Sorry, Anatech, I made a mistake in the noise.
I don't want to make too many changes to the amplifier. At present, I want it to run close to the original circuit. But the deviation of the horizontal mos must be changed or it cannot operate.I don't believe that any circuit is modified without understanding the principle, which will no longer be Counterpoint.
Thank you, Anatech. But I really need to confirm whether the output DC is biased to be modified.
I don't want to make too many changes to the amplifier. At present, I want it to run close to the original circuit. But the deviation of the horizontal mos must be changed or it cannot operate.I don't believe that any circuit is modified without understanding the principle, which will no longer be Counterpoint.
Thank you, Anatech. But I really need to confirm whether the output DC is biased to be modified.
Hi William,
I hear you.
The original circuit is heavily flawed. Counterpoint didn't do power very well at all. That goes for solid state amps and even tube based high voltage regulators.
I'll be honest with you. If you change the design and it stills sounds like a Counterpoint, it's a Counterpoint as if someone who knew what they were doing designed it. The design isn't greatly deviated and I used the original PCB in early adaptations. Added are better housekeeping stuff, and the output stage change.
The original output design is garbage. it is unreliable, non-linear and simply a source of trouble. There is zero point in attempting to preserve that part of the design. But, you do you. I can only tell you what decades of experience has taught me.
I hear you.
The original circuit is heavily flawed. Counterpoint didn't do power very well at all. That goes for solid state amps and even tube based high voltage regulators.
I'll be honest with you. If you change the design and it stills sounds like a Counterpoint, it's a Counterpoint as if someone who knew what they were doing designed it. The design isn't greatly deviated and I used the original PCB in early adaptations. Added are better housekeeping stuff, and the output stage change.
The original output design is garbage. it is unreliable, non-linear and simply a source of trouble. There is zero point in attempting to preserve that part of the design. But, you do you. I can only tell you what decades of experience has taught me.
Thank you very much for sharing your valuable experience and helping me. I understand that it's stupid for me to use mosfet, but I have bought exicon... It seems that I can only continue to repair at present.
Well, how can I make this stupid output design safer?
I saw that the content of your discussion with pars 10 years ago ended with burning... I also saw that the case of repairing sa100 a few months ago also used horizontal mosfet from Hitachi seems to be successful.
Well, what should I do?
Thank you very much.
Well, how can I make this stupid output design safer?
I saw that the content of your discussion with pars 10 years ago ended with burning... I also saw that the case of repairing sa100 a few months ago also used horizontal mosfet from Hitachi seems to be successful.
Well, what should I do?
Thank you very much.
Hi William,
Nowhere did I say you were stupid, sorry you got that impression.
Okay, so you have them. You can certainly try to utilize them, so I would suggest examining other output circuits that use them and adapt one of those to this design. I also understand no one is handing you a schematic to follow, and that can be frustrating. I get it.
My designs are still in progress, but let me share some things with you. This design has no overall feedback at all. What that means in a practical sense is that any non-linearities in the output stage will not be corrected for, and the output impedance is not reduced by feedback. It also means that any non-linearities in drive requirements from the high impedance tube circuit will also cause distortion. So, keep this in mind and it will explain some design decisions I made.
So, design considerations are an output section that is very linear, low impedance and constant impedance presented to the drive circuitry. Does that sound right to you? The direction I took was for a power diamond buffer (BJT devices). I have a lot of experience with this type of output stage and it does satisfy most of the requirements.
Study this type of output stage. At the end of the day, the output transistors you have purchased would make great amplifier. So they would not be wasted.
-Chris
Nowhere did I say you were stupid, sorry you got that impression.
Okay, so you have them. You can certainly try to utilize them, so I would suggest examining other output circuits that use them and adapt one of those to this design. I also understand no one is handing you a schematic to follow, and that can be frustrating. I get it.
My designs are still in progress, but let me share some things with you. This design has no overall feedback at all. What that means in a practical sense is that any non-linearities in the output stage will not be corrected for, and the output impedance is not reduced by feedback. It also means that any non-linearities in drive requirements from the high impedance tube circuit will also cause distortion. So, keep this in mind and it will explain some design decisions I made.
So, design considerations are an output section that is very linear, low impedance and constant impedance presented to the drive circuitry. Does that sound right to you? The direction I took was for a power diamond buffer (BJT devices). I have a lot of experience with this type of output stage and it does satisfy most of the requirements.
Study this type of output stage. At the end of the day, the output transistors you have purchased would make great amplifier. So they would not be wasted.
