Footswitch for Delay chip selection

[that fat bastard]

Hi,

I am pretty new to this whole DIY pedal building. As my second project I wanted to have a bit of a challenge and just like every other green builder, I have bitten off more then I can chew so I will need to ask for some help.

I am building a Mega chorus and Vibrato kit from BYOC. In their marketing material they claimed that I could fit another chip for longer delays (replacing the MN3207 with a V3208).... but I actually want both if possible via a footswitch. Now I have some VERY basic knowledge but I can not figure out pinning and what it all means so I could use the help in figuring out A) Can the switching even be done? B) How many pins do I have to use via the switch and what pins can I connect in a parallel to the PCB? C) What pins, if possible to use?

I have made a bit of a guess as per the image but I could really use the advice of someone that actually knows what they are doing..... I have marked in blue as to what I think need to be wired via the switch but I would love to hear from someone that isn't guessing wildly.

Thanks a ton and have a wonderful day

[Mark Hammer]

1) I wouldn't recommend it.
2) What are you hoping to achieve with the additional chip?
3) The requisite daughter board for an additional BBD would require more than simply a second chip.

[ElectricDruid]

I'd say you can parallel up the power supply pins and the Egg bias voltage. The others are not such a good idea.

In theory, you could parallel up the clocks, but that increases clock input pin capacitance, which isn't great. It's possible that whatever is driving it will have enough oomph to overcome the extra, but then again it might not. Hence, not a great idea.

Paralleling up the two outputs is a no-no since we want to switch from one delay to the other, so they've got to be separate.

That only leaves the input. Paralleling the two inputs will increase the load on whatever is driving the delay line. Again, this might work, but again, it's not a fantastic idea.

So, in summary I'd say you *have* to switch the two outputs, and *most likely* you have switch the input and the clock pins too - so five connections in total.

[Scruffie]

It's not a perfect solution but the simplest way I can think of would be to just use the v3208 and have a switch to halve the clock cap to take it to 3207 delay time territory.

Literally switching between two BBD's is probably a non-starter as has been explained, you'd really want to have two 3207 in series always in circuit and switch between the outputs which is much more complicated on an existing board than the above suggestion.

[Mark Hammer]

Scruffie's suggestion is the one more easily realized, since typically it would only involve switching one component and an SPST switch.

The caveat I would note is that changing the clock frequency range normally requires adjusting the lowpass filtering for anti-aliasing and noise-control purposes.  If one sets the filtering in anticipation of the slowest clocking, then nothing has to be changed.

[Scruffie]

The caveat I would note is that changing the clock frequency range normally requires adjusting the lowpass filtering for anti-aliasing and noise-control purposes.  If one sets the filtering in anticipation of the slowest clocking, then nothing has to be changed.

While true, that would only be the case in trying to extend the delay time of a pedal via lowering the clock frequency which isn't the goal here. If you're using a higher stage BBD (v3208 in this case), no problem and switching to a higher clock frequency for the shorter delay akin to the 3207 will make the filtering twice as heavy as it needs to be, which isn't a problem.

Now if you tried to use the 3207 to get 3208 delay times, then you'd be running in to noise.