Hello All:
Thank you for the many contributors to diyAudio, including newbies, and those in the know (technical-wise) for the Q&A on this wonderful site.
Being only a very casual peruser and reaching out when a electronics/electric question/issue/need arises, hope it's okay to reopen a long closed thread regarding "Loud pop when switching sources". It's probably agreed that there are/have been various discussions about and related to this topic. However, either I've not found (maybe not searching/reading thoroughly?) a recommended/de facto answer to this issue.
1. It's been noted that a loud pop can occur when a preamp is turned on after the amp and the recommended solution/workaround is to switch the preamp on first (and let it stabilize) and then switch on the amplifier. (Note: Assuming an active preamp.)
2. It's been noted that if the preamp is turned off while the amplifier is on, a (loud?) pop/thump through the loudspeakers can/may (and most likely) occur.
3. It's been noted that when switching off an amp, a (loud?) pop/thump through the loudspeakers can occur. (This may either have to do with design, residual/dissipative capacitive charge, or lack of(?) protective circuitry.)
4. It's been noted that DC (small or large mv-V, hopefully not the later as it can damage/smoke the amp and/or or loudspeaker driver(s)) at the preamp's output can be from either a source device riding along/being outputted or even the preamp itself (due to a design or lack thereof issue).
5. It's been noted that the (loud?) pop/thump can occur when switching between sources on the pramp and the solution/workaround is/was to incorporate AC coupling at the preamp's input(s) and/or the inputs of the amplifier. This being in terms of an RC network in series with the hot/live terminal and ground of the inputs (RCA in this case). e.g. (from Mooly and tomchr below). An alternative would be to incorporate a switching relay in the preamp.
a) If the preamp's circuitry components are hardwired (vs PCB), being a tubed unit (note: it can apply to a hardwired solid state also), and there are multiple (RCA) inputs (either few or all being connected to source device/components), e.g., 6 in total, is it best to add in the AC coupling (RC network) for each input (being left and right)? Given the nimber of inputs, this can amount a bit in the cost outlay side.
b) Can the AC coupling be added/incorporated between just prior to the input selector switch? Or
c) Can the AC coupling be added/incorporated between the input selector switch and the volume control (logarithmic in this case)? (Thereby reducing the number of RC network parts/components required.) Or
d) Can the AC coupling be added/incorporated at the preamp's output jacks? (Again. thereby reducing the number of RC network parts/components required.)
e) Figure that the best practice would be example 'a)'.
f) Is there an alternate solution?
g) Side note: Can a shorting (RCA) plugs on unused jack alleviate the loud(?) pop/thump when switching between sources on the preamp?
7. The AC coupling can be done at the amplifiers input (and in turn reduce the parts/componnents cost/outlay) but then this would need to be done/added to each amplifier (in one's collection - LOL) that does not already incorporate this feature.
8. Have missed some other scenario/thought?
Thanks for reading my (long?) ramblings. Would like to get a workable and cost effective solution/answer - if possible - LOL... and, hopefully, in turn provide some guidance to others with similar issues/thought processes/questions.
Sincerely,
Kingsley.
(aka audiobasic2000)
Thank you for the many contributors to diyAudio, including newbies, and those in the know (technical-wise) for the Q&A on this wonderful site.
Being only a very casual peruser and reaching out when a electronics/electric question/issue/need arises, hope it's okay to reopen a long closed thread regarding "Loud pop when switching sources". It's probably agreed that there are/have been various discussions about and related to this topic. However, either I've not found (maybe not searching/reading thoroughly?) a recommended/de facto answer to this issue.
1. It's been noted that a loud pop can occur when a preamp is turned on after the amp and the recommended solution/workaround is to switch the preamp on first (and let it stabilize) and then switch on the amplifier. (Note: Assuming an active preamp.)
2. It's been noted that if the preamp is turned off while the amplifier is on, a (loud?) pop/thump through the loudspeakers can/may (and most likely) occur.
3. It's been noted that when switching off an amp, a (loud?) pop/thump through the loudspeakers can occur. (This may either have to do with design, residual/dissipative capacitive charge, or lack of(?) protective circuitry.)
