Hello
i fixed a STASIS2 and did change all outputs in MJ15024/25 for one channel. This channel shows the following picture when feeded with 10khz rectangle wave, Sinus wave looks ok.
Do you know what is the reason for, i already did change the driver boards and the power rails and did a complete resoldering on this output board without effekt.
how i should interpret this picture, is it spikes or oszilation?
thanks for your helps
Wolfgang
i fixed a STASIS2 and did change all outputs in MJ15024/25 for one channel. This channel shows the following picture when feeded with 10khz rectangle wave, Sinus wave looks ok.
Do you know what is the reason for, i already did change the driver boards and the power rails and did a complete resoldering on this output board without effekt.
how i should interpret this picture, is it spikes or oszilation?
thanks for your helps
Wolfgang
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Hi Wolfgang,
there are many threads regarding this question, the search function can help... but to keep it simple for you:
remove the fuse of the negative supply voltage and connect a amperemeter - total bias should be around 700 to 750 mA, so that your heatsinks reach 40 to 50 degree celsius.
I guess your setting is ok but a good stasis2 will not have spices nor oscillation as shown on your picture, so check the condensers on the driver board, even the small tantalum pieces will make the problem with oscillation. Whats about the DC offset?
When you have a big silly sound during the switch on process - check the supply condensors.
best regards
Michael
there are many threads regarding this question, the search function can help... but to keep it simple for you:
remove the fuse of the negative supply voltage and connect a amperemeter - total bias should be around 700 to 750 mA, so that your heatsinks reach 40 to 50 degree celsius.
I guess your setting is ok but a good stasis2 will not have spices nor oscillation as shown on your picture, so check the condensers on the driver board, even the small tantalum pieces will make the problem with oscillation. Whats about the DC offset?
When you have a big silly sound during the switch on process - check the supply condensors.
best regards
Michael
That is oscillation, or at least a peaking condition stimulated
by the square wave. You'll end up screwing around with
compensation to get rid of it. I assume that the output RC
network to ground is still there.
I don't recall any tantalums on Stasis amps.
The bias should be set for about 25 deg C. above ambient,
and most of the time it works to about 50 deg.
by the square wave. You'll end up screwing around with
compensation to get rid of it. I assume that the output RC
network to ground is still there.
I don't recall any tantalums on Stasis amps.
The bias should be set for about 25 deg C. above ambient,
and most of the time it works to about 50 deg.
"....I don't recall any tantalums on Stasis amps"
Hi all,
there are some small blue ones there - i have changed them at four amps during the past month...0,15uF/50V - one located at CCS, 2nd one at bias transistor.
I guess the regular types - 470uF/6,3 and the two 47uF/50 are worth changing too.
Mike
Hi all,
there are some small blue ones there - i have changed them at four amps during the past month...0,15uF/50V - one located at CCS, 2nd one at bias transistor.
I guess the regular types - 470uF/6,3 and the two 47uF/50 are worth changing too.
Mike
I have exactly the same problem which gives me headache right now.
I assume the original Statis 2 output transistor is slower than MJ15024/25
http://www.diyaudio.com/forums/showthread.php?postid=723969#post723969
A brief. For CFP output stage, it works OK for output transistors with slow speed (mine is OK with TIP35C ft=3Mhz).
But with the same CFP cct, just changing the output transistor to the faster one (I change TIP35C to 30Mhz C5200), it automaticly becomes an oscilator. It oscilates at Mhz region. It seems it oscilates by itself.
Mr. Pass suggest putting base stoopers with values to be tried. I haven't got the optimal R value here, but what I'm afraid that base stoppers do not sufficient to counter this problem.
Anyone has other suggestion what to do with CFP+highspeed device?
I haven't got the ultimate answer
I assume the original Statis 2 output transistor is slower than MJ15024/25
http://www.diyaudio.com/forums/showthread.php?postid=723969#post723969
A brief. For CFP output stage, it works OK for output transistors with slow speed (mine is OK with TIP35C ft=3Mhz).
But with the same CFP cct, just changing the output transistor to the faster one (I change TIP35C to 30Mhz C5200), it automaticly becomes an oscilator. It oscilates at Mhz region. It seems it oscilates by itself.
