PI Audio

[Mdtoday]

Here is a great little VCO circuit Mickstv posted back 2-3 years ago and I've had veroboard version for use on my bench for so long..it finally gave out so I decided to put it onto a PCB.
I added extra decoupling, changed Fet and added option for audio amp connection..all vanilla stuff.

Had 10 Blank PCBs made by PCBway for $25 Au and $20 of that was delivery.. Thanks for the heads up on that Moodz.

I normally use a digital audio version of this but sometimes analog is a better fit and Mick's circuit was worthy of a pcb
It is SMD using mainly 0805 parts.



The original circuit is posted in the Minipulse Audio section..

Cheers
Mdtoday

[Elliot]

How might this design vary in functionality compared with the TreasureLinx Mirage Ultra 1?

[Mdtoday]

How might this design vary in functionality compared with the TreasureLinx Mirage Ultra 1?

Hi Elliot,

I'm not familiar with the audio of that detector sorry,so I cant really compare.
This circuit has a nice stable threshold, good sound, good input/output range and can be added to most PI front ends after the integration and filter stage.
You can drive headphones direct or couple the output to the audio amp section shown with little effort.
Its variable pitch variable amplitude back end..

cheers

Mdtoday

[Mdtoday]

Elliot

Ok, now I have looked at the Mirage PI PCB, its a version of Carl's Hammerhead , from what I can see anyway...

In that case the input to the circuit I posted would come from the Output of 3rd gain stage..

The difference in audio stage is that the Hammerhead (version 1 is what I'm referencing) has the option for variable pitch or constant pitch variable amplitude.

Mickstv's circuit has both rolled into one. Maybe the mirage version has both too, I cant tell from looking at pictures


cheers

Mdtoday

[Elliot]

You're good at this - I can tell! Yes, the Mirage is a derivative of the Hammerhead. I don't like VCO outputs generally, so to have the option of a single tone and variable amplitude would be nice. I have attached the schematic of the Mirage. I assume that the output from the Mirage would be around the area I have circled.

[6666]

Mdtoday, thanks Mick has some great circuits, dont know if he is still around.

[Mdtoday]

Elliot,

Thanks for posting the schematic

You could pick off from there, although there will be mods around the threshold...don't need 2 ..

Umm, I think we have wires crossed...Micks circuit has variable pitch and amplitude

[Mdtoday]

Mdtoday, thanks Mick has some great circuits, dont know if he is still around.

No problems 6666, yes, he does. I liked this back end audio and yeah, I'm not sure where he is these days.

[waltr]

Micks circuit works very well. I have simulated and proto-typed it.
It output variable tone and amplitude.
Your PCB's look great (I also use PCBWAY).

It does have lots of parts so I did the variable tone with a PIC12F1501 processor at a constant amplitude. Advantage is it needs only one chip the PIC.
It works well and details are in my HH2 thread here in post #25:
https://www.geotech1.com/forums/show...ake-on-the-HH2

[6666]

Micks circuit works very well. I have simulated and proto-typed it.
It output variable tone and amplitude.
Your PCB's look great (I also use PCBWAY).

It does have lots of parts so I did the variable tone with a PIC12F1501 processor at a constant amplitude. Advantage is it needs only one chip the PIC.
It works well and details are in my HH2 thread here in post #25:
https://www.geotech1.com/forums/show...ake-on-the-HH2

Thanks Waltr, been meaning to try your micro, is there a hex code for it ? thanks
T

[waltr]

Thanks Waltr, been meaning to try your micro, is there a hex code for it ? thanks
T

I know I posted the source code but unsure of the hex.
If not I will post in in my thread soon.

[Mdtoday]

Thanks waltr.

Here is the processor controlled audio I generally use...has variable pitch variable level.
It works well too. It uses 2 pwm outputs from DsPic.

Spice circuit and screenshot attached.



cheers

Mdtoday

[waltr]

Thanks waltr.

Here is the processor controlled audio I generally use...has variable pitch variable level.
It works well too. It uses 2 pwm outputs from DsPic.

Spice circuit and screenshot attached.

[ATTACH]45389[/ATTACH]

cheers

Mdtoday

Looks interesting. Will check it.

I posted the HEX file in my thread last night.

[Mdtoday]

Looks interesting. Will check it.

I posted the HEX file in my thread last night.

ok thanks I'll breadboard one of yours up too

[Mdtoday]

Just to add a bit more info..
My VCA circuit while designed to be driven from PWM outputs of a dspic or similar, is versatile enough to be a standard variable amplitude single tone output by using a 555 , cmos osc etc as audio input and feeding the CV input with a conditioned 0-2v DC signal from your favourite integrator , filter and gain stage. I don't vary the Pulse width into audio input only frequency ..eg digitise front end signal after integrator and filters then pump the value out to the PWM. The CV input is set frequency but variable pulse width which is based on same digitised signal input but inverted and firmware filtering and threshold added to it

cheers
Mdtoday