-Chris
Well, I spent a lot of time looking up the circuit. I think Counterpoint's as series power amplifier circuits are similar, basically drain valve circuits, so the amplification signal processing is all on the two gauge axes in front and behind c5 c6. 2n2222A is temperature compensation and vbe biased to vr2 to adjust DC offset.
Among them, my question is what does R17 do? I want to remove R17 in my modification idea.
I also studied the diamond buffer circuit, which can well achieve differential and impedance matching, and has a good design.
Use two capacitors in Counterpoint to achieve the difference.
I'm trying to understand the compensation
design. I'm curious about the design purpose of the two side panels of the sa220? Output detection? DC protection? The circuit still seems to have nothing to do with signal feedback.
Thank you very much.
Among them, my question is what does R17 do? I want to remove R17 in my modification idea.
I also studied the diamond buffer circuit, which can well achieve differential and impedance matching, and has a good design.
Use two capacitors in Counterpoint to achieve the difference.
I'm trying to understand the compensation
design. I'm curious about the design purpose of the two side panels of the sa220? Output detection? DC protection? The circuit still seems to have nothing to do with signal feedback.
Thank you very much.
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R17 modifies the compensation. You need to keep it, but change the value.
The junk on the side was an analogue protection for temperature thing as I recall. Overly complicated and turned off from the factory (minimum effect). I have always ignored it. So when designing a new output stage, simply ignore that junk. It will hurt your head (I understand it) and it isn't used to begin with. It was an idea to try and calculate instantaneous output device temperature.
A power diamond buffer is used in the Marantz 300DC and Nakamichi 620 (? I think) amplifiers. Probably others as well. It can sound very smooth. My main and bench amplifiers are both modified Marantz 300DC amplifiers. The main speakers are 4 ohm, 86 dB/watt PSB Stratus Gold, so not an easy load. The diamond buffer got my attention in many signal circuits and a few amplifiers that all sounded great (Cyrus Power is another). Some research and experimentation really sold me. So far it seems to be perfect for the Counterpoint amplifiers.
The junk on the side was an analogue protection for temperature thing as I recall. Overly complicated and turned off from the factory (minimum effect). I have always ignored it. So when designing a new output stage, simply ignore that junk. It will hurt your head (I understand it) and it isn't used to begin with. It was an idea to try and calculate instantaneous output device temperature.
A power diamond buffer is used in the Marantz 300DC and Nakamichi 620 (? I think) amplifiers. Probably others as well. It can sound very smooth. My main and bench amplifiers are both modified Marantz 300DC amplifiers. The main speakers are 4 ohm, 86 dB/watt PSB Stratus Gold, so not an easy load. The diamond buffer got my attention in many signal circuits and a few amplifiers that all sounded great (Cyrus Power is another). Some research and experimentation really sold me. So far it seems to be perfect for the Counterpoint amplifiers.
Well, I studied Pass's Zen Variations 5 again. I think this is the closest design to Counterpoint at present, but the offset method is different. Counterpoint has more temperature compensation of 2n2222A. The R17 you mentioned has modified the compensation and temperature compensation? The 2n2222A here seems to be a vbe multiplier. Because the system of exicon is lower than 1.5v, if the voltage required by modifying the circuit must be reduced, the specification of r15 must be reduced, and R17 must be changed. In the circuit simulation, R17 increases the voltage of nearly 1.3v. So the programming range of exicon is usually around 1v, so what does the compensation of R17 bring? Does it make sense?I also saw the official circuit diagram of exicon, in which the vbe multiplier transmitter stage as temperature compensation also has no resistance...... Well, how can I change it?
I finished reading the counterpoint maintenance manual to explain the side panel... It doesn't seem to contain output voltage and current detection, but I didn't see any feedback. The design seems to be to turn off the relay and let the machine re-time when the output problem is detected...
Marantz 300 is great. It will be better after your modification. The diamond buffer circuit is well modified and implemented in Counterpoint sa100 or as20. I think it may even be used to make feedback to reduce distortion. But there are too many parts of the sa220 and the two side versions, so I plan not to modify the circuit. In some aspects, I want to listen to the sound of the original factory settings.
Thank you very much.
I finished reading the counterpoint maintenance manual to explain the side panel... It doesn't seem to contain output voltage and current detection, but I didn't see any feedback. The design seems to be to turn off the relay and let the machine re-time when the output problem is detected...
Marantz 300 is great. It will be better after your modification. The diamond buffer circuit is well modified and implemented in Counterpoint sa100 or as20. I think it may even be used to make feedback to reduce distortion. But there are too many parts of the sa220 and the two side versions, so I plan not to modify the circuit. In some aspects, I want to listen to the sound of the original factory settings.
Thank you very much.
