I need some help understanding the original schematic.
If my power supply is 40V peak, when listening
to music, the rails drop to rms value, approx 28v
under heavy load, ie, the rails bounce from 28v - 40v.
Does the circuit mute when the unregulated voltage
drops below 28v ?
I was looking at the Rob Elliot "fast" mute circuit, pretty cool
circuit, but more complex. I'm trying to figure out which
one to use
If my power supply is 40V peak, when listening
to music, the rails drop to rms value, approx 28v
under heavy load, ie, the rails bounce from 28v - 40v.
Does the circuit mute when the unregulated voltage
drops below 28v ?
I was looking at the Rob Elliot "fast" mute circuit, pretty cool
circuit, but more complex. I'm trying to figure out which
one to use
Just who is the man????
Let me see if I have this right.........
Nelson designs a circuit 28 years ago......puts it in countless units in the field........and now we have experts claiming it is wrong.
Don't you think that he would have lots of angry customers sending them back by now, and that he would have known about it?
Good grief, Charlie Brown.
Jocko
Let me see if I have this right.........
Nelson designs a circuit 28 years ago......puts it in countless units in the field........and now we have experts claiming it is wrong.
Don't you think that he would have lots of angry customers sending them back by now, and that he would have known about it?
Good grief, Charlie Brown.
Jocko
I came to bury the Circuit, not to praise it
"If my power supply is 40V peak, when listening to music, the rails drop to rms value, approx 28v under heavy load, ie, the rails bounce from 28v - 40v."
It's 40 volts DC and it is a preamp! I don't think your supply will drop to 28 volts except when you turn the supply off.
Sorry Moamp I missed your threshold remark in the midst of you telling us the circuit didn't need the upper mosfet. It is funny that the circuit didn't work when I explained it and the same circuit magically works when Mr. Pass logs on to say it works.........
Et tu moamp?
"If my power supply is 40V peak, when listening to music, the rails drop to rms value, approx 28v under heavy load, ie, the rails bounce from 28v - 40v."
It's 40 volts DC and it is a preamp! I don't think your supply will drop to 28 volts except when you turn the supply off.
Sorry Moamp I missed your threshold remark in the midst of you telling us the circuit didn't need the upper mosfet. It is funny that the circuit didn't work when I explained it and the same circuit magically works when Mr. Pass logs on to say it works.........
Et tu moamp?
all the dislexic people, where do they all come from...
"Nelson designs a circuit 28 years ago......puts it in countless units in the field........and now we have experts claiming it is wrong."
"It is funny that the circuit didn't work when I explained it and the same circuit magically works when Mr. Pass logs on to say it works........."
You must be dislexic or something because I certainly have never written the thing doesn't work at all but that it NEEDS REVISION because the design we have been discussing here causes people some problems, namely things around Q25. Then Mr Pass comes along and says:
"Often this circuit has been implemented differently around Q25, where a supply regulator is being used."
Can't you read?! For God's sake, it's written in YOUR MOTHER TONGUE by Mr Pass himself.
Eppure si muove, people, eppure si muove...
"Nelson designs a circuit 28 years ago......puts it in countless units in the field........and now we have experts claiming it is wrong."
"It is funny that the circuit didn't work when I explained it and the same circuit magically works when Mr. Pass logs on to say it works........."
You must be dislexic or something because I certainly have never written the thing doesn't work at all but that it NEEDS REVISION because the design we have been discussing here causes people some problems, namely things around Q25. Then Mr Pass comes along and says:
"Often this circuit has been implemented differently around Q25, where a supply regulator is being used."
Can't you read?! For God's sake, it's written in YOUR MOTHER TONGUE by Mr Pass himself.
Eppure si muove, people, eppure si muove...
Re: all the dislexic people, where do they all come from...
It is not my mother tongue obviously but I read it exactly as I assume Fred and Jocko (clearly by his statement I feel) did. That is not the way you read it as I read it has been built differently and nothing else. Not that I follow the Ono discussion very closely but who are all these people having problems?
moamps said:
It is not my mother tongue obviously but I read it exactly as I assume Fred and Jocko (clearly by his statement I feel) did. That is not the way you read it as I read it has been built differently and nothing else. Not that I follow the Ono discussion very closely but who are all these people having problems?
"Its not enough to speak, but to speak true"
Text in Quotes from moamps post:
"Vunreg drops below Voff=12V, the relays have already reached Vdrop-out value and deenergized."