Mr. Pass suggest putting base stoopers with values to be tried. I haven't got the optimal R value here, but what I'm afraid that base stoppers do not sufficient to counter this problem.
Anyone has other suggestion what to do with CFP+highspeed device?
I haven't got the ultimate answer
Hello all out there
thanks for your fast and active participation
The STASIS is running now for 4 hours on Audiostatic electrostatic speakers , temperature is ok, dc offset is 0,072 V and 0,124 V for the other channel . Is this ok ?, i took BC550 for differentialamp, matched with a cheap digital meter and bond them together for thermal coupling
Bias is about 0,130 V across 1 Ohm resistor
One last small problem left power fuse (6,3A 220V mittelträge) blows every second or third power on, perhabs i should take 8A fuse
The problem shown on the oscilloscope-picture was gone, when I give more bias, only bias to low thats all
Thanks for all the infos i found in this forum, i am a newby, without this forum i wouldn´t start repair this amp
best regards
Wolfgang
I am listening now
thanks for your fast and active participation
The STASIS is running now for 4 hours on Audiostatic electrostatic speakers , temperature is ok, dc offset is 0,072 V and 0,124 V for the other channel . Is this ok ?, i took BC550 for differentialamp, matched with a cheap digital meter and bond them together for thermal coupling
Bias is about 0,130 V across 1 Ohm resistor
One last small problem left power fuse (6,3A 220V mittelträge) blows every second or third power on, perhabs i should take 8A fuse
The problem shown on the oscilloscope-picture was gone, when I give more bias, only bias to low thats all
Thanks for all the infos i found in this forum, i am a newby, without this forum i wouldn´t start repair this amp
best regards
Wolfgang
I am listening now
I am listening now
By the way: do not switch "him" off, the sound is even better when the amp is powered up all the time, because he has all the time the right temperature and the right setpoint for the current...
My stasis is powered up most of the time during the past 15 years, no burned transistors, no problem at all. The only parts i have changed are these small caps i mentioned earlier. Because i run the amp for several years i do not notice that there was no proper control for the low frequencies. (2 pcs. 47/50 and 1 pc. 470/6.3).
But after comparing the stasis to a newer system, i start with the "caps restauration". Now the stasis is back again.
During the past month i have restored some other Stasis equipment. Blown transistors, weak caps and so on... The owners of these amps are switching on, switching off, switching on, switch......
Mike
By the way: do not switch "him" off, the sound is even better when the amp is powered up all the time, because he has all the time the right temperature and the right setpoint for the current...
My stasis is powered up most of the time during the past 15 years, no burned transistors, no problem at all. The only parts i have changed are these small caps i mentioned earlier. Because i run the amp for several years i do not notice that there was no proper control for the low frequencies. (2 pcs. 47/50 and 1 pc. 470/6.3).
But after comparing the stasis to a newer system, i start with the "caps restauration". Now the stasis is back again.
During the past month i have restored some other Stasis equipment. Blown transistors, weak caps and so on... The owners of these amps are switching on, switching off, switching on, switch......
Mike
Hi Mike,
If leaving it on all the time is your choice, then fine. Running your gear 24 / 7 isn't good for it on average. Talking from over 30 yrs service experience. I would not recommend it to anyone else. Mind you, turning it on & off all day long is pretty silly too..
What you have to remember is that your AC power is not perfect and always available. This can be very hard on the rectifiers and caps. And for the most part, you are not there to turn it off if needed. Your amp has been turned on and off briefly many times without you knowing it. Then there are spikes due to lightning strikes during storms. I would not knowingly subject any equipment to that abuse. You have been lucky, and I'm happy for you.
For what it's worth ...
-Chris
If leaving it on all the time is your choice, then fine. Running your gear 24 / 7 isn't good for it on average. Talking from over 30 yrs service experience. I would not recommend it to anyone else. Mind you, turning it on & off all day long is pretty silly too..
What you have to remember is that your AC power is not perfect and always available. This can be very hard on the rectifiers and caps. And for the most part, you are not there to turn it off if needed. Your amp has been turned on and off briefly many times without you knowing it. Then there are spikes due to lightning strikes during storms. I would not knowingly subject any equipment to that abuse. You have been lucky, and I'm happy for you.
