F6 Illustrated Build Guide

[2 picoDumbs]

Don't change anything till you do that

 

[tamra]

Well,yes.
Understanding schematics and measuring is always pleasure.
F6 looks simple to start to learn class A amplifier.

 

[2 picoDumbs]

Please report back what you have.
Adjust both pots to get at least 5V Gate to source on both mosfets.
You should have some current being drawn by the mosfets, maybe not much but at least something.

 

[tamra]

Thank you so much.
I am at work , come back home in 4 hours.

 

[meanie]

Hi Tamra,

Since there is no magic smoke, and the rail voltages are right.
You are so close to making it work.

Good advise from 2PicoDumbs, follow his lead and you will enjoy your F6 soon.

 

[Acoustic Emotion]

Dear audio friends,

It has been a half year from now that you guys helped me during the built of my First Watt F6, and due to several things in life I was not able to reply sooner than this.

I want to thank all of you who helped me during the build and faultfinding, without you guys I was lost. The result is an amazing amplifier, clarity, dynamic, and full grip on the bass! I never want to listen to music without the First Watt anymore!

For 2021 I am planning to build The Loudspeaker (Troels Gravesen's design), and for that I am planning to build two First Watt M2 monoblocks (Mountain View version).

For now, I am just enjoying the First Watt F6 together with the Discovery 3 way Classics, also designed by Troels. This is really a great speaker, very detailed, and the First Watt F6 is the best amplifier that was paired with it. It just does everything right! Even the sensitivity of the 3 way classics is only 88dB, it fills my small room (4x4 meters) with ease.

Again a big thank you to all of you who took the time to guide me, looking forward to a new project next year! :-D

Regards,

Koos

 

[2 picoDumbs]

Awesome

I love my F6 too.

 

[meanie]

@2picoDumbs,

May i know what bias level are you running?

I love mine @1.65A, but HS not up to spec.
Am thinking of a bigger sets of HS for F6...1.65A and beyond.

 

[2 picoDumbs]

1.8A
But anything between 1.5A and 1.8A is good.

In some respects it will be speaker dependent. On my 2.5 way speakers there is a real noticeable improvement going with a higher bias setting. On my high efficiency full range drivers the difference is less prominent.

 

[jameshillj]

Just add a small, quiet, slow, computer fan ...

 

[tamra]

I measured voltage between gate-source pins.
When I turn clockwise,led lights turn bright and voltage reduce. Turn anti-clockwise make led dark and rise voltage until 4.2v maximum.
So then I need to add one more Led?

 

[2 picoDumbs]

4.2 V is not adequate so you will need to add another led.

I am a little concerned that the LEDs are changing in light intensity. This shouldn't happen. Edit: Maybe you're just experience the slow turn on of the amp, which is normal for the amp.
The current through the LEDs should remain constant.

Please check all solder connections just to be certain there is nothing obviously faulty.

 

[2 picoDumbs]

Do you still have the light bulb tester connected?

If yes, then remove it.

Reset trimpots back midpoint and start again.

 

[tamra]

Removed bulb tester then adjust bias setting.
It's 0.5V, 0V between speaker posts.
The magical sound came out only left side.
I had spark around right side transformer before so I suspect transformer failer.
How can I measure to find fail at Jensen transformer?

 

[2 picoDumbs]

Sparks could be from either shorted solder joints or cold solder joints.

I noticed you had foil around the transformer. It might be a good idea to remove it.

There could be a problem with the transformer windings if it were dropped.

 

[tamra]

There is no sound from left speaker.
Right speaker is banging.

 

[2 picoDumbs]

What are the Voltages Gate to Source on the left channel?


When you say right side is banging, do you mean music is playing or banging in a bad way?

 

[2 picoDumbs]

How can I measure to find fail at Jensen transformer?

Initially you could just compare measurements between the good and the bad channel to see if anything is significantly different. Try that first

To test the transformer properly it is probably going to be best to remove it from the circuit.

 

[tamra]

Left speaker sounds great.
Gate-source pins have 4.2v.
It seems maximum.
Now,circuit breaker is sounding ham like zzzzz.
Its shaking, possibly the spark comes from there.
I will change the circuit breaker tomorrow.

 

[Spe@kerBox]

If one channel is still working I don't think the circuit breaker is the problem.