4. It's been noted that DC (small or large mv-V, hopefully not the later as it can damage/smoke the amp and/or or loudspeaker driver(s)) at the preamp's output can be from either a source device riding along/being outputted or even the preamp itself (due to a design or lack thereof issue).
5. It's been noted that the (loud?) pop/thump can occur when switching between sources on the pramp and the solution/workaround is/was to incorporate AC coupling at the preamp's input(s) and/or the inputs of the amplifier. This being in terms of an RC network in series with the hot/live terminal and ground of the inputs (RCA in this case). e.g. (from Mooly and tomchr below). An alternative would be to incorporate a switching relay in the preamp.
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6. What has (maybe) not been well noted/discussed is...a) If the preamp's circuitry components are hardwired (vs PCB), being a tubed unit (note: it can apply to a hardwired solid state also), and there are multiple (RCA) inputs (either few or all being connected to source device/components), e.g., 6 in total, is it best to add in the AC coupling (RC network) for each input (being left and right)? Given the nimber of inputs, this can amount a bit in the cost outlay side.
b) Can the AC coupling be added/incorporated between just prior to the input selector switch? Or
c) Can the AC coupling be added/incorporated between the input selector switch and the volume control (logarithmic in this case)? (Thereby reducing the number of RC network parts/components required.) Or
d) Can the AC coupling be added/incorporated at the preamp's output jacks? (Again. thereby reducing the number of RC network parts/components required.)
e) Figure that the best practice would be example 'a)'.
f) Is there an alternate solution?
g) Side note: Can a shorting (RCA) plugs on unused jack alleviate the loud(?) pop/thump when switching between sources on the preamp?
7. The AC coupling can be done at the amplifiers input (and in turn reduce the parts/componnents cost/outlay) but then this would need to be done/added to each amplifier (in one's collection - LOL) that does not already incorporate this feature.
8. Have missed some other scenario/thought?
Thanks for reading my (long?) ramblings. Would like to get a workable and cost effective solution/answer - if possible - LOL... and, hopefully, in turn provide some guidance to others with similar issues/thought processes/questions.
Sincerely,
Kingsley.
(aka audiobasic2000)
I think the simple answer and the one I would work to is that any audio component should be silent on power on and power off and to ensure that usually means it needs some effective form of output muting. This should reliably hold a mute condition for as long as needed for the circuit to stabilise and operate very quickly (milliseconds) on power off. The later usually needs some form of sensing of removal of AC input but its all text book stuff really.
Switching between inputs should also be silent and that means ensuring no DC is being switched, in other words no 'step change' in DC occurs as inputs are switched over.
AC coupling removes any DC and the two diagrams you show would allow silent switching between any such stages provided enough initial time had elapsed for the caps to fully charge... which comes back to a suitable switch on muting delay.
Inputs themselves (the floating input and shorting plugs question) should be tied to ground via a suitable high value resistor if they are simply AC coupled at the input (with an unterminated coupling cap).
So you really need all these techniques deploying as appropriate to get a silent experience. A combined (integrated) amp for example only needs a speaker delay, not one on the preamp as well (unless you happen to have a pre out used to feed other things).
Mains on/off switches can generate a burst of noise as they open (contacts arcing as they separate) and that has to be addressed with suitable snubbing if it proves a real issue (which is fairly unlikely if suitable switches are used).
Switching between inputs should also be silent and that means ensuring no DC is being switched, in other words no 'step change' in DC occurs as inputs are switched over.
AC coupling removes any DC and the two diagrams you show would allow silent switching between any such stages provided enough initial time had elapsed for the caps to fully charge... which comes back to a suitable switch on muting delay.
Inputs themselves (the floating input and shorting plugs question) should be tied to ground via a suitable high value resistor if they are simply AC coupled at the input (with an unterminated coupling cap).
So you really need all these techniques deploying as appropriate to get a silent experience. A combined (integrated) amp for example only needs a speaker delay, not one on the preamp as well (unless you happen to have a pre out used to feed other things).
Mains on/off switches can generate a burst of noise as they open (contacts arcing as they separate) and that has to be addressed with suitable snubbing if it proves a real issue (which is fairly unlikely if suitable switches are used).
