Mile, my problem isn't the trimmer sensivity but the high bias setting by me.Difficult setting due to resistors absence.
Finally i have add a 18R/5W resistor in series with the positive supply and i measure the voltage to calculate the current.
After bias setting this must be shorted.
In any case you will be surprise when i post results
Terry this pcb must be more robust especially into the mosfet area, use bigger (fat) traces.
Bimo, because i know nothing about simulation can you inform me what are the alternative parts?
Thanks all of you for your interesting!
PS. who can answer what is the absolutely maximum bias setting that is safe?
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My modification using bias servo, so it safe to set bias current high, but I recommended bias current is 150mA for compromise good THD and efficiency.
Maybe you can ask Prasi to make PCB layout.
Hi Thimios,
I did enlarge the power and output traces. I didn't think the gate needed more. I will try to populate tomorrow and give mine a go. I plan to use an ammeter on V+ to set the bias. Wish me luck.
Blessings, Terry
Please can you post the schematic?In any case as it, i don't think that is a high THD that is audible and the gole is to keep amplifier's character.
high bias test
Power Supply=+/-50v
offset about 7mV
Idle current about 280mA OR More... be carefull,not safe!
Input current=3mA
VAS current=4mA
VAS transistor=2sc3902.
Power Supply=+/-50v
offset about 7mV
Idle current about 280mA OR More... be carefull,not safe!
Input current=3mA
VAS current=4mA
VAS transistor=2sc3902.
Attachments
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Testing this on a real 3way speaker
In this test a real 3 way speaker used as load.
Bias=50mA
I must run this last test again because another, different divider, was used.
I hope that all these will be useful....
I would like to dedicate this work to a very good friend from Belgium who made me an incredible donation
He does not want his name to be published.
In this test a real 3 way speaker used as load.
Bias=50mA
I must run this last test again because another, different divider, was used.
I hope that all these will be useful....
I would like to dedicate this work to a very good friend from Belgium who made me an incredible donation
He does not want his name to be published.
Attachments
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I just use minimal bias on my 240/9240 amps.
Connect a speaker.
Turn bias to zero.
Apply signal, monitor output on scope.
Turn up bias until cross over distortion goes.
Simples.
Peavey use a similar method as they prefer lower bias currents.
I have try 5mA VAS current just now(4k7+4K7)but THD increased.
I will post the results latter.
Bias=50mA.
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