Something I always wanted to ask:
Why did you (Nelson Pass) use 72 output devices in the 200 watts Threshold Stasis 1 monaural amplifier? Why so many? In general Threshold always used many output devices relatively for a given power-rating, but the Stasis 1 used the most of them. Has it anything to do with the Stasis design dictating it?
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https://www.diyaudio.com/forums/attachment.php?attachmentid=900505&stc=1&d=1607545855
Why did you (Nelson Pass) use 72 output devices in the 200 watts Threshold Stasis 1 monaural amplifier? Why so many? In general Threshold always used many output devices relatively for a given power-rating, but the Stasis 1 used the most of them. Has it anything to do with the Stasis design dictating it?
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No I'm serious.
A monaural Levinson ML-2 amp from that same era had 8 output transistors (and 4 for the regulator) and produced roughly the same current (It could drive the Apogee Apogee directly).
I've had a pair of S/1000's and SA/1's in the past that had 40 output devices and now I've only a Stasis 3 that has 14 per channel.
So what's the benefit and/or necessity for having so much (72 in case of the Stasis 1) outputdevices. I'm just curious.
explicitly confirmed (for ooomphteentht time) in newest Stasis thread - cascoding was Papa's solution to achieve higher rails with transistors available then ; post #222
sort of soon after that, newer transistors became available and you can see non-cascoded OS Treshold amps right after
sort of soon after that, newer transistors became available and you can see non-cascoded OS Treshold amps right after
Okay but only a handful of those 72 output devices were used in the Stasis part as the directly to the load connected Voltage section maybe only the Beta selected ones. That still leaves over 70 of those devices for the currentmirror.
Patent US 4,107,619
Hello RobertS61,
The subject was granted to Nelson S. Pass. It answers many STASIS [R] questions; e.g. distilled in its ABSTRACT.
Best
Anton
Hello RobertS61,
The subject was granted to Nelson S. Pass. It answers many STASIS [R] questions; e.g. distilled in its ABSTRACT.
Best
Anton
There are six banks, three banks for each push-pull polarity.
They are the Common-Collector primary output devices themselves (at
the vertical center), and the next banks out are Common-Emitter current
sources that augment the output of those followers, and then the top
and bottom rows which are cascodes.
Central to the idea is that the output followers are in charge, normally
capable of driving the load by themselves in an ordinary amplifier.
The current sources are designed to provide additional current, lightening
the load on the output followers, reducing the current variations of their
current and so lowering the distortion, while still leaving the output
followers "in charge" of the output.
The Cascodes hold the voltages of those banks at relatively constant
Collector-Emitter voltage.
By reducing the variations in gain from voltage and current changes,
the circuit reduces distortion to the point where a global loop is no
longer required to meet a particular distortion figure.
Back then, there were not bipolars with both decent bandwidth and
high safe operating areas, so parallel devices were used to ensure
performance and reliability.
And they proved to be highly reliable, with the exception of some
tantalum caps on the control logic supply....
Thank you very much for your elaborate explanation.
You probably explained this a lot of times already...
You probably explained this a lot of times already...
That's indeed the logic board. I have never seen a schematic for that board. Maybe Zenmod or Nelson have something for that but in later incarnation for the Stasis 1, the S/1000 and SA/1 there was no logic board anymore only small meterboard in front.
Here is the logic board. I recently had the pleasure of repairing one - the tantalum caps had gone bad.
Thank you.
Unfortunately, I missed out on the deal. The pair were not working (both mono blocks), there was some cosmetic damage to both faces and there looked like there had been some "monkeying" around inside. A bad combination and I wasn't willing to pay as much as the next guy.
Oh well, next time. What I'd really like is a pair of the 1600e. I'm not sure why, it's kind of like buying a dragster to pick up groceries. But, I still want a pair!
Thanks,
Eric M.
Unfortunately, I missed out on the deal. The pair were not working (both mono blocks), there was some cosmetic damage to both faces and there looked like there had been some "monkeying" around inside. A bad combination and I wasn't willing to pay as much as the next guy.
Oh well, next time. What I'd really like is a pair of the 1600e. I'm not sure why, it's kind of like buying a dragster to pick up groceries. But, I still want a pair!
Thanks,
Eric M.
Mine assessment is that Threshold did not sell much of these S/1600e's. They did sell the Class A variant of them, the SA/12 with basically the same hardware. In the brochure it said that the S/1600e could deliver 1 hp at 8 Ohms which was kind of funny.
Nothing out of order with that; rumor sez that Wayne did repair Porsche's for living
I have a pair of the SA/12e also which really makes my desire for the 1600e even more odd. I've compared the schetics of both, as I remember they are very similar. It's been a while but I think they are parallel vs bridged design .... I think ....