PI Audio

[h9361]

I didn't see your post as I was replying just now to your original. see that post.

No, don't increase the gain , 2 totally different circuits and please, run the sim if you haven't already, it will help you understand it more.

Cheers

Hello Dear Mdtoday
I hope you are in a good health. As you know, i am using Mr. Mickstv's schematic (post #1) (by your guiding) and it works very nice.
But now i am going to add two extra options on the schematic. For doing this, i need your help, i hope you accept it.
For better understanding, please first see the following pictures. It is a part of GPX 5000 menu, its audio part.
As you see, the machine uses two options the named Signal and Audio Type.




Now, please consider Mr. Mickstv's schematic. Can you guide me how to add two pots (variable resistors ) for controlling the signal and audio type?
Thank you

[Mdtoday]

Dear Mdtoday
I have a technical question about your schematic. First, please see Mr. Mickstv's schematic (U1A). As you see, its Gain for CV is 100 (R14/R1)
Now, please see your schematic, Gain of CV is 1 (R14/R11). Question that arises here is that, do you think i should increase its Gain as 100 like Mickstv's schematic?!
Because i tested his schematic on my HHd, the 100 Gain is worked.
Thank you.

I didn't see your post as I was replying just now to your original. see that post.

No, don't increase the gain , 2 totally different circuits and please, run the sim if you haven't already, it will help you understand it more.

Cheers

[Mdtoday]

Thank you for your information.
I am going to add your audio to my HHD+GB.
First for testing, I want to connect CV_PWM to T5 and 7555 for Audio_PWM.
Do you think it is true the connection?
In addition, I want to use TL072 and 2n3819 as your component (through hole). Do you think it is ok?

To be honest, Carl's HH audio will give you the same result as what you are trying to achieve with this circuit. You already have it on the board. You just need to select the audio option you want.
I was under the impression you were building a digital based detector, my bad.
I would suggest, if you haven't already, use LTspice and run the VCA sim, change the input value timing and please read the notes in the original post. Understand what it does and experiment using the sim.
As I've stated a number of times, this was designed for use with 3v logic level PWM as inputs not from post integrator outputs.
For an exercise, if you have a scope, look at the signals at the points on the HH you were thinking of using, take note of the voltage swings (or there's probably scope shots on the forum you could view, or HH article,not sure)
Once you know that, you can modify the input signal of the CV_PWM, re-run the sim and see what happens.
I could do this for you but I would encourage you to try and understand the sim and HH signal chain yourself first.
Hint, if you right click over V6 in the sim you can change Function tab to none, change the DC value to suit. Start with say a value of 2 and run the sim, then change to a negative number see what happens.
You will soon see the range limits.
Sims might not be perfect but they sure get you close enough to see most things you may not have thought about way before committing the soldering iron.

TL072 will be ok, as will 2N3819, just double check your pinouts of the FET from manufacturer, they are not all drawn the same.
You might have to tweak the FET BIAS as described last post.

I'll leave you with it for now, I have some catching up to do.

Cheers

[h9361]

Um, that's what this circuit is for its a PWM voltage controlled attenuator (VCA) in this case.
Threshold can be done in firmware if you are going mostly digital. If not, you use your existing threshold and final stages. (I'm not really sure what you are wanting to do).
Pitch or frequency can also be firmware controlled, or can be a 555 timer osc, whatever. I used 3v logic to the inputs.
This circuit used the PWM outputs of a micro to generate the audio.

See attached from scope. 40Duty.png shows min output, 1Duty.png shows Max output. AUDIO output (purple trace), yellow trace = AUDIO, Blue trace = CV_PWM.
Notice the inverse amplitude vs PWM.
The FET Bias voltage around R7/R4 can be tweaked to suit the JFET used but the values shown worked ok with a number of different replacements, not critical, however it does affect the range of attenuation.
R5/R3 ratio can also be adjusted to suit the audio input. I think the Sim shows 47k/1k but the actual board had 470k/10k when I used the OPA1642.
R6/R9 were used with some replacement OPamps during testing, you can probably just leave out R6 and use a link or zero ohm resistor in place of R9. Prob leave as is.
I don't use this circuit any more but it was useful.

