synthy filters for guitar..

[nick d]

                                                 

                         Amended schematic , old-school cut'n'paste using real scissors . Also added control labels and
                          + and - inputs to second half of 13700 . And switched flash on .
                         

                          Yeah , you can max the resonance and play sirens with the LFO , no bother !

[nick d]

           Oh dear , it really isn't my day , is it ?   + and - inputs , I accidentally swapped them .
           
            Pin 14 is + , i.e. non-inverting , 13 is - , i.e. inverting .

            Fingers crossed , it's all correct now .

[nocentelli]

 Oh dear , it really isn't my day , is it ?   + and - inputs , I accidentally swapped them .
           
Pin 14 is + , i.e. non-inverting , 13 is - , i.e. inverting .

Fingers crossed , it's all correct now .

So the connections you've drawn are correct, just the + and - labels are swapped?

[nick d]

            Yeah , pin 13 goes to 10k to pin 9 , pin 14 is from the 10k that comes from pin 8 .
           
             Checked against my 12 V schem and the rats nest on the breadboard , which works !

[nocentelli]

Just logged in to say I layed out this circuit last night and had a quick play this morning and it works fine. I could do with a little more resonance, but I'll have a play with the "feedback" opamp and see if I can get a bit more. I'm going to try it with the envelope detector section from the BJFE snow white autowah, which looks like just drop in there. Thanks, nick d.

[deadastronaut]

cool, look forward to hearing your results...

(waiting on my 13700's..)

[nick d]

               Got a bit further on with this . Video demo included , you may wish to cover your ears .
               
                 Two LFO's tried , value of C changed to 47nF . Vr now from a buffer using similar circuit as for filter Vref .
                  - this is definitely an improvement .
               
                Added buffer/boost to input to counter volume drop . This works a treat , straight lift from the Cliff Schecht
                  design .
         
                The LFO's definitely need level controls , particularly for fast rates . Not done this yet , I'm thinking a 47k pot
                   if using a 33k resistor , and the bottom end of the pot should be Vr , NOT Gnd ?

         

[nick d]

[youtubehttp://www.youtube.com/watch?v=9UY-fVUos2E&feature=player_detailpage][/youtube]

[deadastronaut]

Here ya go..

[nick d]

       Cheers Rob !  @ nocentelli , no lack of resonance here , too much if anything !

[deadastronaut]

@nick, sounds really great man..great slow sweep.....that'll be nice with an envelope detect too...awesome.

[nick d]

                Thanks Rob ! Yeah , that long sweep is mega , with the res well up . I'm looking at envelopes
                 too - either follower or triggered . There's a fairly simple ( ! ) on  MFOS in the Noise Toaster
                 project , might be good with a momentary stomp to fire a one-off Attack/Release sweep .

[nocentelli]

I'll check over mine carefully this afternoon, problem just user error.

[nick d]

             With my values ( 47k pot + 12k res ) , the resonance increases up to around 90% pot rotation ,
              then oscillation kicks in .  I found two things that kill the resonance while I was wiring up - either
              the bottom end of the resonance pot , OR the 4k7 from IC3 , pin 2 not connected to Vref .

[deadastronaut]

@nick: just listened to the vid again...really nice.

did you get any further with this?.

[nick d]

    I am in the process of a final build - basically the circuit from the demo with a few minor tweaks , plus an expression pedal jack  .
    Didn't get any further with envelopes - it's an eight-knobber as it is !
   
   When it's done I'll post pics , clips and schemo . The vero is fairly huge and sprawling , so I won't attempt to draw that up , I'm
   sure someone else will do a neater job !
   
   

[deadastronaut]

8 knobs 

lfo leds?

lfo volumes?.

anyway, cool, look forward to the build demo man...

i now have my 13700's..

[nick d]

  Two LFO's , each with level and rate pots  and LED , resonance , filter frequency , input boost , output level . The input boost is set-and-forget so could be a trimmer , but it just adds a bit of flexibility . I might add another jack for external CV , so envelopes , sequencer , random etc. could be added later . That's what voltage control as all about !

[deadastronaut]

very nice...

[Strategy]

well done! is this HP and LP together like original MS20, or just LP?

very nice...