Hi to all diyAudio friends
Here is a link for downloading the STAX DA-100 schematic.
http://fileshare.eshop.bg
and enter da100
This is are a rare and hard to find original japanese schematic.
Some years ago i built this amp,whit 2SC3381 and 2SA1349 double transistors.
Currently a friend has this unit,the amp work perfectly from 8 years.
The listen features ,he said,are very good.
If someone download this schematic a little discussion can be started 😱 😱 😱
Here is a link for downloading the STAX DA-100 schematic.
http://fileshare.eshop.bg
and enter da100
This is are a rare and hard to find original japanese schematic.
Some years ago i built this amp,whit 2SC3381 and 2SA1349 double transistors.
Currently a friend has this unit,the amp work perfectly from 8 years.
The listen features ,he said,are very good.
If someone download this schematic a little discussion can be started 😱 😱 😱
Nice.
How old is the original design?
Is it supposed to run in class A ? (idle current =XXX?)
regards
How old is the original design?
Is it supposed to run in class A ? (idle current =XXX?)
regards
1980/1981, 100 watts class A.
Called DA-100M.
And a very light chassis for such an amplifier, heatsinks placed within the case. The stax had heatpipes.
This schematic is one of those rare occasions.
Called DA-100M.
And a very light chassis for such an amplifier, heatsinks placed within the case. The stax had heatpipes.
This schematic is one of those rare occasions.
Thank you parsecaudio, I always wanted to see/hear some Masao Noro work. I belive that this amplifier is based on his patent from '80s...J. Carr should be here any moment, Noro is his idol from the past😉
http://www.pat2pdf.org/patents/pat4406990.pdf
http://www.pat2pdf.org/patents/pat4406990.pdf
Parsecaudio,
did you manage to source Fujitsu RETs or did you use something like 1215/2921 ?
Posting this schematic is a treat.
While we wait for Michael Kiwanuka's comment on the V/I-limiter :
What an elegant thermal protection solution on the DA-100.
did you manage to source Fujitsu RETs or did you use something like 1215/2921 ?
Posting this schematic is a treat.
While we wait for Michael Kiwanuka's comment on the V/I-limiter :
What an elegant thermal protection solution on the DA-100.
Stax SOA Protection..
Double slope limiter used; could be improved by changing reference from ground to supply rails.
However, the resistor values used are very dubious indeed!
Probably need recalculating.
Double slope limiter used; could be improved by changing reference from ground to supply rails.
However, the resistor values used are very dubious indeed!
Probably need recalculating.
Hello to all.
I hope that this Stax can be one good school of amplifier design for all the diyers.
The person who currently uses and listen this amplifier says that the DA100 clone sound better regarding its Musical Fidelity XP200(with ProAC Studio 130 loudspeaker system).The idle current on this amp is set to 0.7 A each transistor.
The foldback protection stage with shutdown on the audio section is one of the bad thing on this amp.
I do not want to bore to you with the calculations, but this protection is however enough permissive.
An improvement of this circuit could be disconnect D111 and D112 from the Q115 and Q116 respectively and connect the two diodes to an external control circuit (for a relay control,as an example...)
Mike,why do you want to connect R164/D113 and R165/D114 to its respective supply rails?
I hope that this Stax can be one good school of amplifier design for all the diyers.
The person who currently uses and listen this amplifier says that the DA100 clone sound better regarding its Musical Fidelity XP200(with ProAC Studio 130 loudspeaker system).The idle current on this amp is set to 0.7 A each transistor.
The foldback protection stage with shutdown on the audio section is one of the bad thing on this amp.
I do not want to bore to you with the calculations, but this protection is however enough permissive.
An improvement of this circuit could be disconnect D111 and D112 from the Q115 and Q116 respectively and connect the two diodes to an external control circuit (for a relay control,as an example...)
Mike,why do you want to connect R164/D113 and R165/D114 to its respective supply rails?
Looking at the DA100M picture it's kind of funny now that a set of Stax's cost $7000 in 1980 at the current $ exch. rate. (+4$k for the 50 watters)
Liquid Sodium heatpipes are still used to cool main processors in laptop computers.
Liquid Sodium heatpipes are still used to cool main processors in laptop computers.
parsecaudio said:
Not to supply rails, but to reference connected to respective rail. See article i sent you.
Hi Mike
Thank for the posting but i cannot receive the article because my e-mail is changed.Please resend thearticle to my new address.
Very thank you
Vittorio
Thank for the posting but i cannot receive the article because my e-mail is changed.Please resend thearticle to my new address.
Very thank you
Vittorio
David,
wrong person to ask, i've had a great respect for Stax gear for ages.
If it weren't for the K1000 i'd have a Stax headphone and headphone amplifier, the Stax 81 ESLs were marvellous.
You can see from the picture that the DA100Ms were designed for electrostats.
In those days it wasn't that easy to find an amplifier that could handle ESLs, most couldn't.
And most of the ones that could did not match well, ESLs overemphasize the weaknesses of an amplifier.
Most tube amps were not strong enough, and the ones that were had a shocking price tag.
A lot of the SS designs that could had a price starting at $10,000
What i like about live music and being on a dancefloor is the sound all around me.
I was just in the bathroom and through the open bathroom door i could hear noises coming from downstairs, from the second floor, and from the room adjacent to the bathroom where my g/f was working on her desktop/printer.
Hearing exactly where the sound is coming from, through a hole in the wall. Why i love ESLs.
A lot of amplifiers make the sound produced by ESLs a flat picture. Others aren't clear in the high frequencies, make voices sound dull, wobly or booming lows.
