Audio

[Jose]

Thanks mickstv
Now I think I understand.
Positive signal, IC11A deals, It follows the path through the two resistors 10K. No voltage low due to the high input impedance of IC11A.
Jose

[mickstv]

That looks like a very nice design. Does the 4046 output sine waves? Is this all the circuitry after the integrator? If so you could make a very nice smooth sounding VCO audio by using a LDR based attenuator following the 4046 and then have it drive the speaker/ headphones directly via a power amp like the LM386.
Also by using low offset precision quad op amps you do this with only two chips and eliminate the offset adjust.

Hi Old cart, sorry I missed your post.

The 4046 is square wave output and it sounds fine. When I sort out a way of recording the sound, i'll post it here.

This circuit is after the integrator and LPF stages.

I may try some precision op amps in the future but whilst it's working I'm not going to bother.

[Old cart]

Hi Old cart, sorry I missed your post.

The 4046 is square wave output and it sounds fine. When I sort out a way of recording the sound, i'll post it here.

This circuit is after the integrator and LPF stages.

I may try some precision op amps in the future but whilst it's working I'm not going to bother.

I do not blame you. A working circuit is a thing of beauty! I asked only because many people have shown favor for the more sine wave like audio that the original produces. Square wave are inherently nasty sounding becuase they have odd harmonics which are offensive to many ears. Triangle waves or sine wave are much smoother sounding. A capacitor between the gate and the 10K drive resistor should remove some of the drive harmonics. The approximate starting value should be 1/2*PI*F*R where F is the lowest frequency out of the VCO. This can be tweaked up or down to adjust the smoothness of the sound. This will also attenuate the sound as the pitch rises which should prevent the shrieking that many complain about in VCO sound. Of course if this is set to just make a ticking sound with no target this is less of an issue.
Regarding using precision op amps only IC10 A would be it from this. The others have low, or no voltage gain.

[Old cart]

Actually misstated. It should read "'a capacitor between the gate of the fet and the 10K resistor to ground"

[Sean_Goddard]

Hi all, on Christmas hold ATM so will be in and out when I can. HAPPY CHRISTMAS and GOD BLESS You ALL.

Looks like good work.

Let's try to get the smoothest audio ever. Think That King Cole attached to a metal detector ��

[localbug]

Playing with frequency generator app on my phone. I found these as results

-squarewave can be heard at 20hz.
-sawtoothwave can be heard at 20hz but weaker than square.
-trianglewave can be heard at 20hz but weaker than sawtooth.
-sinewave below 150hz sinewave hardly to hear, this require amplification on wave amplitude to become audible.

using squarewave for audio offers lowest frequency audible in the range 20-20khz.

[Old cart]

Playing with frequency generator app on my phone. I found these as results

-squarewave can be heard at 20hz.
-sawtoothwave can be heard at 20hz but weaker than square.
-trianglewave can be heard at 20hz but weaker than sawtooth.
-sinewave below 150hz sinewave hardly to hear, this require amplification on wave amplitude to become audible.

using squarewave for audio offers lowest frequency audible in the range 20-20khz.

That is becuase the speaker you are using has limited low frequency range. Square waves have all the odd harmonics so a 20 Hz sq wave has frequency components at 20, 60, 100,140, 180 ....Hz. Since waves have only the fundamental frequency, in this case 20Hz which wil only be audible on the largest speakers and then only at pretty loud volumes. Most phones have only a very smal speaker and very limited bass. Try your earbuds to get more low frequency extension.

[localbug]

I believe this is why eric foster using 555 for goldscan.

[Polymer]

Here's the audio circuit I use for all my Ground Balancing PI detectors. It's designed to work on detectors that use a Nch Mosfet for the TX.

The input capacitor 2.2uf, depending on target time constant sees a varying voltage +/-5 volts from the previous integrator stage, IC10A amplifies that signal. IC10B changes the varying voltage too, all targets going to +5v. IC11A is a buffer so as the previous stage doesn't get loaded down. IC11B is basically threshold control.

The CD4046 produces a varying pitch dependent on target time constant. The amount of variation is limited by the two led's.

So the output audio is varying pitch plus no or low output until the target breaks through the threshold level then the volume increases the closer the target gets.

Given link does not work anymore. Here new one:

https://postimg.cc/bG0s7gkB

[Polymer]

Given link does not work anymore. Here new one:

https://postimg.cc/bG0s7gkB

Silly me, could have uploaded the picture to the forum right away
to circumvent external link failures in the future. Hope that's OK mickstv!

Heres the pic uploaded to forum now:

[liekwang]

can i combine scematic audio mickstv, for audio replacement from scematic dooley please tell me ...

[waltr]

can i combine scematic audio mickstv, for audio replacement from scematic dooley please tell me ...

ot sure what those schematic are...Links?

The schematic posted by Polymer does work.

N

[liekwang]

yes it seems that it works scematic polymer for audio td3x dooley, power supply for voltage + 4v for coil change to + 5v take from power suplly from scematic mpp

[liekwang]

please tell me which pin to input mickstv audio schematic
please tell me which pin to input mickstv audio schematic

[fathallah]

HI Friends
Had anyone tried 4046 vco attached with surfmaster audio section ?