Babelfish XA252 / Babelfish XA252 SIT / Babelfish XA252 SET

Official Court Jester
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Thank you. How could I have missed these? I guess I blinked. The SIT adds character (more 2d harmonic).

Zen Mod, please do you expect a big difference in distortion at higher frequencies between the two devices? I saw your frequency sweep but am wondering if the SIT geometry offers any advantage up there when pushed. (Probably not given they are both large devices but who knows...)

Too many attractive options here!

more from experience with SissySIT than from Freq. graphs I posted - I'm not losing my sleep about details as that
 
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to clarify that - I wrote around noon, in time of first morning coffee (damn, last evening I was tired but got some idea to try - first draw on back of napkin, then to put in LTS, then - wonder - in Eagle and work on pcb ....... so I really dunno what time was when I got to bed; did I? :rofl: )

all MOS iteration, even if we can see tiny roll-off at 20K, in listening tests didn't rise a brow regarding bloody anything

so, looking just at Freq. graphs, comparing all MOS and DEF iterations, DEF is looking more linear up, but - as I said - MOS is flawless, so what one can expect from even more flawless?

I know main culprit why there is little sag at 20K in MOS version - generally, I was overcautious with cap compensations everywhere, main reason for that being that I wanted to have relatively broad range of BFR values, without need for varying feedback lag cap ( there is none in present amp, even if there is position on pcb, and it is shown on sch)

so, I got that ; looking at 10K squares, with 22R for BFR , there is sliiiight overshoot at leading edge, while with 510R as BFR - there is sliiiight softening of leasing edge

pretty much as I wanted it

in short - if you're younger than 17, maaaaaaaaaybe you'll hear difference in highs between MOS and SIT versions ..... though - hardly ...... even not taking in account fact that with 17 one is mostly interested in other things, not flybating with amps and speakers
 
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Thank you Zen Mod. I was not clear, sorry. The small roll off, especially above 15K, is of little concern to me, having played with speakers, placement, crossovers, etc... Agree with you there are bigger factors at play there.

I was referring to your distortion vs frequency graph. The Stereophile measurements of Papa's amp at 8.9V output show that distortion rises at higher frequencies, and I am wondering whether the THF51 in your design behaves the same, better or worse. The distortion remains very low in level considering the size of the devices. After re-reading your SissySIT (thank you for hint) this sounds like an academic question, so please feel free to disregard! Thanks for sharing.
 
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Babelfish XA252 SIT - graphs , 8R load, BFR=510R

.... everything same (rails +/-30V, Iq 1A7)
 

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Official Court Jester
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Babelfish XA252 SIT - graphs , 4R load, BFR=510R

Load changed to 4 Ohms

post 1 of 2, more pics than allowed for one post
 

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Official Court Jester
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Babelfish XA252 SIT - graphs , 4R load, BFR=510R

post 2 of 2
 

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Official Court Jester
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have some workshop unrelated things today and tomorrow, so second visit to SSE, with Babelfish XA252 SIT is postponed for Thursday

as I said, due to too much happenings (both in reality and in my head), I'm far from being capable of both critical and objective listening, thus need for visiting SSE

however, as I completed both SIT channels on T-Bed 2 yesterday, couldn't resist today afternoon and I did some listening in my workshop

Spoooooky and so much ball$$!

dunno (as said) how's in comparison with anything (I need probably just time to re-set, peaceful time without making new ones) but it's as microscope size of Palomar ......... Rocking!

sense of foundation and authority, as I remember, even greater than with 100W Babelfish Aleph XJ

go figure

ZM, Mad Hatter
 

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I’ve been to Palomar, and it was amazing. It was the rockstar of observatories in the Seventies and remained the best until the big multi-mirror arrays were in place. Then there was the Hubble Space Telescope.
If the XA252 (either version) has similar rockstar quality, then it will be well worth the wait.
 
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