| Nelson Pass |
This series is no longer called Bag O Fun. This is
my sister's joke, and it's only good for about a week. ;)
So.
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.
www.passlabs.com/temp/stasis2-3schem.tif
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 |
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| thylantyr |
..... A silly question to ask...., perhaps asked by many
before, but since I'm new here..... Inquiry minds want to know..
..WooT..!
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..... |
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| cyclotronguy |
My take (from the desk across the room) is that Nelson does this cause he thinks it's fun stuff.
Cyclotronguy |
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| jacksquats |
| 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: |
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| Nelson Pass |
Nakamichi licensed the patent and trade name. The
product they produced was compliant with the Stasis
design, but obviously rendered with Japanese parts
and construction. |
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| jam |
No.... Thank you Mr.Pass.
Jam :drink: |
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| planet10 |
Reinhard,
Nice link. Last i saw one of your posts i meant to ask about your use of the Moof, Clarus, the famous cow-dog as your avatar? Are you another Mac user?
dave |
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| ppl |
| I sure would like a Schematic to my old SA-1000's Monoblocks any Help TIA |
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| jacksquats |
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...
Greg |
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| phase_accurate |
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 ?
Regards
Charles |
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| W.O.L.F. |
| quote: | Originally posted by planet10
Reinhard,
Nice link. Last i saw one of your posts i meant to ask about your use of the Moof, Clarus, the famous cow-dog as your avatar? Are you another Mac user?
dave |
Sure, but i hope we are not the only Mac user here.
My first mac was a 64k mac :rolleyes:
Reinhard |
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| planet10 |
| quote: | Originally posted by W.O.L.F.
Sure, but i hope we are not the only Mac user here.
My first mac was a 64k mac :rolleyes:
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We aren't. You mean 128k Mac -- mine, heavily tweeked, is holding up a corner of my coffee table.
dave |
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| Nelson Pass |
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.
:Pirate: |
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| ppl |
| 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. |
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| phase_accurate |
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 ?
Regards
Charles |
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| Nelson Pass |
The amps measured about the same both ways, so the
decision was from a sonic and marketing basis.
:$: |
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| Samuel Jayaraj |
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. |
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| planet10 |
| quote: | Originally posted by Samuel Jayaraj
Can someone please help |
shrunk, tweaked, & attached
dave |
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| Samuel Jayaraj |
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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| docjoe |
I have a Stasis II and am concerned about the fact that the VBE transistors are in fact MPSA 6571 on both channels (vce 20 w).
I do not know wether the've been seviced with a replacement or built that way; Are the MPSA 42 the original parts as on the drawings? |
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| jam |
Sam,
I have two Stasis 3's sitting in front of me. The Vbe multiplier is not attached to the heatsink. The thermal breaker is attached to the heatsink. If you look at the diagram you will find that the resistor is 4.7k. The unknown device is a thermister.
Regards,
Jam
P.S. If photographs are required I may be able to provide them next week. |
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| UrSv |
| quote: | Originally posted by Samuel Jayaraj
--snip--
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.
--snip--
[/COLOR] |
Reading the schematic it says that values are for Stasis 2 and the values in parantesis is for Stasis 3. |
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| jwb |
| The Statis 2/3 drawing is beautifully inked and lettered. I wish we could get decent output from modern CAD schematic capture. |
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| Nelson Pass |
Well, the gentleman who did those , Kirk Rader, is dead. But
now his name lives on forever on the Internet!
(Don't ever say I didn't do you a favor, Kirk.)
He came to Threshold from Audio Research, and so if you ever
get hold of some older AR schematics you might note a
resemblance (except for the tube parts).
:cool: |
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| joan2 |
thank you mr nelson pass, now i can have a closer look at your amps, whereas many years back i can only look at them from the pages of the Audio Magazine, wondering what circuit topology you used....
you are God's gift the the audio industry and diyaudio.com is God's gift to DIY'ers like me.... |
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| GRollins |
One trick that works in getting a schematic to look like that is to draw it by hand, but at 2X scale. Then photograph it and reduce to 1X. All the little jiggly places drop out of sight and leave behind an elegant looking drawing. Should be easy with a digital camera and all the fancy photo manipulation software available today.
I run across old drafting books at book sales for a dollar or two that show the conventions used, but someone with an eye for detail can pick up the right tricks just by looking over a lot of old, hand-drawn schematics.
It still helps to have a steady hand.
Grey |
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| ACD |
| Can somebody please inform what the component I have marked is ??? :scratch: |
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| Netlist |
Thermistor 1K?
/Hugo :) |
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| docjoe |
HI again
I wonder if it goes wrong to attach the mpsa 42 vbe multiplier to the headthink through short links from the back face of the pcb(approx. 6 to 8 cm). so that it senses more of the overall temp of the amp?( the plastic can could be glued in a flat metal pipe )
what do you think of that? would mr Pass be ok?
thanks for the advice
:confused: |
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| Nickolas K. |
Does anybody know the type of output devices used in stasis amps (the ones marked A6, A8)?
Nick |
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| Nelson Pass |
A6 were 2N5876 and A8 were 2N5878.
Later parts in the more powerful amps were the MJ1502X
devices. |
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| docjoe |
dear nelson
I am having trouble getting my Stasis II in good working condition,
can you help?
the problem is a sudden loss of control of the bias current after some time (variably from a couple of minutes to some 10 mn.)on one channel.
Bias adjustement is now set by a 10 turn trimmer,( as the original trimmer was worn out) and everything is fine up to about 0.5 A bias, but when set to 0.8 or 0.9 A ,after a while bias jumps suddenly to 6A !
it occurs always on the same channel, the other one works fine
we've checked all components, changed mpsa 42, thermistor, driver transistors, checked all connections and circuit board for cuts, etc
point to point checking is identical on both channels unpowered
but we cannot perform checking while under power because of the bias instability
Have you any comment or hint? It would certainly be the most helpfull and welcomed
Thanks for taking time to answer us
Docjoe |
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| Nelson Pass |
Replace the trim pot first. After that, look for high frequency
oscillation when the current jumps up.
Do this at lower AC voltage, supplied by Variac or with big
light bulb in series with AC line technique. |
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| docjoe |
THANKS ALOT
we shall do what you suggested and keep you informed
warm (class A) regards!
docjowe |
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| KBK |
| quote: | Originally posted by cyclotronguy
My take (from the desk across the room) is that Nelson does this cause he thinks it's fun stuff.
Cyclotronguy |
I have the same problem Nelson..and I get squashed by the commerical concerns. Darn. It bugs my butt -big time- that I cannot just come up with the idea, and then share.
my Origins are sharing and DIY. The money machine keeps food on the table but sacrifices the fun sometimes. |
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| docjoe |
Hi Nelson
We have done what you suggested and everything was fine during an hour or some, with bias set at 0.75 amp.
then we fed some output from a preamp, the oscillation was there again and bias was up to 6 A.
Next step we shall cross the cards and output transistors to watch if the problem moves sides; and then ...
Regards.
docjoe |
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| Nelson Pass |
That's how I keep my 30 odd computers working - swapping
parts. |
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