Troubleshooting 3.0

7 years 6 months ago #585 by Ray
Replied by Ray on topic Troubleshooting 3.0
Hi,

Yes you should be able to get a gain around 21 times (the formula for that non inverting op-amp is G=1+(100K/4.7K)).
Maybe there is something wrong in your circuit around the trimmer resistor, C3, C4, R4, R5...

Did you try to listen to it with the maximum gain that gives you a peak to peak signal of 2V at the output pin of the input op amp? is it better?

You are right, the offset value between pins 5 and 6 should not be that big, maybe something wrong in the feedback loop (trimmer resistor, C3, C4, R4, R5) is making the op-amp to change that offset.

Please Log in to join the conversation.

7 years 6 months ago #590 by Ray
Replied by Ray on topic Troubleshooting 3.0
Yes, is definitely something weird with the signals at the op-amp pins.
Sounds silly but are you sure that is not plugged upside down or something like that?

I think that you tried before on a vero board that part of the circuit with the op-amp and you made it work, It is as simple as replicate this little part.... on the pcb you can see all the tracks and all the connections so you can try to see if you can replicate the connections and follow them on the PCB.

The circuit is not complex, just placing the part in the right holes and having them connected makes a successful build. I have seen some Arduino UNO replica boards not having good ADCs and some dodgy IC sockets but right now I cannot see where is the problem...

Please Log in to join the conversation.

7 years 6 months ago #593 by Ray
Replied by Ray on topic Troubleshooting 3.0
Hi, no, you cannot place the LM741 into the pedalSHIELD UNO board. It is a single op-amp and you would need a double.
But maybe you can take the TL972 from the pedalSHIELD UNO board and place it into your veroboard and see if it works fine there...

Please Log in to join the conversation.

7 years 6 months ago #596 by Ray
Replied by Ray on topic Troubleshooting 3.0
Hi the LM358 is not a rail-to-rail op amp which is what you need here, it will saturate at 3.7V (when supply is +5V and 0V), but if you dont apply much gain you can use it just as a test, the pinout is compatible with the tl972 and there is no harm trying it.
The following user(s) said Thank You: johnmarksamuel

Please Log in to join the conversation.

7 years 4 months ago #644 by Ray
Replied by Ray on topic Troubleshooting 3.0
The tremolo effect is maybe one of the most noisy effects, because it modulates the input signal with a sinewave, and if there is noise at the input it also modulates the input noise making it more noticeable...
Maybe we should re-write that effect just attenuating the input signal so the input noise never gets amplified.... I will think about it.

Have you tried using a different power supply to see if the noise is still there? pedalSHIELD uno is pretty quiet by design.

Please Log in to join the conversation.

7 years 6 days ago #808 by AaronMichael
Replied by AaronMichael on topic Troubleshooting 3.0
UPDATE:
When I build the UNO shield I had a lot of high frequency noise. I blamed the PWM conversion and tried some changes to frequencies etc. to no avail. I will admit my soldering wasn't great due to crap soldering iron.
Anyway in the long run;
To check if the noise is from Arduino system short out PINS 3-7 which should allow the sound to travel straight through - This removed loads of noise for me (Still not the solution but at least isolated it). Nice warm sound though from opamp.
So the SOLN (for me ) was 0.1uf CERM Cap. across pins 3 to GND. I didn't really check the effect on volume but noise cleared right up. So maybe C5 should be increased??????
Anybody any comments??????

Please Log in to join the conversation.

7 years 5 days ago #809 by Ray
Replied by Ray on topic Troubleshooting 3.0
Hi, thanks for your work on this!

Firts of all I dont really get what do you mean when you talk about shorting pins 3 and 7.... are you talking about the 3PDT?

Again when you talk about a cap between pin 3 and gnd is not clear for me which pin 3 are you referring.

The cap C5 togueter with R6 forms a low pass filter with the cut frequency around 5KHz, if you increase C5 you may loose some high freq content of the original guitar signal but it may be a good idea.
This week I am out on holidays but as soon as I return I would try your idea.
Regards!

Please Log in to join the conversation.

7 years 5 days ago #810 by AaronMichael
Replied by AaronMichael on topic Troubleshooting 3.0
Apologies for confusion -
I mean pins 3& 7 on IC (OPAMP) - Thjis wshorts out the ARDUINO from circuit feeding input direct to output stage - thus allows you to check is shield ok.
When I say pin 3 to GND - I mean pin 3 on IC ...
Makes a big difference on noise.

Please Log in to join the conversation.

7 years 4 days ago #814 by Ray
Replied by Ray on topic Troubleshooting 3.0
Ok, thanks for making it clear, I will check it out as soon as I am back next week.

Please Log in to join the conversation.

7 years 3 days ago #815 by Caca
Replied by Caca on topic Troubleshooting 3.0
I read all you have written and i had the same problem. today i have check and verify one by one all connection and the noise is gone when i use an external battery idk if the probleme was the connection or my computer but now it is completly clean :D

Please Log in to join the conversation.

Time to create page: 0.090 seconds
Powered by Kunena Forum
Joomla SEF URLs by Artio

Follow us

You can also follow us on:

facebook   google   instagram

pinterest   youtube   twitter