F4 power amplifier

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#543
@Veteran

sorry to hijack this thread, but you don't seem to reply to emails and neither respond to the Zen#9 group buy thread, where people would be very much interested in another group buy!

Is any planned? If not, could you please say so? Otherwise people are just waiting and hoping...it's here:

http://www.diyaudio.com/forums/showthread.php?s=&threadid=75876&perpage=10&highlight=&pagenumber=29

In case you're not doing another run, could I maybe have the gerber files? It's such a nice pcb artwork!

Thanks a lot!

Cheers, Hannes
 
#544
carpenter said:
That's a cool idea, Magura. BTW how's the amp coming?

🙂
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:blush: I'm not too happy to admit this....

I got around to testing the inductor theory IRL last week, it seems that I get about 50% extra inductivity by winding parallel air cores the bifilar way.

As for the amps...ouch, not good....there is a woman that have been taking up an awful big part of my spare time latly. I have made the PCB's but I havn't gotten around to testing them. Things are though not at a complete halt, but just moving real slow 🙂

Magura 🙂
 
#550
twitchie said:
I got my F4 (original circuit) wired up last night and just as with CVILLER's first attempt, my heatsinks are cold. Please forgive the newbie questions, but can anyone please let me know some points to measure/check?

I was able to adjust DC offset properly, and measured 6.97V across D1 and D2 (zeners). I used all the exact values from the original PDF, except for 2N4736 zeners, where I used 1N4736 (someone said the 2N was a typo and should actually be a 1N).

I also have to admit I got lazy/anxious to get this powered up, so I have 1 channel with a dead 2SJ74 after running +- 26V through that channel (when toshiba says 25V max, they mean 25V max). Currently, I'm holding the voltage down to 22V with a small variac in front of the PSU (400VA capacity variac).

Thanks,

Stephen
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Update: Actually, it turns out the problem wasn't with running 26V through the amp - the JFETS are fine (so far) with this voltage, it was a incomplete etch in the source resistor and output device that caused one of the source resistors to overheat (it turned red and discoloured). With both amp boards connected, I measured the PSU output at around 23V on both + and - sides.
 
#551
Re: Re: Matched

massimo said:


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!
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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
 
#553
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.
 
#554
massimo said:
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.
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Thank you for clarifying that for me, learn something new every day.
 
#556
Netlist said:
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
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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.
 
#559
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.
 
#560
massimo said:
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.
Click to expand...


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
 
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