Saturday, 18 February 2012

Split 'n' Blend

I like these little "utility boxes"



(Please take note! This circuit will not work as a blend for pedals that invert the signal polarity (or phase). For a few examples of such pedals; the likes of Dyna Compressor/Ross Comp and their derivatives and Marshall Bluesbreaker among others. The symptom of inverted signal polarity (phase) will be significant drop in level when the blend pot is set near its middle position. This is caused by two polarity phases cancelling each other out. If you need a way to control the phase, then you need to address this accordingly.)

139 comments:

  1. Could you advise me on the what caps I should use ? Im not sure what those yellow ones are.
    Overall it looks just like what I need for my setup .

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  2. Any caps with a 5mm pitch would be perfect, or even a 2.5mm pitch and you can bend the legs out. You can get a kit of useful values from here:

    http://www.bitsbox.co.uk/polyfilm.html

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    1. thanx 4 that quick response ! as you can probably tell this is my introduction into the world of home builds :)
      Caps in particular are so varied in appearance that I thought it best to identify your choice . Ive noticed that some people stick some massive looking caps into tiny pedal circuits but is the main choice here fundimentaly one of size or audio effect ? so many caps to choose from all look so different , Values being the same .

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    2. Don't worry so much about the colours or dimensions, the vast majority of the time you would choose small and compact caps. With that in mind, for picofarad values, get yourself a collection of ceramics, nanofarad a selection of polyester film (mylar) and everything above 1uF look at electrolytics. You can get all of these is value packs from Futurlec here:

      http://www.futurlec.com/ValuePacks.shtml

      Which is a good way to start your stash for not a lot of cash.

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    3. Youve been a great help Ivlark .

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    4. Hi again lvlark .
      Ive been having some fun with this circuit for some time now ...is there any way I can bring the gain up a bit by chainging a resistor value somewhere ? The only reason I ask is because I added a bypass swich which has revealed a slight drop in signal when the circuit is engaged . If yours works at unity gain what should I be looking at chainging ?

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    5. The JFET's in this are source followers which are at most unity gain. If you've lost some signal you'll need some sort of gain recover stage like a clean boost (take your pick) to get it back up. If you like using JFETs, then maybe something like the AMZ JFET booster:

      http://www.muzique.com/tech/bipolar-j.htm

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    6. OK in that case I think I know what I have to do with a gain stage between (in) and (board) also i'd like to bring down the dry signal a notch before the pot because dry is slightly louder than wet (maybe this is because of the cheap parts i was using ?!)

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  3. How would I wire this with a 3PDT switch?

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    1. Well the send and return goes to the external effect so you don't have to worry about that. If you switch the input and output wires as with any other effect then you bypass the whole thing, like this:

      http://1.bp.blogspot.com/-k5Sh68yVU18/TzGRFKbiALI/AAAAAAAAAlk/CbfaaduUjYQ/s1600/!Offboard+wiring.png

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    2. thanks for the quick response! I'm new at this so bare with me hear but I just wanted to make sure, for the jacks would I be soldering to the tip or the sleeve?

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    3. The wires from the boards go to the tips, then all the sleeves are connected up together with all other points of ground.

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  4. verified. if not already..

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  5. Replies
    1. Putting an effect in parallel with your dry signal.

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  6. I thought about something like this yesterday. I don't see any reason why this couldn't be used with analog spring reverb tank.. But i guess it would need pre and post gain stages to recover levels after the tank. So 2 LPB1 circuits in series with send and return wires could make this analog spring reverb..

    There are a few projects still going on, but i'll promise to take this "slight mod" on before fall. I'm visioning a 19'' rack unit with two or three tanks switchable :)
    +m

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  7. just built this one and it seems to work well but loses a little level and mids/mid bass when used with my P bass. also didn't work all that well with my lovepedal silicon fuzzmaster since it actually changed the sound of the pedal due it it's lower output impedance, but IME,fuzztone/overdrives are extremely sensitive as to what level and impedance that their seeing at the input.

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  8. We don't need to ground the other open terminals of the In/Out/Send/Return sockets? or we leave it like this only?

