PI Audio

[h9361]

Looks ok, now go build it and try it out, build the power supply and audio amp first, make sure it works, then add Mickstv circuit, do it in stages, test each stage then move to next one. Dom44 did a through hole version, others have built that one too, he used an Lm386.
As Mickstv and others have said, the circuit works, so why not build as per the schematic posted first, give it a try then start changing things.
It is the best way to start, try not to complicate things, I’m sure you will do just fine.

Hello dear mdtoday
Please forgive me for my wrriting here.
I have a question about your schematic, 100k trimmer.
For doing 0mv out of first amp, do you think i should do it before connecting my pi to c8 or it is better to be connected my pi?!

[Mdtoday]

Hello dear mdtoday
Please forgive me for my wrriting here.
I have a question about your schematic, 100k trimmer.
For doing 0mv out of first amp, do you think i should do it before connecting my pi to c8 or it is better to be connected my pi?!

No problems.
Adjust to 0V with no input to C8, see notes on schematic at start of the thread and Mickstv’s original drawing.

Cheers

[h9361]

No pin1 of IC8a. Forget about the HH sat, the rest of the circuit has a manual threshold control, which is better for small target detection.

It's easier to do three samples the you only need one integrator.

S1 about 5us, S2 130us and S3 125us all approx. Then you adjust the delay between S1 and S2 to ground balance

Hello
Dear mickstv
Before everything, thank you for your nice Audio schematic.
Dear mickstv, i'm going to change your audio tone.
According to Mr. surfdetector's guidance, i changed R1 of CD4046 (pin 11) with a pot 100K, but the tone is still the same!
Is it possible to tell me how i can do it?

[h9361]

No problems.
Adjust to 0V with no input to C8, see notes on schematic at start of the thread and Mickstv’s original drawing.

Cheers

Hello
Dear Mdtoday
I changed R1 and c10 of CD4046 (pin 11, 6-7), but the tone is still the same!
Can you help me how to change the tone audio?
Thanks

[h9361]

No problems.
Adjust to 0V with no input to C8, see notes on schematic at start of the thread and Mickstv’s original drawing.

Cheers

Hello
Dear Mdtoday.
I hope you see my post and guide me.
I built your schematic with TL072, 2N3819 Fet (Q2) and BC557C (Q1) and 47uF (instead of 100uF).
I also adjusted pin 1 of U1a to zero and can hear a clear sound without connecting to C8.
After adjusting, i connected it to my HH1 (after SAT) and have clear action in audio with target over coil.

But i have two problems:
1- My threshold pot generates a very very weak sound up to its center position. As soon as passing from its center, my sound is very very big and very instable (is connected to HH1).
2- As you know, my HH1-SAT (TP9) is 0 mv and i don't connect my coil to HH1 at all. Other words, My HH1 is connected to C8 without any coil. In this case, my base audio is very instable (not clear) but it will be stable as soon as it's disconnected from my HH1!

Do you have any suggestion for check?!
Thanks

[Mdtoday]

"1- My threshold pot generates a very very weak sound up to its center position"

It is a threshold adjustment and meant to adjust until you hear the audio just breaking through. At some point of the adjustment, yes you will have a constant audio tone.
I might be misunderstanding what you are referencing so perhaps post a short video of it being adjusted.

"2- As you know, my HH1-SAT (TP9) is 0 mv and i don't connect my coil to HH1 at all. Other words, My HH1 is connected to C8 without any coil. In this case, my base audio is very instable (not clear) but it will be stable as soon as it's disconnected from my HH1!"

Again, if there is no input to Mickstv circuit and you adjust the threshold pot until a tone is heard, just touching the input with your fingers should produce a variable pitch and volume. It is an very sensitive circuit, coupled to the HH circuit the overall gain may be too high and unstable...

I am also getting a bit confused as you say at the top of your post it is producing a tone with coil connected and over a target... Is it variable pitch and volume as you move the target towards and away from the coil, or is it coming on full volume and really high pitch sound?

Your threshold pot...what value is it?

Does you HH circuit work with it's original audio?

One other thing to note, with such high gain circuits, you should expect some "hunting" around the threshold stability if you are near to a PC or Wifi, flouro lights etc turned on.

Please post a short video and maybe some photos of your PCB build if possible.

As I have said in the past, if the circuit is built to the schematic shown, it will function as detailed. Once you start substituting values and components, without first proving with the original, you widen the chances of it not working. I get why you would substitute, we all do it but once you do it, you have to be prepared to do some data sheet comparisons to make sure your substitutes are fit for purpose.