For what it's worth ...
-Chris
I happen to agree with you on this at least to some extent. My KSA-80B sounded best after about three days of on time. At the present I don't have any amps that require this sort of warm up or should we say optimization time. Even my DIY KSA-50 and Aleph 2's require some warm up to optimization, but not days worth. The 80B was the only one I can remember that needed this. Mix Engineers at CBC prefer the Brystons to be left the weekend before any important mix work is to be done ...This was posted by someone in the threads here on DIY a year or two ago who knew someone there. So yes, there are cases of this being a necessity.... but not in all realms.
Chris,
Transformers and supplies are somewhat immune to really short line spikes and transients. These spikes occur so fast and are of shuch short duration at times that the magnetic field in some trannies barely has tome to change to account for it nor does the charge on the caps. But I do agree with long spikes occuring..... thats a bad thing that can lead to rectifier or even tranny failure at times.
Mark
P.S. So far my home computer has been up and running now for over 5 years except for normal down time to blow out dust and do minor upgrades. I attribute it always being on to the fact that it has had zero problems.
Hi Mark,
Bryston has a bias circuit problem in their amps, they sound really bad until they warm up. The bias compensation is not active enough. They have a strong positive tempco until hot. Coupled with a power switch that can't handle the inrush current. That left them no choice but to tell people to leave the amp on all the time. I am really very familiar with the older Bryston amps and some personel in that company. Oh, the faces used to rip off when roaded too.
Have you ever watched the current spike on an amp when the power is briefly interrupted? Believe me, there is a surge. Extremely brief interruptions in current may not have an effect depending on when they occur in the cycle. I think we both agree there.
In my humble opinion, there is no reason an amp should take 1/2 hour or more to settle down. If it does, I'd be looking for a design defect. Even calibration quality lab gear is good after two hours. That's to an accuracy far greater than anything we listen to. Actually, those would be the standards your equipment is certified to with at least a 4:1 TUR assuming you're using HP, Wavetek, Fluke ....
-Chris
Bryston has a bias circuit problem in their amps, they sound really bad until they warm up. The bias compensation is not active enough. They have a strong positive tempco until hot. Coupled with a power switch that can't handle the inrush current. That left them no choice but to tell people to leave the amp on all the time. I am really very familiar with the older Bryston amps and some personel in that company. Oh, the faces used to rip off when roaded too.
Have you ever watched the current spike on an amp when the power is briefly interrupted? Believe me, there is a surge. Extremely brief interruptions in current may not have an effect depending on when they occur in the cycle. I think we both agree there.
In my humble opinion, there is no reason an amp should take 1/2 hour or more to settle down. If it does, I'd be looking for a design defect. Even calibration quality lab gear is good after two hours. That's to an accuracy far greater than anything we listen to. Actually, those would be the standards your equipment is certified to with at least a 4:1 TUR assuming you're using HP, Wavetek, Fluke ....
-Chris
Yes and the best way to capture it is on a storage scope and using a current probe. On longer spikes it can be really nasty but doesn't seem to matter much on shorter spikes. Where I kive we have our own local power company and the power is very stable, comes right up from Glen Canyon dam! But the power but two countiessouth of here, mainly Utah County, its horrible. The 15/70 (Imax Clone) theatre down there had to install a complete battery back up system just to keep the system from crashing(literally). The film there runs at close to 400 fpm and at that speed X 2 projectors any film pile up is huge and costly. The battery backup eliminated any problems there.
As for my amps... 3 hours for the KSA-50 and 1 hour for the Aleph 2's to reach best sound quality and stabilization. These I consider about normal optimization times. The KSA-80 I owned a few years back improved in sound quality each day up to about three days in and then there was no noticable change. It may needed to have been calibrated but it also met all specs and bias seemed to be just fine. I suspect that the old Bi-polor stuff was just somewhat critical of temperature/vs hfe and the amp was also all differential so that may have added to its sensitivity issues. The Pass stuff sounds really good after a half hour with some change still taking place up to about an hour. I've also left them on for long extended periods but not to hear any further improvement. I've always believed that alot of on-off od the worst thing there is for any electronics so when I'm home I always leave the stuff on all day long, even if I go out for an hour or two to do some errands.... I always have some sort of music playing!!