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    Replies
    1. Yes, you'll definitely need to ground them.
      +m

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  9. think this would work well with the ts808 to be able to blend dry/wet mix?
    it's not supposed to change the sound really, or?

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    1. also, what are the 245, are they A or C?

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    2. They're just unity gain buffers so it won't really matter, justuse whicheverones you can get cheaapest! :o)

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  10. I made this today and I also found a big volume drop in the center position.. It's a shame as I would of quite liked it otherwise.

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    1. I'm pretty sure that one buffer before the out and one before the return will solve this.

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  11. i've built 6 of these now. one as a stand alone unit, and the others built-in to some of my pedals. i've used J201's, 2n5457's and BF245C's and all of those transistors sound great in them (but all of them have a slightly different tone). IME, out of the three, BF245C's seem to add a little warmth and mid bass the most, and the 2N5457's are the most transparent, but the J201's are just as nice in their own way.

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  13. Just built one and it works great. I get unity volume right through the entire throw of the pot too. I used 2n5458s.

    http://i203.photobucket.com/albums/aa227/axe_34/IMG_6081_zpsc82d46b5.jpg

    http://i203.photobucket.com/albums/aa227/axe_34/IMG_6082_zps412ac1e7.jpg

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    1. which paint do you use? And how do you do those black letters?

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  14. Would it make sense to build it in a wah/volume pedale enclosure to use it to smoothly fade in and out effects that are in the loop ?

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  15. Could this be used to blend to signals from a stereo bass? As in only connecting cables to input, return and output.

    Thanks.

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  16. If I want to build this into a box together wih an effect, do I just connect in and out to the jacks and send to input of the effect and return to the output? Seems to be a useful feature to lots of pedals.

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  17. Hi, does Split'n'Blend disconnect loop when the effects inside loop are nonactive?

    What happend when effects inside loop are active, do i hear a clean guitar with sound from loop or just from loop?

    Sorry for my english...

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    Replies
    1. No. Depends on the setting of the "blend pot", it blends from the (now buffered) input signal to the loop signal. If the pot is set at noon you hear the input signal and the loop signal....

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  18. I built this a while back, and it works great, but it really darkens my signal. I used j201's for my fets, but everything else is whats on the layout. Is there any way to preserve the high end? I put a boost circuit in front of it and turned it into a dual pedal, which slightly helps the problem.

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  19. I'm confused (big surprise). I'd like to add this to the DBA Robot. Do I have this right?

    IN --> 3PDT IN Lug
    OUT --> 3PDT OUT Lug
    SEND --> FX INPUT ???
    RECEIVE --> FX OUTPUT ???

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    Replies
    1. You got it, that's right. You may want to put a boost circuit like a LPB in front of it to preserve the high end a bit more. I use it right now for my bass rig to blend in effects, and preserve the low end.

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  20. I've got plenty of 25 k Pots but no 100k pots.
    Can I just use those instead without altering the circuit?

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    1. There's no reason you can't use 25k pots for this, I'd stock up on 100k pots though, almost every circuit uses one.

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    2. Yeah I know and I already ordered a couple of them at Banzai but they seem to have run out of em...

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    3. could you give me the full schematics of this blend ?
      Thanks

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  21. If I want to remove the pot from the vero and make it a 50/50 blend, can I just skip the pot and wire the return/output together or do I need mixing resistors? Two 50k resistors in this case?

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    1. I just used an internal trimpot to blend the signal to 50/50, which works fine. I'm getting a little noise from this circuit though. I built it in an A enclosure. The noise is only there when daisy-chaining the effect, when I use an isolated ground from a pedal powersupply it's quiet. Does anyone know what the problem could be?

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    2. noise bleeding from another effect pedal through the non-isolated daisy-chain? just an idea, i've read it in some other places :D

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  22. this thing is really amazing, you can easily use an LPB one between the board and the output to mix 3, to boost your signal to your needs, if your effect is too strong :) it just happens to need an isolated power supply because the external effect bleeds through the power feeds into the mix :)

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  23. Hi all. I've built this and am not getting any signal. I've been over the layout quite a few times. I tried all the usual suspects, swapped out the bf245s a few times, and checked for solder bridges. I installed it in an enclosure with a rat, and put the send to input of the rat, and the return to the output of the rat coming from the volume pot. What could it possibly be? I'm stumped.

