PI Audio

[Mdtoday]

Do you remember audio Frequency of CD4046 in your schematic?

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

[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?

[surfdetector]

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

Put a potentiometer as R1 and you can easily adjust the center frequency

[h9361]

Put a potentiometer as R1 and you can easily adjust the center frequency

Thank you dear surfdetector.

[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 think TDI also is variable frequency and variable amplitude?

[Teleno]

I'm sharing my design for audio. A logarithmic voltage-to-current converter charges the capacitor of a multivibrator based on NE555.

The log function means that small input changes translate into larger frequency changes, weak targets get more audible.

Resistor Rthreshold controls the threshold, obviously, and resistor Rgain adjusts the maximum frequency.

The log amplifier is compensated for Is of the transistors and conforms very well to the theoretical transfer function:

I(Q5) = 0.026 * (ln( (V(in)-V(com)) / R9 ) - ln( (Vcc-Vcom) /Rthreshold) / Rgain

It should be independent of the transistors used.

The input has to be positive relative to the analog ground COM.

[h9361]

I'm sharing my design for audio. A logarithmic voltage-to-current converter charges the capacitor of a multivibrator based on NE555.

The log function means that small input changes translate into larger frequency changes, weak targets get more audible.

Resistor Rthreshold controls the threshold, obviously, and resistor Rgain adjusts the maximum frequency.

The log amplifier is compensated for Is of the transistors and conforms very well to the theoretical transfer function:

I(Q5) = 0.026 * (ln( (V(in)-V(com)) / R9 ) - ln( (Vcc-Vcom) /Rthreshold) / Rgain

It should be independent of the transistors used.

The input has to be positive relative to the analog ground COM.

Very thanks for your info.

[Elliot]

The input has to be positive relative to the analog ground COM.

It would be great to see a circuit that caters for both positive and negative input signals to work with ground balancing PI designs.

[Carl-NC]

It would be great to see a circuit that caters for both positive and negative input signals to work with ground balancing PI designs.

Should be possible using a circuit similar to what the TDI-SL has. I'll see if I can figure it out. Realize though that by making the VCO more responsive near the balance point you will end up with a much more "lively" audio threshold.

[h9361]

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

Hello
Dear Mdtoday.
Is it possible to tell me application of the two LEDs in your Audio schematic?
Thanks

[surfdetector]

If anyone wants the board here it is

http://s000.tinyupload.com/index.php...41575894685837

This link doesn't appear to work anymore, at least for me.

[dbanner]

The common I think is referenced to battery positive, so yes, it seems correct. The ground shown in the schematic for the lm386 is battery negative.
Use any general purpose nfet.

Oh oh, must have been tired.
On the surf pi, I think the rail voltages are referenced to battery negative pole.
On the layout, Q1 emmiter is tied to ground and so is the collector!? ( From where the output is taken from the pot wiper. This cannot be. The emitter should be tied to the negative rail.

Or you can put the pot on the emitter and take the output from there, connecting the other end of the pot via a resistor to the negative rail. In which case, the collector would go to ground. LM 386 pin 4 is also connected to ground, this is correct.

[mickstv]

Hello
Dear Mdtoday.
Is it possible to tell me application of the two LEDs in your Audio schematic?
Thanks

The two leds, limit the range of the 4046.

[h9361]

The two leds, limit the range of the 4046.

Thanks Dear mickstv.
Can you tell me your opinion about best point of HH1 for connecting to Mdtoday's Audio or your audio schematic ?

[surfdetector]

Thanks Dear mickstv.
Can you tell me your opinion about best point of HH1 for connecting to Mdtoday's Audio or your audio schematic ?

See post #64