F6 Illustrated Build Guide

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TungstenAudio

Member
Joined 2014
One of the simplest tweaks is to replace the bias setting zener diodes with three small green LEDs in series. These have better voltage regulation and a negative temperature coefficient.
The F6 can run very well at +/– 26V, and at bias currents of 1.8A. At that power level, the LED bias circuit lets the amp reach thermal equilibrium more quickly, and with greater stability.
I will also recommend FQH44N10 output Mosfets. They have much higher trans conductance than the standard IRFP parts.
 
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edwinjones4

Member
Joined 2021
@DennisHuit,

Let's try that again:

583987D0-E869-4A3F-A2A3-419008675E01.jpg
 
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Sunscreen

Member
Joined 2021
Does post number 3 have the parts list for the power supply board. And I'm assuming that it is the power board offered on the DIY audio website?

What transformer do i need and where do I order it from? A list of the other parts would really help as well, thanks.

I figure why not dive in. So I plan on building the power supply first.

Thanks in advance for the help I'm going to be needing
 
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chanthing

Member
Joined 2013
Sunscreen said:
I was wondering how much of a sonic listening difference there is between the F6 and the Amp Camp Amp. I've built a few DIY kits, but never one I had to part out myself. So I'm a little nervous.

I plan on starting a ACA soon but I would like to explore the F6.
Click to expand...

I went from ACA monoblocks to an F6 and the difference with my relatively inefficient speakers is substantial.

Aside from the complications of putting together the power supply, imho, the assembly of the F6 is not that different or harder than the ACA. The materials here on both the F6 and the power supply (using the DIY audio store board) are extensive.

I posted this information previously about parts not included in the kit that you will want to acquire: https://www.diyaudio.com/forums/pass-labs/371008-f5-f6-power-supply-guidance-2.html#post6620430. You will also need appropriate fuses.

Good luck!

-- Thing
 
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chanthing

Member
Joined 2013
Sunscreen said:
Does post number 3 have the parts list for the power supply board. And I'm assuming that it is the power board offered on the DIY audio website?

What transformer do i need and where do I order it from? A list of the other parts would really help as well, thanks.

I figure why not dive in. So I plan on building the power supply first.

Thanks in advance for the help I'm going to be needing
Click to expand...

I used AS-3218 - 300VA 18V Transformer - AnTek Products Corp, but it is unfortunately out of stock at the moment, as is the 400VA version.

Also, the advice from poseidonvoice about moving slowly and with intention cannot be emphasized enough. Understand the schematic and it's relationship to the PCB before starting. Enjoy the process.

FWIW, I built mine with the 3 LEDs for bias instead of the Zener. Just be careful of the polarity as it will be reversed from the zener. There's a post with a picture somewhere in the F6 thread that covers this. When in doubt, ask. There are some awesome folks here that are generous with their knowledge.

-- Thing
 
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edwinjones4

Member
Joined 2021
poseidonsvoice said:
Edwin Jones the 4th,

R7 and R8 ideally should be 3K-5K (most choose 3.3K) to make biasing easier.

Z1 and Z2 can be anywhere from 5V to 9V, but most choose something like the 1N4733 which is 5.1V.

The F6 is a very fluid design, as such many of the parts can be deviated quite a bit and still have a working amplifier. The fluidity of the design also assists in encouraging considerable experimentation, like completely changing the input stage or using degeneration resistors with the output devices, etc...done properly, no F6 build should sound completely alike but all will sound quite 'good'!

Please double check and measure all your resistors with a DMM prior to soldering them. Ideally, one should measure caps, diodes, etc...as well but not all newbies have that capability. Set the pots, P1, P2 for 2.5K ohms or less (which is in the middle of its range) prior to turning the amp on. Make sure Q3 is a K170 and Q4 is a J74. Make sure they are matched pairs. Note the locations of Q3 and Q4 are different on each board.

Make sure you have tested your power supply first prior to connecting it to the main amp boards. You should get +/- 22 to +/-28V DC without question. Design spec is about +/-24V DC. After that is done, move on to connecting it to the main amp board. Use a variac or build a dim bulb tester for initial testing.

