# Harmonic tremolo "The Pit and the Pendulum:



## chongmagic (Jan 21, 2021)




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## chongmagic (Jan 21, 2021)

Gut shot










						New item by Jonathan Freeman
					






					photos.app.goo.gl


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## chongmagic (Jan 22, 2021)

thewintersoldier said:


> How does it sound, especially against the cardinal tremolo?



I haven't directly compared the two, it sounds really good though. Of course the Cardinal has more controls.


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## zgrav (Jan 22, 2021)

I built this new pedal as well and really like it.  It has a lot of volume to boost your signal if you need/want it.  My overall impression is that it sounds a little darker than the trembling loon, and silky smooth.  The difference between the harmonic tremolo and a traditional (Trembling Loon, MBP Wavelord, EA Tremolo, or VFE Oldschool) tremolo is very subtle as far as trying to understand why it is different, but it is striking.

I like the enclosure design posted above,  I had a similar Pit & the Pendulum idea in the back of my mind, and called mine the Pendulum Tremulum.  

And for Mr. Pedalpcb --  could we get the schematic posted in the build docs, please?


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## zgrav (Jan 22, 2021)

there definitely is more of a swirling lush leslie "vibe" to the harmonic pendulum but I would not describe it as a phasing sound.


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## TheSin (Jan 22, 2021)

I have a friend wanting me to build a tremolo pedal. I’ve never built one because I’ve never needed one. Which would you recommend? Thank you!


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## zgrav (Jan 22, 2021)

If you want a simple tremolo with only rate/depth/volume you could build the Moonshot or Pendulum.   If your friend likes lots of knobs that tweak the sound go for the Trembling Loon.  And FWIW, I think the Moonshot is a simplified build of the Trembling Loon.


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## cooder (Jan 22, 2021)

Excellent! I'm a sucker for harmonic tremolo, must check this out!


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## mywmyw (Jan 23, 2021)

you should make a demo of it if you can! nice build!


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## spi (Jan 23, 2021)

I have this PCB and I'm getting ready to order some missing parts for it.

@chongmagic  Thanks for posting the inside shot, it clarified for me how to orient those photo-resistors.

Hard for me to tell from the picture, but did you use 5mm or 3mm for the opto-coupler LEDs?  The build doc says 3mm but seems like plenty of space for 5mm to fit, and I'm wondering if there's any difference in using one or the other.


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## chongmagic (Jan 26, 2021)

spi said:


> I have this PCB and I'm getting ready to order some missing parts for it.
> 
> @chongmagic  Thanks for posting the inside shot, it clarified for me how to orient those photo-resistors.
> 
> Hard for me to tell from the picture, but did you use 5mm or 3mm for the opto-coupler LEDs?  The build doc says 3mm but seems like plenty of space for 5mm to fit, and I'm wondering if there's any difference in using one or the other.



These are 3mm, I really doubt you can hear a difference if you use a 5mm.


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## jasarien (Mar 26, 2021)

I'm in the middle of building my pendulum, and I've done the optocouplers the same way you've done them here (just bending the LDR over to face the side of LED). Is the "correct" way? I've read about 'vactrols' where the LDR and LED are oriented so that the face of the LDR is touching the top of the LED, and then sealed in heatshrink (or some other opaque covering). Is there any difference, really? Will the light from the LED on the opposite side of the board interfere if not obscured?


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## zgrav (Mar 26, 2021)

ideally the only light reaching the LDR will come from the LED next to it.  it does not take much effort to shield them with the plastic cap from a soda bottle, heat shrink tubing, or even two or three wraps of electrical tape.   if the only other light source is the LED on the other side of the board that is mounted for the on/off status of the footswitch, you may not need any more isolation.   

When you are testing the board to see if it is working, though, it is important to remember the led/ldr combo needs to be in the dark for you to determine whether it is working OK.


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