开云体育

Hi all,

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I own a QCX Classic and two Mini's and wonder why de sidetone from the Mini's sound smoother than the Classic.

Not that the Classic sounds bad but gives the idea that it is more a sawtooth than a sinus.

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So I compared both manuals en found a few changes in the Mini.

1) R49, R50 and C39 from AUDIO2 (pin 24 Atmega328p) to the wiper of R27 are expired

2) Couple capacitor C21 (output IC9A to top volume pot) decreased from 10uF to 1uF

3) Same for C22 (wiper volume pot to IC10B)?

4) Capacitor C24 increased from 10uF to 470uF (pin 5 IC10B)

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Does these adjustments affect how the sidetone sounds? I have searched the mods page but can't find info on that.

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73, Carel PA0CMU

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Apparently I have modified C21/C22 in the past by replacing them with 1uF ones. One ceramic and the other an electrolytic because I didn't have two ceramic ones, I guess!

It turned out that C22 was a 100nF (104) instead of a 1uF (105) and that caused the sound difference. I have put a 1uF electrolytic in it and the sidetone is now a nice sine wave on the oscilloscope.