I have finished constructing ZV9 recently.
The heatsink of my ZV9 is not big enough, so the heatsink become a little bit hot.
I removed R6 to reduce the bias current from 2A to 1.3A.
The heatsink is still hot, but I think it is within reasonable level.
There are three methods for choosing the value of R3 in ZV9 document.
I think two methods are only valid for 2A bias level.
So I hope to try 3rd method.
I do not have a distortion analyser, but I have a function generator and an oscilloscope with FFT function.
My plan is like this.
- Connect a 8ohm resistor at the output terminal of ZV9.
- Apply 1kHz sinewave to the input terminal using function generator.
- Adjust the magnitude of sinewave until the output power become 1watt(peak of output voltage is 4V).
- Adjust the R3 until 2nd and 3rd harmonics in output voltage become minimum.
Is this correct method for finding optimum R3?
Are there any other components(such as R17, R19) to be changed for new bias current level?
The heatsink of my ZV9 is not big enough, so the heatsink become a little bit hot.
I removed R6 to reduce the bias current from 2A to 1.3A.
The heatsink is still hot, but I think it is within reasonable level.
There are three methods for choosing the value of R3 in ZV9 document.
I think two methods are only valid for 2A bias level.
So I hope to try 3rd method.
I do not have a distortion analyser, but I have a function generator and an oscilloscope with FFT function.
My plan is like this.
- Connect a 8ohm resistor at the output terminal of ZV9.
- Apply 1kHz sinewave to the input terminal using function generator.
- Adjust the magnitude of sinewave until the output power become 1watt(peak of output voltage is 4V).
- Adjust the R3 until 2nd and 3rd harmonics in output voltage become minimum.
Is this correct method for finding optimum R3?
Are there any other components(such as R17, R19) to be changed for new bias current level?
you can do all that , but take care of fact that Iq and voltages are pretty much optimized for LU ........ say , sweet spot
for Iq change ,, you need to alter value of LU source resistance , then to introduce 200K trimpot (connectedd as variable resistor) between Q5 base and positive of C4 , and trim it to have approx. 23V at positive side of C1
all that referring to last schm in ZV9.pdf
I'm expecting things will get worse (sound)
before changing anything , try babysitter instead
for Iq change ,, you need to alter value of LU source resistance , then to introduce 200K trimpot (connectedd as variable resistor) between Q5 base and positive of C4 , and trim it to have approx. 23V at positive side of C1
all that referring to last schm in ZV9.pdf
I'm expecting things will get worse (sound)
before changing anything , try babysitter instead
Thank you, Zen Mod.
Your babysitter would be good solution for overheat problem.
But there is another reason why I reduce bias current.
In case of 2[A] bias level, output DC voltage of power supply is 40[V].
When it is reduced to 1.33[A], power supply voltage become 44[V].
Maybe two 160[VA] transformers used in my ZV9 do not have enough power capacity.
Bias current of ZV9 is 2[A]. But, bias current of F3 is 1.75[A].
I think 2[A] is not a only one point for 'sweet spot'.
That is why I've tried to reduce the bias current.
Your babysitter would be good solution for overheat problem.
But there is another reason why I reduce bias current.
In case of 2[A] bias level, output DC voltage of power supply is 40[V].
When it is reduced to 1.33[A], power supply voltage become 44[V].
Maybe two 160[VA] transformers used in my ZV9 do not have enough power capacity.
Bias current of ZV9 is 2[A]. But, bias current of F3 is 1.75[A].
I think 2[A] is not a only one point for 'sweet spot'.
That is why I've tried to reduce the bias current.
- Status
- Not open for further replies.