Hi all.
I'm building an Aion Tempest, a copy of Friedman's BE OD / Dirty Shirley. Everything is working as it should but I'm getting a high pitched noise when I crank the gain pot. Link to the audio https://sndup.net/53q2 (https://sndup.net/53q2). If I bring the gain all the way down (0:22) the noise disappears. Could you please have a look into this? This is my first build and I don't know what to do. Thanks in advance.
I'd suggest to post clean pictures of your pcb (soldering side and components side). Might be a short somewhere... or a mistake with the pots values ?
Please check the images below. Merci beaucoup! :)
(https://i.ibb.co/m6Lh2hq/IMG-20210128-132157.jpg) (https://ibb.co/m6Lh2hq) (https://i.ibb.co/Wc7cDLq/IMG-20210128-132500.jpg) (https://ibb.co/Wc7cDLq) (https://i.ibb.co/dPnpRD1/IMG-20210128-132541.jpg) (https://ibb.co/dPnpRD1) (https://i.ibb.co/W3CxT3t/IMG-20210128-132659.jpg) (https://ibb.co/W3CxT3t) (https://i.ibb.co/RNMHDb8/IMG-20210128-132821.jpg) (https://ibb.co/RNMHDb8)
Your soldering seems fine. Time for the multimeter !
You can set it on continuity (with a bipping sound when there is connection) and check the suspicious soldering joints. It can be surprising sometime how the tiniest little thing can jump two soldering points. When it bips, if you have doubts, check the schematics to see if the two components should be connected.
Maybe it 's a faulty power supply? try with a different one (9VDC).
Check also every ICs. Double check if they are at the right place. Also, they can be hard to properly fit in the sockets. You should feel a "click" when you push them into the sockets (but not always, it can be ok without the click thing), you can check with the multimeter if there is a good contact between the IC legs and the soldering joints, on the other side of the board.
Are your pots properly isolated ? I don't see anything and some of them are close to the pcb. Some tape or a piece of non conductive thing should be placed in the back of each pots to prevent shorts.
If you still have trouble after all that. Get every Ic names and google them with "datasheet".
ex : TL072 datasheet
check if the values at each pin are correct according to the datasheet. There is also Topic: DEBUGGING - What to do when it doesn't work (Read 136229 times) that will greatly help you narrow it down. https://www.diystompboxes.com/smfforum/index.php?topic=29816.0
To check the ICs values, you need to set the multimeter on alternative current. Set the black probe on ground (any ground locations on the pedal will do, like jack's ground, or DC power jack's ground) and touch the IC pins with the red probe. To do that, your pedal is connected to the power supply and switched on, so you can measure the amount of current in these pins.
And wait, you speak french ?
Quote from: xingchoolin on January 28, 2021, 08:03:53 AM
If I bring the gain all the way down (0:22) the noise disappears.
I suggest to pay some special attention to the components related to the gain section of the circuit, including components near the gain trimmer.
Edit: That would be resistors from R7 to R13, all the diodes (D2, 3, 4...D9), and four capacitors, from C5 to C9.
Don't forget to take out the IC in the area where heat is applied from the soldering iron, to protect them from overheating. You can't stay more than 2 or 3 seconds with a hot iron on the pcb, or there is a chance of permanent damage by overheating it. Although it is important to carefully clean the tiny spaces between soldering joints, if they shouldn't be connected.
I noticed on your pics that a little more solder wouldn't hurt on the pots's pads, it looks a bit light to me.
Welcome. :)
Any reason why you've swapped those two pots round? Those long flying leads in a high-gain pedal are inviting coupling and feedback.
Quote from: eh là bas ma on January 28, 2021, 12:51:21 PM
I suggest to pay some special attention to the components related to the gain section of the circuit, including components near the gain trimmer.
Thanks for your help mon ami. I think everything is in the right place because everything works: I get sound and all the pots respond as expected. The only issue is that weird whistle.
BTW I studied French for some years but I haven't used it in a long time.
Quote from: bluebunny on January 29, 2021, 03:45:04 AM
Welcome. :)
Any reason why you've swapped those two pots round? Those long flying leads in a high-gain pedal are inviting coupling and feedback.
Thank you!
In the original layout the pots were, from left to right, Treble-Mid-Bass. My OCD wouldn't take it so I decided to move them around.
I thought about the chance of those cables behaving like an antenna of sorts but it doesn't make a difference when I move the pots to different positions, even farther away from the board.
I was doing some testing last night and I noticed that the noise interacts with the tone control of my guitar. It lowers its pitch when I darken the tone and disappears when I close it completely. I don't know if that's obvious or it points to something being wrong in the Input section of the pedal.
Try using a buffer in front of it. Many high-gain circuits behave the same way when connected directly to the guitar (the HM-2 is another example). If the problem goes away when it's fed by a low-impedance source, then it can likely be mitigated somewhat by using shielded input wire.
Also try adjusting the gain trimmer and see if that changes anything. If it's all the way up then even low drive knob settings will still be pretty high gain overall.