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F6 Illustrated Build Guide
F6 Illustrated Build Guide
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Old 8th April 2020, 07:53 PM   #1771
LATB is online now LATB  United States
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Quote:
Originally Posted by TungstenAudio View Post
Yes, the FQH44N10 is pretty much a drop in replacement for the IRFP 140 or 240. As you expect, it will need an adjustment to the bias and offset. The 6.1V Zener should still be sufficient, though you might consider switching to three green LEDs in series instead. It will help to have a negative tempco bias circuit. The FQH part will also perform well with higher Iq, so you might also try pushing 1.8A through the output stage.

re/ the three green LEDs for temp compensation, which ones would work well re/ temp, noise etc? Could somebody propose a part number (Mouser)?

Thanks a lot! LATB
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Old 8th April 2020, 08:03 PM   #1772
Dennis Hui is offline Dennis Hui  Canada
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F6 Illustrated Build Guide
Hi LATB,

Pico wrote about the temp compensation here, including parts he tested with:

Dumb Biasing Mod, applicable to F6 and other Papa Amps. Possibly My Dumbest Idea Yet

Cheers,
Dennis
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Old 8th April 2020, 08:27 PM   #1773
LATB is online now LATB  United States
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awesome! 3 x LTL-4231N LTL-4231N Lite-On | Mouser

Thanks for the pointer, I should spend more time on diyaudio to read all these threads...!
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Old 8th April 2020, 09:22 PM   #1774
TungstenAudio is offline TungstenAudio  United States
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Yup, those are the ones.

I will also be using a Semitec E-562 current regulating diode in place of the load resistors in the bias circuits. It also has a slight negative tempco, and will help keep the LEDs at a constant voltage.
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Old 9th April 2020, 09:43 AM   #1775
meanie is online now meanie  Singapore
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Click the image to open in full size.

The 3 Led in series are able to squeeze into the zener location, makes install neat!
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Old 12th April 2020, 04:32 AM   #1776
meanie is online now meanie  Singapore
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Make some progress today.

Click the image to open in full size.

It works!
Currently cooking on bench @1.65A, the output is solidly stable near Zero after proper trimmings.
Noticed the temp on the heatsink climb at a faster rate and plateau out quickly too.
Meaning i don't have to wait too long for the amp to get heated up to optimum temp.
Awaiting for the SLB, classis then go full bias!

Thanks NP and TA for sharing your design.
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Old 12th April 2020, 05:21 AM   #1777
twitchie is offline twitchie  Canada
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F6 Illustrated Build Guide
Fugly!!!

Those are some cool looking mosfet heatsinks but points deducted for such a clean bench!!! just kidding, I'm just super jealous
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Old 12th April 2020, 05:26 AM   #1778
meanie is online now meanie  Singapore
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They are made by Conrad Engineering.

350x151x50 dimension. Perfect for 25W classA applications.
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Old 12th April 2020, 05:24 PM   #1779
ItsAllInMyHead is offline ItsAllInMyHead  United States
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F6 Illustrated Build Guide
@Meanie - That is very cool! Thanks for sharing the source.

Also, thanks for the clear pics of the LED implementation. I had read Pico's post thoroughly. Technical piece flew a bit over my head, but I got the gist and began to understand TempCos and whatnot. Seeing it implemented now makes perfect sense from purely an execution standpoint.

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Old 13th April 2020, 03:33 AM   #1780
dcbingaman is offline dcbingaman  United States
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Hi guys. I have a whole set of F6 parts for sale - see my ad in the SWAP meet section. $200 with free shipping for the amplifier sections (almost all the parts you need to stuff the boards including the transformers). Another $50 will get you a stuffed power supply board + (2) IXYS Hexfred bridge rectifiers.

I have too many projects laying around to finish - someone needs to pick this up and run with it. I also have a notebook stuffed with documentation that I will throw in for free.
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