Speaker popping when amp turned on with sound already channelled through. When turned on and source silent, is fine.

bonapardo

Standard Member
Hi,

The description of my issue is as described in the title.

I have been getting repeated popping issues through the right channel on my amp and am looking to fix. It's very sporadic but when it occurs, it continues to happen every 20 mins or so until powering off.

I managed to narrow this down to it happening when I have started the amp and already have sound playing on the selected source. If I start the amp and no sound is yet playing, everything seems to be okay. This is very confusing to me but I hope someone might be able to shed light on what component/s might be affected by this different startup order.

It happens on one channel only and is not related to cables, or source input channels. All behave the same way.

Any help much appreciated. I'm keeping the model of the amp off the thread to keep things at high-level first principles.


Thanks!
 

dobrykamil

Active Member
Hi

The brand/model of your amp would be very helpful.
 

bonapardo

Standard Member
Hi

The brand/model of your amp would be very helpful.
Ok, I'm reluctant because that can lead to others searching out all the same model-specific info I've already found on the internet.

I was hoping we could work on first principles - e.g. whether say caps (energy storage) or transistors (amplification) might be the likely cause.

I suspect it's the caps as the sound itself is fine when it's not popping and as caps have to charge themselves at start up, it ties in with the sequence of events. When I've previously had a transistor die, I didn't get any sound at all. But I'm not an engineer so was hoping someone might know more.

The model of amp is: Rega Mira 3. I have read every post available on google regarding similar issues with the Mira but the solutions seem to differ quite a bit.

As stated in the OP, I would prefer to start a high-level discussion rather than digging into specific models as I suspect the electrical principles can help others when troubleshooting too.


Thanks!
 

dobrykamil

Active Member
To start a high-level discussion, we need to know model of the amplifier. Why? To determine what type/class your amplifier circuit has. Class A and AB has many similarities but Class D is completely different, and popping can occur at other stages.
Popping sound is basicaly a very short impulse of DC voltage that "leaks" into amplified audio signal. Unfortunately I couldn't find service manual for your model, so popping noise could be caused by:
- dodgy operational amplifier which usually sits in pre-amp circuit. Some of them are quite sensitive to symmetrical voltage fluctuations.
- dodgy capacitor in the amplifier circuit (significant loose of its capacity and high ESR value)
- dodgy transistor which is a part of the audio signal path. The one that runs very hot would be my fist
suspect
-zener diode that struggles to maintain specific voltage level
This type of fault isn't an easy fix I'm afraid, but oscilloscope would be your best friend in this case.
 

bonapardo

Standard Member
Thanks for the answer, just the info I was looking for. I'll see what I can find.

I don't understand schematics and can't find one for the Mira 3 but apparently the Mira 2000 is very similar. Attached.

I should add that in this case, the popping only occurs if I start the amp with audio already playing through it. Then the popping happens every 20 mins or so until I power off, even when no sound is playing through it.

If I start the amp with NO signal, then start playing music AFTER amp has powered on, I can continue to listen with no popping for the rest of the day.

Could this give a clue as to what might be the problem component?
 

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bonapardo

Standard Member
Thanks again for the info.

I'm leaning towards capacitors being the issue as they hold charge and need to charge during start up. Maybe having a signal passing through before its fully charged corrupts it's operation until it gets a chance to discharge again. As everything works fine when started without a signal (it has just been on for two days with no pops at all), I feel fluctuating voltage is not an issue in my setup (unless the fluctuations are coming from the dodgy cap). And if the transistors/diode were faulty, I assume I would expect artefacts during normal operation (after signal-less start).

This high-level information has convinced me I need to replace the caps. I'll do so and eventually post my results. If it doesn't work, I'll move to the transistors.
 

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