Thanks for the run down (or should that be run-through? - LOL), Mooly. Suspected that you would be the first to respond. 😉
Yes, totally agree that the audio components should be silent on power on and power off. For the most part that that case when the proper sequence of powering on/off is observed (or probably even not observed due accidental sequence or forgetfulness).
Based on your explanation, there's doesn't appear to be an easy/quick solution aside from incorporating all aspects in the design rather than remediating after the fact. (Which is the case in my situation - i.e., pre-esigned/pre-made/constructed hardwired tube preamp. 😕
It's not so much as the power on/off pop/thump that may occur but more so when switching form one input to another (and back). Can a mute switch be incorporated as a solution/workaround to mute the signal when the rotary switch is rotated to another input source? If so, where to add it (and would it be a SPST or SPDT in a stereo/2-channel configuration)? Before the input rotary selector switch, or between the input selector switch and the volume control, or after the volume control? Oh, by the way, a wiring diagram would be much appreciated.
Thanks.
Yes, totally agree that the audio components should be silent on power on and power off. For the most part that that case when the proper sequence of powering on/off is observed (or probably even not observed due accidental sequence or forgetfulness).
Based on your explanation, there's doesn't appear to be an easy/quick solution aside from incorporating all aspects in the design rather than remediating after the fact. (Which is the case in my situation - i.e., pre-esigned/pre-made/constructed hardwired tube preamp. 😕
It's not so much as the power on/off pop/thump that may occur but more so when switching form one input to another (and back). Can a mute switch be incorporated as a solution/workaround to mute the signal when the rotary switch is rotated to another input source? If so, where to add it (and would it be a SPST or SPDT in a stereo/2-channel configuration)? Before the input rotary selector switch, or between the input selector switch and the volume control, or after the volume control? Oh, by the way, a wiring diagram would be much appreciated.
Thanks.
Wiring or circuit diagrams would be unique to every case I suspect 🙂
Input switching noise should be fairly easy to rectify I would have thought. As a first step I would measure the voltage between the common output side of the switch and all the input pins on the switch. Measure across the pins (not to them from ground) and see if any voltage is present. Even a millivolt or two is enough to make a click. If the inputs and output from the switch are correctly AC coupled there should be no noise. Having said that if the switch is a break before make then the ins and out are all floating as the switch moves and that makes it really important to ensure all signal lines are properly ties to ground.
Adding a mute as the switch rotates isn't easy as everything depends on timing. The mute would have to become active before the audio contacts moved over from one input to the other and you would need a spare set of contacts to generate some kind of pulse to activate a mute (that bits easy using a 555 timer for example).
Yes, you are correct circuit diagrams would be unique.
Will measure across the output pin(s) with regards to the input pins of the rotary switch to see if there's voltage. The rotary switch is a Sieden 2 pole 6 positions (bought from UK's HiFi Collective).
Wasn't thinking of adding a a mute as the switch rotates (but that sure is creative thinking 🤔) plus I don't have enough electronics knowledge to implement one, i.e., the 555 timer. Was thinking more along the lines of wiring a (SPST or) SPDT (upon further thinking, I think it should be a DPDT for 2-channels (left and right)) toggle switch on the output(s) of the Sieden rotary switch and then from the switch to the Sieden rotary switch, and finally to the input(s) of the volume control - so when the toggle switch is engaged it mutes the signal, the selector switch is rotated to the next source input, and then the toggle/mute switch is disengaged. If this works as a solution/workaround to silence the loud(?) pop/them when switching sources, then it would be probably be the easiest (and simplest parts count) to implement. However, not sure how to wire this correctly. Usually the DPDT has 6 solder terminals and usually the center tags are like the common terminal (up and center terminals linked and down and center terminals are linked - of course there are slight variations based on what the purpose/function). When the toggle is up, that's usually for signal flow and down is no signal flow. Am suspecting that the toggle down position (being more likely the upper terminal plus the center ones) the non-center terminals would necessarily be tied to ground via the RC network?
Thanks.
Will measure across the output pin(s) with regards to the input pins of the rotary switch to see if there's voltage. The rotary switch is a Sieden 2 pole 6 positions (bought from UK's HiFi Collective).
