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Old 4th July 2012, 08:50 AM   #41
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Hi destroyer!

I'm trying to make an amplifier based on things already available,
I will try to learn more and practice more!

Thank you!
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Old 4th July 2012, 08:59 AM   #42
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Default This approach is very good..... i do believe you will have nice results

Congratulations.

regards,

Carlos
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Old 4th July 2012, 09:02 AM   #43
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by quanghao View Post
I have complete amplifier circuit diagram, I'm doing to try and test measurements.
I have given up the high distortion first stage JFET amp. Please measure the distortion of the first stage. You might want to connect the zener of the BJT cascode to JFET sources. To lower the distortion from the JFET, you need to bias it very high (14mA is top). If you can do it, this will get my vote and I will build the amp, no matter the simulated performance as long as reasonable as an amp. If not (not low distortion at JFET stage), it will be just another Goldmund clone.
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Old 4th July 2012, 09:12 AM   #44
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Quote:
Originally Posted by Jay View Post
I have given up the high distortion first stage JFET amp. Please measure the distortion of the first stage. You might want to connect the zener of the BJT cascode to JFET sources. To lower the distortion from the JFET, you need to bias it very high (14mA is top). If you can do it, this will get my vote and I will build the amp, no matter the simulated performance as long as reasonable as an amp. If not (not low distortion at JFET stage), it will be just another Goldmund clone.
yes!

14mA for J-fet ???

why you like it is big?
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Old 4th July 2012, 09:18 AM   #45
Jay is offline Jay  Indonesia
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Originally Posted by quanghao View Post
yes!

14mA for J-fet ???

why you like it is big?
If you can make the distortion low with 1mA, that's better. The point is the distortion not current. It just happens that JFETs like high current.
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Old 4th July 2012, 09:44 AM   #46
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Quote:
Originally Posted by Jay View Post
If you can make the distortion low with 1mA, that's better. The point is the distortion not current. It just happens that JFETs like high current.
1mA for each j-fet, is simple, but are sure it will be better than 2mA? you can show me something you did with fet j?
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Old 4th July 2012, 09:49 AM   #47
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Default I will look forward to your progress

I do not like the CCS...too much complicated....too many parts.... to small result compared to the added complexity.

Well...this is something that cannot kill your design...but make it larger, more expensive and complicated to build.

regards,

Carlos
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Old 4th July 2012, 10:13 AM   #48
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Originally Posted by destroyer X View Post
I do not like the CCS...too much complicated....too many parts.... to small result compared to the added complexity.

Well...this is something that cannot kill your design...but make it larger, more expensive and complicated to build.

regards,

Carlos
yes, I know it, but the simple css would cause a great noise!

I want it clean as possible? How do you think of this?

thanks your advance!
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Old 4th July 2012, 10:15 AM   #49
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Quote:
Originally Posted by quanghao View Post
1mA for each j-fet, is simple, but are sure it will be better than 2mA? you can show me something you did with fet j?
Just measure THD at the output of the first stage (i.e. between Q2 and R6), or between JFET and Q2, you will be surprised. Running higher current is the best way to lower the distortion.

If I'm not mistaken, the latest versions of Goldmund have higher current. (ADD: 2mA in Mimesis3, 4.5mA in Metis3. But it doesn't mean that Metis is better)

Last edited by Jay; 4th July 2012 at 10:19 AM.
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Old 4th July 2012, 10:28 AM   #50
Jay is offline Jay  Indonesia
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yes, I know it, but the simple css would cause a great noise! I want it clean as possible? How do you think of this?
I thought the complex CCS was for stable current (The effect of current variation is not good).

I want to listen to LM317-based current source someday. I'm curious why it is not widely used. It is noisy, yes, but leds are noisy as well but are still good sounding.
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