Minimum what you have to use for C3 is good polypropylene capacitor, you can go for more expensive one here, but I can't say abut differences.
I used paper-polypropylene-aluminium-oil here, as I got it as a gift.😉
Input selector with relays is a good choice.👍
Hi Pavel,
Nice to see you here. Output stage is stable, I use it to years with no problem.
I had a stability problem during designing the layout, it's sensitive how the different ground lines were layout, oscillation started between input and output, you can see the ground wires on the back of the PCB, that I changed the input grounding cutting printed ground lines and changing with wires.
Output stage did not have stability problem when I tested in separation on small temporary board.
Best wishes, Damir
Nice to see you here. Output stage is stable, I use it to years with no problem.
I had a stability problem during designing the layout, it's sensitive how the different ground lines were layout, oscillation started between input and output, you can see the ground wires on the back of the PCB, that I changed the input grounding cutting printed ground lines and changing with wires.
Output stage did not have stability problem when I tested in separation on small temporary board.
Best wishes, Damir
Some audiophiles prefer the sound of single ended triode amplifier even with a THD up to 1%. Reason and explanation, THD second harmonic is much higher then the rest of the harmonics.
John Broskie shows here: https://www.tubecad.com/2024/01/blog0593.htm a Harmonic Restoration circuits (why he calls restoration something what was not there on the recording?).
My preamps and amps are all type of PP where second harmonic is canceled to lower lever and it does not dominate FFT.
Here I use a current conveyor where second harmonic cancelation depends on transistors and CM resistors matching. I use 0.1% tolerance resistors there, but I unbalance same of those resistors, let say R14 in last GW schematic(I use 47k paralleled to 1k R14 resistor) I got this, first plot without the resistor and second one with, so called "Harmonic Restoration" active. I use a switch to activate it.
John Broskie shows here: https://www.tubecad.com/2024/01/blog0593.htm a Harmonic Restoration circuits (why he calls restoration something what was not there on the recording?).
My preamps and amps are all type of PP where second harmonic is canceled to lower lever and it does not dominate FFT.
Here I use a current conveyor where second harmonic cancelation depends on transistors and CM resistors matching. I use 0.1% tolerance resistors there, but I unbalance same of those resistors, let say R14 in last GW schematic(I use 47k paralleled to 1k R14 resistor) I got this, first plot without the resistor and second one with, so called "Harmonic Restoration" active. I use a switch to activate it.
Attachments
He calls it “restoration” because you say this.
Regardless, I kind of agree with you. Distortion is distortion.
In my case, and with some kinds of music, I want no distortion. Other times, 2nd harmonic distortion is very pleasant.
In general, I do not like circuits that favor odd harmonics because that tends to be dissonant.
This looks great, but why all your nice preamps have so low slew rate?
On your schematic this preamp have 35V/us.
Is't better to design high slew rate that is on full power 200V/us?
Faster slew rate means more dynamic, detailed music and you will hear some new music that you did not hear when using low slewrate preamp.
On your schematic this preamp have 35V/us.
Is't better to design high slew rate that is on full power 200V/us?
Faster slew rate means more dynamic, detailed music and you will hear some new music that you did not hear when using low slewrate preamp.
Dadod:
It's possible you might be able to learn to hear the difference with training, choice of test music and low enough age.
😉
If the slew rate really is 35V/uS for this design, for preamps for audio systems, this is not so "low".
Especially if the other factors have been appropriately weighted/dimensioned in the design execution.
Such as noise, linearity, power supply rejection, EMI immunity, recovery from clipping, etc.
Especially if the other factors have been appropriately weighted/dimensioned in the design execution.
Such as noise, linearity, power supply rejection, EMI immunity, recovery from clipping, etc.
I tested my preamp again and found that one capacitor(C6) per chanel is not needed even square vave is much better without it, so here is new schematic and square wave simulation.
This is now in use and I think is better sounding now, but the problem is I am quite old and I don't hier frequences over 14 kHz.
Damir
This is now in use and I think is better sounding now, but the problem is I am quite old and I don't hier frequences over 14 kHz.
Damir
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I prefar this one with no GNFB over the one CFA. I am planing to design SMD layout and eventually offer the board pupulated with all SMD components and left fo DIYers to finish with trough hole component. Now is very hard to find suitable trough hole transistors.
This is going to be the best headphone/line preamplifier ever.😉
I would like to hear if there is going to be interested for this kind of board?
Damir
This is going to be the best headphone/line preamplifier ever.😉
I would like to hear if there is going to be interested for this kind of board?
Damir
This is a good idea. However the SMD parts needed (e.g. SOT-23) won't be difficult to assemble. There are now various versions of your design around which one do you prefer?