A lot make the sound sound slow.
The STAXs made a transparent 3D picture, and fast, a very "neutral" amplifier.
Downside of these amplifers is that they are anaemic, a Luxman M05 had much more force.
US amplifiers like JRs, MLs, and Thresholds had even more, but at twice the cost.
I suppose it's because of the overcautious design of the DA100Ms, the horrid output coil and the V/I-limiter.
But don't you love how they look: a totally different and very modest design, novelty output devices in those days with superhigh Ft and heatpipe cooling technology.
State of the Art.
wrong person to ask, i've had a great respect for Stax gear for ages.
If it weren't for the K1000 i'd have a Stax headphone and headphone amplifier, the Stax 81 ESLs were marvellous.
You can see from the picture that the DA100Ms were designed for electrostats.
In those days it wasn't that easy to find an amplifier that could handle ESLs, most couldn't.
And most of the ones that could did not match well, ESLs overemphasize the weaknesses of an amplifier.
Most tube amps were not strong enough, and the ones that were had a shocking price tag.
A lot of the SS designs that could had a price starting at $10,000
What i like about live music and being on a dancefloor is the sound all around me.
I was just in the bathroom and through the open bathroom door i could hear noises coming from downstairs, from the second floor, and from the room adjacent to the bathroom where my g/f was working on her desktop/printer.
Hearing exactly where the sound is coming from, through a hole in the wall. Why i love ESLs.
A lot of amplifiers make the sound produced by ESLs a flat picture. Others aren't clear in the high frequencies, make voices sound dull, wobly or booming lows.
A lot make the sound sound slow.
The STAXs made a transparent 3D picture, and fast, a very "neutral" amplifier.
Downside of these amplifers is that they are anaemic, a Luxman M05 had much more force.
US amplifiers like JRs, MLs, and Thresholds had even more, but at twice the cost.
I suppose it's because of the overcautious design of the DA100Ms, the horrid output coil and the V/I-limiter.
But don't you love how they look: a totally different and very modest design, novelty output devices in those days with superhigh Ft and heatpipe cooling technology.
State of the Art.
A folded cascode does not deliver Mr Noro's intentions, not according to the posts by Mr Carr.
The way i read the patent is that the layout of the second cascoded stage enables to drop the influence of PSRR which in turn enables lower speed/bandwidth numbers.
(i have the da50/100m data somewhere inbetween the piles, see if can post them)
The way i read the patent is that the layout of the second cascoded stage enables to drop the influence of PSRR which in turn enables lower speed/bandwidth numbers.
(i have the da50/100m data somewhere inbetween the piles, see if can post them)
Hi, Jacco,
Where's the posts by Mr. Carr?
Hi, Everybody,
Reading the patent, like Jontie, I feel it is about folded cascode.
I'm not sure about this, but I think that what makes the amp has 155dB S/N ratio (input equivalent noise : less than -125dB) cannot be separated from the good regulators for the front end voltage supply (CCS+Zener+Transistors).
Raise one question : What's wrong with ordinary VAS?
I've seen that +rail and -rail are not pure DC. They are disturbed, like sea waves, following the music.
When bass notes hits, the supply will dips.
But if we see the schematic, even if +rail and -rail are dirty like sea waves, what's driving B-E junction of VAS transistor (point C towards D) is actually the voltage drop of the R (point A towards B).
If A-B is fluctuated by the seawave, so does point C-D. If both the driver and the driven has the same fluctuation, they are common to each other, current flowing from VAS collector will not be affected.
What's the truth about this. Folded Cascode VAS > differential VAS > singleton VAS (ordinary VAS). Are these 3 in the right position when it comes to the question about PSRR for VAS, from the most good PSRR to the worst PSRR?
Is that Folded Cascode VAS referenced towards ground (Like this STAX patent) is really better than ordiary VAS?
Where's the posts by Mr. Carr?
Hi, Everybody,
Reading the patent, like Jontie, I feel it is about folded cascode.
I'm not sure about this, but I think that what makes the amp has 155dB S/N ratio (input equivalent noise : less than -125dB) cannot be separated from the good regulators for the front end voltage supply (CCS+Zener+Transistors).
Raise one question : What's wrong with ordinary VAS?
I've seen that +rail and -rail are not pure DC. They are disturbed, like sea waves, following the music.
When bass notes hits, the supply will dips.
But if we see the schematic, even if +rail and -rail are dirty like sea waves, what's driving B-E junction of VAS transistor (point C towards D) is actually the voltage drop of the R (point A towards B).
If A-B is fluctuated by the seawave, so does point C-D. If both the driver and the driven has the same fluctuation, they are common to each other, current flowing from VAS collector will not be affected.
What's the truth about this. Folded Cascode VAS > differential VAS > singleton VAS (ordinary VAS). Are these 3 in the right position when it comes to the question about PSRR for VAS, from the most good PSRR to the worst PSRR?
Is that Folded Cascode VAS referenced towards ground (Like this STAX patent) is really better than ordiary VAS?
Attachments
Does a 555 timer not already have folded cascodes ?
Must be well over 30 years old by now, my guess would be a guy like Bob Widlar.
You'd have to do a search, David.
Jonathan Carr posted a number of times on folded cascodes and Moro.
(wish i was smart enough how to save the links for quick reference)
Must be well over 30 years old by now, my guess would be a guy like Bob Widlar.
You'd have to do a search, David.
Jonathan Carr posted a number of times on folded cascodes and Moro.
(wish i was smart enough how to save the links for quick reference)