F6 Illustrated Build Guide

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#961
Around hour ago finished one channel PCB and PSU, connect them together and looks that everything is working, but looks like that amplifer produce only less than watt at output (<1watt) 🙁
Output mosfets are hot, BIAS are 0.5V and offset around zero. I try to play some music via it, but it too quiet...

Look's like first issue when i have trouble with zeners, now i'am using LM329, i cut first pin and use another two like generic zener, resistor are 3.3k.

What problem that may be? Maybe you tell me what measure in control points?
Thank you!
 
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#963
6L6 said:
What input are you giving it?

Please post some well-lit, in-focus photos.
Click to expand...

I don't think that photos something change. I need to measure, but measure what? Hmm.
Input connected to Apple iPhone 7.
Anyway when i touch +IG (input positive) by screw i won't feel that 25watts (class A) in my speakers.

P.S One moment i add photos...
 
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#965
6L6 said:
We can't help without photos. If bias and DC offset measure OK you most likely have a wiring error.
Click to expand...
https://i.imgur.com/xowP6Jl.jpg
https://i.imgur.com/Hx86NQa.jpg
https://i.imgur.com/PUVStXt.jpg
https://i.imgur.com/HJKnyjn.jpg

Images added, but it's look's like with my first issue when i build my first F6 build, now i'am solder precision components, but again back to the roots... 😀

Also, you remind me something, try to connect to DAC instead of the phone and report here.
 
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#967
Connected to DAC and... problem is solved.
Okay.
One question. Can i use 5.1V (or 6.1V) zener with 3.3k resistor? I'am currently do not have LM329 to make two channels identical.

What is the value of your installed gatestopper resistors? R11 and R12
Click to expand...
Vishay Z-Foil (TX2575) 47ohms 1/4w 0.1%
 
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#970
Yes, but 5.1V may or may not be enough to bias correctly
Click to expand...
Thanks, i understand that after that moment when i solder 5.1 v zener, so i cut it and solder to leads 6.1V zener, to avoid damage to PCB holes.
Input JFETs are seems to me fakes.
Or these are LSK ones?
Click to expand...
LSJ74/LSK170 Directly from LinearSystems.
IFRP240 from DiyAudioStore.
I absolutely hate fakes.

Now it's time:

1) To understand where is bass and what happen with sound quality (i know that amplifer can deliver exceptional quality), i already swap two pair of capacitors, but that won't solve problem, because very strange that Z-Foil resistors sound worse instead of Vishay / Dale MF60.
2) Think how to mount all inside amplifer enclosure, PCB standoffs, wires, back panel wiring e.t.c

Anyway Vishay / Dale MF60 awesome resistors for their price and they sound nice too!

k43JFgQ.jpg
 
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#971
The TC2575 don't usually make good gate stoppers - far too bright (for me, anyway), and the value could be higher too - they also take an age to settle down - I would also suggest you don't use susumi's either

Kao carbon's or Manganin's are good here, but can't really go wrong with the RN60's
 
#972
As i understand R5, R11, R12 (F6 Mosfet version) is only on signal path all other resistors are "third-party".
And again i swap capacitors, i put my lovely Nichicon FG 1000uF 25V.
Maybe i'am wrong but my ears make following conclusion, Z-Foil sound too clinical (sterilely).
So how about PR9372 in sound signal path if no, then downgrade to MF60.
 
#976
Spend around 6-7 hours today for listening tests, desoldering/soldering and i get what i want!
Solder to (R1, R2, R3) Panasonic 3W Metal Oxide Film Resistors and success! Yay! 🙂

Next try to swap again back R5, R11, R12 to Z-Foil, maybe it's improve sound quality, currently it's PR9372 resistors.

Also i remember one note from vegalab forums member, that mostly all resistors acts same in low's frequencies, but may differently in mid and high's.
 
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#978
reference schematic is ?

no way that you're going to add trimpot at C2 ....... maybe across it etc.

but , from experience , precision is half of job done , so let be precise in question ....

I'm sure there is somewhere Zen Amount Pot , and I believe that's reply you're looking for
 
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