12 V - 3 V (Vds of Q26 turned on for conducting relay coil current) is 9 V
"I'm telling you that IN PRACTICE Vdrop-out is about 7 V for a 24 V relay"
9 V is greater than the 7 V at which you say the relays actually drop out. So Q25 has muted the relays before the dropout voltage of 7 V you give.
"Switching off relays via MOSFET Q25 is therefore useless because they are already switched off, i.e., Q25 can be left out."
If the relay voltage is 9 V when Q25 mutes, which is greater than 7 V at which you observe that relays drop out, Q25 is opening the relay before the relay coils drop out by themselves. If one designs for the design sheet 2.4 minimum for the particular relay Passlabs is using, one could conceivably have the relay not mute until the supply voltage of 5.4 volts. One designs for actual parameter variation of a large number of parts rather than for a few parts under test in the lab.
You have not specified what relay you are testing with, so one can hardly jump to the assumption about the particular drop out voltage of the relay Passlabs is using. Ironically you gave best reason for including Q25 relay that you said is unnecessary, the adjustability of the power supply voltage point at which the relay mutes via selection of the voltage divider resistor values.
"Now I don't know why I even bothered as you can obviously think of no other argument besides Mr. Pass-knows-best mantra (with all due respect to Mr. Pass) that you keep repeating post after post."
"WhoDaMan !
Thank you Mr. Pass"
I believe I started out with a disscussion of the circuit before expressing the opinion that the circuit worked fine as drawn and had no extra parts, before mentioning Mr. Pass. Hardly a mantra in my eyes. The circuit works and is quite adjustable, result of the design, and not of Mr. Pass's reputation (which is a result of his skill as a designer.) I didn't even know if he designed it at the begging of this thread.
Are you still asserting Q25 is unnecessary?
Text in Quotes from moamps post:
"Vunreg drops below Voff=12V, the relays have already reached Vdrop-out value and deenergized."
12 V - 3 V (Vds of Q26 turned on for conducting relay coil current) is 9 V
"I'm telling you that IN PRACTICE Vdrop-out is about 7 V for a 24 V relay"
9 V is greater than the 7 V at which you say the relays actually drop out. So Q25 has muted the relays before the dropout voltage of 7 V you give.
"Switching off relays via MOSFET Q25 is therefore useless because they are already switched off, i.e., Q25 can be left out."
If the relay voltage is 9 V when Q25 mutes, which is greater than 7 V at which you observe that relays drop out, Q25 is opening the relay before the relay coils drop out by themselves. If one designs for the design sheet 2.4 minimum for the particular relay Passlabs is using, one could conceivably have the relay not mute until the supply voltage of 5.4 volts. One designs for actual parameter variation of a large number of parts rather than for a few parts under test in the lab.
You have not specified what relay you are testing with, so one can hardly jump to the assumption about the particular drop out voltage of the relay Passlabs is using. Ironically you gave best reason for including Q25 relay that you said is unnecessary, the adjustability of the power supply voltage point at which the relay mutes via selection of the voltage divider resistor values.
"Now I don't know why I even bothered as you can obviously think of no other argument besides Mr. Pass-knows-best mantra (with all due respect to Mr. Pass) that you keep repeating post after post."
"WhoDaMan !
Thank you Mr. Pass"
I believe I started out with a disscussion of the circuit before expressing the opinion that the circuit worked fine as drawn and had no extra parts, before mentioning Mr. Pass. Hardly a mantra in my eyes. The circuit works and is quite adjustable, result of the design, and not of Mr. Pass's reputation (which is a result of his skill as a designer.) I didn't even know if he designed it at the begging of this thread.
Are you still asserting Q25 is unnecessary?
I am not so sure I was confused.....
Someone started the thread saying.....well, we all know what he said.
He is the one confused. I admit, I do not know, or really care who he is. I think we should force someone to apologize for being a twit and inducing yet another rock throwing contest. As entertaining as it might be...............
Everyone else can chose for their own if they feel a need to apologize.
Jocko
Someone started the thread saying.....well, we all know what he said.
He is the one confused. I admit, I do not know, or really care who he is. I think we should force someone to apologize for being a twit and inducing yet another rock throwing contest. As entertaining as it might be...............
Everyone else can chose for their own if they feel a need to apologize.