Which brings me back to a request for a short video and some build photos.

Cheers

[h9361]

"1- My threshold pot generates a very very weak sound up to its center position"

It is a threshold adjustment and meant to adjust until you hear the audio just breaking through. At some point of the adjustment, yes you will have a constant audio tone.
I might be misunderstanding what you are referencing so perhaps post a short video of it being adjusted.

"2- As you know, my HH1-SAT (TP9) is 0 mv and i don't connect my coil to HH1 at all. Other words, My HH1 is connected to C8 without any coil. In this case, my base audio is very instable (not clear) but it will be stable as soon as it's disconnected from my HH1!"

Again, if there is no input to Mickstv circuit and you adjust the threshold pot until a tone is heard, just touching the input with your fingers should produce a variable pitch and volume. It is an very sensitive circuit, coupled to the HH circuit the overall gain may be too high and unstable...

I am also getting a bit confused as you say at the top of your post it is producing a tone with coil connected and over a target... Is it variable pitch and volume as you move the target towards and away from the coil, or is it coming on full volume and really high pitch sound?

Your threshold pot...what value is it?

Does you HH circuit work with it's original audio?

One other thing to note, with such high gain circuits, you should expect some "hunting" around the threshold stability if you are near to a PC or Wifi, flouro lights etc turned on.

Please post a short video and maybe some photos of your PCB build if possible.

As I have said in the past, if the circuit is built to the schematic shown, it will function as detailed. Once you start substituting values and components, without first proving with the original, you widen the chances of it not working. I get why you would substitute, we all do it but once you do it, you have to be prepared to do some data sheet comparisons to make sure your substitutes are fit for purpose.

Which brings me back to a request for a short video and some build photos.

Cheers

Thanks dear Mdtoday.
Yes, with no input to Mickstv circuit, a tone is heard, just touching the input with my finger produce a variable pitch and volume.
My TH pot is 10K. I have no problem for detecting target with coil because it easily generates variable pitch and volume.
My problem is its constant audio with no target or not connecting coil to HH1.
I tested my HH1 and audio out of city or clear place from PC or Wifi, flouro lights etc.
I try to capture a video and some pics.

[h9361]

Please see the HH1 schematic, pointer a red circle.
Do you think it's OK to decrease the 100K to 50K for decreasing (coupled sensitivity) overall gain?
I want to test this method.

[Mdtoday]

"My problem is its constant audio with no target or not connecting coil to HH1."

Ok, well this is normal for this particular audio circuit, you should be able to adjust the threshold so it is just breaking through at a level that is comfortable to you.

For gold prospecting, I adjust threshold so that I have a constant low level tone. This helps with small or faint target signals, sometimes, just breaking the threshold.

Mickstv circuit is actually designed this way, he designed it for gold prospecting.

cheers

[Mdtoday]

Please see the HH1 schematic, pointer a red circle.
Do you think it's OK to decrease the 100K to 50K for decreasing (coupled sensitivity) overall gain?
I want to test this method.
[ATTACH]55980[/ATTACH]

Ok, now I think it might be time to back track a little.

Could you post a schematic of how you connected both circuits please, cut and past if you can.

I don't think you need to decrease the gain, leave it as is (100k)

Cheers

[h9361]

"My problem is its constant audio with no target or not connecting coil to HH1."

Ok, well this is normal for this particular audio circuit, you should be able to adjust the threshold so it is just breaking through at a level that is comfortable to you.

For gold prospecting, I adjust threshold so that I have a constant low level tone. This helps with small or faint target signals, sometimes, just breaking the threshold.

Mickstv circuit is actually designed this way, he designed it for gold prospecting.

cheers

I cannot adjust Threshold pot so that constant audio be stable. Other words, i rotate threshold pot so that hear a tone but the tone never be stable.
I think i have to decrease gain of coupled of hh1.
Do you think it is correct to decrease 100k to 50k?

[h9361]

you can see my Audio Schematic and the connection point of my HH1.

[Mdtoday]

No connect input to c19 on HH so you still have SAT, so junction of c19 and SW2

No need to change gain of HH stage.

cheers

[h9361]

Is your mean the point?

[Mdtoday]

Is your mean the point?
[ATTACH]55984[/ATTACH]

correct. You can also connect to the other side of C19 at IC8

you don’t need anything past the SAT section

ill leave you to it for now, I’m off for some sleep

Cheers