F5 Turbo Builders Thread

[jacco vermeulen]

With rails of 32 volts, you may get 28 volts of swing, this gives you MAX 50 watts Class A with 100 watt peak.

28.3 volts peak in 4 ohm is 100 watts Class A continuous.(with sufficient dynamic bias)

 

[buzzforb]

The dance of power begins.

 

[Rush]

28.3 volts peak in 4 ohm is 100 watts Class A continuous.(with sufficient dynamic bias)

Yes, of course I forgot to say into 8 ohms.

Rush

 

[buzzforb]

I cant find a dance emoticon.

 

[jacco vermeulen]

Yes, of course I forgot to say into 8 ohms.

You also forgot the presence of commercial full Class A power amps, optimised for continuous output power in other than 8 ohm.
Unless you didn't know.

 

[a.wayne]

IN my new speakers setup, 10W will deliver 110 dB

Doubt that .....

 

[Renron]

Planet10, Dave,
What do you think about 110dB with 10W? Possible?

 

[buzzforb]

Maybe not, just going by MJK worksheet. I msut admit I am not good with numbers. Should learn, but end up spending my time building stuff.

 

[jacco vermeulen]

I must admit I am not good with numbers.

Buy (build) a headphone set instead.

(Hey, I got some math books in English I could Xerox for ya)

 

[buzzforb]

Is this to mean I am wasting my time? Are the MJK sheets wrong?

 

[WalterW]

28.3 volts peak in 4 ohm is 100 watts Class A continuous.(with sufficient dynamic bias)

"only" 7.07 Ampere needed

 

[buzzforb]

THe V3 , biased according to article, has roughly 6.4-7.2A of bias, depending on how high you bias, correct?

 

[WalterW]

THe V3 , biased according to article, has roughly 6.4-7.2A of bias, depending on how high you bias, correct?

Yeah, pity that my heatsinks don't allow more than 5 Ampere but hey, who needs 100 Watts continuous...

 

[Renron]

Is this to mean I am wasting my time? Are the MJK sheets wrong?

Not at all Buzz. I know Planet10 knows this stuff . Was hoping for his perspective.

 

[jacco vermeulen]

"only" 7.07 Ampere needed

Which is not equivalent to 7.07A bias level, in an F5T.

 

[buzzforb]

Jacco, you know I am slow. What are you saying?

 

[buzzforb]

F5T has a bit of an advantage is this regard, as the diodes give it more current swing than a normal output stage. In most cases, folks F5T will be voltage limited rather than current limited, correct?

 

[abadsantos 7]

With rails of 32 volts, you may get 28 volts of swing, this gives you MAX 50 watts Class A with 100 watt peak. If you bought this amp it would be listed as a 50 watt amp. That is a lot of class A power, but less power than an 80 watt Accuphase class AB. You are lacking rail volts to get higher wattage. I suspect you will not notice any lack of power between the two amps, the class A may even sound more powerful due to better control, etc.
You would have to go to 44 volt rails to get to 100 watts average class A power and your total bias current would need to go up to 2.5 amps. That's a lot of heat for you to get rid of.

Rush

Hi Rush,

Thanks for the information.

 

[jacco vermeulen]

What ?

In a standard push-pull Class A output stage, the 'bias' swing is like a string cord.
5A bias level is +5A and -5A, looking at/from the output node.
Max Class A output current is either +10A, or -10A.

In the F5T, 'bias' swing is like a string of rubber.
The T output stage has an asymmetrical behavior, due to the added diodes.
Means that 5A quiescent current level, corresponds to more than 10A peak Class A output current.
Aka, one gate opens faster than the other gate closes.

 

[buzzforb]

Thank you. Best description I have heard to this date.