thinking about building a F6 would increasing the rail voltage increase power output like you do in the f5
Watch out for the voltage rating of the input fets. I think the F6 would be current limited at
higher rail voltages, especially below 8 Ohms.
Last edited:
There is a short explanation in the BOM...Those using the originally specified 5.1 didnt supply enough voltage to reach full bias. It goes on to note that those who used the 9.1v version have had no issues. That's what I prefer, no issues so that's what is on my boards.🙂 Of course this build thread isnt about using Laterals...Good old IRFP240.
Russellc
Last edited:
If you pull the Zener out with just the pot the max voltage drop across the pot is around 7V so having a 9V Zener doesn't make sense (to my understanding) the way the circuit is configured. The main thing is if you only need around 5.5 volts for biasing, then adding a 9V zener makes things a little more difficult to adjust (but I'm anal bastard), it also puts you at risk of destroying the devices.
I was always told to scale my graphs properly at school, after a while I understood what they were saying. I try to do the same thing in my amps ie custom to my requirements.
If people understand the reason for other people's choices then everyone learns and can make informed decisions.
Either way you set it up it won't affect the performance of the amp, I just have a certain way of doing things.
Last edited:
Me too, the certain way for me is that which has proven most successful! 6L6 has built many, many more Pass devices than I and he has never led me astray in these builds. I find second guessing at my level of understanding things electronic usually leads to rebuilding it the way I should have in the first place. Desoldering is my least favorite activity! Why do I do it that way?Well it has apparently been documented that the 5.1 has resulted in trouble for some builders while the 9.1 has not. Those with better ideas can be free to deviate. Maybe 6L6 will comment, seems like this very discussion happened once before on either this thread or the initial F-6 thread. The results of that conversation cemented my decision to go with the 9.1. At least the Zener is an easy desolder if it should prove necessary. I doubt it will.
Hows your F-6 coming along? I'm at a standstill waiting for more chassis in the store, and play money in my hand. 🙂
Russellc
Last edited:
hogwash
all we need is some simple logic
10K from 23 to 9V1 will let 1,39mA through
5K pot across 9V1 will eat 1.82mA ........... if available ....... which isn't
so replace 10K with 3K3 , put 6V8 zenner and there you go
that way :
3K3 will let ~5mA through , from 23V to 6V8
5K will bleed 1.36mA across 6V8 , leaving (5-1.36)mA through zenner , absolutely stable
all we need is some simple logic
10K from 23 to 9V1 will let 1,39mA through
5K pot across 9V1 will eat 1.82mA ........... if available ....... which isn't
so replace 10K with 3K3 , put 6V8 zenner and there you go
that way :
3K3 will let ~5mA through , from 23V to 6V8
5K will bleed 1.36mA across 6V8 , leaving (5-1.36)mA through zenner , absolutely stable
I have the boards and transformers just need to complete an order for parts.
Trying to do the order carefully so it covers all my unfinished projects not just F6.
Zenmod, you certainly are light years ahead of me, but if nothing is there to be available, how is it that it is working? ( or so I'm told by notes in BOM ).
As previously stated, my boards are assembled, but that's it...nothing to measure.
So I should order 3K3 resistor to replace 10K, and 6.8 zener to replace 9.1? Should BOM be modified? With as many finished amps that are out there, could someone comment as to their measurements and part choices?
What values are in factory version using IRFP240 outputs?
Oh, and as to 10k to be replaced, just R9 and R10, or are R7 and R8 required to be changed out as well?
Thanks in advance for any additional clarity,
Russellc
Last edited:
It's working like I explained. If you take the Zener out you have around 7 to 8 Volts across pot. So thats why it works.
Do it like Zen Mod says. His is the correct approach.
Do it like Zen Mod says. His is the correct approach.
resistor 10K could be practically replaced with anything from 2K7 to 5K1 ...... but shooting at 4-5mA is best from several reasons (Tempco , noise blahblah)
zenner (for mosfets!) could be replaced with anything from 5V6 to 6V8 , if we are speaking of standard zenner values
or put 3pcs green LED in series , having 3 x 1V93
BOM ?
I don't care for BOMs ..... yrs ago I decided to learn from schematics and just having finished amps is not more interesting than making them
so - schmtc is object of dreaming ...... print 20 copies , put one in each place where you can meet it and stare at it
when you dream enough , BOM is produced in your head
zenner (for mosfets!) could be replaced with anything from 5V6 to 6V8 , if we are speaking of standard zenner values
or put 3pcs green LED in series , having 3 x 1V93
BOM ?
I don't care for BOMs ..... yrs ago I decided to learn from schematics and just having finished amps is not more interesting than making them
so - schmtc is object of dreaming ...... print 20 copies , put one in each place where you can meet it and stare at it
when you dream enough , BOM is produced in your head
The one on the very first post of this thread. My boards are also store boards
here as well.
It say "Nelson Pass 2014"
Thanks
Russellc
Last edited:
The 10k resistor directly from psu, is the one you change.
The 10k resistor connected to 1000uF leave exactly the way it is (do not change that one).
The 10k resistor connected to 1000uF leave exactly the way it is (do not change that one).
resistor 10K could be practically replaced with anything from 2K7 to 5K1 ...... but shooting at 4-5mA is best from several reasons (Tempco , noise blahblah)
zenner (for mosfets!) could be replaced with anything from 5V6 to 6V8 , if we are speaking of standard zenner values
or put 3pcs green LED in series , having 3 x 1V93
BOM ?
I don't care for BOMs ..... yrs ago I decided to learn from schematics and just having finished amps is not more interesting than making them
so - schmtc is object of dreaming ...... print 20 copies , put one in each place where you can meet it and stare at it
when you dream enough , BOM is produced in your head
Thanks ZM. Your explanation has really helped me.
Correct me if my understanding is incorrect but using the values you mention now allows the zener to act like a voltage regulator in this branch of the circuit. Right?
Now could you help me to figure out from this how to calculate the turn on Vgs needed for the IRFP240 fet which I believe is about 4.5V?
Thanks. Nash