Audible relay popping in a speaker

[Odysseas]

Hello there,

I have had some problems with audible popping coming from a relay in my self-brewn amplifier. Sometimes, when the relay opened, there would be a pop in the speakers (I am not sure, which one of the speakers, it was not clearly discernable), and a small, visible spark between the contacts at the end of the reeds inside the relay.

I have googled for this a bit, and apparently this problem could be solved by disengaging the input signal for the amplifiers a few milliseconds before the relay opens. However, I do not see how this can be accomplished without an elaborate DSP.

Would it help if I turned off the power for the internal preamps? I suppose this would simply cause the pop to originate from somewhere else, is that correct?

To kill off popping from power switches, there are small ceramic capacitors found across the switches - would this work here, too?

Can anyone help me with disengaging the input signal, or come up with another solution to get rid of this relay popping?

Thanks for any help!!

 

[mvs sarma]

Hi
you meant that when a relay switches a signal to the amplifiers, the thump is heard.
yes possible --
case 1.
the input capacitoe discharges in to the previous(and/ or ) next stage thro the relay contacts. instead of switching signal thro rely contacts, perhaps you may try thro solid state switches like cd4066 or any other suitable device.

Case 2. the relay coil derives poer from the same line which also powers the audio amplifier/preamplifier and the returen path of relay coil supply is common to sinal return-- if so try seperate power for drive relays ( only secondary winding being common and keep its path isolated.

case.3 any rely switching power inthe home to any device gives a contact bounce, which may give spark and it could be avoided by suitable spark quench.
hope these will sort out the issue.

 

[ljcox]

Hello there,

I have had some problems with audible popping coming from a relay in my self-brewn amplifier. Sometimes, when the relay opened, there would be a pop in the speakers (I am not sure, which one of the speakers, it was not clearly discernable), and a small, visible spark between the contacts at the end of the reeds inside the relay.

Thanks for any help!!

It seems to me that the pop is due to the back EMF from the relay coil when it is opened.

The simplest solution is to connect a diode across the coil so that the cathode is at the positive end of the coil. When the relay is energised, the diode is reverse biased, but when the circuit is opened, the the doide is forward biased by the back EMF so the EMF is clamped at about 0.6 Volt.

This will also stop arcing of the contacts that open the coil.