# Captain Bit Filter



## GabeC (Jul 4, 2021)

I seem to have issues with ONE pot, and that’s the filter knob. It doesn’t seem to attenuate any of the signal. I’m not familiar with the original pedal, so I’m not sure how it reacts appropriately, but in my build it’s not doing anything at all. I checked and rechecked to make sure the right pot was installed and soldered up right, but it’s the only pot that doesn’t do anything to the signal. Is there a certain input range it responds to? Or perhaps it only handles higher frequencies?


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## Mcknib (Jul 4, 2021)

It should change the tone 

Check C13 value and solder joints 

*Filter* – Controls the overall tone of the circuit, noon is flat and gets darker counter clockwise and brighter when turned clockwise


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## GabeC (Jul 5, 2021)

Mcknib said:


> It should change the tone
> 
> Check C13 value and solder joints
> 
> *Filter* – Controls the overall tone of the circuit, noon is flat and gets darker counter clockwise and brighter when turned clockwise


Yeah, I seen that, but it’s not doing anything in my build. Every other pot does, and it works great, but not a thing with the filter.

Going to double check C13 and see if maybe it was a bust.


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## Mcknib (Jul 5, 2021)

GabeC said:


> Yeah, I seen that, but it’s not doing anything in my build. Every other pot does, and it works great, but not a thing with the filter.


Weirdly enough I just posted about getting a few duff alpha pots over the last couple of years 

Did you check your pots all good changes resistance as you turn it etc 

There's not a lot around that part so if you haven't already continuity check everything connects as it should 

As I said I'd double check C13 make sure the ground side is connected to ground


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## GabeC (Jul 5, 2021)

Mcknib said:


> Weirdly enough I just posted about getting a few duff alpha pots over the last couple of years
> 
> Did you check your pots all good changes resistance as you turn it etc
> 
> ...


I do have a bit too much trust in components being acceptable as delivered. Let me check it out and see, fingers crossed it’s just a wonky pot. Thanks for the feedback!


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## Cucurbitam0schata (Jul 6, 2021)

For what it's worth: My filter pot always made me wonder, too. The diff is very subtle compared to the more drastic pot neighbors on the pedal.


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## giovanni (Dec 29, 2021)

Just built this and I also noticed that the filter knob is really subtle. I think it does make a difference, especially when the octave up is in the output, but it's much more subtle than I expected. Watched some demos, and I think it may just be normal.


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## giovanni (Dec 29, 2021)

This one is pretty clear:


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## daeg (Dec 30, 2021)

GabeC said:


> I seem to have issues with ONE pot, and that’s the filter knob. It doesn’t seem to attenuate any of the signal. I’m not familiar with the original pedal, so I’m not sure how it reacts appropriately, but in my build it’s not doing anything at all. I checked and rechecked to make sure the right pot was installed and soldered up right, but it’s the only pot that doesn’t do anything to the signal. Is there a certain input range it responds to? Or perhaps it only handles higher frequencies?


This is a common complaint with the Bit Commander and I've seen it a dozen times on other forums. A pedal like this really needs a multi-pole filter, but that would have added a lot of complexity.

A simple fix would be to double the size of C13. Up it to 47nF. That will bring the corner frequency of the Filter control (at max) from 1488hz to 678hz. You'll be doubling the range of the Filter pot without sacrificing anything. _-- The reason being that the inverting opamp that's feeding the LPF has very low output impedance._


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## giovanni (Dec 30, 2021)

That’s a good idea and can be also easily done after the facts by soldering a second cap in parallel with C13.


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## Bricksnbeatles (Dec 30, 2021)

daeg said:


> This is a common complaint with the Bit Commander and I've seen it a dozen times on other forums. A pedal like this really needs a multi-pole filter, but that would have added a lot of complexity.


Yup. I’m planning a synth station build of sorts, and I’m planning on entirely bypassing the filter of the bit commander and then adding a ladder filter to the end with a footswitchable envelope control of the cutoff frequency. The filter on the OG pedal seems like it was just an afterthought to make it have a nice 6 knob layout.


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## daeg (Dec 30, 2021)

Bricksnbeatles said:


> The filter on the OG pedal seems like it was just an afterthought to make it have a nice 6 knob layout.


Spot on. A multi-pole filter on a toggle switch would have been a much better option.


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