FV-1 mix - possible mod for full wet?

[Andyhannaman]

Hey everyone!

I'm hoping to modify the FV-1 schematic shown below from pedalpcb threeverb.



I am hoping to implement a momentary stomp for full wet (dry kill).  I noticed this schematic seems to keep the full analog dry rather than mixing within the FV-1 which makes things easier. I see a couple ways this could be possible. One, is it possible to adjust the way the mix knob is set up to have a full range to all wet, then momentary stomp could just bridge lugs on the pot.



Or, a dpdt could be used to cut off the dry signal path, but what is the best way to set this up? I am assuming when engaged (dry cut), sending the dry signal to Vref is probably best right?  I am very new to fv-1 and circuit design so please bear with my ignorance. Any other things I should consider? 

Thanks everyone for your help lately. New to the forum and everyone has been very welcoming and helpful.

[MikeA]

And a continued welcome to you!

Thinking about this, with the Balance pot set fully CW or fully CCW, you're getting full dry or full wet, with the other side shunted directly to Vref (AC ground.)  Set in between, you have the sum of both sides, attenuated.  If you have Balance set for less than 100% wet and you kill dry, you'll hear a level drop at the output.  So you need to bump up wet to 100% whenever you kill dry.   

One way to do that is with a momentary switch that opens the (normal) connection between the Balance pot lug 2 and Vref, and closes a (temporary) connection between Balance pot lug 3 and Vref.  That way, you'll get full wet and zero dry while the switch is closed.  When you release it, you'll go back to whatever ratio the Balance pot was set for. So your momentary switch should transfer Vref from lug 2 of the Balance pot (normal) to lug 3 of the Balance pot (engaged/momentary) while leaving lug 2 open.

Wire Vref to the swing contact of the momentary switch, Balance pot lug 2 to the normally-closed contact, and Balance pot lug 3 to the momentary contact as well as to the usual connection at the intersection of R4 and R9. The swing contact alternates Vref between lug 2 and lug 3 of the pot.

SPDT momentary foot switches are scarce, but DPDT can be found.  Take a look at the data sheet for SF12011F-M or similar, Small Bear and Mouser carry these.

I can't guarantee you won't hear switching noise, but it's worth a try. 

[Andyhannaman]

Thanks for the reply! The volume drop suggestion is great, and the solution seems straightforward. 

[iainpunk]

this would solve it,

cheers, Iain

[antonis]

+1 to Iain's proposal..

It saves any LED indication need due to audible popping..

[Fender3D]

+1 to Iain's proposal..

It saves any LED indication need due to audible popping..

^^
... only if you place a bleeding resistor for C2 

[antonis]

... only if you place a bleeding resistor for C2 

Or different bleeding resistors value for both caps for different intensity/duration audible sign..

[iainpunk]

+1 to Iain's proposal..

It saves any LED indication need due to audible popping..

haha, forgot to add a 1M across the switch poles

cheers

[Andyhannaman]

I do like Ian's proposal for simplicity sake.  So I should put 1M across switch poles to solve popping issue?

I already plan to send the dry path to VREF upon activating the switch. Would this be good enough?

[iainpunk]

I do like Ian's proposal for simplicity sake.  So I should put 1M across switch poles to solve popping issue?

I already plan to send the dry path to VREF upon activating the switch. Would this be good enough?

can you draw out what you have in mind? sending stuff to Vref is generally not a good idea, but i could be confused.
http://falstad.com/circuit/circuitjs.html
this is a free on-line, in-browser circuit simulator, quite basic, but does the job for 90% of things i do pedal related.

cheers, Iain

[Andyhannaman]

Sure thing! I am using kiCAD for the circuit editing/design. I guess I should include the entire plan for clarity. I plan to use a 4PDT on/on/on toggle switch to select between dry kill (as we have been discussing), full reverb length (by bridging lugs 2 & 3 on CNTRL1 pot), and both together. A 3PDT momentary stomp switch will be used to activate these settings. Here are two pictures of the thru holes around the mix knob for the dry kill, and the CNTRL1 pot for the full reverb that will be necessary for the toggle/mom switch. The 3rd picture shows the routing to the toggle and stomp to *hopefully* achieve this goal. Thanks for the help!

The dry signal path is sent to VREF when it is killed, as I figured this would be best, because this is what it is sent to when the mix is set to full wet.

*CNTRL1_lug4 is typo.... (lug3)







Also for the 4pdt toggle, I am assuming this type:

[antonis]

So I should put 1M across switch poles to solve popping issue?

Not exactly..
Put 1M from each cap "floating" plate to GND..

[iainpunk]

if you insist on sending the dry signal to a stable DC point, i suggest ground, like this,
i have a hard time seeing why antonis used the double 1M on the switch, since there is always a path to ground smaller than 1M for the wet mix capacitor.