Typical Klon circuit, buzzing when Gain pot is at 50, and gets faster as it gets to 100%

Forum dedicated to helping people debug and troubleshoot non-functional pedals or builds. Please use an clear and informative title, indicating circuit and basic problem. Don't forget to mark the issue as fixed if this is the case.
Post Reply
User avatar
Ferniff
Information
Posts: 38
Joined: 16 Sep 2022, 22:25
Completed builds: Midi controller
State Variable Filter
Has thanked: 11 times
Been thanked: 2 times

Post by Ferniff »

Typical run of the mill Klon clone, but I'm having trouble finding my exact issue online. Pedal works fine in bypass mode, and tone/gain seem to function to some degree. There is a buzzing noise that gets introduced to the output when the gain pot is about half way. The buzzing sound gets faster as the gain pot continues to max out. Schematic included, A1-3 and B1-3 is the dual 100k Potentiometer for gain. I realized on paper that one side of that is reversed and I already fixed that but the problem persists.


User avatar
Manfred
Tube Twister
Information
Posts: 1964
Joined: 04 Apr 2009, 23:42
Has thanked: 1691 times
Been thanked: 1376 times

Post by Manfred »

It is not possible to enlarge the image with the schematic.

User avatar
Ferniff
Information
Posts: 38
Joined: 16 Sep 2022, 22:25
Completed builds: Midi controller
State Variable Filter
Has thanked: 11 times
Been thanked: 2 times

Post by Ferniff »

Manfred wrote: 02 Jun 2024, 20:21 It is not possible to enlarge the image with the schematic.
What about this:





https://imgur.com / a/ en9J0fm

My guess is it's the charge pump (IC3 TC1044).
Attachments
chargepumpboard.JPG
3dKlonk.JPG
Klonk.png

User avatar
mauman
Cap Cooler
Information
Posts: 453
Joined: 17 Jun 2017, 20:01
Location: Texas, US
Has thanked: 456 times
Been thanked: 188 times

Post by mauman »

Charge pump would be a constant whine, not likely varying with Gain setting. What op amps are you using? The problem sounds like oscillation.

User avatar
Ferniff
Information
Posts: 38
Joined: 16 Sep 2022, 22:25
Completed builds: Midi controller
State Variable Filter
Has thanked: 11 times
Been thanked: 2 times

Post by Ferniff »

PXL_20240602_230631236.MP.jpg
mauman wrote: 02 Jun 2024, 22:58 Charge pump would be a constant whine, not likely varying with Gain setting. What op amps are you using? The problem sounds like oscillation.
TL072, from Digikey I think.

I used my cheap Amazon Oscope and found the oscolation begins at pin 7 of U2, pin 5 and 3 are stable. The oscillation changes only when the gain pot moves, not the treble/tone pot.

This snapshot is touching C13. It's pretty much the same signal I get when I connect straight to output.

User avatar
mauman
Cap Cooler
Information
Posts: 453
Joined: 17 Jun 2017, 20:01
Location: Texas, US
Has thanked: 456 times
Been thanked: 188 times

Post by mauman »

You're missing a connection. The left side of C13 and R18 should tie to op amp U2B pin 6.

User avatar
Ferniff
Information
Posts: 38
Joined: 16 Sep 2022, 22:25
Completed builds: Midi controller
State Variable Filter
Has thanked: 11 times
Been thanked: 2 times

Post by Ferniff »

mauman wrote: 03 Jun 2024, 02:24 You're missing a connection. The left side of C13 and R18 should tie to op amp U2B pin 6.
You're right! Thank you. I'll solder that in tonight but that's a big mistake on my part.

Thanks!

User avatar
plush
Cap Cooler
Information
Posts: 654
Joined: 08 Dec 2015, 09:29
Location: Moscow, Evil Russia
Has thanked: 36 times
Been thanked: 175 times

Post by plush »

mauman wrote: 02 Jun 2024, 22:58 Charge pump would be a constant whine, not likely varying with Gain setting.
Nope. Larger the gain, larger the charge pump whine.

User avatar
FiveseveN
Cap Cooler
Information
Posts: 603
Joined: 25 Oct 2009, 21:20
Location: Romania
Has thanked: 216 times
Been thanked: 121 times
Contact:

Post by FiveseveN »

plush wrote: 03 Jun 2024, 15:35 Nope.
"Fast" relates to frequency.
"Large" relates to amplitude.
The OP is describing the former.
Ignorance more frequently begets confidence than does knowledge. (Charles Darwin)

User avatar
plush
Cap Cooler
Information
Posts: 654
Joined: 08 Dec 2015, 09:29
Location: Moscow, Evil Russia
Has thanked: 36 times
Been thanked: 175 times

Post by plush »

FiveseveN wrote: 03 Jun 2024, 15:41
plush wrote: 03 Jun 2024, 15:35 Nope.
"Fast" relates to frequency.
"Large" relates to amplitude.
The OP is describing the former.
Sorry, I've misinterpreted the thing.
Then, yeah, the issue is unconnected feedback network.