Dear Mdtoday
I have a technical question about your schematic. First, please see Mr. Mickstv's schematic (U1A). As you see, its Gain for CV is 100 (R14/R1)
Now, please see your schematic, Gain of CV is 1 (R14/R11). Question that arises here is that, do you think i should increase its Gain as 100 like Mickstv's schematic?!
Because i tested his schematic on my HHd, the 100 Gain is worked.
Thank you.

[h9361]

Um, that's what this circuit is for its a PWM voltage controlled attenuator (VCA) in this case.
Threshold can be done in firmware if you are going mostly digital. If not, you use your existing threshold and final stages. (I'm not really sure what you are wanting to do).
Pitch or frequency can also be firmware controlled, or can be a 555 timer osc, whatever. I used 3v logic to the inputs.
This circuit used the PWM outputs of a micro to generate the audio.

See attached from scope. 40Duty.png shows min output, 1Duty.png shows Max output. AUDIO output (purple trace), yellow trace = AUDIO, Blue trace = CV_PWM.
Notice the inverse amplitude vs PWM.
The FET Bias voltage around R7/R4 can be tweaked to suit the JFET used but the values shown worked ok with a number of different replacements, not critical, however it does affect the range of attenuation.
R5/R3 ratio can also be adjusted to suit the audio input. I think the Sim shows 47k/1k but the actual board had 470k/10k when I used the OPA1642.
R6/R9 were used with some replacement OPamps during testing, you can probably just leave out R6 and use a link or zero ohm resistor in place of R9. Prob leave as is.
I don't use this circuit any more but it was useful.

Thank you for your information.
I am going to add your audio to my HHD+GB.
First for testing, I want to connect CV_PWM to T5 and 7555 for Audio_PWM.
Do you think it is true the connection?
In addition, I want to use TL072 and 2n3819 as your component (through hole). Do you think it is ok?

[Mdtoday]

Thank you for your sharing.
Do you remember how to control threshold and volume in output audio?

Um, that's what this circuit is for its a PWM voltage controlled attenuator (VCA) in this case.
Threshold can be done in firmware if you are going mostly digital. If not, you use your existing threshold and final stages. (I'm not really sure what you are wanting to do).
Pitch or frequency can also be firmware controlled, or can be a 555 timer osc, whatever. I used 3v logic to the inputs.
This circuit used the PWM outputs of a micro to generate the audio.

See attached from scope. 40Duty.png shows min output, 1Duty.png shows Max output. AUDIO output (purple trace), yellow trace = AUDIO, Blue trace = CV_PWM.
Notice the inverse amplitude vs PWM.
The FET Bias voltage around R7/R4 can be tweaked to suit the JFET used but the values shown worked ok with a number of different replacements, not critical, however it does affect the range of attenuation.
R5/R3 ratio can also be adjusted to suit the audio input. I think the Sim shows 47k/1k but the actual board had 470k/10k when I used the OPA1642.
R6/R9 were used with some replacement OPamps during testing, you can probably just leave out R6 and use a link or zero ohm resistor in place of R9. Prob leave as is.
I don't use this circuit any more but it was useful.

[h9361]

Here are some project files that I could find without pulling everything out of storage.

Cheers

Thank you for your sharing.
Do you remember how to control threshold and volume in output audio?

[Mdtoday]

Here are some project files that I could find without pulling everything out of storage.

Cheers

[Mdtoday]

I have found the gerber files and some blank circuit boards but not schematic.
The gerbers are for an smd board which is all I do.
The Ltspice circuit is acurate though. Opamps are not critical, the type I used are noted on the sim.
Having recently moved, some boxes are still in storage so the files are probably on one of the old desktop drives there.

cheers

[h9361]

Thank you dear Mdtoday.
No need to share your detector schematic, only your Audio part (VCA) and its notes.
I again thank you for your kindness.

