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Old 23rd April 2013, 10:03 PM   #751
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Thanks, design without boundaries, i start to like it.
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Old 23rd April 2013, 10:05 PM   #752
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Quote:
Originally Posted by Stefanoo View Post
EDIT: I have the prototype running that way and output offset is about 1mV!
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ok now I agree with this
Wow, finally The main point is, we are looking for the best solution, not for one that works (only)
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Old 24th April 2013, 03:47 AM   #753
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Wow, finally The main point is, we are looking for the best solution, not for one that works (only)
Yes we are looking for the best technical but mostly sounding solution.

For instance I have checked the bias on the IF3602 and it is lower than what I thought with only 16mA.
In this case however is not so high, the big difference in sound was made by part itself!
In short, maybe this buffer with this part might not be the top or the best in term of specs, nevertheless if it will end up sounding better than Calvin for instance, I would have no indecisions in choosing this one over the latter although it has better specs.
Just to give you a background on my philosophy in this design and I think that here we all agree on that which is pretty amazing.

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Old 24th April 2013, 02:18 PM   #754
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Question:

is there a particular "optimum" voltage for thermal stability to create on the emitter resistor of the current mirror?
Maybe we can select better values on the mirrors.
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Old 24th April 2013, 03:44 PM   #755
MiiB is online now MiiB  Denmark
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I believe that the most important part is that you have same beta in all mirror transistors, making quad arrays a very good choice, in some of my paradise variation i have used 3906/3904 quads with good results. I have always used about 120 ohms as degeneration, this is solely based on experience. In power-amps with larger currents I use smaller, in order not to loose to much rail voltage.
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Old 24th April 2013, 03:50 PM   #756
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I believe that the most important part is that you have same beta in all mirror transistors, making quad arrays a very good choice, in some of my paradise variation i have used 3906/3904 quads with good results. I have always used about 120 ohms as degeneration, this is solely based on experience. In power-amps with larger currents I use smaller, in order not to loose to much rail voltage.
makes total sense.

What is the manufacturer for the semiconductors you are recommending?
I would like to check the specs out.
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Old 24th April 2013, 04:08 PM   #757
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one thing that might make quad not usable here is power dissipation.
Some of the devices on the mirror dissipate up to 400mW, which is not possible for a plastic IC.
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Old 24th April 2013, 04:33 PM   #758
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A dip8 can do 1W.
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Old 24th April 2013, 04:56 PM   #759
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A dip8 can do 1W.
oh really? Didn't know that.
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Old 24th April 2013, 11:24 PM   #760
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I also think 120 Ohm is about optimum. Making it much smaller will amplify the noise of the mirror, not a big problem in power amps but here i think it is critical not to worsen the noise of the input stage. Making it bigger makes the output impedance of the mirror higher
and yes, it will eat up some dynamic range. The output impedance of this cascoded mirror is already sky high so i think we are fine.
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