Threshold Stasis Model 3

GRollins · 2007-02-16 10:42 pm

Check the bias. It may have drifted.

Grey

MashBill · 2007-02-17 6:50 am

Ozscan said:
MashBill, I have a Threshold S-150 that I bought new as I recall in the early eighties. (previously had a Threshold 400A, then a 4000, preamp NS-10 and then SL-10). ...got rid of the wrong amp (s). What PS capacitors did you use in your S-150? How does your amp sound subsequent to the replacement? Mine is all original and sounds too bright and lacks authority on the bottom end especially in contrast to my Krell KSA-100. I don't expect the S-150 to perform like the KSA-100, but I would be very interested to hear if the bottom end improves with a cap change after 25 years. Thanks in advance.

Oz

I use the S-150 in my office system. I'll check the cap brand/size on Monday. I don't run it full range so I can't comment on any bottom end improvements. In my system, this amp has never sounded bright and I haven't heard any sonic differences with the new caps.

Bill

MashBill · 2007-02-17 7:06 am

GRollins said:
Check the bias. It may have drifted.

Grey

Do you have a recommended bias setting? I would like to go to a higher bias setting. I read somewhere here that 180mV is the cold start factory value. My heat sinks are barely warm and I run the amp from 8 to 5. Also, I see 2 potentiometers on the driver board. Which one sets the bias current?

Thanks,
Bill

MashBill · 2007-02-19 4:31 pm

Ozscan said:
MashBill, I have a Threshold S-150 that I bought new as I recall in the early eighties. (previously had a Threshold 400A, then a 4000, preamp NS-10 and then SL-10). ...got rid of the wrong amp (s). What PS capacitors did you use in your S-150? How does your amp sound subsequent to the replacement? Mine is all original and sounds too bright and lacks authority on the bottom end especially in contrast to my Krell KSA-100. I don't expect the S-150 to perform like the KSA-100, but I would be very interested to hear if the bottom end improves with a cap change after 25 years. Thanks in advance.

Oz

The caps I used in my S-150 Series II (manufactured 12/23/1983) are Mallory CGS 25,000uF 75V (95V surge). They are the same physical size as the original caps which were also Mallory CGS.

Bill

barchetta · 2007-02-22 11:12 pm

I'm sorry to butt in.. but I have a threshold 400a with 2 9800MFD 100v caps for filters.. any recommendations on replacements? Something readily available and reasonable perhaps? And why does my value seem low to most of your posts here? I cant find this specification on any schematic or I would not ask.

(they are the screw type).

Regarding the original post.. if you cant solder and arent willing to take the time to learn (its easy).. dont touch your amp.. I bet someone on your street can solder.. or just bring it to a tech and spend $$$$..

Also, I will do all the work in exchange for the amp

AndrewT · 2007-02-23 8:50 am

Hi,
what voltage is across the smoothing caps and what is the corresponding mains voltage?

What is the maximum voltage declared by your supply company?

jacco vermeulen · 2007-02-23 9:20 am

MashBill said:
the original caps which were also Mallory CGS.

Mallory computer grade big cans have also been the PS capacitors in many of the later production Threshold series.

Barchetta,
a 25KuF/75V has ~1.4 times the energy of a 9.8kuF/100V capacitor.
High bias level needs more uF on the rail, care to hear how much uF the Threshold SA/12e had ?

AMV8 · 2007-02-23 2:08 pm

Jacco

This is slightly off thread so aplologies to everyone else.

If you have any information on the SA/12 or SA/10e I would appreciate that. The Stasis 2 I have has a plate riveted to the back by Threshold to say that it was modified by Threshold in 1991 and converted to "E" status by replacing the circuit boards with the SA/10e boards - but I have no info on the SA/10e. Maybe this is why I find it sounds so good and why it gets so hot?

Don

barchetta · 2007-02-23 2:45 pm

Barchetta,
a 25KuF/75V has ~1.4 times the energy of a 9.8kuF/100V capacitor.
High bias level needs more uF on the rail, care to hear how much uF the Threshold SA/12e had ? [/B]

So are you saying its always good to increase uF on these? I am going to try and push the bias on this unit.. I hear it helps with the high end..

AndrewT · 2007-02-23 3:37 pm

barchetta said:
So are you saying its always good to increase uF on these? I am going to try and push the bias on this unit..

no.
Don't increase the bias until you are sure the amplifier will survive at the increased temperature.
Extra bias will increase the ripple on the supply rails. This in turn will demand more from the PSSR of the amp and you may hear hum and/or buzz leaking through to the speakers.

I asked the voltages and you have not answered yet.

barchetta · 2007-02-23 3:49 pm

AndrewT said:
no.
Don't increase the bias until you are sure the amplifier will survive at the increased temperature.
Extra bias will increase the ripple on the supply rails. This in turn will demand more from the PSSR of the amp and you may hear hum and/or buzz leaking through to the speakers.

I asked the voltages and you have not answered yet.

I didnt realize you were asking me.. I dont remember exactly.. I want to say about 70v.

Hahaha.. and ho would i know it would survive the increased temperature without doing it? I was really only thinking about taking it to the max spec which is 45c +/- 2c so I would go to about 47-48c.. thats all.. but that is really hot at idle!

anatech · 2007-02-23 3:50 pm

Hi Joe,
Your question may best be answered by Nelson himself in your repair thread. It's on topic over there.

