Mooly (and Co.):
Sorry to come back at you again, but I'm struggling as to whether to power a diyAudio Speaker Protection Board (V2 vintage) from either a 13 VAC secondary or from a dedicated 17 VDC power supply (probably with just 220 to 330 uF capacitance). Early in this thread, JoJo seemed indifferent to this question (see Posts 50, 52). I want to build something elegant and reliable. The relays I have on order are Omron G5LE-14 DC9. Is there any benefit to building that tiny PS for the Speaker Protection Board?
Thank you,
Scott
Sorry to come back at you again, but I'm struggling as to whether to power a diyAudio Speaker Protection Board (V2 vintage) from either a 13 VAC secondary or from a dedicated 17 VDC power supply (probably with just 220 to 330 uF capacitance). Early in this thread, JoJo seemed indifferent to this question (see Posts 50, 52). I want to build something elegant and reliable. The relays I have on order are Omron G5LE-14 DC9. Is there any benefit to building that tiny PS for the Speaker Protection Board?
Thank you,
Scott
Each case is unique. If the intended 13 volt secondary floats then use that. Remember the board needs a ground reference to the main amplifier although it can be lifted with a low value resistor if needed.
As long as the supply meets the requirements you can use whatever is easiest.
1/ It must float to allow that ground connection to be made without causing ground loops or other unwanted interaction.
2/ The supply must remain present even if the amp fails, blows rail fuses, puts a short across the amp PSU secondary etc etc. The board has to remain powered under all possible fault conditions.
3/ The rail must have a short time constant so that it rises quickly at power on and falls quickly at power off.
As long as the supply meets the requirements you can use whatever is easiest.
1/ It must float to allow that ground connection to be made without causing ground loops or other unwanted interaction.
2/ The supply must remain present even if the amp fails, blows rail fuses, puts a short across the amp PSU secondary etc etc. The board has to remain powered under all possible fault conditions.
3/ The rail must have a short time constant so that it rises quickly at power on and falls quickly at power off.
Mooly:
Thanks for the response, but I remain confused. On the one hand, powering the Speaker Protection board from a beefy power supply would be helpful because it would allow the board to continue operating for a few seconds after a catastrophic failure (e.g., the amp or the fuse blows or a short occurs across the amp's PSU secondary), preventing damage to the speakers. But under normal operation, we want the Speaker Protection board to perform as intended almost immediately after the amp is turned off to prevent thumps, which suggests powering the board directly from a transformer secondary or from a low capacitance dedicated power supply. I get it that each case is unique, and I also understand that sometimes the answer is a balanced compromise. Are you saying the Speaker Protection board should be separately fused and have its own small dedicated transformer or is that just an ideal? In the past, I've powered these boards directly from an amplifier's sole transformer. I haven't had a problem with those boards, but perhaps that's just good fortune and not a result of good design.
Your thoughts?
Regards,
Scott
Thanks for the response, but I remain confused. On the one hand, powering the Speaker Protection board from a beefy power supply would be helpful because it would allow the board to continue operating for a few seconds after a catastrophic failure (e.g., the amp or the fuse blows or a short occurs across the amp's PSU secondary), preventing damage to the speakers. But under normal operation, we want the Speaker Protection board to perform as intended almost immediately after the amp is turned off to prevent thumps, which suggests powering the board directly from a transformer secondary or from a low capacitance dedicated power supply. I get it that each case is unique, and I also understand that sometimes the answer is a balanced compromise. Are you saying the Speaker Protection board should be separately fused and have its own small dedicated transformer or is that just an ideal? In the past, I've powered these boards directly from an amplifier's sole transformer. I haven't had a problem with those boards, but perhaps that's just good fortune and not a result of good design.
Your thoughts?
Regards,
Scott
The board relies on its own supply rail dropping very quickly on power off in order to disconnect the speakers quickly and so prevent a thump (which of course is amplifier dependent, some make more noise than others and also vary in how long after power off they make that noise).
If you have a 'beefy' supply the amp may make a noise before the relays drop out.
What happens with a true fault depends entirely the nature of the fault and its effect on the power supply to the amp. Ideally the protection board should be operational at all times.
It is not dodging the question saying each case is unique because it really is. It depends on the protection of the basic amp in the first place. For example are the secondaries fused or not and are the DC rails fused or not. You have to look at all scenarios and every combination of fault and ask whether the board safely disconnects the speakers in each case.
The speaker board should always be fused in some way imo because a failed D6 or C6 for example would short the supply feeding it.
If you have a 'beefy' supply the amp may make a noise before the relays drop out.
What happens with a true fault depends entirely the nature of the fault and its effect on the power supply to the amp. Ideally the protection board should be operational at all times.