Wasn't thinking of adding a a mute as the switch rotates (but that sure is creative thinking 🤔) plus I don't have enough electronics knowledge to implement one, i.e., the 555 timer. Was thinking more along the lines of wiring a (SPST or) SPDT (upon further thinking, I think it should be a DPDT for 2-channels (left and right)) toggle switch on the output(s) of the Sieden rotary switch and then from the switch to the Sieden rotary switch, and finally to the input(s) of the volume control - so when the toggle switch is engaged it mutes the signal, the selector switch is rotated to the next source input, and then the toggle/mute switch is disengaged. If this works as a solution/workaround to silence the loud(?) pop/them when switching sources, then it would be probably be the easiest (and simplest parts count) to implement. However, not sure how to wire this correctly. Usually the DPDT has 6 solder terminals and usually the center tags are like the common terminal (up and center terminals linked and down and center terminals are linked - of course there are slight variations based on what the purpose/function). When the toggle is up, that's usually for signal flow and down is no signal flow. Am suspecting that the toggle down position (being more likely the upper terminal plus the center ones) the non-center terminals would necessarily be tied to ground via the RC network?
Thanks.
For the toggle mute switch configuration, it would be something like this (but for left and right 2-channel)...
Maybe something like this. Adding a mute switch across R7 would leave the switch out of the audio path. Any DC present at the inputs and any at the output would not appear at the switch contacts.
Perhaps this "Push to Turn Rotary Switch" with a momentary push button switch below the knob could mute the output when the rotary switch is turned.
Avoid the “2 caps in series” scenario as low roll off may occur. This may be a challenge but less so with modern DC coupled sources where just 1 input cap per channel at the power amplifier both is the minimum (a “DC fuse”) and the maximum (the less coupling caps the better). Also when having 2 caps in series that 2 caps will both be charged so twice the issue 😉
Relay based muting to Audio Ground is very adequate in solving power on/off plops and just like speaker protection it should be standard. Relay based power on/off muting is retrofittable to devices that lack muting with tiny PCBs. Only buy/build stuff that has muting.
There are relay based volume boards with relay based source selection that also mute outputs to Audio GND when switching inputs. Many issues solved at once in a nice way with shortest possible signal path closest possible to the RCA/XLR inputs. Farthest away from power transformers. Good stuff.
Relay based muting to Audio Ground is very adequate in solving power on/off plops and just like speaker protection it should be standard. Relay based power on/off muting is retrofittable to devices that lack muting with tiny PCBs. Only buy/build stuff that has muting.
There are relay based volume boards with relay based source selection that also mute outputs to Audio GND when switching inputs. Many issues solved at once in a nice way with shortest possible signal path closest possible to the RCA/XLR inputs. Farthest away from power transformers. Good stuff.
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Thank you gentlemen for some wonderful suggestions.
Mooly, I like the circuit diagram you drew up (in LTSpiceworks - don't use nor know how to (but suppose I can learn if need be))! It's simple enough to implement. The cap values are small (and economical) and along with the resistors are easy enough to obtain. Like how you clearly separated each input. Now, not sure exactly what the leftward pointing arrow signifies but it probably signifies the toggle up and up positions. ☕😉
1. Just to clarify - input 1 jack will have the RC network at the positive/live and negative/ground terminals and the positive/live from the RCAs is in turn connected to the upper toggle switch terminal, the positive/live input of RCA 2 to the center toggle switch terminal, and finally the 3rd RCA positive/live terminal connected to the bottom toggle switch terminal?
2. Also, from the circuit diagram, the center terminal of the toggle switch is connected to the psitive/live of RCA input 2 and thereby facilitating a 3-way/input mute toggle?
3. Tthe center toggle terminals in series to C4 and grounded via resistor R7 and the junction of C4 & R7 connected to the Siemens rotary siwtch or to the preamp's positive/live output jacks?
4. Given that each input in the diagram (3 in this case) seems to account for one channel, what kind of toggle switch would be used/required for 6 source input? Would two toggle switches (to handle left and right channels) be needed? Or can the positive/live terminal of each the RCAs go to the Siemens rotary switch terminals/pins respectively and thereby negating the toggle mute switch entirely?
