Catalinbread Antichthon

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
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Gila_Crisis
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Post by Gila_Crisis »

Do anybody here have informations and gut pictures of this pedal?
I was wonder why nobody still has opened one.
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DSV
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Post by DSV »

Hi everyone,

I'd like to share my thoughts on the tremolo section for the Antichthon and especially the control of the rate through the guitar volume pot.
As a note, I do not own the pedal nor have played it - this is my best guess.

My impression is that the pedal works based on an RC phase oscillator - think tremolo in Blackface Fender amps, but with a transistor instead of a tube.
It would look something like this:
Image
Figure 5.6.2 - Transistor Based Phase Shift Oscillator from https://sound-au.com/articles/sinewave.htm

Now, if you make one of the resistors variable (i.e. a pot), you can control the rate of the oscillator.
The higher the resistance, the slower the oscillation and the rate of the tremolo.
Again, this is done in Fender amps (SPEED knob ):
Image
from here: https://robrobinette.com/Compact_Reverb.htm

My guess is that in the Antichthon the volume pot of the guitar is used as one of these resistors.

To the pedal input, a guitar volume pot looks like the resistance between ground and the middle lug.
However, we do not have to forget that at high volume, the resistance of the pickup (~5-10k) is in parallel with the one of the volume pot (~250-500k).
In this case, the overall resistance seen by the pedal will be small.

So:
* at 0 volume, we have R=0 -> fast speed, but of course no sound.
* at middle volume, we have R=Rpot/4 -> this is actually the slowest speed.
* at high volume, we have R=Rpickup which is small -> fast speed.
- and this is what actually happens in the demos. I guess it should not work with active electronics, since the pots are usually much smaller than for passive pickups and the oscillation will be much faster.

I find this a pretty interesting feature of the Antichthon pedal - something unique I have not seen anywhere else.

What are your thoughts?

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