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    1. What are the transistor voltages?

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    2. on Q1: G=8.68, S=8.62, D=9.2, Q2: G=8.68, S=8.62, D=9.45

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    3. There's little to no current flowing, thus the high voltages. Check all the ground/earth connections for starters

      G

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    4. checked for cold solder joints/tiny bridges.nothing. next idea?

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  24. This comment has been removed by the author.

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    1. This comment has been removed by the author.

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  25. Is there any way of adding power supply filtering to this circuit to remove the interference caused by other daisy chained effects - or must it have it's own P/S?

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  26. I have a Line6 M5 stomp box modeler that I mostly use for time-based effects, and wanted to keep my core signal intact. I built it using MPF102 JFets I bought t the local radio shack. First off I made the rookie mistake of using a metal DC power jack. Since I didn't have any plastic ones, I put a switch in the hole and hung a battery clip off it. I'll get around to ordering a proper jack soon.

    First impressions: I'm stoked! Exactly what I wanted, and I can't believe how much more "pro" my rig sounds just with keeping my pure signal out of any A/D or D/A converters. My only complaint is the volume drop in the middle. When I engage the M5 I notice it right away, and when I bypass I get my signal back. So that's a little weird. Hopefully adding a recovery buffer will help. I'm also going to add a 3PDT switch to bypass the wet signal. I'll post a pic once I have my jack installed. Currently it looks a bit disheveled with the battery hanging out the back. Not bad for my first build all in all. :)

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    1. I think that might be down to the source follower / buffer ..Ive found that simple neat circuits often perform slightly under unity including most buffer circuits . you can either incorporate a clean boost circuit in the box or stick one in the loop to bring things back up to unity . I dont think adding more buffers will cure it more likely to cause even more volume drop .

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  27. Neat circuit, very good for running two amps side-by-side. It doesn't sound exactly like I had imagined. There's a bit of volume drop on all settings which I don't like.

    I'm going to tweak it to get unity gain and then use it solely for running multiple amps.

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  28. Just finished this and it works beautifully. At least for pedals with their own volume control, easy to match the levels when you've found the right blend setting. For those of you trying it with 2n5457's, the layout has the transistors facing the "other" way (they're drawn to represent a different type). Newb mistake.

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  29. as in: a mistake that I made..

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  30. I'm building this with J-201's - am I right in thinking that I need to reverse the pinout relative to those in the schematic?

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  31. Will putting 10K trimpots instead of those 4k7 resistors...solve anything with that volume drop?
    I would like to build this for myself, because i HATE my 6534+'s serial loop...can't do anything with it...

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  32. a user on the madbeanpedals forum said that he used 2n5458 and had no volume drop in any position. worth a try i think

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  33. Hey!
    Could I use the yellow and grey wire without the pot for signal split? The input will be the "send" from another effect.

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  34. If I put delay pedal on send-return, is the signal parallel to input-output?

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    Replies
    1. Yes. So you could run a digital pedal 100% wet and the unconverted dry signal will route around the side in parallel with it. That is basically what I do with an Eventide Eclipse and TC G-Force in the loop of my amp but using a more advanced mixer.

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  35. Hi Would like to build this but with a true bypass switch Can anyone see a problem with this layout?
    http://i912.photobucket.com/albums/ac323/Bat_fastard/splitblendwithtruebypass_zps449b7e14.png

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  36. So, is that correct? Split 'n' Blend with 3PDT?
    http://s29.postimg.org/72qigfirb/Sn_B_3_PDT.jpg

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    1. One more question - what is the right position of a S'n'B? Version1 or Version2?
      http://s9.postimg.org/xxe6sxflr/ver1.jpg
      http://s21.postimg.org/54q0aufev/ver2.jpg

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    2. Either way is fine, it just depends on the usual positioning of the effects in your chain. If you have overdrive, distortion or fuzz effects permanently in your chain, and want to put a delay pedal in the blend loop, then use version 2. If you have a delay pedal permanently in your chain and want overdrive, distortion or fuzz effects in the blend loop, then use version 1. Or you can have permanent chain effects before AND after if you want.

