I don't trust myself.

 

[Zen Mod]

as Dr. Haus sez - Everybody lies
so, when speaking of my precious speakers, I don't trust anyone

@Dudeisms - give me pics to see how you organized things thermally

in this construction first possible is always P channel Mosfet, simply because it's most stressed member

 

[Dudeisms]

Is that what you want to see?

 

[Zen Mod]

yes, all proper - if what I see is Keratherm 86/82, under the mosfet

first diode-test mosfet (that will cover shorts, even if with positive offset that's unlikely) and presence of 5V at 7805
be careful with probe while testing that

see in 7805 datasheet for pinout - numbers to you, pins down , left in, mid gnd, right out

 

[Dudeisms]

Just caught a wiring mistake I recently made 🙃…. Everything is ok now

 

[Zen Mod]

 

[Dudeisms]

Probably was a very very hot cl60 somewhere for a few days 🙄… but apparently miracles do happen because nothing went 💨 and it’s all fine now. 😆

 

[Zen Mod]

most important is that speakers are OK, if I understood you weren't cussing and cringing .......... as I would in case of ....... hate even to think about it

 

[Eric]

After too much time sitting in ziplock bags in my parts box, I'm just starting to build my SissySIT with the original PCBs. I ordered a set of high-nickel Cinemags that should arrive in the second week of July and have a pair of 200mm x 400mm sinks with 40mm tall fins. Bummer that Antek is out of 300VA 18v transformers, but I suspect they'll be back in stock shortly.

Before I begin, I have a question about the Tokin devices (sourced from Pras). The mounting surfaces seem to be a bit convex. Is there any value to wet sanding the mounting surfaces with some fine grit paper to flatten them out a bit? The gap at the mounting ears is about 0.2mm.