Some Stax stuff was really nice stuff but I fear that most of the selling price was wrapprd up in the chassis they used as they were quite fancy.
Thanks for the schematic!! What was the rail voltage on this amp? And is this the complete schematic? I find the lack of output inductor interesting if this is the whole schematic. The outputs are very old stuff and the amp might work and sound alot better with newer devices in it.
Mark
Thanks for the schematic!! What was the rail voltage on this amp? And is this the complete schematic? I find the lack of output inductor interesting if this is the whole schematic. The outputs are very old stuff and the amp might work and sound alot better with newer devices in it.
Mark
Actually, the big succes numbers were the DA models, like the DA-50M and DA-100M.
Which were kinda small, as they employed heat pipes for cooling the output stage.
The big critters were the X1 and X2 models, of which i gathered very few have been sold.
In their price range the X2 has an outfit that is of the same standard as its competitors.
The X1 looked like a server computer, and imo not in accordance to what it cost. The insides were though.
I've only seen the X1, on sale in one of the fancy French audio palaces, not able to judge its qualities.
The X2 i did both see in the flesh, and heard it in action on Martin Logal CLS's.
The DA300 is from the early 70s, never seen one, but the stories are that it did have bragging rights when it comes to driving electrostats.
Even on ESL63s, which, for 70s and early 80s amplifiers, makes it prime beef. Krell KSA50 and KSA100 are also supposed to be members of that list.
Are you sure about that 90 volts ? Not peak to peak ?
Half would be nearly enough for the 150/8 of the Stax.
And 90 volts is way too high for the kind of output devices, the 2SA747 certainly is not up to rail voltages of such magnitude in a pushpull output stage. The circuit even has the Hfe number of some of the devices mentioned, as the output devices do not they must be low voltage types.
Which were kinda small, as they employed heat pipes for cooling the output stage.
The big critters were the X1 and X2 models, of which i gathered very few have been sold.
In their price range the X2 has an outfit that is of the same standard as its competitors.
The X1 looked like a server computer, and imo not in accordance to what it cost. The insides were though.
I've only seen the X1, on sale in one of the fancy French audio palaces, not able to judge its qualities.
The X2 i did both see in the flesh, and heard it in action on Martin Logal CLS's.
The DA300 is from the early 70s, never seen one, but the stories are that it did have bragging rights when it comes to driving electrostats.
Even on ESL63s, which, for 70s and early 80s amplifiers, makes it prime beef. Krell KSA50 and KSA100 are also supposed to be members of that list.
Are you sure about that 90 volts ? Not peak to peak ?
Half would be nearly enough for the 150/8 of the Stax.
And 90 volts is way too high for the kind of output devices, the 2SA747 certainly is not up to rail voltages of such magnitude in a pushpull output stage. The circuit even has the Hfe number of some of the devices mentioned, as the output devices do not they must be low voltage types.
Here is the data for the outputs... Pretty old stuff and should be improved upon in a clone. I agree with Jacco that the rails were probably about half the devies ratings. They would not be very reliable at 90 volts!! I coulodn't read is the NPN'swere 2SC 1116 or 1118 on the photo so I posted the 1116.
2SA747: PNP / 120V / 10A / 100W / 15MHz
2SC1116: NPN 180V / 10A/ / 100W / 10MHz
Mark
2SA747: PNP / 120V / 10A / 100W / 15MHz
2SC1116: NPN 180V / 10A/ / 100W / 10MHz
Mark
Hi Thinkbad,
It's rather ho-hum... nothing special. Nice FET cascode front end then downhill to a heavily slugged cascode Vas which will have characteristically poor +ve supply rejection, and then to matched multiple bipolar EF outputs. Itwould need to run Class A so your not listening to +ve supply AB commutation artefacts.
An expensive exercise and waste of power for little or no benefit- it's a dinosaur & should be left extinct.
Cheers,
Greg
It's rather ho-hum... nothing special. Nice FET cascode front end then downhill to a heavily slugged cascode Vas which will have characteristically poor +ve supply rejection, and then to matched multiple bipolar EF outputs. Itwould need to run Class A so your not listening to +ve supply AB commutation artefacts.
An expensive exercise and waste of power for little or no benefit- it's a dinosaur & should be left extinct.
