Threshold!

[kekropas]

Hi guys!I have a question.Does anyone know what transistors were used in the threshold 4000 ?Are they the same with the stasis ii. Is there a sound difference between those two amplifiers?I know that back then Threshold had a pyle with extra parts from the model 4000 and they used them to built and bring to the market the stasis ii.Is it true that the 4000 sounds more tube like than the stasis ii.Were the same transistors that were used in to the 4000 originally used in to the 800a.Furthermore did Mr.Pass built the stasis ii himself or they were realised after he was gone from threshold?Thank you for your time!

[Nelson Pass]

The 4000 used 2N5878 and 2N5876 outputs, as did the 800A.

No, the 4000 sounds less like tube than the Stasis amps.

I don't have any information on items made after 1991, and
prior to that I did the amplifiers and preamplifiers. The T series
and amplifiers using IGBT's were not connected to me.

[kekropas]

Thank you so much for your time Mr.pass.You are Gods gift to the audio world.Thank you for the information.I love the picture where you put a pizza box on top of a threshold 4000 to keep it warm,that is funny.

[GRollins]

I always wondered why Nelson's amps run so hot.
Now the secret is out...pizza.
Call in an order 30 minutes before you want to listen. When the doorbell rings, you're ready to go. Beware though, when the pizza gets cool the sound goes. Better have another pizza on the way!
(Just kidding...)

Grey

[Nelson Pass]

Originally posted by kekropas
Thank you so much for your time Mr.pass.You are Gods gift to the audio world.Thank you for the information.I love the picture where you put a pizza box on top of a threshold 4000 to keep it warm,that is funny.

Actually that picture was from Telarc.

[tmblack]

To Mr. Pass:

can you tell me what constitutes a STASIS amplifier design?

Thanks

Tom

[Nelson Pass]

This would get a long answer, but the essential idea is
to take the gain devices and externally reduce the variation
in voltage and current they experience going through the
waveform, thus reducing their distortion but leaving them in
charge and directly connected to the load.

Voltage variation can be dealt with cascoding, and current
variation is reduced by "current bootstrapping" where an
external current source shoulders some of the load. You could
see this as a cousin to the Quad error correction amplifier and
the Aleph current source.

There is some old Threshold literature and a patent, but it still
sums up to the above.

[tmblack]

Thanks for clearing that up Mr. Pass.
How do the old Threshold amps and preamps compare with the Zen designs?

Tom

[mastertech]

Mr Pass the Aleph current source has boosted efficiency, all i want
to know is at what cost to the performance of a class-a amplifier?
you use a current source to reduce distortion in the principal
amplifying device now that the current source behaves it self as
an amplying device what is the whole net effect on circuit's performance, do you trade efficiency for distortion, i am sorry
i sometimes cant resist asking the tough questions and putting
people on the spot

[Nelson Pass]

No, the active source gives greater efficiency and also lower
distortion. Does it sound better? That depends on the
application and your taste, but in the general case, yes.
There's a certain push-pull efficiency to it, but the distortion
component remains 2nd harmonic, but at a lower value.