Is there a formula to calculate output power for parallel tubes?
The recommended loading for triode connected EL84's in push-pull is 10k, which gives 5w output. I am assuming that paralleling them will allow a 5k load, but calculating the theoretical output power at the secondary winding while allowing for the different winding ratio is beyond me.
The recommended loading for triode connected EL84's in push-pull is 10k, which gives 5w output. I am assuming that paralleling them will allow a 5k load, but calculating the theoretical output power at the secondary winding while allowing for the different winding ratio is beyond me.
2xEL84 in parallel should give the same output power as in push pull provided the PP is class A also.
As for secondary impedance taps the power will be the same. In other words, an 8 ohm speaker connected to the 8 ohm tap will have the same power output as a 4 ohm speaker connected to the 4 ohm tap etc.
As for secondary impedance taps the power will be the same. In other words, an 8 ohm speaker connected to the 8 ohm tap will have the same power output as a 4 ohm speaker connected to the 4 ohm tap etc.
two parallel pairs will work with half the transformer impedance of a pair, and should provide twice the output, provided you use a transformer of the correct power rating.
Thanks for the replies, but I think it's more complicated than that. The parallel setup will allow the same voltage swing but twice the current into a primary winding which has half the impedance, but I think the winding ratio, and therefore the voltage ratio, will change from 35:1 to 25:1.
What calculations show the output power will double?
What calculations show the output power will double?
If the winding ratio goes down from 35.35:1 to 25:1 (i.e. by the factor of 1.41), the voltage ratio indeed drops by the 1.41 factor, but at the same time the current ratio goes up by the same 1.41 factor, so the power (=voltage*current) ratio stays the same.
Remember, that regardless of the ratios involved, the reflected impedance is what matters. As long as the core and windings are made of wire sufficient to handle the current then the power will be dictated by the reflected load. The ratio is taken into account by the tech that designs and winds the transformer.
It's not directly a concern for the end use other than for academic purposes really. The impedance reflected is the load multiplied by the square of the winding ratio.
It's not directly a concern for the end use other than for academic purposes really. The impedance reflected is the load multiplied by the square of the winding ratio.
Suppose you swing 280Vrms into a 10k primary, divide by 35, you get a secondary 8V into 8 ohms = 8W.
Parallel the EL84s: primary swing is still 280V, but secondary will be 280/25 = 11,2V.
11,2^2 / 8 = 16W.
So in your PPP triode setup, power will be 2x5= 10W.
Parallel the EL84s: primary swing is still 280V, but secondary will be 280/25 = 11,2V.
11,2^2 / 8 = 16W.
So in your PPP triode setup, power will be 2x5= 10W.
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I needed to think a little, but now it is clear.
The primary voltage swing remains the same. But because of the lower transformation ratio, output voltage will be higher, so output power is higher.
The primary voltage swing remains the same. But because of the lower transformation ratio, output voltage will be higher, so output power is higher.