F4 power amplifier

[jleaman]

Originally posted by massimo


NO, they cannot.

Think about the P.S.: it's dual, it has a + and - rail. Thus you need N channel and P channel devices. It's mandatory for a push-pull circuit!

The only reason i asked is because my old N-Channel amplifier used the same configuration EXCEPT i used all IRFP240's and it worked 100% fine, i just wanted to make sure before i ordered them

Thank's for the help.

Jase

[jleaman]

Just so people know or if wondering where to get matched sets of Fet's I am ordering mine from, this person.

http://tech-diy.com/hexfets.htm

[massimo]

You can use an NPN + PNP circuit up to the driver section and then two NPN output devices. This tecnique, knonwn as "quasi-complementary" was used in the past when PNP power devices weren't available.
A great design using a similar circuit was the original version of the British Cyrus integrated amp (very good sound for that time),
but the F4 is different and I don't think you can drop directly in N channel only power mosfets.

[jleaman]

Originally posted by massimo
You can use an NPN + PNP circuit up to the driver section and then two NPN output devices. This tecnique, knonwn as "quasi-complementary" was used in the past when PNP power devices weren't available.
A great design using a similar circuit was the original version of the British Cyrus integrated amp (very good sound for that time),
but the F4 is different and I don't think you can drop directly in N channel only power mosfets.

Thank you for clarifying that for me, learn something new every day.

[Netlist]

The Phase Linear is of course a totally different amp but since this schematic was easily available I pass it on as an example of a quasi-comp circuit so you have an idea.
http://members.aol.com/phasetek2/pl14.jpg

The mosfet citation is another, better example.
http://www.passdiy.com/pdf/citation.pdf

/Hugo

[jleaman]

Originally posted by Netlist
The Phase Linear is of course a totally different amp but since this schematic was easily available I pass it on as an example of a quasi-comp circuit so you have an idea.
http://members.aol.com/phasetek2/pl14.jpg

/Hugo

I used to have one of these, actually still miss it was a great powe-ramp, had some mods done to it too, Could sit in front of that led display for hours and watch it bounce around.

[jleaman]

F4 transformers,

Ive looked on ebay and have found a perfect pair of Antek transformers 400va @ 18-0-18 witch gives 18 * 1.4 = 25.2V dc for rails Is this to high for the F4 ? Im planning to use 2 transformers one per channel.

Thanks

Jase

[Zen Mod]

Originally posted by jleaman
F4 transformers,

Ive looked on ebay and have found a perfect pair of Antek transformers 400va @ 18-0-18 witch gives 18 * 1.4 = 25.2V dc for rails Is this to high for the F4 ? Im planning to use 2 transformers one per channel.

Thanks

Jase

when you saw last time Papa's amp,where is 1,41 adequate factor ?

[massimo]

18-0-18 V looks good and is the same value indicated by the Master the F4 schematics.
18 * 1.4 = 25.2 is purely theorical. Very often you get 1-2 V less.
If you get an higher voltage, you can always use a CRC or (better) a CLC filter to lower the voltage and the P.S. noise.

[jleaman]

Originally posted by massimo
18-0-18 V looks good and is the same value indicated by the Master the F4 schematics.
18 * 1.4 = 25.2 is purely theorical. Very often you get 1-2 V less.
If you get an higher voltage, you can always use a CRC or (better) a CLC filter to lower the voltage and the P.S. noise.

I definatly agree, i just connected my fluke meter back from calibration and i checked our AC wall voltage of 122, then looked at my Alephs that i have now,

Inside is a 300Va with 16V secondary with calculations it should have rail voltages of

16 * 1.4 = 22.4V rails BUT when measuring them i see 20.1V so the voltage is a little dropped i guess.

So i think ill be ordering 2 of these 18-0-18's and use that.

Thanks for your help massimo.

Jase