PI Audio

[h9361]

Measured with input zero it is 400hz, just change to suit your requirement

If i want to change the 400Hz, should i change C10 value?

[Mdtoday]

Do you remember audio Frequency of CD4046 in your schematic?

Measured with input zero it is 400hz, just change to suit your requirement

[Mdtoday]

So, it's better to be connected to -5V, true?
[ATTACH]55072[/ATTACH]

Yes

Build as per the schematic and notes in first post of this thread and it will work.
I’m off for some shut eye

cheers

[h9361]

No, that is not a very good idea!
You need fast response not slow.
The Mickstv circuit produces variable frequency, variable amplitude and for gold prospecting is ideal.
Response is clean and crisp.
Best thing to do is build on breadboard and experiment

Do you remember audio Frequency of CD4046 in your schematic?

[Mdtoday]

Thank you dear Mdtoday. About your schematic, we can add a uF capacitor before Pin 9. In this case, we have a nice delay than target and we can easily detect small change in sound (soft sould) like GPX audio.
Please see the video, time 5:00. He adds a 10Uf in pin 9, then we have a delay in audio.

No, that is not a very good idea!
You need fast response not slow.
The Mickstv circuit produces variable frequency, variable amplitude and for gold prospecting is ideal.
Response is clean and crisp.
Best thing to do is build on breadboard and experiment

[h9361]

AC couple the input to the LM386
Dom44’s board layout doesn’t look correct, emitter of the BC557 should not be tied to GND.
its late, maybe I’m seeing things

cheers

So, it's better to be connected to -5V, true?

[Mdtoday]

Thanks for your tip.
Do you have any idea about adding LM386?

AC couple the input to the LM386
Dom44’s board layout doesn’t look correct, emitter of the BC557 should not be tied to GND.
its late, maybe I’m seeing things

cheers

[h9361]

no need to be sorry, all good.
2n3819 will be fine. Just be mindful of the different pin outs available with T092

cheers

Thank you dear Mdtoday. About your schematic, we can add a uF capacitor before Pin 9. In this case, we have a nice delay than target and we can easily detect small change in sound (soft sould) like GPX audio.
Please see the video, time 5:00. He adds a 10Uf in pin 9, then we have a delay in audio.

[h9361]

Just add R2 into the circuit. All that you are doing with the addition of R2 is ensuring that your minimum end of the frequency range is not zero.

Thanks for your tip.
Do you have any idea about adding LM386?

[Mdtoday]

Sorry for my questions.
I can find JFET 2N3819 in my city. Do you think it's a good replacement for JFET PMBF4393?
Thank you

no need to be sorry, all good.
2n3819 will be fine. Just be mindful of the different pin outs available with T092

cheers