I could be misinterpeting the diagram but thinking that the RC networks soldered at each input RCA and then the postive/live of each to the Siemens rotary switched (left and right respectively) is what was pointed out initially to combat the (variability of DC from the input sources). If this is so, I certainly can make the cahnge. However, what about C4 & R7, can this be implemented at the Siemens rotary switch's oupt terminals.pins or would is better to incorporate it at teh preamp's output terminals?
Chris: That mmentary push switch sure does seem like a simple yet easy solution but wouldn't two of (the 4-pole 3 position) required for 6 inputs? 🤔
jean_paul: Good point/observation of the cumlative negativedeliterious effects of more than one signal cap (especially if implemented at both the preamp's output and the amp's inputs). Took a very quick look at the suggested Relay base muting to Audio Ground and the relay based volume boards. Even though these options may be the beter solution, there is probably not enough space in the casing to implement such and for the latter would also be replacing exisitnng volume (100k logarithmic Audionote) plus the Siemens rotary switch. The wiring length from the RCA inputs would certainly be reduced and my be a plus. 😎
Thanks. 😱)
Mooly, I like the circuit diagram you drew up (in LTSpiceworks - don't use nor know how to (but suppose I can learn if need be))! It's simple enough to implement. The cap values are small (and economical) and along with the resistors are easy enough to obtain. Like how you clearly separated each input. Now, not sure exactly what the leftward pointing arrow signifies but it probably signifies the toggle up and up positions. ☕😉
1. Just to clarify - input 1 jack will have the RC network at the positive/live and negative/ground terminals and the positive/live from the RCAs is in turn connected to the upper toggle switch terminal, the positive/live input of RCA 2 to the center toggle switch terminal, and finally the 3rd RCA positive/live terminal connected to the bottom toggle switch terminal?
2. Also, from the circuit diagram, the center terminal of the toggle switch is connected to the psitive/live of RCA input 2 and thereby facilitating a 3-way/input mute toggle?
3. Tthe center toggle terminals in series to C4 and grounded via resistor R7 and the junction of C4 & R7 connected to the Siemens rotary siwtch or to the preamp's positive/live output jacks?
4. Given that each input in the diagram (3 in this case) seems to account for one channel, what kind of toggle switch would be used/required for 6 source input? Would two toggle switches (to handle left and right channels) be needed? Or can the positive/live terminal of each the RCAs go to the Siemens rotary switch terminals/pins respectively and thereby negating the toggle mute switch entirely?
I could be misinterpeting the diagram but thinking that the RC networks soldered at each input RCA and then the postive/live of each to the Siemens rotary switched (left and right respectively) is what was pointed out initially to combat the (variability of DC from the input sources). If this is so, I certainly can make the cahnge. However, what about C4 & R7, can this be implemented at the Siemens rotary switch's oupt terminals.pins or would is better to incorporate it at teh preamp's output terminals?
Chris: That mmentary push switch sure does seem like a simple yet easy solution but wouldn't two of (the 4-pole 3 position) required for 6 inputs? 🤔
jean_paul: Good point/observation of the cumlative negativedeliterious effects of more than one signal cap (especially if implemented at both the preamp's output and the amp's inputs). Took a very quick look at the suggested Relay base muting to Audio Ground and the relay based volume boards. Even though these options may be the beter solution, there is probably not enough space in the casing to implement such and for the latter would also be replacing exisitnng volume (100k logarithmic Audionote) plus the Siemens rotary switch. The wiring length from the RCA inputs would certainly be reduced and my be a plus. 😎
Thanks. 😱)
The switch I drew is the input selector, not the mute. The centre left terminal on the switch is just one of the three inputs I drew.
The mute switch (not draw) would connect across R7 assuming that R7 sees no voltage from whatever you connect that output side to or it could connect to the other end of C4 and ground as that also has zero volts DC present.
The mute switch is common to all and so a single DPDT or SPDT is fine as you are only using it short the output line. Muting can be wherever is more convenient and at the preamp output has to be the 'best' location because then nothing can get through from anywhere in the preamp.
