SSA is the One . . .
For now I will nicely go with All --->BJT - SSA V-12, and latter maybe just for curiosity will try also the same front end but with IRF VAS drivers.
For the ultimate of All it will be an all FET (N-BFIGFT) - & (P-BFIGFT) - #458
We, all participants and all potential builders have to be most graceful to Mr. Andrej for his genie circuit he generously share to the community and a big thanks also to all other real design expert contributors to this design who make final touch even tastier . . .
I know for sure that this is only the ignition of a big spark which will follow in the future time to come in so many different variants and the default level of any serious music lover will be affected to big positive step forward to much better and natural sounding experiences ----> Thanks to ..
.. Mr. Andrej, All the wide audio community from now will easily distant from default Ipod foggy sound. . . 
Andreas
For now I will nicely go with All --->BJT - SSA V-12, and latter maybe just for curiosity will try also the same front end but with IRF VAS drivers.
For the ultimate of All it will be an all FET (N-BFIGFT) - & (P-BFIGFT) - #458
We, all participants and all potential builders have to be most graceful to Mr. Andrej for his genie circuit he generously share to the community and a big thanks also to all other real design expert contributors to this design who make final touch even tastier . . .
I know for sure that this is only the ignition of a big spark which will follow in the future time to come in so many different variants and the default level of any serious music lover will be affected to big positive step forward to much better and natural sounding experiences ----> Thanks to ..
.. Mr. Andrej, All the wide audio community from now will easily distant from default Ipod foggy sound. . . Andreas
I don't know of any class-d that would work , some say yes ... but in practicality , nah .. the sound is thin too.
We will see with SSA-V12..
Urban Legend OMHO. A lot of prestigious amp manufacturers*, are now moving to class D. A friend of mine with a lot of restored legendaries amplifiers and a 'state of the art' system had just removed the huge amp of his main system for a stupid little thing in D class, as it sound better, more transparent, powerful and dynamic than everything he had listen to, he said. I lie on him enough to believe-it. Will try to do the same for the basses of my own system as well, while the treble will be a little SSA.I don't know of any class-d that would work , some say yes ... but in practicality , nah .. the sound is thin too. We will see with SSA-V12..
The same guy says it get better listening results with a SMPS on several analog amps (Including Quads) than with linear PSU, while it is the contrary with class D. So, his class D amp use a huge linear oversized PSU.
Well all listeners said that Class D amps sound warm, hot dynamic and airy, and are fantastic for basses. I believe in analog Current-feedback for treble cause the limitation and problems caused by the switching frequency filter on Class D amps. Keeping a frequency margin at a factor of 100 seems to be ok for me, as my basses cuts at 2000 Herz ;-)
*
Bel Canto
Martin Logan
Bowers & Wilkins
Adam Audio,
Jeff Rowland,
Mark Levinson
B&O,
Rotel,
Pionneer etc...
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Depends on which urban ...
Driven by sales not sonics..
Have access to a few SOTA systems , I have tried Rotel, jeff Rowland and last but not least bel canto , they cannot drive 1 ohm and have a bright thin sound, well ....when they are not shutting down ..
Speakers i have heard them on :
Quad esl 57, 63, 57 stacked and triple stacked
Magnapan 1.6,1.7 , 20.1
Martin Logan CLS, summit
Appogee Duetta, Studio grand,
My own custom hybrid ribbons, large and small bi- amped version
My conclusion is that if they do not sound bright and or thin then you have a speaker that is lacking in details and or balance . In regards to the Quads, i would suggest they be refurbished, when done you will hear the class-d sound. Funny you should mention bass as this is where they are lacking the most IMO.
That aside, i have a few friends with class-d and they like them in their setups, they themselves will acknowledge what i have just said, we have done enuff comparisions to know ...
Not my cup of tea ..., well not yet ......
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Well i'm on the way to make my own opinion, as i have on my table two of those little amazing circuits. At least, i just believe in what i listen, when i believe in something, despite all the respect i deserve for you or my friend ;-)
I keep preciously my 2 Crescendo 140watts SSA modified powered under +- 70V to compare with those Class D 250W powered by +-70V (see what i mean ;-). And 2x 800W +- 70V SPMS to compare with my analog PSU.
You know, for me, like a jump in the 21th century.
To be honnest, my actual system is so good that i'm terrified by this decision to mod-it from passive to digital active filtering, i believe, i'm as crazy as most of the people over there.
I hope we will find in heaven perfect loudspeakers on the other side of the stairway. Oh Lord please, but please, once there, bring-me back my long hairs and my old friends musicians of the 70th, with their Gibson 335 and their Stratocaster Fender. Give-us a recording studio in the clouds and a very old truck to tour all along the sky roads. And we will show you again, Lord, what was a paradise, because we knew for sure what love is.