Jocko
Re: "Its not enough to speak, but to speak true"
In my post #44 I based all my conclusions on the assumption that the relays were connected in series because, in my circuit-designing experience, I would not normally connect 24V relays on power supply that exceeds 24V. If you take a closer look at the picture in that post, you'll actually see two yellow reed relays connected in series. My opinion is that connecting them in parallel would have caused unnecessary power dissipation, higher magnetic flux, etc., especially in situations when those relays would have to switch signals with very low energy. Besides, in this particular case we're discussing, the relays are connected to unregulated power supply (with possibly significant Vripple), which may induce noise to interfere with switch contacts and for which reason one would certainly want to keep the current thru relays as low as possible. I thought you were familiar with this problem so I had hard time understanding why you found it so silly to implement a pre-resistor in a circuit which was designed in a parallel when that very pre-resistor did the job nicely (i.e. keeping current thru relays at a required level).
You apparently think the relays here are connected in parallel and that's why your calculations are different from mine, naturally. However, Q25 should switch off the relays when the voltage Vunreg drops to about 30V, which doesn't happen regardless of whether the relays are connected in series or in parallel. I have already described how to adjust this thing correctly in my post #47 (long before Mr Pass came in the picture). To sum things up, I don't think this transistor is unnecessary, only that it is not optimally adjusted in the original design. (Please, read my post#50. I hate repeating myself.)
The title of this thread might be inappropriate as it has little to do with what I'm talking about and has caused a lot of misunderstanding as to the actual point of my posts (BTW, thanks Grataku!). As far as I'm concerned, this is my final post on this subject. For those who feel like discussing it further, I'd appreciate it if they started a new thread.
Fred Dieckmann said:
In my post #44 I based all my conclusions on the assumption that the relays were connected in series because, in my circuit-designing experience, I would not normally connect 24V relays on power supply that exceeds 24V. If you take a closer look at the picture in that post, you'll actually see two yellow reed relays connected in series. My opinion is that connecting them in parallel would have caused unnecessary power dissipation, higher magnetic flux, etc., especially in situations when those relays would have to switch signals with very low energy. Besides, in this particular case we're discussing, the relays are connected to unregulated power supply (with possibly significant Vripple), which may induce noise to interfere with switch contacts and for which reason one would certainly want to keep the current thru relays as low as possible. I thought you were familiar with this problem so I had hard time understanding why you found it so silly to implement a pre-resistor in a circuit which was designed in a parallel when that very pre-resistor did the job nicely (i.e. keeping current thru relays at a required level).
You apparently think the relays here are connected in parallel and that's why your calculations are different from mine, naturally. However, Q25 should switch off the relays when the voltage Vunreg drops to about 30V, which doesn't happen regardless of whether the relays are connected in series or in parallel. I have already described how to adjust this thing correctly in my post #47 (long before Mr Pass came in the picture). To sum things up, I don't think this transistor is unnecessary, only that it is not optimally adjusted in the original design. (Please, read my post#50. I hate repeating myself.)
The title of this thread might be inappropriate as it has little to do with what I'm talking about and has caused a lot of misunderstanding as to the actual point of my posts (BTW, thanks Grataku!). As far as I'm concerned, this is my final post on this subject. For those who feel like discussing it further, I'd appreciate it if they started a new thread.
Re: Re: Re: Re: Re: delay circuit
moamps said:
Hi,
R77 is 750K resistor, current thru them can be in worst case I=V/R=40V/750000=ca 50uA. Power dissipation on R77 is then P=V*I= 2mW !!!!! , 0,25W is more than enough.
Yes you right. Ok now its a 0,6W Resistor and it works also)
Preresistor R19 can be between zero (maximum heating of relays, Q25, Q26) and about 1k (from my experiments).
From my practical experience with 1,5Kohm or 2,2 Kohm for R19 you can recognize heatings on the relais and Q25,Q26. Now with a 3,3 KOhm Resistor for R19 it works also. After 40 Min on ( i have made some other measurements) Q25,Q26 and the Relais are still at room temperature and i cant observe any heatings at this
parts. I have swichted several times on/of and the switching works without any problems. I think from the past that Q25 was really damaged and works sometimes or not and this was the reason for the switching problems. Perhaps due that i have used the Ono without PQuadrats correction on the PCB-Supply-Board.
Many thanks on all posters for understandings for me of this
circuit-part. I have learned a lot from that.
My last word on this.........
On reading schematics:
The Passlabs schematic does not show two coils in series and states that one channel is shown. It was a pretty sure bet that they were parallel.
On reading data sheets:
If you are going to analyze a circuit, READ THE DATA SHEET.