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Nope. It was an analogue computer that calculated instantaneous power dissipation in the output MOSFETs. It worked exactly as advertised.
It had 4 settings - 100W, 200W, 400W and 800W. You could select the power protection level according to your application.
It greatest weakness was that it was completely bypassed when the amps were in bridged mode
What that resistor does is affect how strong the temperature compensation is, not the voltage.
Counterpoint does not use a diamond buffer at all. Read up on them.
Anyway, the changes Allan and I made to these amplifiers retains the sound. They still sound like Counterpoint amps. Just with much lower distortion, reliability and not nearly as hot. Anyway, the original design was seriously flawed, had high distortion and if you want that - okay. But modified they sound like they were intended to minus the problems.
Counterpoint does not use a diamond buffer at all. Read up on them.
Anyway, the changes Allan and I made to these amplifiers retains the sound. They still sound like Counterpoint amps. Just with much lower distortion, reliability and not nearly as hot. Anyway, the original design was seriously flawed, had high distortion and if you want that - okay. But modified they sound like they were intended to minus the problems.
I think there are some problems with the translation. I mean that if you add a diamond buffer to sa100 or as 20, I know that Counterpoint's differential circuit is completely implemented with two capacitors.
R17 will affect the compensation intensity rather than the voltage. Well, how to calculate its specifications?
That protection circuit does have a watt-hour selection currently installed in 800w. I'm curious about the output fuse 6A*50v=300w. So where does the output power of 800w come from? Under what conditions does this protection start? Does it need to be adjusted in which row of VR? The maintenance manual only mentions that there are 4 watt-hour options 100w 200w 400w 800w There are 4 grids in the corresponding circuit, which can provide a jump option. So should the option be changed to 200w? Otherwise, even if the fuse explodes, the protection circuit will not run?
I will never let this machine work in bridging mode...
Thank you very much
R17 will affect the compensation intensity rather than the voltage. Well, how to calculate its specifications?
That protection circuit does have a watt-hour selection currently installed in 800w. I'm curious about the output fuse 6A*50v=300w. So where does the output power of 800w come from? Under what conditions does this protection start? Does it need to be adjusted in which row of VR? The maintenance manual only mentions that there are 4 watt-hour options 100w 200w 400w 800w There are 4 grids in the corresponding circuit, which can provide a jump option. So should the option be changed to 200w? Otherwise, even if the fuse explodes, the protection circuit will not run?
I will never let this machine work in bridging mode...
Thank you very much
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The only other amplifier I can think of with this power limiting feature was the Marantz 500. There may have been others. I can't say it is a useful feature, maybe if you have kids.
Alan, have you ever seen this feature used effectively? Like I said, factory setting is basically "off". This entire calculation seems to have been a colossal waste and complication for a very simple amplifier.
Are you still installing your upgraded output sections?
Alan, have you ever seen this feature used effectively? Like I said, factory setting is basically "off". This entire calculation seems to have been a colossal waste and complication for a very simple amplifier.
Are you still installing your upgraded output sections?
Hi William,
What I would do is set the bias with the resistor value as it is, then see if the bias remains stable or not. Vary the value of the resistor so the bias remains the most constant with temperature. Run the amp after that to get it warm, then check to see where the bias ends up. Allow the amp to cool while on and just see how stable the bias is. Don't expect perfection, some increase while warm is expected, but it should not go too far high, and also return once the heat sink cools down to normal idle temperature.
Alan is correct. The fuse is only there to open if you have a fault.
I'm sure someone could stick it in spice. I'm not going to even try to work it out.
What I would do is set the bias with the resistor value as it is, then see if the bias remains stable or not. Vary the value of the resistor so the bias remains the most constant with temperature. Run the amp after that to get it warm, then check to see where the bias ends up. Allow the amp to cool while on and just see how stable the bias is. Don't expect perfection, some increase while warm is expected, but it should not go too far high, and also return once the heat sink cools down to normal idle temperature.
Alan is correct. The fuse is only there to open if you have a fault.
The power limiting feature is very useful. Not everyone knows how to match amps to speakers and operate them properly. I would even suggest that few people do, but maybe I am just getting old and grumpy!
Real-time power limiting is seen in all good PA amplifiers and is currently working, as intended, in all the power amplifiers that ship from the day job. One of my tasks is to check/update the code for the next release as the PSU and output stage will be somewhat different and hopefully, a sonic improvement as well.
I installed the SA20/220 upgrade in most (if not all) all the amps we imported. And it is definitely the easiest and most straight forward 'repair' if the output stage smokes.
Yes, I can see it in professional applications for sure! That would not be a Counterpoint SA-220! lol! I think in a consumer power amp, it was a wasted feature, especially being an internal setting. Just my opinion.
