Stasis Amp

[lumanauw]

I got this beautiful schematic here. But unfortunately, the quality is poor, does anyone has the clearer schematic of this?

Some sections I dont understand.

I assume P1 is for adjusting bias. But it is not in the VBE multiplier section, so it is just making a voltage drop for bias. Is this realible?

Q8 and Q9 is VAS transistor. What is Q9 doing, feeding base of Q8? Or should it be Q8' collector is tied to Q9' collector?

The output stage is CFP with gain of 3?

[highbias]

Thats actually from Nelson Pass's archives and is really beautiful no matter how bad your copy may appear. Thats all there is on that amp that he's released.

My S-300 was VERY a reliable amp.

Mark

[Nelson Pass]

Actually I did not have that copy, although I do now.
If you navigate to www.passlabs.com/np you'll see 3
files: thr_fe89.tif thr_fe90.tif and thr_os89.tif
that will give better information. You'll also see stasis2-3
schematic as well.

[lumanauw]

Hi, Mr.Pass,

Thanks for the link.

Those schematics are special. I often think what you have in your head right now

I still see a "major" difference between sch in post#1 with the other Threshold schematics, that is the Q15-Q16. In the other thread you stated it is EC. While other Threshold doesnt have EC (exception 400A-4000 series where you put "clever bias" with 4 Tr)

After reading it more carefully, I still have questions about sch in #1 :

1. Bias controller P1, does it only depending on voltage drop, without getting involved in VBE multiplier?

2. I found that Q1 and Q2 are cascoded by Q4 and Q5, but how come Q1 and Q2 only cascoded at 1 VBE drop (Q3)? Isn't that too low?

Or is it #1 is just a DIYer modified of Threshold schematic?

Mr. Pass, could you tell a story about being sevice technician, Threshold, Adcom and current PassLab?

[lumanauw]

I found a valuable help from Mr.Pass. He said a MOSFET minimal cascode voltage is about 2V5. Don't cascode MOSFET lower than that voltage.

Does anyone know how low can I cascode a Jfet and a Bipolar?

[lumanauw]

http://www.diyaudio.com/forums/showt...942#post625942

Which Statis does this related to? Or which patent?

[Nelson Pass]

Originally posted by lumanauw
Mr. Pass, could you tell a story about being sevice technician, Threshold, Adcom and current PassLab?

I have lots of funny stories, but the names have to be changed
to protect the guilty.

When I was just starting Threshold, before we had released any
product, I was building some little phono stages, and gave one
to the editor of a magazine. He fell in love with it, and ordered
some built to sell or give away, I'm not sure which. When he
got some more he called up and wanted to know why they
didn't sound as good as the first one: "Here, just listen to what
I mean", he said, and held the phone up to his system. "Can you
hear that? Can you hear that?"

I couldn't hear it, but I asked to have the original and one of the
new pieces back to compare them. "Can't do that - I sold it!"

So there was nothing really to do, since all the new ones sounded
the same as each other. A couple months later he called up to
tell me he'd re-acquired the original preamp, but now he wanted
to know whey it wasn't nearly as good as the ones I'd sent since.

That was the last time we talked.

[georgehifi]

Here is the S300 mkII optical if you guys are intereseted.

Cheers George

[lumanauw]

Hi, Georgehifi,

Do you have the component list?

[georgehifi]

No but I'm sure they are embedded in the dark recesses of Nelsons mind. It's a shame the values are not there.
But these should be the same, as this is the Usher clone of the Threshold S500 series II optical, just one extra gain stage, which could be for the better.

Cheers George