# Solving Amplifier Turn-On and Turn-Off Pops



## Mike Warren

Sometimes, particularly when connecting head units to amplifiers via the speaker outputs, a loud pop or thud will come from the speakers when the system is turned on or off. There are several causes, including faulty equipment, but the most common one is due to a DC offset in the output on the head unit taking time to stabilise.

Amplifiers typically have a slight turn-on delay to help compensate for turn-on pops, but sometimes this delay is not long enough.

Similarly, when the head is switched off the DC offset disappears causing a pop as it takes a finite time for the amplifier to shut down once its remote wire loses power. 

This could be eliminated if head unit manufacturers would delay the shut down of the internal electronics for a couple of seconds after they shut down the remote output.

But I'm not aware of any manufacturers who do that.

So we sometimes end up with a system that has these pops. 


*Turn-On Pops*

Turn-on pops are reasonably easy to solve as all we need to do is introduce an extra turn-on delay to the remote wire to the amps.

In theory, the simplest way would be to just add a resistor and capacitor to the remote line to introduce a delay. The problem with that is that this will also cause a turn-off delay, which will cause turn-off pops.

So we need some way to turn on slowly and turn off quickly. There are several ways to do this such as using a 555 timer IC and a relay. I hate using mechanical relays so below is a simple 3 transistor circuit that will delay the turn-on signal for about 4 seconds with the values shown.











*Turn-Off Pops*

Turn-off pops are a little more difficult because we have to tell the head unit to stay on until the the amplifiers have shut down. To do this properly we would have to do an internal modification to the head unit, but that's not practical for most people and would void the warranty. 

However, most of the time we don't switch off our systems via the head unit but rather just let it come on and of with the car key. So we have an opportunity to delay the accessory power feed to the head unit.

The circuit below will hold the accessory power input to the head unit on for about 4 seconds after the key is switched off. When using this circuit it's necessary to drive the amplifier remotes from accessory power rather than the remote output of the head unit.










Note: this will only work for low current accessory wires to head units. Almost all head units for the last 10 to 15 years have been designed like this. You can tell if yours is like this because the red accessory power wire will not have a fuse in it (or if fused will be only something like 500mA or less).


*A more elegant (and slightly more expensive) solution*

I use an ASV3222 Programmable Switch (airsoundvision.com.au/asv3222) for each of these functions. If needing both turn-on and turn-off delays then this has the advantage that the remote output of the head unit is still used.











So what other methods do you use to prevent turn-on and turn-off pops?


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## Darkrider

I kinda wish I still had the factory head unit in my Camaro to try this out. I spent 100's of dollars trying to retain the factory head unit in that car, but the turn-off pop I just couldn't get rid of. From what I could tell about how the factory "smart" amp worked in the Camaro, it actually muted the output of the amp on turn-off. It was a serious mess when trying to pair aftermarket amps with the stock head unit.

I have a pretty long thread over on Camaro5.com where I was trying to get rid of that turn-off pop. I may go and update that thread to link to this one.


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## Hillbilly SQ

Glad I saw this thread. I'm about to put a system behind a U-Connect 8.4 headunit. I'll be getting the turn-on from the plug in the back that turns on with the acc.


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## Hillbilly SQ

I'm quite rusty on reading schematics but can still follow them. What's that triangle with the line below it represent on the turn-off delay?


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## Darkrider

Hillbilly SQ said:


> I'm quite rusty on reading schematics but can still follow them. What's that triangle with the line below it represent on the turn-off delay?


Triangle with line below is a Diode.


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## firebirdude

Hillbilly SQ said:


> I'm quite rusty on reading schematics but can still follow them. What's that triangle with the line below it represent on the turn-off delay?





Darkrider said:


> Triangle with line below is a Diode.


The side with the line represents the cathode end of the diode (the side with the stripe). This tells you which way the diode faces.


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## ARCuhTEK

Mike Warren said:


> *A more elegant (and slightly more expensive) solution*
> 
> I use an ASV3222 Programmable Switch (airsoundvision.com.au/asv3222) for each of these functions. If needing both turn-on and turn-off delays then this has the advantage that the remote output of the head unit is still used.