Yes! Very few people know how to operate an amplifier properly. Mind you - they learn after smoking woofers if they have enough power. I did Carver warranty - and Klipsch! You know how many idiots smoked LaScala woofers using a PM 1.5?
I'm glad you have it looked after. Yes, the only reasonable fix is to forklift the output section. I stopped developing before my wife died, the person I was working with stiffed me for $25K +. This was for other service work I was doing, and he had the two prototypes for the SA-100. I recently bought an SA-12 to develop on, and an SA-220. I'll start again soon. I remember where I was and have next gen boards ready.
To be honest, the new output stage and other changes cost less than US ships are charging for hacking these amps without actually fixing the output stage properly. The new performance is far higher than the original, so really what you are offering is a solid upgrade.
Yes! Very few people know how to operate an amplifier properly. Mind you - they learn after smoking woofers if they have enough power. I did Carver warranty - and Klipsch! You know how many idiots smoked LaScala woofers using a PM 1.5?
I'm glad you have it looked after. Yes, the only reasonable fix is to forklift the output section. I stopped developing before my wife died, the person I was working with stiffed me for $25K +. This was for other service work I was doing, and he had the two prototypes for the SA-100. I recently bought an SA-12 to develop on, and an SA-220. I'll start again soon. I remember where I was and have next gen boards ready.
To be honest, the new output stage and other changes cost less than US ships are charging for hacking these amps without actually fixing the output stage properly. The new performance is far higher than the original, so really what you are offering is a solid upgrade.
LaScala 1w 105db 1m driven by pm1.5? Will the ears be broken... pm1.5 There seems to be 5 pairs of power crystals in one channel.
Well, what are you going to do with your sa12? Remove two capacitors to add a diamond buffer circuit, add a feedback circuit, remove the explosive mosfet and add a set of amplified power three-stage tubes? Become a good machine.
All right 😞 I still have to continue to use exicon mosfet for repair... If R17 decides on the amount of feedback, can I remove it? Complete all the adjustment oil vr1. I know that different specifications can be tested, but the chassis design of Counterpoint is very unfriendly, and the connection cable is very easy to break during the disassembly process... (I don't have an adjustable power supply to do external testing 😞) Thank you very much, Anatech.
Well, what are you going to do with your sa12? Remove two capacitors to add a diamond buffer circuit, add a feedback circuit, remove the explosive mosfet and add a set of amplified power three-stage tubes? Become a good machine.
All right 😞 I still have to continue to use exicon mosfet for repair... If R17 decides on the amount of feedback, can I remove it? Complete all the adjustment oil vr1. I know that different specifications can be tested, but the chassis design of Counterpoint is very unfriendly, and the connection cable is very easy to break during the disassembly process... (I don't have an adjustable power supply to do external testing 😞) Thank you very much, Anatech.
Hello, Vivavee, I'm Not professional enough. Well, what should I do at the output level? I have to continue to use exicon's mosfet. Thank you very much
Hi William,
In every case, the person blew the woofer, tweeter and mid horns were fine. They were not distorting when they failed, but a couple reported hearing the voice coil hit the back plate a few times (idiots!!!). How loud was it? I can't imagine, but it was excessive. You would have to know that particular demographic, it was normal for them. No matter how much SPL they could get, it was never enough.
The prototypes sounded extremely good with a simple diamond buffer. I won't go into details. What I'll do is develop the changes on the SA-12, then install the final design and sell it. I am redesigning every board in to correct problems. The final design will be neat and clean, and mostly the original SA -12/100/220 design.
I talked about R17. You do you I guess. As far as the mosfets you bought are concerned, sure. Continue. What I would do is build a different amplifier with them. You can still do that once you're done if everything survives. I do know that mosfet output stages could use feedback, so a more suitable design would get the most out of them.
In every case, the person blew the woofer, tweeter and mid horns were fine. They were not distorting when they failed, but a couple reported hearing the voice coil hit the back plate a few times (idiots!!!). How loud was it? I can't imagine, but it was excessive. You would have to know that particular demographic, it was normal for them. No matter how much SPL they could get, it was never enough.
The prototypes sounded extremely good with a simple diamond buffer. I won't go into details. What I'll do is develop the changes on the SA-12, then install the final design and sell it. I am redesigning every board in to correct problems. The final design will be neat and clean, and mostly the original SA -12/100/220 design.
I talked about R17. You do you I guess. As far as the mosfets you bought are concerned, sure. Continue. What I would do is build a different amplifier with them. You can still do that once you're done if everything survives. I do know that mosfet output stages could use feedback, so a more suitable design would get the most out of them.