      Tell me which pedals you're using, which you want to blend, and I can tell you the way I would do it.

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  37. Hello,
    I want to had a serial/parallel footswitch but I can't figure how to do it...
    Please, can someone help me?
    Thx

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    Replies
    1. I'm still working on the Serial/Parallel Switch.
      Do you think this can work?
      http://www.hostingpics.net/viewer.php?id=561282photo.jpg
      Thank You!

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  38. Hi, I want to mod this slightly to use in my bass rig. I want to be able to have a 100% dry signal and the use the pot to blend in the loop over the top and keep the dry 100%. Is this as simple as making a link from the buffer just before the pot to the out jack, or can I bypass the buffer and link the in to the out jack?

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    Replies
    1. I'd re-jig it slightly. Take the light blue wire from the board and lug 2 straight to the output jack, take Return to lug 3, and ground lug 1. Then your dry signal will be buffered and taken straight to the output so unaffected by the pot, and the pot will be acting as a volume control over the effect in the loop and mixing the level you choose back in with your buffered dry signal. So in the far clockwise position the full effect signal is passed to the output jack, in the far counter clockwise position the entire wet signal is dumped to ground.

      That would be a better way of doing it, as the blend control as it is won't silence the wet signal, just put 100K of resistance between it and the output.

      You can't bypass the buffer. If you do there is nothing to split the signal in the first place. If you mean could you still use the split but daisy chain out of the input straight to the output instead of passing the dry signal through the buffer and coming out of the light blue wire, then it really wouldn't make much sense. You'd get none of the advantages provided by the buffer and load down your signal immediately with the connections and passive components hanging off it, without having the benefit of anything to prevent that happening. It's a bit like buying a car and asking if you can set it going and walk alongside it :o)

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    2. That makes a lot more sense cheers, and thanks for the super fast reply!!

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    3. Hi, I have one problem that I can't get my head around. After wiring the blend up as your describe I have found that the pot is turning off the buffered signal as well as the loop signal when turned all the way off. Then when you begin to blend in the loop, the buffered signal cuts back and is then unaffected by the pot. Any ideas?

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    4. It would appear that when the return is dumping to ground so is the output which is connected to the buffered signal. But only when in the clockwise position. It is also causing some volume loss in the buffered signal.

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    5. Hi, any more advice anyone can give me on this? thanks

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    6. I've wired mine as mentioned above and I'm having the same issue with the pot cutting both signals out when turned completely off. Any ideas?

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  39. where is the best place to add a booster? last, after output? and with 2x3pdt so you can run it anyway you want it (4 ways, incl full by pass)

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  40. Would it be possible to introduce a footswitch before the pot to give the option of two pots and therefore two settings so that I could leave my Holy Grail on full and have it awash with reverb for single notes replacing chords but instantly tame it where clarity is more important? I think it's one knob is a blend anyway because on full you lose your dry signal.

    Would it need to be a 3PDT switch?



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  41. Hi

    Sorry to pester with the same/similar question. I've been playing with this circuit and have come to a halt.

    I'm trying to create a blend pedal where you can set two levels of blend and switch between them via a 3PDT and have wired that circuit into a standard 3PDT true bypass wiring.

    I've connected a 3PDT switch between two identical 100k lin pots as follows:

    3PDTSwitch - - -
    3 2 1
    - - -
    Centre switch terminal 1: connects Lug 1 on the pots to the tip of the return Jack
    Centre switch terminal 2: connects Lug 2 on the pots to the terminal on the bypass switch that is normally used for the output of the circuit board.
    Centre switch terminal 3: connects Lug 3 on the pots to the grey wire on the diagram (board output, I'm assuming)

    From then on I've wired the Bypass switch as usual and made a common ground strip of stripboard connecting the grounds from all four rings of the jacks, the board and the power socket.

    Connected up, I get the bypass signal but nothing when the bypass switch is engaged.

