Power Amplifier Vcc

[ecestudent]

i'm making a power amp to drive an 8-ohm speaker and reach the output of 50w. The datasheet says that it needs +-30v. Would the power amp reach the 50w output with just a single Vcc?

 

[crutschow]

No, it will not.

 

[Nigel Goodwin]

Rather a strange answer?.

Obviously it will, as long as the Vcc is 60V, and the circuit is designed correctly.

If you only feed it 30V and not 60V, then obviously not.

 

[Hero999]

If it's bridged you can get 50W into an 8Ω load at 30V.

 

[ecestudent]

I've decided to use a dual supply for the vcc. I'm planning to do it with lm317 and lm337. These two regulators has about the output of 1.5 A. This current isn't harmful for my power amp right? And btw, can a 220v to 12-0-12v step down transformer be used to attain an output voltage of +-30v using lm317 nd lm337 or am i to look for a transformer with higher voltage ouptut? Tnx in advance...
This is the power amp that i'm gong to use: http://www.datasheetcatalog.org/datasheet/stmicroelectronics/1565.pdf

 

[Nigel Goodwin]

You don't need regulators for a power amp, and a 12-0-12 transformer is too low even without regulators - the datasheet normally specifies the voltage for the transformer you need (20-0-20 or 22-0-22 probably).

 

[duffy]

Rather a strange answer?.

Obviously it will, as long as the Vcc is 60V, and the circuit is designed correctly.

I don't think so, unless your definition of "designed correctly" expands all the way out to include an active rail splitter circuit.

 

[Nigel Goodwin]

I don't think so, unless your definition of "designed correctly" expands all the way out to include an active rail splitter circuit.

Mostly all it needs is a speaker coupling capacitor, and a pair of resistors to give the 'split' - no need for active splitters.

But regardless of that, +/-30V gives the exact same power output as a single 60V rail - and many datasheets give the connections for both.

 

[ecestudent]

Would the current applied to the vcc of the power amp affect the output of the power amp?

 

[Nigel Goodwin]

Would the current applied to the vcc of the power amp affect the output of the power amp?

Current isn't 'applied' the circuit will simply take the current it needs, if the PSU can provide it - or the PSU will probably die.

 

[ecestudent]

would 1.5 A do?

 

[Nigel Goodwin]

would 1.5 A do?

Should be just about enough - why the limitation?.

 

[ecestudent]

I might still use a voltage regulator for my power amp. I'll be testing the design tomorrow or the next day.

 

[Nigel Goodwin]

I might still use a voltage regulator for my power amp.

Feel free, but I fail to see why you would want to restrict the design, plus pay more for a larger transformer, capacitors etc. - bear in mind you need these considerably larger to compensate for the losses in the regulator.

 

[duffy]

Yes, you don't need or want the regulator. The amplifier regulates it's output by comparing it to it's input anyway, so it's redundant, and just more things to go wrong and generate heat.

 

[ecestudent]

I see. So it will just be a 3A 24-0-24 transformer filtered by some caps connected to my power amps +-Vcc right? Would that be ok or am i missing something important?

 

[ecestudent]

A 3A 24-0-24 transformer wid caps connected to my power amp's +-Vcc would do the job perfectly right? Or am I forgetting something important? Tnx..

 

[ecestudent]

The datasheet is saying that the quiescent current of tda7295 is typically 30mA. Is this the minimum requirement of the current that i would supply? Cause i think i can use a smaller transformer for that purpose.. tnx in advance..

 

[kchriste]

A 3A 24-0-24 transformer wid caps connected to my power amp's +-Vcc would do the job perfectly right? Or am I forgetting something important? Tnx..

The rectifier diodes?

The datasheet is saying that the quiescent current of tda7295 is typically 30mA. Is this the minimum requirement of the current that i would supply? Cause i think i can use a smaller transformer for that purpose.. tnx in advance..

No, use the 3A transformer. The 30ma is the MINIMUM current that it will draw.

 

[ecestudent]

I see.. so i need a current higher than 30mA and a 3A transformer would do the job... Did i got it right?