Audible pop when switching monitors on / off remotely

[john12ax7]

I have 3 sets of studio monitors that I power on / off from a power strip.  1 set makes a popping sound when doing this,  the other 2 are fine.  There is no signal going to the monitor.  It doesn't do this if I use it's own on/ off switch located on the back panel,  which is rather inconvenient.

I don't have a schematic,  so wondering what could be different with the monitor internal switch and what possible remote solution there is.

 

[JohnRoberts]

At Peavey we invested a lot of effort into silent turn on/off but in reality almost zero failures are caused by such noises.

However many sales can be lost at point of sale.

JR

 

[Bo Deadly]

You need a power sequencer. I have a monster power pro 2500 that's worked great for years. You can pick them up on Ebay for $100.

 

[john12ax7]

It's not a sequencing issue, everything is sequenced properly.  The issue is one set of monitors behaves differently when switched from a power strip vs it's own on board power switch.  Any kind of built-in soft start should be independent of the switch itself. But in this case the switch seems to be doing something more than just turning mains on and off. The question is what.

 

[Bo Deadly]

So if you terminate the inputs and then power on with the power strip, do they pop? That would be seriously bazaar.

I refuse to believe that they could differentiate between power applied with the builtin switch or externally. It would be a challenge to design such a circuit. Even if they used another pole, the circuit would need power to operate.

Maybe a capacitor is not fully discharging? How long are you waiting between trying?

 

[pucho812]

Some designs just do that. I have yet to see it actually cause a  woofer, mid or tweeter to have an issue because of it. 

In our live room, we have some JBL 4320''s  that we run off of a DBX drive rack P.A. as a crossover  and 2 x  power amps, a Bryson for the L.F. and a halfler for H.F. even with the amps off,  if I power up or power down the DBX unit there is an audible tick/pop whatever you wish to call it on the speakers. It's annoying but has not caused a fault.

 

[user 37518]

If you are so worried about it, you could try adding a MOV to limit inrush current and experiment.

 

[JohnRoberts]

If you are so worried about it, you could try adding a MOV to limit inrush current and experiment.

To repeat these are mostly cosmetic issues and not a source of significant failures. If they were the SKUs with poor turn-on/off behavior would be rejected by the marketplace already.

For TMI back last century at Peavey I (we) used a popular op amp in many output circuits because of its benign on/off behavior, it was not the best bang for the buck op amp for noise and slew rate, but did not "bang" during turn on/off  and scare customers away.

I would caution against looking for easy answers. In some cases the circuit behavior is strongly influenced by how the power rails come up initially. One engineer working for me even went so far as to design in a PS sequencing circuit that would not allow one rail to come up, until the other one was already up ( I don't recall which one had to be first, but it mattered).  In power amplifier design a great deal of design effort goes into managing turn on/off pops, clicks, bangs, and wheezes. Another common cosmetic fault is a power amp that goes through a momentary period of instability as the rails decay between valid on and off states. I recall in some early class D designs that special attention had to be paid on making sure the output drive didn't get stupid, before the PS collapsed to harmless levels to avoid self destruction. 

It can help to put all of the line level gear, feeding a power amp on its own power strip, so you can turn it on first, and off last, especially if using exotic gear designs that don't pay attention to such cosmetic issues. Back last century I even considered a dedicated power strip that would delay and sequence power, but the market was far too small, and price sensitive for a Peavey product. I expect there are expensive solutions that do just that.

JR

 

[Audio1Man]

Hi John12ax7
Your amplifiers may have a different RC on time and the AC LINE pulse on turn on may be the culprit. The amplifiers ON/OFF switch could have a cap across the power switch witch could reduce the arc/pop noise. You did not specify the model numbers and even if they are the MFG model could be different rev#.

In my power amplifier designs @ BGW, JBL & others I used SLOW ON & FAST OFF circuity. Several models had opamp’s inputs and they needed to used relays for the on/off noise pop’s suppression. For the all discrete amplifiers I controlled the input circuit currents to achieve the SLOW ON & FAST OFF modes.
Duke

 

[john12ax7]

There seems to be some consensus that it's more annoyance than risk of damage,  so that's good.

The monitors are krk v6 series 2. They make a good cheap secondary reference.

