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TOPIC: Loud pop when engaging/disengaging pedal

Loud pop when engaging/disengaging pedal 7 months 1 week ago #1727

  • martcus2727
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Is it normal for the pedal to make a loud pop when you engage or disengage it? Also, even with the mix volume all of the way up the pedal is sucking some of my volume.
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Loud pop when engaging/disengaging pedal 7 months 1 week ago #1730

  • aalbinger
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I too am getting a noticeable pop when turning the pedal on and off using the footswitch. I don't hear any volume difference between on/off with the mix at 10.

I haven't gone looking for the source of the pop yet but LEDs engaging when the footswitch is engaged is a common culprit. In the case of the Time Manipulator both of them come on at the same time.

I haven't done any code hacking yet but it should be fairly straight forward to temporarily alter the LED behavior and see if the pop goes away.

-Andrew
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Loud pop when engaging/disengaging pedal 7 months 5 days ago #1735

  • Ray
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Is it normal for the pedal to make a loud pop when you engage or disengage it?
We have added a pull-down resistor mod in the instructions, basically adding a 1M to 2.2M resistor from the input to ground so the C1 cap gets discharged and attenuates the pop when the pedal is engaged:
POP.jpg


It helps but some engaging sounds are still present when the pedal is stomped, maybe as aalbinger mentioned, is worth to have a look to the software side and check if the current taken by the 2 LEDs are adding a current spike that makes all pop. Thanks for pointing it out.



Also, even with the mix volume all of the way up the pedal is sucking some of my volume.
I have been testing it these last 2 days, if you have a look at the output adder:

Time-Manipulator-Output-Adder_2019-04-06.png


It works under the typical op-amp adder formula:
-Vout = (R29/R25)Audio_in + (R29/R28)Taps
In theory R29 = R29=R28=R25=4.7K, so there should be no attenuation, BUT the analog switches (CD4066) have a 300Ω Typical On-State Resistance. This resistance can inbalance the equation, resulting in a marginal attenuation.

That's an easy to fix issue, just making the R29 a bit bigger (instead of 4.7K, make it 5K or even bigger up to 6K) will make a bigger Vout.
Using an oscilloscope, with the standard circuit I measured:
r29-4k7.png

So the output signal is 925mV, a 3.34% smaller than the original 957mVpp input signal

At this point, I changed the R29 for a 5K resistor:
r29-5K.png

And the output is exactly as big as the input, showing that the maths are correct.

It is a very small difference, and for the sake of a reduced (easier to source) bill of materials, I believe is better to keep R29 as 4.7K, but please feel free to experiment and make it bigger :P
Last Edit: 7 months 5 days ago by Ray.
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