I'm interesting to hear how the SSA setup worked for you and in what config are you running , i would build two identical ones and bi-amp the speaker (passive bi-amp).
Going from good analog to digital xover ...
not so sure on that one..
Well, my firt comparison between the same amp modified SSA or not (Voltage Feedback against Current Feedback) don't kill the flies. But i can assure a slight improvement in transparency and speed. Basses are a little better separated (Bass and Kick drums) and a yet little more "solid" and compact (don't thought it was possible). Treble smother, fluid, natural, some artificial brightness removed. As fast and dynamic as before, with a little more realism and comfort, if it was possible. "Easier" less aggressive.
Not a huge difference, of course, but i appreciate.
My loudspeakers are 2 ways systems. A 30CM 96db/w, crossover at 1000hz in 100L bass reflex, and a JBL 1" driver in a spherical horn 110db/w, with, for the moment, 24db/oct Butterworth symmetric crossovers with Zobel and Motional impedance compensation. Build and tuned for best group delay and nice frequency linearity . Home made, with a special damping and spherical wave exponential circular horn in wood, 20 years old, now, with brand new foam suspensions.
For the crossover in the digital domain, it is an old story. As a sound engineer, when appeared the first CDs, i was so happy to finally be able to listen to my mixs as they where and no more destroyed by those hated Vinyls, so happy with the digital tape or hardisk recorders, comparing to the previous slow destruction of the analog tapes all along the mixing sessions, or just with the time, that i devoted myself to this technology. And i know now, for sure, how to work transparent in the digital domain in electronic designs. Easier than in the analog domain.
This kind of DSP filtering gives a lot of ability to smooth the response curve of Loudspeakers to less than +-1db, have a perfectly flat group delay from 100Hz to 16 000, and easy opportunities to try and compare different crossover arrangements. Not to mention the room correction abilities and re-mastering of the albums, if you don't like their sonic balances, without changing phases or coherency, and all that for little money.
All my system will be in digital domain up to 4 DACs (bass+ treble x 2channels), the amps in the enclosures, symmetrical lines, with remote level inside each one.
Esperado I am glad that you actually made modification to Crescendo amplifier and listened to it. Look at this, maybe you'll like it even more.
So Crescendo is an amp with the right topology to be easily upgraded to SSA, which opens quite a lot of possibilities for the owners to make a sonical upgrade to their long term companion. Great.
Fluid, very transparent, accurate, but not hard on the ears or cynical. In short well behaved music listeners amp
There is only one design situation where your SSA or current feedback cannot be implanted in an existing amp: Where first stage is not symmetrical and has his emitter with a DC offset. But it is not a sSa by nature ;-)
I would like we discuss about the issue with your low values resistances for feedback i encounter in my sims, described in my thread. Can be a global issue ?
What am I missing?
This is the version that I plan to build, but the fact that the bias current highly depends on the load impedance makes me doubt. Why is this (the varying bias), and can I improve/correct this?
The versions I build will or will not have the CFP’s, I will try them both.
The IRF’s are at a slightly elevated bias, this is to isolate them from the varying IB’s of the power transistors (the simulator tells me that it improves (marginally) by upping the IRF’s bias).
As you can see I am planning to build a power supply that delivers 4 voltages (+/- 40V and +/-15V).
Regards,
Frans.
This is the version that I plan to build, but the fact that the bias current highly depends on the load impedance makes me doubt. Why is this (the varying bias), and can I improve/correct this?
The versions I build will or will not have the CFP’s, I will try them both.
The IRF’s are at a slightly elevated bias, this is to isolate them from the varying IB’s of the power transistors (the simulator tells me that it improves (marginally) by upping the IRF’s bias).
As you can see I am planning to build a power supply that delivers 4 voltages (+/- 40V and +/-15V).
Regards,
Frans.
Very very beautifull....... new PCB for SSA LOW IMPEDANCE HP .....
Alex.
Just my two cents: Why don't use 10X1000µF instead of those huge 10 000 ? It feat better on board (size and height). it is easier to find. It gives better values (average), it is less expensive, and most of all, each one will have lower ESR & ESL, that will be divided by... 10 !
The only annoyance is, all the 15/20years, you'll have to change 20 caps instead of 2 ;-)
ALEX . . . PURE BEAUTY of an ART
Alex, You become a master of this art,
this one is as beauty as it can be, & the only cousin missing here is the balanced one and the family will be complete . . . . . . 
...... new PCB for SSA LOW IMPEDANCE HP .....
Alex.
Alex, You become a master of this art,
this one is as beauty as it can be, & the only cousin missing here is the balanced one and the family will be complete . . . . . .
Thanks for your feedback . let me know the important thing's like which transistor pairs should be matched . hfe important or Vbe matchig or both ? what is the output bias current settings and output offset voltge limit.
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