This Amp will work?

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With a +/- 70V supply, a sine wave can swing over a 140V amplitude (assuming no losses whatsoever). The RMS voltage of such a sine wave is 70/sqrt(2) ~ 50 Volts.

Power = Voltage^2/load = 2500/4 = 625 Watt.

Please don't tell me that max. square wave power is higher (this indeed is 1250 W); nobody listens or dances to square waves 🙂

Regards,

Dirk
 
Dj BASS AMP said:
So whow can i get 2000W ?

Do i need to use a bigger power supply?

If you parallell two 4 ohms speakers, you get 2 ohms.
For to put 2000W out,
you need 90 Volt peak, that is 45 Ampere peak. (90volt/2 ohms)

So your Power supply need plus/minus 100 Volt
And a lot of Ampere.

Trafo should be 2x70 volt 15-30 Ampere, Minimum!
Two 70 volts 15 Ampere or more = (Two >=1000 VA)

:att'n: Always remember that Amplifier can not give power.

It is Trafo and power supply that gives power!
See what Nelson recommends.
He want good BIG power supplies, because he knows! 😉
 
DJ,

Please bear in mind that Rod's amp has no current limiting, so if a short is placed across the ouput its output stage will be destroyed. A design with short circuit protection, like the Leach amp or (I think) one of Anthony Holton's designs, is preferred for PA use.

In a live sound / DJ situation, its not so much _if_ an amp will be driven into a short, more like _when_ it will be driven into a short!

Tim.
 
DJ,

Your amp will not work as it is. Assuming the led is an ordinary red led (not high efficiency led) the total current in the differential pair is abt 1 mA. That is 0.5 mA for each transistor.

In order to obtain correct biasing for the following transistor MJE350, you have to modify the resistors inserted in the collector of each BC557, 1.2 kohm is the right value.

If you use green led, the right value may be different. Il all cases the dc current must be the same in each of the two BC557, and the base of the MJE350 must be biased at abt 0.6 V.

To prevent HF oscillations, it seems to be necessary to add some filtering in the supply rails between the input / driver stages, and the finals. Also, add a little resistor (47 ohms) in series in emitter connexion of each of the BC557 in the differential pair. Or use 100 ohms variable resistor with center tap : so you can cancel the offset of the amplifier.

Regards, Pierre Lacombe.
 
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