The 1st page of this thread has a lot of this advice. Read it several times and try to understand it. The F6 is less of a cookie cutter in design than the ACA is. Newbies tend to fail because they may make erroneous assumptions. There is less hand holding compared to the ACA, and the fact that you have to build your own supply and test it is also a pitfall. Realize that the F6 (and most Pass designs especially for newbies) is actually 2 project learning curves at once. The first is the F6 board itself. The second is building and testing a linear power supply which should be done first.

Ask Questions first, solder last. Be really, really, anal retentive! You need to be 100% sure the part is right prior to soldering it to the board. And practice soldering prior to soldering on any of the DIY Audio store based boards. Use flux if necessary.

DO. NOT. RUSH.

Good luck,

Anand.
Click to expand...

@Anand,

Thanks for the response Z1,2 = 1N4733A-TAP and catching my mistake on R7/8. Would an acceptable part number for R7/8 = CMF553K3000FKBF?

See revised part list below:

Amplifier Part Description Mfr. #
R1 0.56ohm 3W (ERX-3SJR56A)
R2 0.47ohm 3W (ERX-3SJR47)
R3 100ohm 3W (CPF3100R00FKE14)
R4 18ohm (RN65D18R0FB14)
R5 1K (CMF551K0000FEEK)
R6 47K (CMF5547K000FHEK)
R7,8 3K3 (CMF553K3000FKBF)
R9,10 10K (CMF5510K000FKEA)
R11,12 110ohm (CMF60110R00FKEB)
R13 10K-15K (CMF5515K000FHEB)
P1,2 5Kohm 25 turn Bourns 3296W or equivalent (3296W-1-502)

Capacitor Part Description
C1,2 1000uF 25V (493-14501-ND)

Thank you
 
poseidonsvoice

poseidonsvoice

Member
Joined 2004
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Edwin Jones the 4th,

That part number for R7/R8 (3.3K ohms) looks good.

You can go dual mono on the Toroids if you like and have space. That being said, I am more interested in you getting the thing safely running first, then tweaking or doing another build if you like. You may or may not love DIY like the rest of us, so no use assuming.

Best,
Anand.
 
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edwinjones4

Member
Joined 2021
poseidonsvoice said:
Edwin Jones the 4th,

That part number for R7/R8 (3.3K ohms) looks good.

You can go dual mono on the Toroids if you like and have space. That being said, I am more interested in you getting the thing safely running first, then tweaking or doing another build if you like. You may or may not love DIY like the rest of us, so no use assuming.

Best,
Anand.
Click to expand...

Much appreciated. I actually have the antek 4218 up and running (the LED's on the PSU v3 are lit anyway). Additionally, I have the soft start board in front of the 4218...both the soft start board and PSU seem to be functioning/measuring correctly.

I used a dim bulb tester to ensure nothing was wrong, prior to hooking up my previous F6 board. Unfortunately, I realized the LED's were installed backwards and I wasn't able to successfully unsolder them without damaging the board.

Since I'm starting over (again) I wanted to build them using blue LED's, and I hope the part I purchased will work (word on the street is that the amp sounds best with blue LEDs ;))

D1 = C5SMF-BJF-CR0U0352

I'm in the process of moving and the PSU is in storage for the next week or so; otherwise, I'd share pics of the build progress.

Thanks again for the support!
 
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TungstenAudio

Member
Joined 2014
Sunscreen,
You may share a single power supply between two channels, or build a separate one for each channel. A dual-mono configuration refers to a pair of channels and their supplies in a single chassis.
It will be easier to start with a single, shared PSU for both channels. Ultimately, the best sound will come from separate supplies for each channel.
 
thompsontechs

thompsontechs

Member
Joined 2019
Ya, they are still out of the 18v 300-400va. I have one 300VA 18v, but I like a little more than less. I also have a couple of 22, but I would have to try and drop it a bit. Other than cutting them open and cutting on the secondaries, which is not happening, I will probably build with the 300VA 18V and design for a bit more and swap later.

JT
 
Z

zman01

Member
Joined 2011
JT,

A suggestion for the transformers with 22V AC secondaries that you you have - if you use them with an SLB power supply, there should be a drop of ~4V, and that should bring the voltage in a useable ballpark for the F6. If you have an SLB power supply, you can connect it with the transformer with load, and see what voltages you get.

With a standard power supply 300VA, 2 x 18V secondaries will work fine too. If you feel you need a bigger transformer you can always get one later - just leave enough space in your build.

Spe@kerBox,

You are using a CRC type power supply for your build?
 
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