Cheers,
Greg
I have one of these amps
A Stax DA-300. It's a nice amp, well built. Undoubtedly it does get the 150w from all class-A. It runs hot, and has two silent fans to dissipate the heat. It's heavy, and pretty rugged overall. I havent' used it in a couple years but it had more than enough power to run the ML CLS I have to plenty high levels of volume. It has switchable AC and DC coupling and a few other interesting things on it. Let me know if you end up cloning it and need pictures or something from the insides. I don't have a schematic or manual, unfortunately.
the Stax japan website has some info on it, not much but there is a little on the net in other places. It was their first reference amp built to drive their electrostatics. It was the biggest and best they made except for hte DMA-X1 / X2 series. Mark Levinson reportedly used it as a reference to compare against when building the first Mark Levinson amplifiers. Originally it sold for about $4k in 1975 or so, the equivalent of about $15k today.
-Ed
A Stax DA-300. It's a nice amp, well built. Undoubtedly it does get the 150w from all class-A. It runs hot, and has two silent fans to dissipate the heat. It's heavy, and pretty rugged overall. I havent' used it in a couple years but it had more than enough power to run the ML CLS I have to plenty high levels of volume. It has switchable AC and DC coupling and a few other interesting things on it. Let me know if you end up cloning it and need pictures or something from the insides. I don't have a schematic or manual, unfortunately.
the Stax japan website has some info on it, not much but there is a little on the net in other places. It was their first reference amp built to drive their electrostatics. It was the biggest and best they made except for hte DMA-X1 / X2 series. Mark Levinson reportedly used it as a reference to compare against when building the first Mark Levinson amplifiers. Originally it sold for about $4k in 1975 or so, the equivalent of about $15k today.
-Ed
The story overhere is that ML refused to demonstrate their amplifiers with big Stax amps present.
I for one would be very interested to know how the cooling setup of your Stax is, if it does deliver the goods in full class A as you say.
From the size of the amplifier, mentioned in a Stax story or brochure in the past millenium, i found it hard to calculate how it can cope with the heat if it runs full class A. (believe it was the brochure of one of the later models)
The output devices may be TO3's, but the number and their power rating confirms that it would be very difficult. Supposing mica was used at the time for insulators.
Especially in the climate you are enjoying.
If the fans are silent running the heatsinks of the DA-300 must be out of this world.
I for one would be very interested to know how the cooling setup of your Stax is, if it does deliver the goods in full class A as you say.
From the size of the amplifier, mentioned in a Stax story or brochure in the past millenium, i found it hard to calculate how it can cope with the heat if it runs full class A. (believe it was the brochure of one of the later models)
The output devices may be TO3's, but the number and their power rating confirms that it would be very difficult. Supposing mica was used at the time for insulators.
Especially in the climate you are enjoying.
If the fans are silent running the heatsinks of the DA-300 must be out of this world.
The early 80s models, DA-100M and DA-50M, served as reference amplifiers for years in these parts of the world.
Quite compact because of the heat pipes, only seen a number of integrated low power class AB Japanese amplifiers that used this type of cooling.
http://www.stax.co.jp/ENG/History.html
Stax's ELS F8* loudspeakers panels were also very impressive.
Quite compact because of the heat pipes, only seen a number of integrated low power class AB Japanese amplifiers that used this type of cooling.
http://www.stax.co.jp/ENG/History.html
Stax's ELS F8* loudspeakers panels were also very impressive.
further info
well, I guess it depends on what you mean by best. the da-300 was the most powerful and most expensive save for the DMA-x series. Does that make it 2nd to top of the line? IMHO yes (among other reasons).
Anyway, I will try to take some pics if anyone is interested. it has big heatsinks which are within the fan area, in a circle-type configuration. It sheds a lot of heat when running, I am pretty sure it is supposed to be 150w full class A. There are other (more modern) SS amps that run that much class A power without fans, so it should be doable.
in any case, a neat amp and a rare piece of history. Wish I had some Stax ELS-8X BB to go with them!
-Ed
well, I guess it depends on what you mean by best. the da-300 was the most powerful and most expensive save for the DMA-x series. Does that make it 2nd to top of the line? IMHO yes (among other reasons).
Anyway, I will try to take some pics if anyone is interested. it has big heatsinks which are within the fan area, in a circle-type configuration. It sheds a lot of heat when running, I am pretty sure it is supposed to be 150w full class A. There are other (more modern) SS amps that run that much class A power without fans, so it should be doable.
in any case, a neat amp and a rare piece of history. Wish I had some Stax ELS-8X BB to go with them!
-Ed
Dear Ed Sawyer,
It might be a littele late, but I have got a pair of ELS 8x speakers for sale.
I live in the Netherlands. If you are interested, mail me
jcensj@casema.nl
Jan Consemulder
It might be a littele late, but I have got a pair of ELS 8x speakers for sale.
I live in the Netherlands. If you are interested, mail me
jcensj@casema.nl
Jan Consemulder