I might try some other power strips,  perhaps the internal circuitry is dependent on switching hot and neutral vs hot only.

 

[abbey road d enfer]

If you are so worried about it, you could try adding a MOV to limit inrush current and experiment.

A MOV would not limit inrush current. MOV's protect against overvoltage.
An NTP would actually reduce inrush current. However I don't think that's the issue.

 

[abbey road d enfer]

I refuse to believe that they could differentiate between power applied with the builtin switch or externally. It would be a challenge to design such a circuit. Even if they used another pole, the circuit would need power to operate.

You are usually more well-advised.
There are amps that feature a soft-start circuit that is triggered by a low-level switch. Indeed it takes some kind of standby power.
Ther are also powered monitors that include level-sensitive turn-on, where a part of the circuitry is constantly powered. The turn-on behaviour could be quite different depending on how the system is turned on.

 

[john12ax7]

The on board power switch is a 3 position rocker switch,  on,  off,  and auto.  I tried it on auto and there is no pop at turn on, as they don't actually power on or are muted until signal is applied.  They still pop at turn off,  but haven't yet waited long enough to see if they auto power down as well.

 

[moamps]

There seems to be some consensus that it's more annoyance than risk of damage,  so that's good.

May I disagree?

The monitors are krk v6 series 2.

You should set it to Auto and keep it all the time on mains, IMO.

 

[JohnRoberts]

A MOV would not limit inrush current. MOV's protect against overvoltage.
An NTP would actually reduce inrush current. However I don't think that's the issue.

NTP are not very practical for serious power amps because of losses after turn on. 

Indeed many Peavey powers amps used a low current power switch to turn on/off a high power triac.  I am not sure it makes any difference to the power amp if this is left on and switched by plugging a cheap power strip, but the switch on the power strip may not be that robust. More of a reliability concern than noise.
=====
Back in the 70s I designed a 4x250W amp for personal use into an old WE chassis. It had an old 3 position power switch (for tube heaters).  I used the first ON position to current limit the PS through a power resistor, then the second ON position shorted across the current limiting resistor and connected the speakers (using relays).  OFF disconnected the speakers immediately so was silent.

JR

 

[moamps]

NTP are not very practical for serious power amps because of losses after turn on.

I know of several hi-fi companies that put NTC in their amps in primary side. I once received for service one amplifier that worked, but the mains fuse would always burn out when the user changed it to silver or gold variant of the same characteristics. And they're not exactly cheap. And that was pretty frustrating for that user. The problem was that the internal NTCs were still hot during fuse replacement, so they didn’t actually limit the inrush current after. The medicine I prescribed is to let the amplifier cool down for at least 8 hours before turning it on again. 8)

The power loss on NTCs is usually low, 10W max IIRC.

 

[JohnRoberts]

I know of several hi-fi companies that put NTC in their amps in primary side. I once received for service one amplifier that worked, but the mains fuse would always burn out when the user changed it to silver or gold variant of the same characteristics. And they're not exactly cheap. And that was pretty frustrating for that user. The problem was that the internal NTCs were still hot during fuse replacement, so they didn’t actually limit the inrush current after. The medicine I prescribed is to let the amplifier cool down for at least 8 hours before turning it on again. 8)

The power loss on NTCs is usually low, 10W max IIRC.

I don't doubt they are used in some really low power stuff, but no serious amplifier designer wants another 10W heat source inside the amplifier chassis. 

I have seen them used in line level gear in place of a fuse.

JR

PS: I actually used PTC fuses to power limit a boost capacitor re-charging circuit inside my old capacitor doubled rail audio amplifier design (PMA70+)

 

[moamps]

I don't doubt they are used in some really low power stuff, but no serious amplifier designer wants another 10W heat source inside the amplifier chassis. 

Tell that to Nelson Pass, for example.
Except in larger power amplifiers NTCs are used in almost all SMPS, where the continuous power can be 600-800W and more.

 

[user 37518]

A MOV would not limit inrush current. MOV's protect against overvoltage.
An NTP would actually reduce inrush current. However I don't think that's the issue.

Sorry I meant an NTC, I was recently working with MOVs so it stuck. My idea is that perhaps limiting the inrush current would limit the initial transient.

 

[john12ax7]

May I disagree?

Certainly.  Have you experienced any failures due to this?