It is not dodging the question saying each case is unique because it really is. It depends on the protection of the basic amp in the first place. For example are the secondaries fused or not and are the DC rails fused or not. You have to look at all scenarios and every combination of fault and ask whether the board safely disconnects the speakers in each case.
The speaker board should always be fused in some way imo because a failed D6 or C6 for example would short the supply feeding it.
Hello everybody,
I'm going to build a mono block amplifier with one protector circuit V3 board. I'd like to know if the circuit can work with only one relay. As an example, without mounting K2 and R12 and replacincing D4 with a short circuit. In addition relais voltage should be 12 V with an input voltage of 12 VAC. Should it work this way?
Thanks!
I'm going to build a mono block amplifier with one protector circuit V3 board. I'd like to know if the circuit can work with only one relay. As an example, without mounting K2 and R12 and replacincing D4 with a short circuit. In addition relais voltage should be 12 V with an input voltage of 12 VAC. Should it work this way?
Thanks!
Folks:
I built the Speaker Protection board mentioned above (a V2 version, which I understand is virtually identical to the current V3 version other than connector options) and it appears to be working perfectly fine. After the amplifier has been on for a brief period, DC offset is 1.4 mV (L ch) and 0.9 mV (R ch) (I will be reducing it further). There is a problem, though: it seems that the Wolverine amplifier, when initially turned on, generates enough DC offset to trigger the Speaker Protection circuit. In short order the DC offset stabilizes and drops, but I'm guessing the Speaker Board isn't resetting or recognizing that DC offset has dropped to a non-threatening level. I'm no engineer, so please let me know if my speculation seems implausible. If it is a possibility, what changes to the board can I make that will cause the circuit, once triggered, to reset?
Thank you in advance for your guidance!
Regards,
Scott
I built the Speaker Protection board mentioned above (a V2 version, which I understand is virtually identical to the current V3 version other than connector options) and it appears to be working perfectly fine. After the amplifier has been on for a brief period, DC offset is 1.4 mV (L ch) and 0.9 mV (R ch) (I will be reducing it further). There is a problem, though: it seems that the Wolverine amplifier, when initially turned on, generates enough DC offset to trigger the Speaker Protection circuit. In short order the DC offset stabilizes and drops, but I'm guessing the Speaker Board isn't resetting or recognizing that DC offset has dropped to a non-threatening level. I'm no engineer, so please let me know if my speculation seems implausible. If it is a possibility, what changes to the board can I make that will cause the circuit, once triggered, to reset?
Thank you in advance for your guidance!
Regards,
Scott
I would have thought any initial DC offset from the amp would not make any difference because the delay circuit is under control of the R6/C3 switch on delay. As soon as that delay times out the relay should operate and connect the speakers. The circuit has no latching action.
Try it with no speakers connected and lift one end of the 10k (R10) that connects the offset sensing part of the circuit to the relay driver. The LED should flash for about 6 seconds and after that the relay should connect and the LED light.
Make sure you have the grounds correctly connected and that the circuit is referenced to the ground of the amplifier.
Also check the DC supply to the circuit and that it is within the range it should be (is it about 15v from memory)
Try it with no speakers connected and lift one end of the 10k (R10) that connects the offset sensing part of the circuit to the relay driver. The LED should flash for about 6 seconds and after that the relay should connect and the LED light.
Make sure you have the grounds correctly connected and that the circuit is referenced to the ground of the amplifier.
Also check the DC supply to the circuit and that it is within the range it should be (is it about 15v from memory)
Mooly:
Thanks for the very prompt response! Your recollection is pretty good, but I'm actually powering the Speaker Protection board off of one of the toroid's 12.8 VAC secondaries, not one of the power supplies, per your earlier guidance. The relays on the board are Omrom G5LE-14 9VDC units.
With R10 (10k) removed and no speakers connected, LED1 blinks rapidly for about a second and then stops blinking and stays lit. The relays engage once LED1 stops blinking. With R10 reinstalled, LED1 blinks continuously and the relays do not engage.
I'm uncertain what it means for the circuit to be "referenced to the ground of the amplifier." It is powered directly from a secondary and the other connections are the output from the two amp channels and the connections to the speakers. There is no ground connection on the Speaker Protection board.
Any further thoughts?
Much appreciated,
Scott
Thanks for the very prompt response! Your recollection is pretty good, but I'm actually powering the Speaker Protection board off of one of the toroid's 12.8 VAC secondaries, not one of the power supplies, per your earlier guidance. The relays on the board are Omrom G5LE-14 9VDC units.
With R10 (10k) removed and no speakers connected, LED1 blinks rapidly for about a second and then stops blinking and stays lit. The relays engage once LED1 stops blinking. With R10 reinstalled, LED1 blinks continuously and the relays do not engage.
