Monday, 23 January 2012

Mini JFET Blend

A simple mini blend layout based on Sean's JFET schematic here:

http://seanm.ca/stomp/minblend.html

Will easily fit in a 1590A box and I probably wouldn't even use a stomp switch with this because in the unblended position of the pot, this will essentially be just a JFET buffer.  You could always add a mini toggle to bypass it completely if you wanted to.

This will make a useful little tool to experiment with blending dry and effect signals together, or to allow you to use a digital effect 100% wet so your dry signal isn't being digitised.

27 comments:

  1. hmm, wired it up, seemed to only act as a volume knob though

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  2. then again, i was using a 100kA instead of a 50kB

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  3. It isn't going to work properly with a logarithmic pot. With a linear pot, the best blend would be the middle position which lets signal in from the buffer and external signal equally. A logarithmic pot has a different sweep so in the half way position the majority of the signal with be coming from one of the two sources. To get an even blend you'd be almost at the end of one of the rotations.

    http://www.geofex.com/article_folders/potsecrets/pottaper.gif

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  4. hi mate, where does input/send go? i'm guessing "send" goes to the vero "in" on the circuit you're trying to add blend to and "return" is vero "out" of the circuit, yeah?

    and the "input" and "output" act as the new input/output to be wired to the 3pdt footswitch?

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  5. I have the same question as nicholas, can you please explain how to wire this up in more detail. thank you.

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    1. The send daisy chains from the input and then the returns comes back to Blend 3. Then when you rotate the Blend pot you're blending between the dry buffered and effected signal.

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  6. i just built one of these today. it works great, however it does seem to lose a tiny bit of level and some top end when it's running in the 100% dry side (fully CCW). i would assume that it's because the signal is being split (y'd) at the input, and if the effect, in my case a fuzz tone, has a an output level quite a bit higher than the dry signal, the fuzz slightly leaks into the clean blend. i'm going to try the split and blend next and see if that one works a little better with my particular pedal (a lovepedal silicon fuzzmaster).

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    1. Yes I think the Split and Blend would be better in most cases. That would be the one I'd go for so the send doesn't just daisy chain off the input and is actually buffered first.

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  7. Could this be made with a npn transistor? Are there any phase issues when blending with these?

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    1. Can't see why not - as it is basically just a buffer that blends two signals. You'll just need to take good care of the pinout. You'll want (from top) CEB. Or you could just insulate and twist the legs.

      Build it with a socket and you'll see if it works the same.
      +m

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    2. Thanks mirosol. And just out of curiosity, what happens to the phase of the input signal after passing through the buffer?
      Cheers

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    3. It's a source follower and so there's no phase inversion

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  8. Can someone please further explain the wiring of this? I'm just a bit confused as to how I could implement this into a fuzz circuit.

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  9. Hi could I use another linear pot different from 50K?

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  10. Hi Mark,

    Can the blend pot be eliminated and resistors used for equal gain?

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  11. Hi Man! This is a great one, but I'm having problems with pahse issueas, you know, when the pot is at 50%-50% the overall signal is almots half of the normal signal... is there some way of fixing it? Thanks!

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  12. ive been thinking of putting a blend circuit into the keeley 4 knob i finished today... but man no blend circuit has ever worked as well as the barber tone press blend. are they doing something different in there? anyone got info on that blend?

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    1. I never got this miniblender to work the way i wanted. Try this:
      http://tagboardeffects.blogspot.fi/2012/02/split-n-blend.html
      +m

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  13. Threw this together quickly tonight and it's a lot of fun. I find it works best with super weird, zany effects (I had it blended a warbly chorus, wah, phaser combo that sounded like an underwater helicopter just beneath my clean signal). Struggles a bit to share the signal with fuzzes, etc., but could be a very useful little guy in the right application. Thanks!

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  14. Could I use any blend pedal inside a box with another circuit effect or I always must to construct a new box only to the blend circuit ??

    Well, the idea is to add a Blend pot to a overdrive.

    thank you

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    1. short answer is yes, long answer is no. as long as the effect is not based on the ross compressor (Ross compressor, Dynacomp, Keeley 4-knob comp) or an effect that puts inverts the input signal with the original signal (essentially put the input signal out of phase with the original signal). i don't think you'll have that issue with many, if any OD's though, so you're good.

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  15. I built this up and I have the same problem as several others have had - just acts as a volume pot...

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  16. Just a testimonial : I’ve built this blender, and it just work wonderfully !
    At first, I had the same problem as many: a drop in volume at 2/3rd of the blend taper course. But then I realize that I put the only potti I had, a 250K log. Change it for a 50K Lin, and it now works as a breeze. Just great.
    I put it in my 3-in-one pedal for my bass (ie. Compressor, Valvecaster and phazer). The blend bypass all the chain, and I can add a bit of lows if needed by seting the sound dryer.
    That little Vero realty changed my sound.

    Many thanks to FX Guitar Layout team !!

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  17. Just ran into this, Interesting, except the link to the schematic is no longer functional ....
    Maybe it could be remedied? Or someone could e-mail it to me if it's handy?
    Or maybe I'll just have to trace it & draw it out myself.
    As always, thanks for your great work!

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