Stax Da100 Link For Download The Schematic

[parsecaudio]

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

[Nrik]

Nice.

How old is the original design?
Is it supposed to run in class A ? (idle current =XXX?)

regards

[jacco vermeulen]

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.

[aparatusonitus]

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

[jacco vermeulen]

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.

[Alex helge]

Hi,
her pic of the Da 100M:

Alex

[mikeks]

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.

[parsecaudio]

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?

[jacco vermeulen]

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.

[mikeks]

Originally posted by parsecaudio

Mike,why do you want to connect R164/D113 and R165/D114 to its respective supply rails?

Not to supply rails, but to reference connected to respective rail. See article i sent you.