F5 power amplifier

[nigelwright7557]

Originally Posted by tinitus

I dont think you should do that without monitoring bias at the same time

But now I talk about something Im not sure about, as I havent built my F5 yet

I usually turn the bias down to zero first then set the DC offset before attaching a speaker.

Then I put a multimeter across a source/emitter resistor and set it to just get rid of crossover distortion on the scope which is usually around 5mV across 0r22 resistors.

If its a new design i would then put a household iron on the heatsink and make sure the bias doesnt do anything silly as the ehatsink heats up.

[bluewater]

My other channel (right) is working great. The one that is having the problem (left channel) was working great. It actually sound better the other (right) channel. I'm not sure but where all the values were 2.2k they were brought up to 2.21k ohms.
Anyways I'm wondering if there is a way to trouble shoot my problem. I can turn it on with the input isolated and doesn't seem to hurt anything. Is there a way to check for voltage drops to find out if the jfets are causing the issue or could it even be part of what is causing my problem?

[tinitus]

Just read the F5 manual
You get zero DC when both bias trimpots are balanced
If you have DC problems, I suppose one half/side is not right
Or you may have very poorly matched Jfets
Or maybe too much heat from your soldering

Even if you think your soldering is perfect, you might be surpriced if you look through a magnifying glass
Or you may find a small bit of solder waste making a shorting
I check ALL my solder joints carefully with magnifying glass, and proper light
Just a thought

[joselito-1988]

i have a problem guys. i need to the data sheet of my f4-1600 4 channels... my firend had it and it blowed a transistor, he took all of them off and to use it for parts... now i have it and need to change all of the transistors can any of u help me??

[bobodioulasso]

Download the pdf there and you will have the F4 schematic

First Watt: Products: F4

[jacco vermeulen]

Oye Joselito,

este forum es para los amplificadores caseros de Nelson Pass, no para esos en coches, este de usted es un amplificador del coche.

[bobodioulasso]

Cuantos lenguages puedes hablar?

[Zen Mod]

Jacco is nuckin futz , in any case .

[Audiofanatic]

Hi Jacco, dejate de eso hombre Help hem even met zijn F4

Back to topic.
"Bleuwater"
Perhaps one of the output transistors is tighter than the other? That way you'll have a difference in cooling the device which will give you DC offset.

Just my 2 cents.

Best regards,


Audiofanatic

[alazira]

Originally Posted by Zen Mod

just trow them in , and follow biasing procedure .

instead of one IRF(P) pair - it's wise to use at least two pairs of laterals , because of xconductance ( lacking in laterals) .

all these questions are beaten to death in this thread ..... twice or trice .....

make it more fun - make two F5s with one supply - one with verticals , one with laterals; connect one to PSU and listen ..... change to other one and listen

use same gate stoppers for both iterations - varying them +/-50% you'll not hear difference .

Hi ZM

Please excuse me if this is a silly question, but can the mosfets share the gate (R13&R14) and source resistors (R11&R12) or do they each need their own? I was planning on trying other variations (i.e. 20R/100R feedback) but NP's comment has intrigued me.