Could this schematic be used, but instead of sending the remote power to the amps, send the remote power to a digital signal processor, which in turn would then remotely power on the amps?

I see no reason this slight modification would not work. I am thinking of this since I know a lot of people have pops when using a DSP.

Thanks,
Kevin


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## unix_usr

A lot of DSP have the option to delay the remote turn on to the amplifiers - as mentioned turn on pops are much easier to solve. The miniDSP adds a 3 second delay to turn on - if your DSP and/or head unit do not offer such a feature they happen to sell a board with this circuit too; a miniDC power conditioner that does the same, has the added benefit of a clean dc-dc power supply and costs like $15 bucks... 

https://www.minidsp.com/products/accessories/minidc-isolator


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## bbfoto

Good info above. Yes, check your DSP for this feature if you are using one. In addition, a lot of car audio interface/installation companies also offer these devices, some with adjustable delay. Check out David Navone Engineering, Metra/Axxess, PAC, Scosche, Directed Electronics, Stinger, etc.


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## ARCuhTEK

Thanks guys. I have a brand new Helix DSP and it is still in the plastic (delivery yesterday) I am trying to learn all about it, but to be honest, my question was derived from my experience with my previous DSP which did not have turn on pops but did have some turn off pops. I am just trying to avoid introducing as few problems to the DSP as possible. As I learn my Helix, it may very have the necessary solutions for the pops. I just happened across this thread and it piqued my interest enough to pose the questions. Thank you again.


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## lashlee

The Helix is a great processor, and I can tell you from personal experience that you'll need to use the Helix's turn on output to the amps. Helix has designed the unit to turn off the amp(s) when switching between sound sources. This helps with any noise that would be generated when switching between presets.


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## ARCuhTEK

lashlee said:


> The Helix is a great processor, and I can tell you from personal experience that you'll need to use the Helix's turn on output to the amps. Helix has designed the unit to turn off the amp(s) when switching between sound sources. This helps with any noise that would be generated when switching between presets.


I did know that. As I stated in my first post, I was just curious if this thread recommendation from Mike could be placed between the HU and the DSP. 
This would allow the remote wire from DSP to amp to stay as designed (and required) The idea being that the schematic shown would turn off the DSP a few seconds after the vehicle has been turned off. But I supposed in that case there could still be turn off pops from the amps because their power would still be cut abruptly as soon as the DSP powered off. 


I looked at the MiniDSP device suggested above but it seemed to perhaps not be compatible with anything other than the devices the mfr stated.

Overall, I am just snooping around trying to learn what I can learn...


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## Cunfused guy

Hillbilly SQ said:


> Glad I saw this thread. I'm about to put a system behind a U-Connect 8.4 headunit. I'll be getting the turn-on from the plug in the back that turns on with the acc.


 Were you able to avoid the turn on pop? I'm still having that issue


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## chrisurya

Delay circuit can overcome pops on turn-on.
For pops on turn-off, I use simple solution, cause I'm tired of looking for various other things.

I use high wattage DPDT switch for Power switch.
The switch has 2 pole, each pole has 2 terminal.

I use pole 1 for on/off power, pole 2 to disconnect 1 terminal of speaker from amplifier output.
Thus when I press the switch for powering off, the speaker disconnected right away. No mode pops sound on speaker on turning off.


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## bbfoto

chrisurya said:


> Delay circuit can overcome pops on turn-on.
> For pops on turn-off, I use simple solution, cause I'm tired of looking for various other things.
> 
> I use high wattage DPDT switch for Power switch.
> The switch has 2 pole, each pole has 2 terminal.
> 
> I use pole 1 for on/off power, pole 2 to disconnect 1 terminal of speaker from amplifier output.
> Thus when I press the switch for powering off, the speaker disconnected right away. No mode pops sound on speaker on turning off.


(Old thread)

Huh?

How many speakers do you have in your system? You would need a switch for each speaker, unless you have a large multi-gang switch with the # of speakers you are using.


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