How to avoid "pop" with UCD when switching on?

[ackcheng]

Hi! I have just DIY UCD180 and is using a a relay to contol the /on. This way, i can put the module on standby/active mode. But each time I wake up the module from standby mode, I get a "pop" sound.

Is this normal? If I put a 0.1uF cap across my relay, will that solve the problem?

ackcheng

 

[fumac]

not normal
if have a softstar, is no any pop .

u can check ur dc voltage of output pin.
or slow down the softstar

 

[RX5]

Hi! I have just DIY UCD180 and is using a a relay to contol the /on. This way, i can put the module on standby/active mode. But each time I wake up the module from standby mode, I get a "pop" sound.

Is this normal? If I put a 0.1uF cap across my relay, will that solve the problem?

ackcheng

what diy ucd180 scheme are you using?? there are many..

and what MOSFET?

 

[ackcheng]

Oh! I think I did not make it clear, I actually the hypex modules. I did not DIY from scratch, I just put the modules and PSU together.

 

[ackcheng]

I tried noticed that the pop does not come on immediately when the relay is activated. It comes on about 1-2s later. So, i think this is the time when the /0n is pull to ground

 

[fumac]

check
1. dC offset
2. the damp does not on before the relay had on

rg
fumac

 

[ackcheng]

problem solved. It turns out to be the problem of the cap that is in series with the tweeter. The UcD180 has DC when there is no load. When the cap is in series, there is basically no load. the cap get charged. and discharged when the /on is grounded giving a loud pop.

I change the cap to a reistor instead and solve the problem

 

[BWRX]

I change the cap to a reistor instead and solve the problem

Removing the capacitor will certainly get rid of the pop because there is no capacitor to charge but the whole point of the cap was to provide DC protection for the tweeter.

To implement this properly, it seems like you would need to have the capacitor directly on the output of the amp followed by a higher value resistor going to ground and use a relay to connect or disconnect the tweeter AFTER the capacitor has been charged up by the amplifier output.

 

[Javin5]

Put a 1K rsistor across the UcD-output. Then you have no DC-Offset with zero load. Works for me.

 

[tawn10]

I read something in the ucd180 questions about using a resistor on the outs to stop the dc voltage at NL, its a long thread but its in there! its got something to do with overcurrent protect circuit or something??

 

[Javin5]

Yes, I think there is something in the long thread, but if I remember correctly, the proposal there was different (I could be wrong). Use a 1 or 2 Watt resistor. I hear absolutely no plops when switching on or off.

Both with and without the speaker load, my offset is about 4 mV (coupling caps shorted). I have the UcD180AD version.