F6 Illustrated Build Guide

[6L6]

iFi will be a great preamp for F6.

 

[lukrez]

Thank again @itsallinmyhead & @6l6 - I'll go on with the speaker selection and then start also with the F6, at the moment the basic kit set for the F6 is not available... but I'll be notified. 🙂 Let's see how the amp (building) is going on... then a DIY pre-amp could be a good idea.

Again, thanks!

 

[Dennis Hui]

If you order the Pcb and Jensen transformer kit and the jfets from the store then the other electronic parts is a single mouser / digikey order. You will need to do that anyway for power supply parts.

Cheers,
Dennis

 

[YouAgain]

Hi Martin,

ItsAllInMyHead has given you lots of good suggestions.

Since you're in the EU, for power transformers I recommend Toroidy:

Transformatory toroidalne - Producent transformatorow Toroidy.pl

Cheers,
Dennis

I will second the recommendation for the Toroidy transformers from Poland. They will wind you custom voltages if you need and the quality and prices are excellent. I suggest getting the high grade options of electrostatic shielding, potting into the polished metal shell and the mounting frame for it and whatever else I may have forgotten about.

I've noticed good high quality products coming out of Poland. In addition to Toroidy, I can recommend Shipibo.Audio for DIY headphone parts and upgrades. Also Lampizator has amused me for years with their postings of DIY explorations that demonstrated their comitmant to quality that ultimately resulted in a HiFi company that has achieved success.

 

[laverda]

Here's another F6 just finished (well two days ago) built into a 5U case..

Sorry about the rubbish photos...

Sounding really really good straight off the bench. Takes a while for it to get going, 45 mins but when it does, really nice.

 

[meanie]

modding F6

^
I have been using different Mosfets in my F6, the FQH44N10 instead of the IRFP240.

Hi TungstenAudio,
I m thinking of modding my F6, Is the FQH44N10 a direct drop-in replacement?
Currently using 6.1V Zener, I probably will have to rebias again after the changes. What kind of bias current should I target for? My heatsink is around 45degC after hours of music on the IRFP240.

Is there anything else I can do for the F6?

Thanks.

 

[TungstenAudio]

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.

 

[meanie]

Thanks for your advice, @TungstenAudio!

 

[LATB]

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

 

[Dennis Hui]

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

 

[LATB]

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...!

 

[TungstenAudio]

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.

 

[meanie]

The 3 Led in series are able to squeeze into the zener location, makes install neat!

 

[meanie]

Make some progress today.



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.

 

[twitchie]

Fugly!!!

Those are some cool looking mosfet heatsinks but points deducted for such a clean bench!!! just kidding, I'm just super jealous

 

[meanie]

They are made by Conrad Engineering.

350x151x50 dimension. Perfect for 25W classA applications.

 

[ItsAllInMyHead]

@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.

 

[dcbingaman]

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.

 

[Nicky Hansen]

Bridging

Hi guys! Looking into a f6 build but the amp is under the mínimo watt limit of my speakers. With balanced input can it be bridged? Like the f4 o f5 ?
My speakers are 4ohm 30-160watt
I would do 2 stereo set into balanced bridge..

Thx guys

 

[Dennis Hui]

Accoring to here

FIRST WATT PRODUCTS

F6 does 50W into 4 ohms so it might be worth trying it as-is.