MAX 1044 charge pump noise

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Alejonqn
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Joined: 19 May 2021, 13:51
Completed builds: Klon Centaur,
Location: Argentina

Post by Alejonqn »

Good day felows, I think this topic has been discused in numerous threads but I have some specific question, may someone would like to help me with.
I´ve built a Klon clone based on Effects Layout blog, I got it right from the first time, but with the rather common problem of the charge pump making high pitched tone (oscliator frecuency) even though I used IC 7660S.
I have IC lug 1 connected to V+ (oscilator boost).

I read somewhere that sending oscilator (LUG 7) to ground will solve the problem, whell it did, butit ruined IC [smilie=a_doh.gif] , Ive realized this because on higer gains settings it started making a rapid pop noise like a helicopter blade (I think was the second Opamp clipping)
Anyway I´ve got a new one, this time I tried MAX1044, but noise was there again.
This time I´ve spent some time reading specsheets, and tried installing a capacitor from lug 7 to ground and it worked getting rid of the noise, but here came the questions:
- With the capacitor in this place I´m altering oscilator frecuency, slowing it down.
-by connecting lug 1 to V+ I´m boosting oscilator, as datasheets says:
connecting the BOOST pin to the V+ pin raises the oscillator frequency by a factor of about 6.
and then says
Increasing the frequency reduces audio interference, output resistance, voltage ripple, and required capacitor sizes. Decreasing frequency reduces quiescent current and improves efficiency.
So I´m doing both at the same time or by connecting the capt to ground I´m decoupling?
I´ve tried different caps sizes, 100uF did not stopped the noise, just changed pitch, but with 10uF and smaller ones the noise disappeared
Now what I´m hearing is like a static discharge a fast tic at equals period of time, I supose this is the capt discharging, I tried different sizes and the smaller the value the faster the repitition os the tics noise.
In my poor knowledge I installed an small size capt so as to alter the oscilator frecuency the least posible. Am i right on this?, First I tried 0.22 uF cap, but the tic was too often to be noticeable, so i tried 0.47 and 1 uF, the last worked the best obviulsy but I decided to sitck to 0.47 so as to don´t change frecuency much.
Is there any better solution to this?
I´ve read about decoupling caps and resistors but I´m not sure where to install them to try it out.
I thought of disconecting pin 1 from V+, but the Klon uses 1uF caps in the charge pump, while the specssheet recommend 10uF when pin 1 isopen, and does not specify a value when using the IC combined positive and negative converter:
1044.png
1044.png (11.76 KiB) Viewed 1439 times
By the way I´ve changed the zener to a 9.1V in order to protect th MAX1044, as it won´t be happy with more than 10 V
Thanks!! and sorry for my poor english.

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plush
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Post by plush »

Hi

Connect pin 1 to v+
Leave pins 6 and 7 floating. And make sure there's no ground polygons close to pin 7.

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Alejonqn
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Joined: 19 May 2021, 13:51
Completed builds: Klon Centaur,
Location: Argentina

Post by Alejonqn »

Hello Plush, Well pin 6 and 7 where disconnected before installing the cap.
By a ground polygon you mean ground lines around the IC?
I´m adding a picture of how its layout. I´ve build it with a perfboard.
Klon.png
Thanks

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