I'm uncertain what it means for the circuit to be "referenced to the ground of the amplifier." It is powered directly from a secondary and the other connections are the output from the two amp channels and the connections to the speakers. There is no ground connection on the Speaker Protection board.
Any further thoughts?
Much appreciated,
Scott
All these grounds shown should be one and the same on the protection PCB but they must also then be referenced to (connected to) the zero volt line in the power amplifier. If that isn't done then the protection board has no knowledge of what is happening at the speaker terminals.
You need to be careful because all this depends on your own unique wiring set up. There should be no voltage between these grounds and the amplifiers zero point (check it) but I would probably recommend that you connect the grounds from board to amp via a resistor (say 10 ohm) which would in any case serve to isolate any possible ground loop issues.
You need to be careful because all this depends on your own unique wiring set up. There should be no voltage between these grounds and the amplifiers zero point (check it) but I would probably recommend that you connect the grounds from board to amp via a resistor (say 10 ohm) which would in any case serve to isolate any possible ground loop issues.
Mooly:
I'm not trying to be argumentative -- my goal is to learn -- but given that I have two separate amplifier channels that are each powered by the same power supply, would it be reasonable to simply connect the power supply's ground to one of the ground points you indicated on the schematic above via a 10R resistor, or should I connect the grounds on each of the two amplifier channels to one of the grounds you circled (each with a 10R resistor)?
Thank you,
Scott
I'm not trying to be argumentative -- my goal is to learn -- but given that I have two separate amplifier channels that are each powered by the same power supply, would it be reasonable to simply connect the power supply's ground to one of the ground points you indicated on the schematic above via a 10R resistor, or should I connect the grounds on each of the two amplifier channels to one of the grounds you circled (each with a 10R resistor)?
Thank you,
Scott
Mooly:
A further thought: I'm starting to understand what you're suggesting about connecting the amplifier(s) to the Speaker Protection board, but the three ground points you circled all connect to the ground at the power input on that board. If the Speaker Protection board was powered from a DC supply, there would be no issue. But the Speaker Protection board was designed to operate with either a DC or AC supply, and I'm using the latter. In my case won't there will be a short if I connect the Speaker Protection board to the amps (or power supply) as you've suggested unless the board is supplied with DC? Stated another way, is there no effective way to use the Speaker Protection board with an AC supply?
This is a curiosity.
Regards.
A further thought: I'm starting to understand what you're suggesting about connecting the amplifier(s) to the Speaker Protection board, but the three ground points you circled all connect to the ground at the power input on that board. If the Speaker Protection board was powered from a DC supply, there would be no issue. But the Speaker Protection board was designed to operate with either a DC or AC supply, and I'm using the latter. In my case won't there will be a short if I connect the Speaker Protection board to the amps (or power supply) as you've suggested unless the board is supplied with DC? Stated another way, is there no effective way to use the Speaker Protection board with an AC supply?
This is a curiosity.
Regards.
If the amps share a supply then you just need a single ground connection from protection board to amp.
They will do if you have used the official boards
The board is self contained. I mentioned it because I wasn't sure if you had used an official board or something else (homemade PCB, Veroboard etc) where you might have had separate grounds to deal with.This is the important bit. If the 12 volt AC winding is floating, spare and available then there is no issue. If it is already in use then it all depends on how it is used and configured as to whether connecting a newly created rail (the half wave rectified supply of the protection board) will cause a problem.
If you connect the grounds together as I suggest using a 10 ohm (use a small 0.25 or 0.5w) and there is a problem then all that will happen is the resistor will burn. So if you're not sure then it's a good initial test.
Mooly:
First off, thank you for all of your help! I now have a far better understanding of the circuit and how it needs to be integrated in an amp. After playing with things for a bit (and following your guidance), I decided to add a little complexity to my project by building a tiny power supply for the Speaker Protection board. Two 100 uF caps, 1N4004 diodes and that's it. The little supply is connected to the amplifiers' power supply (with a 10R 1W resistor) and all is working perfectly.
Much appreciated!
Regards,
Scott
First off, thank you for all of your help! I now have a far better understanding of the circuit and how it needs to be integrated in an amp. After playing with things for a bit (and following your guidance), I decided to add a little complexity to my project by building a tiny power supply for the Speaker Protection board. Two 100 uF caps, 1N4004 diodes and that's it. The little supply is connected to the amplifiers' power supply (with a 10R 1W resistor) and all is working perfectly.
Much appreciated!
Regards,
Scott
I thought the LED should flash when a DC offset was present. I've never built one of these but the circuit suggests that would happen and the simulation confirms it. The LED should flash in the same way it does at power on.
The LED is controlled just by D5. The cathode should rise to the supply voltage when an offset is detected. Check that this happening.
The LED is controlled just by D5. The cathode should rise to the supply voltage when an offset is detected. Check that this happening.
