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F6 Illustrated Build Guide
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Old 13th September 2015, 03:03 AM   #21
zeepup is offline zeepup  Canada
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thinking about building a F6 would increasing the rail voltage increase power output like you do in the f5
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Old 13th September 2015, 03:21 AM   #22
rayma is online now rayma  United States
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Quote:
Originally Posted by zeepup View Post
thinking about building a F6 would increasing the rail voltage increase power output
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 by rayma; 13th September 2015 at 03:23 AM.
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Old 13th September 2015, 03:27 AM   #23
zeepup is offline zeepup  Canada
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Originally Posted by rayma View Post
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.
maybe i should stick to the f5 then
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Old 13th September 2015, 04:02 AM   #24
Russellc is offline Russellc  United States
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Originally Posted by 2 picoDumbs View Post
An explanation about why you chose 9V Zener could be useful.
Eg If someone is useing lateral mosfets or some other device, then 9V wouldn't really be optimal.

The back panel kit link takes you to ACA. Is this kit still available in the store?
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.

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Last edited by Russellc; 13th September 2015 at 04:04 AM.
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Old 13th September 2015, 05:49 AM   #25
2 picoDumbs is online now 2 picoDumbs  Australia
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Quote:
Originally Posted by Russellc View Post
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
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.
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Last edited by 2 picoDumbs; 13th September 2015 at 05:53 AM.
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Old 13th September 2015, 04:27 PM   #26
Russellc is offline Russellc  United States
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Originally Posted by 2 picoDumbs View Post
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.
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.



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Last edited by Russellc; 13th September 2015 at 04:30 PM.
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Old 13th September 2015, 04:37 PM   #27
Zen Mod is online now Zen Mod  Serbia
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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
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Old 13th September 2015, 08:49 PM   #28
2 picoDumbs is online now 2 picoDumbs  Australia
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Quote:
Originally Posted by Zen Mod View Post
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
Very nice explanation Zen Mod. This is the preferred approach.
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Old 13th September 2015, 09:03 PM   #29
2 picoDumbs is online now 2 picoDumbs  Australia
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Quote:
Originally Posted by Russellc View Post
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
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.
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Old 13th September 2015, 09:20 PM   #30
Russellc is offline Russellc  United States
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Quote:
Originally Posted by Zen Mod View Post
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
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
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Last edited by Russellc; 13th September 2015 at 09:27 PM.
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