-Chris

barchetta · 2007-02-23 4:00 pm

anatech said:
Hi Joe,
Your question may best be answered by Nelson himself in your repair thread. It's on topic over there.

-Chris

I know; I asked but its buried deep.. Okay I will stop hijacking this.. sorry guys.

steenoe · 2007-02-23 4:01 pm

Barchetta, I wouldnt fiddle with the bias setting if I were you! I would pop in a pair of 100v Rifa's though. I think the 400A used 15.000uF's from the factory and you might just be able to squeeze two of those in there

Funny to see the 9800uF listed!

Steen

barchetta · 2007-02-23 4:04 pm

steenoe said:
Barchetta, I wouldnt fiddle with the bias setting if I were you! I would pop in a pair of 100v Rifa's though. I think the 400A used 15.000uF's from the factory and you might just be able to squeeze two of those in there Funny to see the 9800uF listed!

Steen

I have to fiddle anyway.. bias is ay off after replacing all the power trans.

Okay thanks.. I will look for a Rifa? I take it thats a brand.

steenoe · 2007-02-23 4:15 pm

By incident (or because I prefer to use nothing else

) I had a few of the Rifa buggers on the table. Yep its the brand and they are swedish. The best are PEH169 but they are nearly impossible to get! The PEH200's are also hard to find, but still possible....

They are the best, and the Threshold deserves it

Screw terminals to boot at that

Steen

barchetta · 2007-02-23 4:42 pm

steenoe said:
By incident (or because I prefer to use nothing else ) I had a few of the Rifa buggers on the table. Yep its the brand and they are swedish. The best are PEH169 but they are nearly impossible to get! The PEH200's are also hard to find, but still possible....
They are the best, and the Threshold deserves it Screw terminals to boot at that

Steen

Oh those are are so sexy! (Cant believe I just said that!).. lol

Well; if I cant find em' do you know how usefull this is to me?

I'll start looking.. .. already been to their site.. you saved me a bunch o time by giving me the model #.. thanks.

BTW, those cans look too skinny.. but I could always rig something up.

steenoe · 2007-02-23 5:49 pm

Well; if I cant find em' do you know how usefull this is to me?

Not a lot

But now you know what to look for

Steen

nailzgun · 2007-03-12 9:42 pm

Just for info...

When I replaced the power supply capacitors on my Stasis 2 I initially put in the same capacitance - that is 15,000uf per rail per channel. It improved the sound a lot. But I could still hear that transiants were lacking power. That is cymbols and drum rolls loacked the hard impact. I tried a different make of capacitor but found the same result.

I then read in the threshold manual that speakers below 8ohm were not recommended for the stasis 2 and as my speakers are 3 ohm I thought it worth trying to increase the capacitance to see if that might improve the sound. I initially tried 30,000uf per rail and that helped. I kept adding untill the sound stopped improving. I now run with 60,000uf per rail. I am really really impressed by the Stasis 2 amplifier.

I hope you all don't mind me dropping in to ask a question. I'm new to this forum and this thread is on topic to what I'm looking to do. Sooo..

I have an S500 II and an S300 II Threshold that I would like to updatethe main capacitors on. I had the caps updated on my 400A a couple of years ago and it made a tremendous improvement. My question is with the S500 I've read where Jon Soderberg ups capacitance to 4 x 37,000 uF from the original 29,000 uF, can this be increased more and does it make a difference. Is there a point where increasing the size of the capacitors has no effect or is even detrimental to the sound?

Thanks

Scott

barchetta · 2007-03-12 10:10 pm

nailzgun said:
Just for info...

When I replaced the power supply capacitors on my Stasis 2 I initially put in the same capacitance - that is 15,000uf per rail per channel. It improved the sound a lot. But I could still hear that transiants were lacking power. That is cymbols and drum rolls loacked the hard impact. I tried a different make of capacitor but found the same result.

I then read in the threshold manual that speakers below 8ohm were not recommended for the stasis 2 and as my speakers are 3 ohm I thought it worth trying to increase the capacitance to see if that might improve the sound. I initially tried 30,000uf per rail and that helped. I kept adding untill the sound stopped improving. I now run with 60,000uf per rail. I am really really impressed by the Stasis 2 amplifier.

I hope you all don't mind me dropping in to ask a question. I'm new to this forum and this thread is on topic to what I'm looking to do. Sooo..

I have an S500 II and an S300 II Threshold that I would like to updatethe main capacitors on. I had the caps updated on my 400A a couple of years ago and it made a tremendous improvement. My question is with the S500 I've read where Jon Soderberg ups capacitance to 4 x 37,000 uF from the original 29,000 uF, can this be increased more and does it make a difference. Is there a point where increasing the size of the capacitors has no effect or is even detrimental to the sound?

Thanks

Scott

What did you update your 400a to?

I think you can go as high as you want but you will blow fuses on power on if you have a line fuse.. you can go with a cl60 thermister to limit current to 5 amps. Nelson Pass recommended that to me for my 400a. I installed 2 33kmfd's and have not listened closely yet.. now I want to

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