Thanks for the clarification, Mooly. It's appreciated! 😊 (And definitely doable/solderable.)
jean-paul: Thanks for a sizing perspective. Still would be a tight squeeze as there are already glued down components on the metal casing (which already is not the standard 17-19" width and respective depth & height) and not very much room unless the board is raised via tall spacers or possibly mounted vertically (horizontally). Also from the looks of it, it would need to be powered for it to work (versus passive) not that that's a bad thing/inconvenient. 😎
Thanks again.
jean-paul: Thanks for a sizing perspective. Still would be a tight squeeze as there are already glued down components on the metal casing (which already is not the standard 17-19" width and respective depth & height) and not very much room unless the board is raised via tall spacers or possibly mounted vertically (horizontally). Also from the looks of it, it would need to be powered for it to work (versus passive) not that that's a bad thing/inconvenient. 😎
Thanks again.
Why not give it a try, I'll attach the file in case you do 🙂 It will just click and run. You can play around with values then.
If you want to try then its here:
https://www.analog.com/en/resources/design-tools-and-calculators/ltspice-simulator.html
For W10 and W11 you want the latest version, for W7 use the 'End of Support LTXVII link' and for Vista or XP use the XP link:
The signal source has been set at 100mv DC offset. You can follow the DC values (fV is not a lot 😉 Femto volts in the simulation because the caps are 'perfect') You can see the response in the second image and I have assumed a 100k load on the output.
What is the actual problem here being discussed that cannot be solved by turning the volume knob completely down before switching the source?
Hi Mooly. Will definitely think about LT Spiceworks (hope it's not a steep learning curve - 😢).
Hi madis64: Yes, in a perfectly/silent/working as it should system, this is definitely the de facto way (besides having a mute switch). But, when one usually sets the volume to the desired level (no markings/steps repeatable), I know, it's a minor inconvenience (even though each/different source(s) probably have different output signal levels. And, it's also may not be the best solution especially if one forgets/neglect to 'Turn down the volume'. Thanks. 🤔😎
Thanks.
Hi madis64: Yes, in a perfectly/silent/working as it should system, this is definitely the de facto way (besides having a mute switch). But, when one usually sets the volume to the desired level (no markings/steps repeatable), I know, it's a minor inconvenience (even though each/different source(s) probably have different output signal levels. And, it's also may not be the best solution especially if one forgets/neglect to 'Turn down the volume'. Thanks. 🤔😎
Thanks.
If you do not want to burn down your gear then learn not to forget.
The signal source output levels can be substantially different nowadays so the only safe way for your eardrums (and your gear) is to turn down the volume knob before switching the source (been there, done that, burnt something).
There is no right way of doing a wrong thing 🙂
Having said that I am out of here.
Hi madis64:
Thank you for the reminder(s). Hope I don't end up burning any gear although I've made the mistake of not turning off an amo before disconnecting an RCA interconnect and that caused a loud screech which took out an ESL panel. Live and learned the hard way - ouch! 😵😢
By the way, hope I haven't offended you in any way.
Thanks.
Thank you for the reminder(s). Hope I don't end up burning any gear although I've made the mistake of not turning off an amo before disconnecting an RCA interconnect and that caused a loud screech which took out an ESL panel. Live and learned the hard way - ouch! 😵😢
By the way, hope I haven't offended you in any way.
Thanks.
Hi, no the PSU is onboard except the tiny 2.3VA transformer for which I designed a tiny PCB.
It has 64 step volume control and 3 inputs all done with bistable relays. It has a rotary switch for all functions. It can be made to switch a power relay too and it has an aluminium remote control. In fact it has all the really necessary bells and whistles I was looking for. Replacement for potentiometers with enough steps and no more crackling switches. Clean and short signal path without semis. Close to the back, far away from transformers. No caps
= no plops 🙂
The whole thing is small with large added value. And then when I just finished it….I had a balanced amplifier 😀
BTW I think a predefined power on/off sequence is silly. Stuff should be made to withstand human errors and be silent while switching sources. Volume should be low at power on. Possible with some decades known simple logic. The more expensive audio stuff is the less one sees such implemented. Incomprehensible and unacceptable. Just don’t buy or build hampered stuff. Grandparents, parents, kids, wife, dog, you yourself the morning after the night before: all should be able to use devices in a home without consequences.
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