question about power capacitors

[dean95]

I must build an audio amplifier and I have a doubt:

Do I have to place power capacitors on the pcb or in another board in order to avoid problems?

thanks a lot🙂🙂

 

[Mooly]

The big reservoir caps can be off the board (chassis mounted) and connected with thick wiring to the amp pcb. You must have "local decoupling" on the power amp pcb though, typically smaller (say 100uf) caps which are usually bypassed with a small film type. That ensures a low AC impedance of the supply and helps keep things stable.

 

[dean95]

if I understand your answer:
I put power capacitors on external board then I connect them with large cables to decoupling capacitors close to power pin.

what do you mean with "chassis mounted" ? Do I connect the ground of capacitors to earth?

I don't understand what decoupling capacitor I must put on the amplifier pcb..
give me right values of these...

thanks a lot...🙂
please be patient with me 🙂

 

[Mooly]

By chassis mounted, I meant caps that are to large physically to be PCB mounted. So they "bolt" to the chassis using the appropriate clamps.

The grounding depends on the actual amp and power supply you are building. Whether you connect the big caps to ground again depends on the amp and case and so on, but yes, its common to do so.

Decoupling caps can be anywhere from a couple of micro-farads (uF) to several hundred uF. Again the amp you are building will have recommended values shown on the circuit.

 

[dean95]

I'm building the powered version of tda7294( with 2sa1943 and 2sc5200) and there are no decoupling capacitors...🙂

 

[Mooly]

Do you have a circuit we can see ? Is it the one in the data sheet ?

 

[dean95]

http://www.diyaudio.com/forums/chip-amps/206591-tda7294-power-transistors-amp-tda7293-come-also.html

I'd like to avoid noise and hum problems🙂

 

[Mooly]

OK, first time I've seen that thread...ho-hum 😀 what can I say, amps like aren't really my thing at all.

Only at post #187 does the question of decoupling come up,
http://www.diyaudio.com/forums/chip...ors-amp-tda7293-come-also-10.html#post3567279

To get any amplifier hum free requires an understanding of how things interact and how to wire an amp up to avoid that.

http://www.diyaudio.com/forums/diya...udio-component-grounding-interconnection.html