Power amplifier with TDA2616

macle

Member
2001-09-28 1:36 pm
Italy
I have made a simple 2*12 watts amplifier to be used for a multi-room application. This power amplifier is based on TDA2616 Phlipps chip. The TDA2616 data sheet tells that "..No switch-on/switch-off clicks... ".

My unsolved problem is that at the first switch on ( main 24 Volts on) I got a "bump" on my loudspeakers. I think it depends on output stage capacitors. Infact if turn off an turn on again, after a short period of time, the amplifier, this "effect" is not audible.
I' m using an asymmetrical power supply (24 Vdc).

I tried to delay the loudspeaker insertion with relays with non success.

Any idea ???

Thanks a lot in advance

C. Mauri
 
I think your on the right track with the output caps charging at turn on causing the pop.

I can think of 2 ways to stop this.
1. You said that you had tried using relays to stop the pop. If you opened the amp output connection to the speaker at turn on and closed the relay later the relay closure would then cause a pop in the speaker. (You still need to charge the output cap.) If at turn on the amp output is connected to a 8 ohm wire wound resistor via the relay and after some small delay the output is switched to the speakers that should stop the pop.

2. The other choice is to use +/- 12VDC power supply. This way the output cap will not need to charge to 12VDC (half the power supply voltage) and no pop will result.
 
The charge resistor mentioned in the previous post does not need to be a high power 8ohm type. A 1kohm standard resistor will do and this can be left permanently connected, so only the speaker connections need to be switched via the relay.

If dual supply rails are used, as in the second suggestion, the output capacitor should be removed since there will no longer be a dc voltage across it. Electrolytics should not be used without a polarising voltage.

Geoff