I went through the effort to post a link so people would see how the relay works, i.e., switching voltages, coil resistance, allowable voltages.
Reliability:
The data sheet says that 48 volts (at 50 degrees C) is the maximum voltage, well above the 37 volts the relay actually sees.
Coils in series or parallel?
The data sheet give a +/- 10% spec for the coil resistance. Worst case gives 2592 for one limit and 3168 for the other limit. These coils in series give 16.65 volts of the 37 volts across the coil with lower coil resistance. The spec state at worst case you need 16.8 to turn the coil on. Under these maximum spreads, one of the relays in series will not mute. You have a day where the AC voltage sags (summer in Texas with everyone's air conditioner on) your DC rail will sag a bit and you have even less voltage and be further below the max required 16.8 volts. This is called designing for the worst case tolerance spread. You will might get small enough variations that in the large majority of cases, things work. But sure as hell the tolerances can stack up such that some won't work. Allowing for the tolerance variations and staying as far away from operating area where the cards can stacked against you, is a real good idea.
"However, Q25 should switch off the relays when the voltage Vunreg drops to about 30 V, which doesn't happen regardless of whether the relays are connected in series or in parallel."
I don't know where this number came from. The regulated supplies will track the unregulated minus about 3 volts until the zeners turn on. I will agree that a higher value rail voltage for the mute threshold might be good idea but 30 V is an arbitrary number and the regulated supplies are even a few volts from going into actuall regulation at that point.
"Switching off relays via MOSFET Q25 is therefore useless because they are already switched off, i.e., Q25 can be left out."
Later:
"To sum things up, I don't think this transistor is unnecessary, only that it is not optimally adjusted in the original design."
I guess this means you changed your mind? Actually the thread wasn't a waste: since it went from" it doesn't work", to "it has extra parts", to how it actually works in quite some detail; including how to adjust the threshold, the relay choice and configuration, and how to adapt it to other voltages. I suppose Mr. Pass can forgive us in the end; after a bit of confusion in the beginning and middle. It's a great circuit and should be quite useful (if all the parts are included.....) It shows greater subtlety for a simple circuit than apparent at first glance.
On reading schematics:
The Passlabs schematic does not show two coils in series and states that one channel is shown. It was a pretty sure bet that they were parallel.
On reading data sheets:
If you are going to analyze a circuit, READ THE DATA SHEET.
I went through the effort to post a link so people would see how the relay works, i.e., switching voltages, coil resistance, allowable voltages.
Reliability:
The data sheet says that 48 volts (at 50 degrees C) is the maximum voltage, well above the 37 volts the relay actually sees.
Coils in series or parallel?
The data sheet give a +/- 10% spec for the coil resistance. Worst case gives 2592 for one limit and 3168 for the other limit. These coils in series give 16.65 volts of the 37 volts across the coil with lower coil resistance. The spec state at worst case you need 16.8 to turn the coil on. Under these maximum spreads, one of the relays in series will not mute. You have a day where the AC voltage sags (summer in Texas with everyone's air conditioner on) your DC rail will sag a bit and you have even less voltage and be further below the max required 16.8 volts. This is called designing for the worst case tolerance spread. You will might get small enough variations that in the large majority of cases, things work. But sure as hell the tolerances can stack up such that some won't work. Allowing for the tolerance variations and staying as far away from operating area where the cards can stacked against you, is a real good idea.
"However, Q25 should switch off the relays when the voltage Vunreg drops to about 30 V, which doesn't happen regardless of whether the relays are connected in series or in parallel."
I don't know where this number came from. The regulated supplies will track the unregulated minus about 3 volts until the zeners turn on. I will agree that a higher value rail voltage for the mute threshold might be good idea but 30 V is an arbitrary number and the regulated supplies are even a few volts from going into actuall regulation at that point.
"Switching off relays via MOSFET Q25 is therefore useless because they are already switched off, i.e., Q25 can be left out."
Later:
"To sum things up, I don't think this transistor is unnecessary, only that it is not optimally adjusted in the original design."
I guess this means you changed your mind? Actually the thread wasn't a waste: since it went from" it doesn't work", to "it has extra parts", to how it actually works in quite some detail; including how to adjust the threshold, the relay choice and configuration, and how to adapt it to other voltages. I suppose Mr. Pass can forgive us in the end; after a bit of confusion in the beginning and middle. It's a great circuit and should be quite useful (if all the parts are included.....) It shows greater subtlety for a simple circuit than apparent at first glance.
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