Not too long ago I received a request for some help from an owner of
an old Threshold Stasis amp, whose amp was broken and where some
previous work had left some issues with the circuit board.
As many of you will know, I have lots of time on my hands 😉 and a
sentimental desire to revise old product in light of the wisdom I have
acquired in 50 years.
So.
I revised the circuit, making it more simple, and laying out a circuit board
which should be usable for all known versions with minor adaptation.
Attached are various schematics and graphics and also the gerber files
for the circuit board, which was made my pcbway.com, who will ask
what dimensions are, which is 5.5" x 3.5"
This thread will also serve as the location for asking additional questions
and so on.
EDIT --
Gerbers and info for Nelson's front end that fits the old Stasis chassis and has mounting holes (post #281) - https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/page-15#post-6447824
@Zen Mod made PCB for this project, information and gerbers can be found here :
Front End (post #282) - https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/page-15#post-6447826
6-deep output stage (post #283) - https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/page-15#post-6447831
8-deep output stage (post #284) - https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/page-15#post-6447835
--
an old Threshold Stasis amp, whose amp was broken and where some
previous work had left some issues with the circuit board.
As many of you will know, I have lots of time on my hands 😉 and a
sentimental desire to revise old product in light of the wisdom I have
acquired in 50 years.
So.
I revised the circuit, making it more simple, and laying out a circuit board
which should be usable for all known versions with minor adaptation.
Attached are various schematics and graphics and also the gerber files
for the circuit board, which was made my pcbway.com, who will ask
what dimensions are, which is 5.5" x 3.5"
This thread will also serve as the location for asking additional questions
and so on.
EDIT --
Gerbers and info for Nelson's front end that fits the old Stasis chassis and has mounting holes (post #281) - https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/page-15#post-6447824
@Zen Mod made PCB for this project, information and gerbers can be found here :
Front End (post #282) - https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/page-15#post-6447826
6-deep output stage (post #283) - https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/page-15#post-6447831
8-deep output stage (post #284) - https://www.diyaudio.com/community/threads/new-stasis-front-end.363701/page-15#post-6447835
--
Attachments
Last edited by a moderator:
Well Nelson you have opened a pandora's box with this thread - you are so very generous. I may as well say that I will be building a Stasis 2 or 3 copy now. Can I ask the following based on looking at the new design.
1. What is switch "T" for?
2. TH1 = 2K - is this NTC or PTC and I assume should be attached to the output stage heatsink?
3. What are recommended +/- DC rails to build a Stasis 2 or 3?
4. Any recommended subs for the 2SA1381 and 2SC3503 - I would say the KSA/KSC types will be fine or perhaps the newer Toshiba TTA004B and TTC004B types?
5. P1 adjusts output offset I assume?
6. P2 adjusts output transistor bias I assume?
7. What is recommended bias per output transistor (Stasis 2 or 3)?
8. For single ended input - I assume one simply grounds the -IN input?
9. What are C9 and C10 values?
10. What are R23 and R24 values?
11. What are R25 to R28 values?
12. Whar are C7 and C8 values?
13.What are D3 and D4 types?
I hope I have not over whelmed you with these questions, but I am sure answers will be appreciated by many members who may want to dabble into some past Threshold history, to bring one of these classics into the new century.
Regards,
Gary..
1. What is switch "T" for?
2. TH1 = 2K - is this NTC or PTC and I assume should be attached to the output stage heatsink?
3. What are recommended +/- DC rails to build a Stasis 2 or 3?
4. Any recommended subs for the 2SA1381 and 2SC3503 - I would say the KSA/KSC types will be fine or perhaps the newer Toshiba TTA004B and TTC004B types?
5. P1 adjusts output offset I assume?
6. P2 adjusts output transistor bias I assume?
7. What is recommended bias per output transistor (Stasis 2 or 3)?
8. For single ended input - I assume one simply grounds the -IN input?
9. What are C9 and C10 values?
10. What are R23 and R24 values?
11. What are R25 to R28 values?
12. Whar are C7 and C8 values?
13.What are D3 and D4 types?
I hope I have not over whelmed you with these questions, but I am sure answers will be appreciated by many members who may want to dabble into some past Threshold history, to bring one of these classics into the new century.
Regards,
Gary..
1. What is switch "T" for?
Thermostat
2. TH1 = 2K - is this NTC or PTC and I assume should be attached to the output stage heatsink?
Classic thermistor - resistance goes down as temp goes up
3. What are recommended +/- DC rails to build a Stasis 2 or 3?
30V to about 60V, I think.
4. Any recommended subs for the 2SA1381 and 2SC3503 - I would say the KSA/KSC types will be fine or perhaps the newer Toshiba TTA004B and TTC004B types?
