Nag,
Study all posts that have either conceptual or actually drawn circuits.
You have to have two feedback loops, one negative (voltage) loop and one positive (current) loop.
The circuit you are drawing here has no current loop. You have to measure the current through the load. This means that if you disconnect the load, there will be no positive feedback at all. This bit is critical and missing from your last schematic.
Sorry if that sounds cryptic but I don't think I want to give away more clues. As Nelson said, there is a post here that contains a decently working circuit. And there are at least three of them.
Study all posts that have either conceptual or actually drawn circuits.
You have to have two feedback loops, one negative (voltage) loop and one positive (current) loop.
The circuit you are drawing here has no current loop. You have to measure the current through the load. This means that if you disconnect the load, there will be no positive feedback at all. This bit is critical and missing from your last schematic.
Sorry if that sounds cryptic but I don't think I want to give away more clues. As Nelson said, there is a post here that contains a decently working circuit. And there are at least three of them.
Attachments
Hi All,
I got below from lt spice.
input impedance 11K.
output impedance -0.150ohm
8ohm load gain 14.665dB
4ohm load gain 14.760dB
2ohm load gain 14.918dB
If above is correct and I will post schematic if permission granted Mr.Papa or Zenmod.
Thanks,
Nag.
I got below from lt spice.
input impedance 11K.
output impedance -0.150ohm
8ohm load gain 14.665dB
4ohm load gain 14.760dB
2ohm load gain 14.918dB
If above is correct and I will post schematic if permission granted Mr.Papa or Zenmod.
Thanks,
Nag.
OK, I am lifelong Adoptee candidate (whom Papa is ignoring all the time ) , but I really have nothing with grants of that sort
however , as one of Greedy Boyz brigade I can tell -- feel free to post fruits of your work, just don't expect confirmation how close is to real F7
all rest of us can and will say is - will it work .....
however , as one of Greedy Boyz brigade I can tell -- feel free to post fruits of your work, just don't expect confirmation how close is to real F7
all rest of us can and will say is - will it work .....
f7
G'Day All,
I have been following this thread having built a F5. See attached schematic, disregard values and output Mosfets. the only problem is is i appear to have one more component to Papas design.... Note r16 and r17 would be a pot.
G'Day All,
I have been following this thread having built a F5. See attached schematic, disregard values and output Mosfets. the only problem is is i appear to have one more component to Papas design.... Note r16 and r17 would be a pot.
Attachments
Last edited:
I have never built an F7. I have no secret knowledge of a real F7.
I can tell you that a negative output impedance is probably a bad thing. Tweak your feedback resistors until you have some small positive output impedance that suits you.
A negative output impedance may indicate too much positive feedback which could indicate that you have built an oscillator.
You have probably the right amount of pos feedback, when the signal at the output is with 8 Ohm speaker load 2db higher than without.
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At which higher value of R6 [ >0.3 Ohms] does the simulation predict oscillation due to a resultant increase in the extent of positive feedback?
With no load you should have around 2dB less gain, because the pos feedback is not effective.
Instead of thinking of R6 as a variable to manipulate, R5 and/or R7 should be the variable(s). Just a thought.