This is my take on the well-known Elektor PreConsonant phono stage. It has been fully built and tested; in fact, I am using it as my main phono stage at the moment. I have finally got around to correcting small silkscreen errors on the PCB, and now I feel comfortable sharing it with the community.
This is what an assembled PCB looks like:
Thanks to @vsmusic for inspiration, it was his post about the PreConsonant over at Lenco Heaven that started my addiction to DIY phono stages, and I even learned how to use KiCAD to design my own PCBs.
I also designed a very simple discrete voltage regulator to go with it. It probably does not perform as well as common 3-pin regulator ICs, but I wanted to use a 24V AC wall-wart that has very poor load regulation. Its no-load voltage is almost 30V, which after rectification exceeds the maximum input voltage of something like a 7824 or LM317. In use I cannot detect any PSU-related hum even with my ear right against the speaker.
Gerbers, BOM and build notes are available here: https://github.com/SpinningVinyl/PreConsonant2021
Gerbers and BOM for the PSU: https://github.com/SpinningVinyl/PreConsonantPSU
This is what an assembled PCB looks like:
Thanks to @vsmusic for inspiration, it was his post about the PreConsonant over at Lenco Heaven that started my addiction to DIY phono stages, and I even learned how to use KiCAD to design my own PCBs.
I also designed a very simple discrete voltage regulator to go with it. It probably does not perform as well as common 3-pin regulator ICs, but I wanted to use a 24V AC wall-wart that has very poor load regulation. Its no-load voltage is almost 30V, which after rectification exceeds the maximum input voltage of something like a 7824 or LM317. In use I cannot detect any PSU-related hum even with my ear right against the speaker.
Gerbers, BOM and build notes are available here: https://github.com/SpinningVinyl/PreConsonant2021
Gerbers and BOM for the PSU: https://github.com/SpinningVinyl/PreConsonantPSU
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Very neat and tidy looking design. 👍
I have one remark on the use of discrete voltage regulators. Their input voltage range is actually a voltage differential range since they are floating devices. So as long as the input to output voltage is not exceded, they are OK to be applied. I never knew this for the longest time, but it's in the documentation. The below is from page 2 of TI's LM317.
The regulator is floating and detects only the input-to-output differential voltage. Thus, supplies of several hundred volts are regulated as long as the maximum input-to-output differential is not exceeded. That is, avoid short-circuiting the output.
I have one remark on the use of discrete voltage regulators. Their input voltage range is actually a voltage differential range since they are floating devices. So as long as the input to output voltage is not exceded, they are OK to be applied. I never knew this for the longest time, but it's in the documentation. The below is from page 2 of TI's LM317.
The regulator is floating and detects only the input-to-output differential voltage. Thus, supplies of several hundred volts are regulated as long as the maximum input-to-output differential is not exceeded. That is, avoid short-circuiting the output.
Thank you for your kind words, @arjen6t8!
And thanks for the information about voltage regulator ICs, that's super interesting! Also I guess it should survive for a while even when the output is shorted, because then the output from the transformer would drop quite significantly. Oh well, at least now I know how to calculate component values for a discrete feedback regulator.
And thanks for the information about voltage regulator ICs, that's super interesting! Also I guess it should survive for a while even when the output is shorted, because then the output from the transformer would drop quite significantly. Oh well, at least now I know how to calculate component values for a discrete feedback regulator.
Remember, that this ONLY applies to 317/337 and similar. NOT for the 78xx/79xx 😉
Not for all, it seems, at least not for the LM79xx according to the datasheet. It talks about an output to input max. voltage differential.
I don't see this mentioned for the uA78xx / uA79xx
Perhaps an LM79xx (and LM78xx ?) are internally fixed output voltage LM317/318's?
That can´t be. They both have "Ground" as reference. Lift the ground to 3 volts on a 7812, and you have a 7815.