    Tests:

    I've followed the wiring from each lug of both pots, through the pot-select switch to their intended terminal points with a multimeter

    I've tested the circuit with one pot on a breadboard and it works

    I've followed the connections for the bypass switch with a multimeter and and they also seem sound.

    I've tried it with two pedals:

    1. Behringer digital delay - this pedal wouldn't come on as though it wasn't connected from each end and needs to be before switching on

    2. EHX Holy Grail this will switch on regardless of connection and while it worked on the breadboard pretty perfectly, in the whole circuit, nothing.

    I do intend to breadboard everything (I was overzealous and wired an idea up without testing it) but just wanted to check if there was anything I was missing or more likely assuming as I'm relatively inexperienced (built about four pedals).

    I appreciate that this isn't a querey directly about this circuit but any advice would be really welcome.

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  42. I added this in to the Keeley 4-knob, and am having an issue when the Blend knob is in the middle - I have barely any output at all. When fully CCW I get the dry signal, and when fully CW I'm getting the signal with the compressor (at least it appears I am).

    I have the input wire coming from the input lug of the 3PDT, the send wire going to the input of the comp, the comp's output (lug 2) to lug 1 on the blend pot, and then lug 2 on the blend pot to the 3PDT switch output lug. I've triple checked the layout and looked for solder issues and everything looks fine, should it be canceling out signal in the middle position or is there another way I should be wiring this up?

    Thank you in advance!

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    Replies
    1. These two circuits won't work properly, since the compression is acting as an inverting amplifer and the split/blend isn't. This means that the middle way of your blend pot is cancelling both signals out with the phase of each signal being in reverse. You'll get similar results with Marshall Guv'nor and Split/Blend if you try it. One way to address this would be to have inverting unity amplifier after the return jack and the blend pot's lug 1.

      But true. As is, this split/blend won't work with effects that invert the signal.
      +m

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    3. Dang, I was really hoping this would work to run parallel compression a la the Deep Six Voyager or Wampler Ego. Would it essentially have the same effect as that if I rewired it as Ivlark mentioned above:

      "Take the light blue wire from the board and lug 2 straight to the output jack, take Return to lug 3, and ground lug 1. Then your dry signal will be buffered and taken straight to the output so unaffected by the pot, and the pot will be acting as a volume control over the effect in the loop and mixing the level you choose back in with your buffered dry signal. So in the far clockwise position the full effect signal is passed to the output jack, in the far counter clockwise position the entire wet signal is dumped to ground."

      Although, with this way the uncompressed signal would still be passing through even if the blend was all the way up though, correct? Or would there still be a phase issue and experience cancelation?

      Thanks!

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  43. Would using a lower resistance pot help with some of the tone drain at center position?

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  44. would i be okay using a couple of 2n5088s

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    Replies
    1. No, because 2n5088's are not FETs. I would highly suggest using 2n5458's if you build this. 2n5457's have a volume loss when the pot is in the middle, but the 2n5458's do not.

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  45. i use 2n5458

    https://www.youtube.com/watch?v=9VwiAHGqpuQ

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  46. built it, very cool.

    however, a question: i expected no sound with nothing plugged in it and in the 100% wet setting, but if there's no effect in the loop (or even a cable in the send but nothing in the return) it is more or less as loud as the bypassed sound in any setting of the pot. is this normal?

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  47. So this won't work with the keeley? I only ask because lvark mentions it in the comments of that pedal. I'd love to add a blend knob to my 4 knob.

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    1. I will not. I think miro posted an explanation as to why it won't. It's due to the type of compressor it is, ie a Ross style compressor. If you search the forums Gieri posted a layout for a blend that will work with Ross style compressors.

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  48. I'm building a ROG Ginger on Perfboard which worked perfectly, and I built it into an enclosure with the Split n Blend before it in the same enclosure. It's working, but not properly - for some reason the Bypass doesn't work. I shoulda tested it out of the box more... ugh.


    Anyway.

    Any ideas why the Bypass wouldn't work? I did use an old 3PDT that is honestly probably faulty, but I was thinking my wiring might be bad. I've never had this issue before though...

