King midas

[Ramilrodriguez]

Hello. New on this forum. I finished building a king midas. To my liking sounds great on the low setting with the bat46 diodes. Replaced the clipping leds for 1n914 diodes because to my liking the clippind voltage was too high with the leds and the signal too strond. Like it more with the 914s. Love the sound of the pedal but I’m getting a whistling noise. With the vol and tone adjusted to match bypassed signal I hear the noise after 9o'clock on the drive. I was wondering if that’s the way this pedal behaves or if there is something wrong. I traced the signal path with a scope and the noise starts to show at the clipping stage at the output of op amp2 (pin7 of the lf347). Any thoughts? Thanks.
PD: The LambChop sounds great too.

 

[Nostradoomus]

Have you got a TL074? Try that for fun

 

[Ramilrodriguez]

Actually yes. I did try that one. Heard it a little clearer but also a little lower gain and vol at same levels on the pots but the differences were very subtle. Both sound great. I wish I could get rid of the whistling noise.

 

[Nostradoomus]

Is it whistling all the time? Which charge pump did you use? Make sure it is IC7660S, the S suffix is extremely important

 

[Ramilrodriguez]

Yes it is a 7660s. And yes whistles all the time when the pedal is at usable levels. When pots are low it stops but when is stops the vol and tone levels are useless. The pedal sounds great when dialed but when you are not playing the whistling is loud.

 

[Ramilrodriguez]

Thanks man. What you said made me decide to try an lt1054 I had. Bended pin 1 and tried it and whistle gone. Seems like a poor quality 7660s. It doesn’t say icl it says cpaz.

 

[Nostradoomus]

Awesome. There’s lots of fake ICs out there!

 

[Ramilrodriguez]

Tried a max1044 and same whistling. I guess I’ll get some more lt1054 because that was my last haha!

 

[Nostradoomus]

Tc1044 work well too, not a bad one to stock up on as lots of the PCBs here use them.

 

[Robert]

I suspect that if it was the charge pump causing the whistling it would do it all the time, regardless of where you set the controls.

Someone else had this issue a while back but I don't recall what the problem turned out to be.... I supposed it wouldn't hurt to try another charge pump, and you'll definitely end up using them, but I would also look at wire routing.

 

[Nostradoomus]

If you’ve got a scope or frequency analyzer of some sort and it’s putting out a constant 10khz...it’s the pump haha

 

[Chuck D. Bones]

Can we get a photo of the inside of your box and a screen shot of the 'scope showing the oscillation?

 

[Ramilrodriguez]

If you’ve got a scope or frequency analyzer of some sort and it’s putting out a constant 10khz...it’s the pump haha

I do have one. I’ll measure but I know for sure it was the charge pump because replacing the pump solved the problem.

 

[Nostradoomus]

I do have one. I’ll measure but I know for sure it was the charge pump because replacing the pump solved the problem.

All good, more of a general remark then one aimed at you hehe