637 Amplifiers

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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.
 
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?
 
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!
 
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)
 
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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.
 
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.

yes, I will try to put the line for even greater JFET, will try at 5mA for each JFET!

ok, the constant current source, I will simplify it! use transistors OPAM probably more appropriate!

thank you, if there are any more ideas, will you just show me!

thanks appreciate your feedback!
 
yes, I will try to put the line for even greater JFET, will try at 5mA for each JFET!

But focus on distortion because higher current doesn't mean lower distortion. I usually check every transistors' parameters to put each transistor at their best operating condition. I can get 1% with 3.5mA (half of it for each JFET).

ok, the constant current source, I will simplify it! use transistors OPAM probably more appropriate!

You know what, if I ever ordered PCB (in big quantity), I will design a PCB that can be used for most topology, any current source, etc etc... One PCB for all projects.

There is nothing wrong with complex CCS circuit board as long as we can substitute it with simpler CCS, such as one single resistor ;)
 
But focus on distortion because higher current doesn't mean lower distortion. I usually check every transistors' parameters to put each transistor at their best operating condition. I can get 1% with 3.5mA (half of it for each JFET).

I will try to 4mA for a JFET, and measured

You know what, if I ever ordered PCB (in big quantity), I will design a PCB that can be used for most topology, any current source, etc etc... One PCB for all projects.

There is nothing wrong with complex CCS circuit board as long as we can substitute it with simpler CCS, such as one single resistor ;)
the pcb simple for me
 
I am not sure if we can perceive the difference, because the standard CCS are already silent.

I think we can perceive the difference, but it is so subtle that I don't want to go the extra mile. If I ever built my own PCB, I will stick with the dual transistor ccs (on the left of the attached picture)
 

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what ccs do you like??

In the past I like the sound of LED-based ccs. Even now I think LED is good for sound :D But nowadays I don't want to waste time getting the most out of ccs (because I can waste my time getting the most out of amp circuit, with ccs replaced with simply a "current source" in a simulator, hehe).

Also, JFET has never let me down for ccs, except for the "price".

One of my latest AlephJ uses resistor as the current source.

Currently I have been thinking about finding special LED or zener that has good properties for sound. Then I will use it everywhere by putting it in series with a resistor (the resistor will set the required voltage). But I don't know the theoretical effect of such approach.
 
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