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## Problem with clicks at the start of every envelope Moderators: altitude, adafruit_support_bill, adafruit, phono, hamburgers

Problem with clicks at the start of every envelope

Hi guys

It has been a long time ago since i've assembled my x0xb0x, but i have this awful problem with a clicking noise.
At the start of every envelope, it makes a huge click (maybe that's what DC-offset sounds like?). If i slide the notes, the click is only in the beginning.

The PSU is supossedly 9V AC, i'm gonna measure it in a few days. I have also measured everything on the board, and the voltages seem to be correct.

So i tried to change Q39, because that was his problem, but it didn't help.

If you have any ideas, hit me up, because i'm quite desperate.

fenster

Posts: 5
Joined: Wed Jan 17, 2018 2:07 pm

Re: Problem with clicks at the start of every envelope

it might help if you can record an audio clip demonstrating the issue

antto

Posts: 1636
Joined: Thu Apr 15, 2010 3:21 pm
Location: 127.0.0.1

Re: Problem with clicks at the start of every envelope

I will do that in two days (i don't have a cable for it atm. ), but it sounds a lot like the 2 audiofiles in the other topic i linked to.

fenster

Posts: 5
Joined: Wed Jan 17, 2018 2:07 pm

Re: Problem with clicks at the start of every envelope

It is a fundamental problem when switching on and off for example a sinus wave.
Only when you switch at the zero crossing then no click is audible.
Switching a sinus at max cause a step from zero to amplitude. When you do a Fourier transform on that you see frequencies appear not only at the fundamental.
This can be overcome when doing fft of a burst for example by windowing. That is to multiply the signal with another signal that cause a certain fade in and fade out behavior.
Here you find details: https://en.wikipedia.org/wiki/Window_function
so you can avoid clicks by fade in and out the signal roughly at a speed given by the lower cut off frequency.
That is you turn volume slowly enough on / off after/ before switching.
Hope that helps.

Remarks for completeness:
An AC light dimmer also switches at zero crossing to avoid high frequency components and thus interference on mains.
The spark between relay contacts when switching AC is depending on the momentary value of the mains sinus.

jps2000

Posts: 627
Joined: Fri Jun 02, 2017 4:12 pm

Re: Problem with clicks at the start of every envelope

I might be misunderstanding your point, but i don't think were talking about the same click.

There are 2 common click problems in the x0xb0x

The first, and most common, is a not so loud click (i can't hear it in all the examples i've listened to)
Here is an example of that: https://www.youtube.com/watch?v=ZKbv-EV ... e=youtu.be - and here is another https://www.youtube.com/watch?v=LGEzdcF ... e=youtu.be

THIS IS NOT MY PROBLEM - if my x0xb0x sounded like this i would be happy!

The second one, and less common, sounds like a DC off-set problem. As if the voltage drops very quick at the start of an envelope, you can hear that here:

And the waveform looks strikingly similar to this: https://www.dropbox.com/s/oj06q2k97x35j ... 3.png?dl=0

Hope this clears any confusion :-)

I will return with recordings on saturday, and thanks for the replies, gives me a little hope that i can find and fix this problem !

fenster

Posts: 5
Joined: Wed Jan 17, 2018 2:07 pm

Re: Problem with clicks at the start of every envelope

Sorry, my previous post has obviously nothing to do with your problem

jps2000

Posts: 627
Joined: Fri Jun 02, 2017 4:12 pm

Re: Problem with clicks at the start of every envelope

Sorry for being so slow!

Here's 4 examples in a rar-file, they are quite low in volume.

I realize now, there's an unhealthy amount of noise coming out of my x0xb0x. I probably have more than 1 error to correct :)

https://www.dropbox.com/s/18z549li86jty ... x.rar?dl=0

Sample 01 is in Random mode
Sample 02 is in keyboard mode, where i show that the slide is not effected by this click.
Sample 03 is the same note pressed, and some knobs turned
Sample 04 is Random mode, while turning some knobs

fenster

Posts: 5
Joined: Wed Jan 17, 2018 2:07 pm

Re: Problem with clicks at the start of every envelope

jps2000

Posts: 627
Joined: Fri Jun 02, 2017 4:12 pm

Re: Problem with clicks at the start of every envelope

jps2000: that page describes a clicking that is specific to the bassbot, i've never seen it happen in a x0xb0x

fenster: how did you record this?
the analog voice (the VCO->VCF signal is very quiet) in your recording
other than that, the actual clicks come from a DC offset before the VCA, which can be compensated by adding a little modification
the first part of this post: viewtopic.php?f=13&t=16764&start=150#p202878

but the volume issue is disturbing

antto

Posts: 1636
Joined: Thu Apr 15, 2010 3:21 pm
Location: 127.0.0.1

Re: Problem with clicks at the start of every envelope

I recorded it from the mix out on the x0x, into my mic-jack on the PC, and then i turned the volume knob up, on the x0x until i could see sound was coming through.
This wasn't played at full volume, because i was concerned that i would damage the soundcard in my PC.

It sounds exactly the same when i listen to it through it's headphone jack, so i the sound you hear is what the x0xb0x makes.

When building it, we tested the VCO, and it looked like it should. So i think all the faults are in the EG and/or filter

fenster

Posts: 5
Joined: Wed Jan 17, 2018 2:07 pm