As for test gear... Its really a whole different ballpark with many pieces being purposely designed to thermally stabilize so all components inside equalize to the same temp. in a normal 2 hour warmup period. Some equipment is built with forced air cooling such as my TEK 465B and many other pieces and this aids greatly in thermal stabilization in an even shorter time period. I think you'll find good test gear designed this way whilst the cheaper leader, B&K, and lesser grades of gear don't necessarily allow for this important thing.
Mark
Hi Mark,
I guess the only point I'm making is that normally, equipment should not be left running unattended for any great length of time. Nor should it be turned on and off all day long.
The other point is that AC power grids are not very nice. I don't know about you, but Hydro (our power guys) like to play at night. Switching transients can be rough on gear. Most equipment is designed with the idea that it's turned on when you want to listen to it and off when you aren't there for a while. The vast majority of unknown failures I've repaired occur with stuff left on all the time. That and parties.
I don't own anything that improves after an hour. I am hard pressed to hear any difference after 15 minutes. Same goes for anything I've made myself..
In closing, I feel it's irresponsible to recommend anyone leave their equipment on 24 / 7 unless there are special circumstances. Like you have an MCI meter bridge on your mixing console. Or it's an SSL computer / mixing board. That kind of stuff.
-Chris
I guess the only point I'm making is that normally, equipment should not be left running unattended for any great length of time. Nor should it be turned on and off all day long.
The other point is that AC power grids are not very nice. I don't know about you, but Hydro (our power guys) like to play at night. Switching transients can be rough on gear. Most equipment is designed with the idea that it's turned on when you want to listen to it and off when you aren't there for a while. The vast majority of unknown failures I've repaired occur with stuff left on all the time. That and parties.
I don't own anything that improves after an hour. I am hard pressed to hear any difference after 15 minutes. Same goes for anything I've made myself..
In closing, I feel it's irresponsible to recommend anyone leave their equipment on 24 / 7 unless there are special circumstances. Like you have an MCI meter bridge on your mixing console. Or it's an SSL computer / mixing board. That kind of stuff.
-Chris
I recently rebuilt an amp for a fellow audiophile which consisted of a new output section and most caps on the circuit board replaced, plus a mod or two thrown in,..and the feedback I got was that the sound was much better with about an hour warmup time, as opposed to the 48 hours he was accustomed to. The biasing was roughly the same. For whatever it's worth, I'd contribute it to better quality parts.
Well, my ultimate feeling on the whole thing is that you just have to experiment and try this on a component by component basis. After all experimentation is what this hobby is all about! If you're paranoid about your house burning down then leave everything off all the time, except when you're listening. Even washing machine malfumctions have been known to burn down homes.... and how many times has one left home with the wash going......? then we get to furnace malfunctions and most of us do leave our heat on all winter.
Mark
Mark
Mark,... I would have to agree with you when it comes down to it and here's why:
In my search for the ultimate amp, I've been working with a particular one. During my work I was forced to come to my own conclusions with original thought since there was no other choice. In the meanwhile, if I had listened to what others had to say on here about various topics, I'd still be light years behind where I am now. Doing my own thing without regard to what I thought others might think or believe, I never would have gotten my system to sound the way it does now. So yeah, it somewhat saddens me to see how many others come on here to look for affirmation in their endeavors from others whose sum knowledge is the reading of what is posted around here. I don't guess it hurts to ask, but I have to wonder how much lab time people who always post on here really get. I am skeptical.
In my search for the ultimate amp, I've been working with a particular one. During my work I was forced to come to my own conclusions with original thought since there was no other choice. In the meanwhile, if I had listened to what others had to say on here about various topics, I'd still be light years behind where I am now. Doing my own thing without regard to what I thought others might think or believe, I never would have gotten my system to sound the way it does now. So yeah, it somewhat saddens me to see how many others come on here to look for affirmation in their endeavors from others whose sum knowledge is the reading of what is posted around here. I don't guess it hurts to ask, but I have to wonder how much lab time people who always post on here really get. I am skeptical.
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