Something nice that fits. I recall using KSC2690 and KSA1220
5. P1 adjusts output offset I assume?
Yes
6. P2 adjusts output transistor bias I assume?
Yes. Maximum resistance on first start up
7. What is recommended bias per output transistor (Stasis 2 or 3)?
Whatever settles in to 50 deg C on the top of the sinks operated for
a hour with the cover on
8. For single ended input - I assume one simply grounds the -IN input?
Yes
9. What are C9 and C10 values?
680 pF was the value for Stasis 2 and 3 - it's on the schematic
and those parts are only to drive cascode outputs - not used
on later models.
10. What are R23 and R24 values?
Typical 1K 3W
11. What are R25 to R28 values?
Typical 1.5K 3W
12. Whar are C7 and C8 values?
10 to 100 uF
13.What are D3 and D4 types?
1N4004 or higher current for flyback protection.
Thermostat
2. TH1 = 2K - is this NTC or PTC and I assume should be attached to the output stage heatsink?
Classic thermistor - resistance goes down as temp goes up
3. What are recommended +/- DC rails to build a Stasis 2 or 3?
30V to about 60V, I think.
4. Any recommended subs for the 2SA1381 and 2SC3503 - I would say the KSA/KSC types will be fine or perhaps the newer Toshiba TTA004B and TTC004B types?
Something nice that fits. I recall using KSC2690 and KSA1220
5. P1 adjusts output offset I assume?
Yes
6. P2 adjusts output transistor bias I assume?
Yes. Maximum resistance on first start up
7. What is recommended bias per output transistor (Stasis 2 or 3)?
Whatever settles in to 50 deg C on the top of the sinks operated for
a hour with the cover on
8. For single ended input - I assume one simply grounds the -IN input?
Yes
9. What are C9 and C10 values?
680 pF was the value for Stasis 2 and 3 - it's on the schematic
and those parts are only to drive cascode outputs - not used
on later models.
10. What are R23 and R24 values?
Typical 1K 3W
11. What are R25 to R28 values?
Typical 1.5K 3W
12. Whar are C7 and C8 values?
10 to 100 uF
13.What are D3 and D4 types?
1N4004 or higher current for flyback protection.
For the ultimate chassis to drive your NEW AWESOME STASIS AMP
Get on the list for this once in a life time opportunity. 😀
https://www.diyaudio.com/forums/pass-labs/360807-ultimate-4u-500mm-chassis-44.html#post6429775
Get on the list for this once in a life time opportunity. 😀
https://www.diyaudio.com/forums/pass-labs/360807-ultimate-4u-500mm-chassis-44.html#post6429775
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Thanks for those replies Nelson - you are awesome.
Just one other question, to build a simple output stage to say deliver 50 watts rms into 8 ohms, and with 30 to 35 VDC rails - how many of the MJ21193/94 TO3 output devices would you use per rail and what would be a good emitter resistor value?
Again, I admire your generosity.
Just one other question, to build a simple output stage to say deliver 50 watts rms into 8 ohms, and with 30 to 35 VDC rails - how many of the MJ21193/94 TO3 output devices would you use per rail and what would be a good emitter resistor value?
Again, I admire your generosity.
But wait there is more, not only will you have acquired the greatest amp chassis within the milky way galaxy, your LEGENDARY STATUS will go up amongst your family, peers, and work colleagues.
Once you have this amp chassis in your stable, your quality of life will improve dramatically.
Your friends will say "Wow how are you so legendary?"
Your partner will say "Come here you adorable wonderful sexy person, I want some loving"
You can have all these things with the 4U x 500mm chassis
😀
https://www.diyaudio.com/forums/pass-labs/360807-ultimate-4u-500mm-chassis-44.html#post6429775
All of this can be yours for between 250 and 300 Euro
Once you have this amp chassis in your stable, your quality of life will improve dramatically.
Your friends will say "Wow how are you so legendary?"
Your partner will say "Come here you adorable wonderful sexy person, I want some loving"
You can have all these things with the 4U x 500mm chassis
😀
https://www.diyaudio.com/forums/pass-labs/360807-ultimate-4u-500mm-chassis-44.html#post6429775
All of this can be yours for between 250 and 300 Euro
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Mr. Pass, stop being so mean and hurtful.
What about guys like me? Guys with an S/500 that they have running great. Guys that really like listening to their S/500? Guys that thought all was good with the world.
Now there is no sleep
Do I take my pride and joy apart,.. a classic,.. a dream? Or do I leave it alone and just wonder how much better it can be?
ARRGGG!
(S/500 is what, +/-75v - too much?)
Thanks, by the way.
What about guys like me? Guys with an S/500 that they have running great. Guys that really like listening to their S/500? Guys that thought all was good with the world.
Now there is no sleep
Do I take my pride and joy apart,.. a classic,.. a dream? Or do I leave it alone and just wonder how much better it can be?
ARRGGG!
(S/500 is what, +/-75v - too much?)
Thanks, by the way.
Been working as a scientist for the last 25 years.
I guess it's never too late to have a career change.
Hahahaha
I guess it's never too late to have a career change.
Hahahaha