Dear Mdtoday,
I hope you were able to find the audio schematic.
Thank you

[h9361]

I have missed a lot of posts over last couple of years due to personal reasons. Have only just surfaced to take it all in again and get back on the horse.
Your's is one of the posts I have just caught up with.
The answer is... Its been a while since I did this circuit and most of my gear has been stored and archived so at present, the only thing I can find is the PCB.
The sims I posted were the same as real schematic but Ill have to search for all my notes again but Yes is the answer to your question.....

I will post the VCA project when I can find it all so give me some time as I have a few things to catch up on atm

I can't share the complete detector circuit as it was designed for a customer so NDAs apply sorry.
The VCA posted is from one of my libraries of building blocks, so that I can share.
I often made sub circuits for bench testing different bits of a design so sometimes there is a complete project, sometimes not.

cheers

Thank you dear Mdtoday.
No need to share your detector schematic, only your Audio part (VCA) and its notes.
I again thank you for your kindness.

[Mdtoday]

Hello
Dear Mdtoday.
Before everything, thank you for your sharing your information.
Dear sir, i built the Mickstv's schematic by your help and it works very nice. Now, i am going to use your schematic over my HHD and to compare it.
If i understand correctly, i want to use a 7555 timer (osc) as input for Audio_pwm and CV connects to TP5, is that true?
Is it possible to share me full schematic with threshold control?
I think i can connect final audio_out as input to lm386 (including volume), but i don't know how to add a threshold to your schematic.
Thank you.

I have missed a lot of posts over last couple of years due to personal reasons. Have only just surfaced to take it all in again and get back on the horse.
Your's is one of the posts I have just caught up with.
The answer is... Its been a while since I did this circuit and most of my gear has been stored and archived so at present, the only thing I can find is the PCB.
The sims I posted were the same as real schematic but Ill have to search for all my notes again but Yes is the answer to your question.....

I will post the VCA project when I can find it all so give me some time as I have a few things to catch up on atm

I can't share the complete detector circuit as it was designed for a customer so NDAs apply sorry.
The VCA posted is from one of my libraries of building blocks, so that I can share.
I often made sub circuits for bench testing different bits of a design so sometimes there is a complete project, sometimes not.

cheers

[h9361]

No, it's not required IMO.
Has this problem just occurred, or has it always been there?
If it was stable and you have made changes then the problem appeared, then you need to back track
Board layout, faulty component, component choice, bad solder joints...
Please post a schematic and photo of your build, then we can see what you have and maybe we can help more.
You can still test most PI designs in house but you need to at least do it away from computers, tvs routers etc.
If you have a variable frequency TX and variable gain RX, then you have a better chance of reducing the noise problem.
I haven't been following your thread much so I'm not aware of all the experimenting you have done, so can't really comment much more.

cheers

Hello
My friend, Are you online?

[h9361]

The two leds, limit the range of the 4046.

Hello Dear mickstv
I hope you are in a good health and see my post.
Before everything, i have to thank you for your nice schematic (audio, Post1).
My friend, please first see attached. It is a signal control in audio of Gpx series minelab.
As you know, the control gives the operator the ability to choose between a target signal that has a large variance of tone, or one which has less variation.
My question is that, can you guide me how to add the control in your schematic?
Thank you.

[h9361]

No, it's not required IMO.
Has this problem just occurred, or has it always been there?
If it was stable and you have made changes then the problem appeared, then you need to back track
Board layout, faulty component, component choice, bad solder joints...
Please post a schematic and photo of your build, then we can see what you have and maybe we can help more.
You can still test most PI designs in house but you need to at least do it away from computers, tvs routers etc.
If you have a variable frequency TX and variable gain RX, then you have a better chance of reducing the noise problem.
I haven't been following your thread much so I'm not aware of all the experimenting you have done, so can't really comment much more.

cheers

I hope you see my post, thank you.