F5 Turbo Builders Thread

[Blink_PT]

Originally Posted by anilva

Thanks, I will check out the Lambda stuff. I can hear my Toroid making different noises when my water pressure pump keeps going on and off....

If you want the schematic say, I send by PM.

[BigE]

AudioSan,

I am looking for 48 V peak output voltage, and 6 amps peak output current for 288 peak watts, or 144 WRMS.

[AndrewT]

for 144W of ClassA power you will need a bias of ~3.1A
the PSU will need to maintain ~ +-53Vdc while delivering that 3.1A of bias.
The ripple on the supply rails will be considerable.

I would expect a 0-38Vac, 0-38Vac 900VA (12Aac) transformer to maintain that +-53Vdc, with acceptable ripple, if you have +-50mF to +-100mF for a monoblock assembly.

Another unhelpful post to augment my previous one?

[AndrewT]

Originally Posted by buzzforb

A toroid that is 3 to 5 times the dissipation amount is the best way to calculate things............

6times to 10times is often stated for a ClassA power Amplifier.
Another unhelpful post?

[buzzforb]

I believe it is in agreement with Nelson's articles, advice, and Firtswatt Implementations..

Your post are very helpful, Andrew, but we have been on the toroid rating topic for 10 pages.

[BigE]

AndrewT,

It would be helpful to know how you obtained your numbers?

In the F5 article, Pass uses:

Peak watts = (I^2*R) where I = 2*bias and R=8 ohms.
He then divides this by two for rms power. When using a 3 amp bias, that is (6 * 6 * 8 )/2 =144 Wrms. This can be achieved by a rail voltage of V = I*R = 48 volts.

This is into a purely resistive load. We know speakers are not like that. The real output power will vary with power factor - a measure of the phase difference between V and I. But, pass ignores that in his calculatuion of power for the F5, as do I.

Also, the notion of 6 to 10 times is 6 steady state and 10 times peak. Which makes me think the 10 applies to class a/b operation, not the. Steady state class A.

[anilva]

Originally Posted by buzzforb

we have been on the toroid rating topic for 10 pages.

I agree. This is a lot of real estate being spent on toroid. This thread cannot be just that for one individual's clarity. One can use the PM route.

[BigE]

So far, I've been the only person that has been trying to formulate things, obviously incorrectly. AndrewT responded valuably to my first effort, from which I made formulas... but AudioSan says they're off by a factor of two.

From the problems in formulating this, either people are not capable of doing it, or they just won't tell anyone how. Are you really content with someone just posting numbers without knowing where they come from? Maybe you can DIY without knowing how to size a transformer and blindly follow others, but I can't.

[buzzforb]

No worries. The ESP site is excellent resource on this very topic. I don't intend to be dismissive, just suggesting that reading and working through the math.

[billyk]

Hey BigE I've been following along trying to understand it all with you. I know what toroid and heat sinks I am planning on buying, but would really like to know the why and how of it all too.