stasis 2 and 3 schematics

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The one and only
Joined 2001
Paid Member
This series is no longer called Bag O Fun. This is
my sister's joke, and it's only good for about a week. ;)


Here is the schematic for the Threshold Stasis 2
and 3. This was a very old photocopy, and I had
to spend some time trying to clean it up, but it
is now readable enough.

You might think that I have copies of all the Threshold
stuff, but actually I don't. Most of what I have comes
from guys like Jam.

Thanks, Jam
..... A silly question to ask...., perhaps asked by many
before, but since I'm new here..... Inquiry minds want to know..

What is the driving motivation for Nelson Pass to
start a diy website and/or to share "commercial" circuit designs/schematics with the public ? hehe

This place seems like a gold mine for the electronics
hobbiest..... Sensory overload.....
Pa-7 Nakamichi

I own a Nakamichi PA-7 (or PA-70, depending on where you plug-it-in) using Stasis technology. Where does this amp fit into the evolution of Stasis and Threshold? Was this amp partially compliant to the NP design with constraints placed by Nak., or another version of the developing architecture. :scratch:
History of Stasis-documented somewhere?

Thank you for the reply, Mr. Pass.

I've searched the Internet and inquired with some of my tech-head friends for history on the Stasis topology, but found nothing to explain the development of the architecture, let alone in terms I, a lay person, might understand. Is there a lineage of succession in Threshold products that inludes Nak products? Or, were they produced only to employ contemporary Stasis functionality without the R&D present in the Threshold progressive designs? Was there a Threshold product similar to this one, the PA-7 (1986)? Was the PA-7 thus a clone of sorts?

:yummy: Wish I was home listening...

Dear Mr. Pass

I know that I have seen this already (but I don't know was it a SAE or GAS model) : NFB not taken from the output but from the VAS or driver stages.
Was there any other reason, apart from stability issues, for doing so ?

The output stage topology per se, I must admit, is quite clever ! :cool: :)

What were the THD figures that could be achieved with this circuit ?


The one and only
Joined 2001
Paid Member
The licensing deal with Nakamichi was purely a $$ deal.

The PA-7 was the approximate equivalent of an S300.

Sorry I don't have schematics of the SA1000's, but it
was simply a balanced version of the other big versions
of the Stasis series.

The THD figures of the Stasis series varied by amplifier, but
were generally in the .00X range at low wattage, increasing
to about .1% at full power. Distortion was flat across the
band, rising to about double at 20KHz.

Leaving the output stage outside the loop made the amp
sound better, and of course was a good marketing decision.

Thanks Mr Pass for the SA-1000 info. These amps are Beautifull Big VU Power Meter and Lots of guts. Mine are in need of service and i no longer use them because of that. I gess if the topology is similar to the Other Threshold amps Ill try and go by the Schematic Presented in this thred.
Mr. Pass

Tanks for the answer.

But there is still a question that bothers me: I assume that the decision about the feedback takeoff point was made due to measurement AND listening tests and that several versions have been tried (am I right ?).
Did both correlate or was the feedback takeoff at the output sonically inferior but superior from the measurement point of view ?


Stasis Schematic - Not Viewable

My repeated attempts to download the Stasis schematics and view them have failed. After the download is complete, attempting to open the file gives an error relating to some Kodak...

I have tried to open the file with MS PhotoEditor, Ulead Photoimpact etc., but to no avail.

Can someone please help with some tips or send a copy through email? Thanks in advance.
Joined 2001
Paid Member
Re: Stasis Schematic - Not Viewable

Samuel Jayaraj said:
Can someone please help

shrunk, tweaked, & attached



  • stasis2-3schem.gif
    30.5 KB · Views: 3,780
Dave, thank you very much for posting the schematic of the Stasis amp.

I have a few questions about the schematic. I know that Nelson is busy at CES, so I don't really expect answers from him. But anyone else...?

The Vbe multiplier is shown as A42. I presume this is an MPSA42. I wonder how the TO92 package is coupled to the heatsink for thermal tracking. There is an unmarked resistor between the Vbe emmiter and output track. What could be its likely value? A meter like diagram is shon in shunt with the 100E resistor in the bias circuit. What could this indicate?

The transistor types are now shown from the driver stage to output stage. Any ideas? The output devices are loaded with resistors which have marking such as 1(.68), 1.5(.3) etc., Does this mean 1E, 1E5 resistors and the numbers in parenthesis the voltage drop.

A thermal braker is indicated in the CCS of the first stage. Where does this connect?

Finally, can modern devices replace the ones originally used. That is the rail voltage, output power and 2ohm capability of this amp?

I ask because I want to compare this with the Leach Amp which I have decided to build as 2ohm capable, in order to drive 2x18" hornloaded paralleled woofers at 1200 watts (4ohms) ie., Bridged Leach Amps.
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