A few weeks ago i listened to a phono preamp made by Aiwa and although i liked the sound of it i thought of using it's scraped circuitry to build a new phono preamp based on an old idea used mostly in Nakamichi cassette players.
That is modeled and built with a 2sk170 and an opa2132 . The real thing has other two stages (impedance adapter -inverted lm4562) for line output and the active subsonic filter(opa2132) that can be bypassed) and a headphones amp based on an inverted topology with a njm4556.The original power supply is very different now, used another external transformer and there are two regulator in series lm7818(7815 plus capacitor multiplier) and another 7918 for the negative rail. In all honesty i have to admit that the original pnp bjt transistor + op-amp based AIWA had a more relaxed sound than what i got from the fet version, even quieter(actually dead quiet) , maybe less analytical than my j- fet version, but better overall. It served me well as a model to simulate and just had some more practice with low noise circuits.I didn't have the time to refine it as i had to leave the country.As it's using the usual +_18v , the maximum input is limited to about 2/3 of the maximum possible signal likely to be generated by a mm cartridge scratching a dirty vinyl.
Next level is a hybrid 1v2-nfb discussed in the 1v2 phono preamp subject.I just finished the modeling and it will be executed most probably when i'll come back home.
An externally hosted image should be here but it was not working when we last tested it.
That is modeled and built with a 2sk170 and an opa2132 . The real thing has other two stages (impedance adapter -inverted lm4562) for line output and the active subsonic filter(opa2132) that can be bypassed) and a headphones amp based on an inverted topology with a njm4556.The original power supply is very different now, used another external transformer and there are two regulator in series lm7818(7815 plus capacitor multiplier) and another 7918 for the negative rail. In all honesty i have to admit that the original pnp bjt transistor + op-amp based AIWA had a more relaxed sound than what i got from the fet version, even quieter(actually dead quiet) , maybe less analytical than my j- fet version, but better overall. It served me well as a model to simulate and just had some more practice with low noise circuits.I didn't have the time to refine it as i had to leave the country.As it's using the usual +_18v , the maximum input is limited to about 2/3 of the maximum possible signal likely to be generated by a mm cartridge scratching a dirty vinyl.
Next level is a hybrid 1v2-nfb discussed in the 1v2 phono preamp subject.I just finished the modeling and it will be executed most probably when i'll come back home.
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Last week i just learned how to use Altium so i made a small project based on the j-fet phono preamp.I could do it in a professional RF-mode, all smd components, ground plane and positive plane all throughout the pcb ,but it was fun to do it this way.
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