Hey guys I am looking to design a amplifier that will take on the form of a solid state pre-amp, and tube power amp. In starting the design, would it be better to start with a desired output wattage and work back from the power source to the input signal, or the other way around.

 

Hey guys I am looking to design a amplifier that will take on the form of a solid state pre-amp, and tube power amp. In starting the design, would it be better to start with a desired output wattage and work back from the power source to the input signal, or the other way around.

I don't see that it really makes a difference.
The amount of power has no effect on preamp design, and the preamp design has no effect on the output power.

 

I always design them from the speaker, backwards. That way you know how much voltage and current each stage has to achieve to drive the stage you just finished designing.

 

I don't see that it really makes a difference.
The amount of power has no effect on preamp design, and the preamp design has no effect on the output power.

Yes I would agree that the pre-amp will not effect the final output power, but I am designing the circuit as one whole circuit. Because of that reason I arbitrarily spoke of them as one unit.

 

I always design them from the speaker, backwards. That way you know how much voltage and current each stage has to achieve to drive the stage you just finished designing.

When calculating the (max) power supply needed for an tube amp and using the formula

V(max supply) = (Vo(peak) + Vd)( Transformer voltage regulation)(Line land variation)

Vo(peak) ^2 = RL * P*2.

Vd = voltage lost across the tube
Would Vd be the voltage across the plate resistor or what voltage from the data sheet would be used?

 

I don't have it down to a simple formula but I'd guess Vd is Volts (diode). A tube rectifier eats a lot more power than a silicon rectifier.
Most designs are easier than you think because you can buy a power transformer and an output transformer for a lot of well known amplifiers. A 6V6, a pair of 6L6, a quad of 6550's...their transformers are available.