User avatar
Ferniff
Information
Posts: 38
Joined: 16 Sep 2022, 22:25
Completed builds: Midi controller
State Variable Filter
Has thanked: 11 times
Been thanked: 2 times

Post by Ferniff »

mauman wrote: 03 Jun 2024, 02:24 You're missing a connection. The left side of C13 and R18 should tie to op amp U2B pin 6.
Connected it. The problem never went away. Gain pot still controls the frequency of the buzzing.

User avatar
Ferniff
Information
Posts: 38
Joined: 16 Sep 2022, 22:25
Completed builds: Midi controller
State Variable Filter
Has thanked: 11 times
Been thanked: 2 times

Post by Ferniff »

[/quote]

Sorry, I've misinterpreted the thing.
Then, yeah, the issue is unconnected feedback network.
[/quote]

Unfortunately that was not the case. I connected that section of the circuit to pin 6 of U2. Buzzing still persists when the gain pot is half way, and speeds up in frequency but not in amplitude when I continue to turn the gain pot.

User avatar
Ferniff
Information
Posts: 38
Joined: 16 Sep 2022, 22:25
Completed builds: Midi controller
State Variable Filter
Has thanked: 11 times
Been thanked: 2 times

Post by Ferniff »

Pictures of the PCBs. Blue wire is connecting the correct side of R18 to pin 6 of U2. Continuity checker confirms they are connected. Two diodes not soldered in are the clipping ones, for testing. Using this power supply at 9 volts.
Attachments
powersupply.JPG
KlonPCBTop.jpg
KlonPCB Bottom.jpg

User avatar
Lani
Solder Soldier
Information
Posts: 211
Joined: 22 May 2017, 11:57
my favorite amplifier: Bassman 5f6a
Completed builds: .....ummmm yeah. Too many to list.....
Location: Ithaca, New York
Has thanked: 142 times
Been thanked: 97 times

Post by Lani »

I would try it with a different power supply and see if it's still there. Try taking the zip tie off the bundle of wires may help as well.

User avatar
Ferniff
Information
Posts: 38
Joined: 16 Sep 2022, 22:25
Completed builds: Midi controller
State Variable Filter
Has thanked: 11 times
Been thanked: 2 times

Post by Ferniff »

Lani wrote: 04 Jun 2024, 10:11 I would try it with a different power supply and see if it's still there. Try taking the zip tie off the bundle of wires may help as well.
I'll try that. There is no zip tie.

User avatar
Lani
Solder Soldier
Information
Posts: 211
Joined: 22 May 2017, 11:57
my favorite amplifier: Bassman 5f6a
Completed builds: .....ummmm yeah. Too many to list.....
Location: Ithaca, New York
Has thanked: 142 times
Been thanked: 97 times

Post by Lani »

Sorry, just assumed there was one hiding behind the LED. If trying a different power supply or even a battery doesn't help then I would agree with you and say its the charge pump... Was it purchased at digi-key as well?

User avatar
Ferniff
Information
Posts: 38
Joined: 16 Sep 2022, 22:25
Completed builds: Midi controller
State Variable Filter
Has thanked: 11 times
Been thanked: 2 times

Post by Ferniff »

Lani wrote: 05 Jun 2024, 12:09 Sorry, just assumed there was one hiding behind the LED. If trying a different power supply or even a battery doesn't help then I would agree with you and say its the charge pump... Was it purchased at digi-key as well?
Charge pump is from Digikey. This one: https://www.digikey.com/en/products/det ... CPA/442765

I didn't experiment with another power supply yet,but earlier in the week when I was probing and looking for the source of the sound, I could not find it while probing the charge pump. It starts from the second TL072. I can find threads on a charge pumps giving noise, but I can't find any trouble shooting threads regarding a buzz that increases in frequency and not volume when the gain pot turns. Turning the treble/tone pot which is connected to the source of the problem does not affect the buzz. It's very bizarre. I was hoping my miss connection with the 2nd opamp was the issue but it was not.

Thank you for your advice.

User avatar
mauman
Cap Cooler
Information
Posts: 453
Joined: 17 Jun 2017, 20:01
Location: Texas, US
Has thanked: 456 times
Been thanked: 188 times

Post by mauman »

I think I would remove U2 and verify all the connections and components around it. Sure sounds like you're getting oscillation out of pin 7.

Post Reply