    Also, when I turn the Split n Blend pot to full clean signal, I get quite a lot of effect bleed. I was thinking this may be due to the fact the Ginger is very loud, but unsure if external issues could be contributing to this. Clues would be great :)))

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    1. DUH, fixed my problem. Circuit input and board input wires were mixed up.

      Had a phasing issue in the 50/50 section using 2N5457s, but I had a friend make up a small circuit to flip the phase of the effect output. This used a couple of caps, resistors, and one 2N5088. Works a charm. :)

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    2. Any chance you could send me the circuit he used to flip the phase ? :)

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  49. Quick general question related to splitters/blenders. Basically I can split the input signal in two directions as long as I put a buffer onto each of those to bump it back up again?

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    1. Basically. That's pretty much what this circuit is.

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    2. Thanks Charles. Yeah I got the impression that's all this was doing. I was asking because I actually have two Klone buffers veros sitting here unused and was thinking based on this layout I might be able to put them to use in a similar manner. Might build one of these as well and see how they both go.

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  50. I've just built this one and I'm getting this weird issue:
    With the pot all the way down I'm getting 100% wet signal, with the pot all the way the other side, it seems that the signal is fed back into the effect over and over. I guess I probably wired something wrong... any hint? :)

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    Replies
    1. I guess make sure that you've wired the sends and returns correctly?

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    2. Send and return have been wired as shown on the schematic (Tip going to the board).
      I checked the board a few times for mistakes but could not find anything...

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  51. Hi,All!
    As I've understood, there should be out-of phase issues when you use this circuit with pedals like woolly mammoth,

    or other, that inverts signal. Will jfet buffer like one of those

    http://tagboardeffects.blogspot.lt/2014/08/buffers.html resolve the problem? If yes, which one and where to inset

    it? Thx.

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  52. in this layout the electrolytic cap is red.
    isn't it aluminum E cap?

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    Replies
    1. Yeah it's just a regular electrolytic cap. I think it's just an older graphics pack on the veroboard layout program :)

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  53. I've got a question about power. Im building this into the same box as a rat, will I be able to power both boards with just 9V eg, by linking the 9V rails on the two boards, or will I need 2x9V (let's say two batteries) with each one powering its own board?

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  54. Friends, I just finished that thing, but got a problem. I have dry sound when pot is all way down, but when i turn it up signal disappears. It becomes even if I use just a short cable from send to return. I turn pot all way up - no sound at all. What'd I do wrong?

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  55. Hey guys. I have a little problem with this one.
    If i turn my pot up and down i'm always getting 95% clean and 5% effect level or the other way around on max settings.
    Is it normal or is there a way to modify that?
    Useful Information:
    I used 2N5485 instead of 2N5458 mistakenly but it does the same with J201.
    My 100k pot only reads 90k.
    thanks.

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    Replies
    1. I'm getting the exact same issue, I added this circuit to a musket fuzz clone. Any help here?

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    2. I'm getting the exact same issue, I added this circuit to a musket fuzz clone. Any help here?

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    3. Same here. When it should be totally clean I still have a whisper of fuzz pedal.

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    4. Impedance mismatch. For starters, try 500K pot.
      +m

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  56. How would I do this with separate volume controls for each part of the signal? I seem to pretty much be able to only get 100% wet or dry with almost no blend effect. Also on any setting I have a huge treble increase and feedback in the wet signal. Makes my rat sound like a metal zone.

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    1. Also I have tried it with a clean boost circuit in front, after , and in between, to little or no avail. Could I use any old buffers for this? I am partial to trying a tl072 instead of the two fets

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  57. Hi, I finished a little angel from here, and I added this split n' blend in the same box, using the 2N5458's which some reported not having volume drop problem, but I'm still having it.
    It's a shame because it makes the split n' blend pointless.
    Any help with this?
    Thanks.

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  58. Anyone know whether a pair of 2n5952s would be OK in this circuit? I'm putting one together and have a spare pair from when I made a Phase 45 (they're not matching, hence they're not in the Phase 45).

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  59. Turns out that the 2n5952s work really well in this application. I also changed the 2 100nf caps at the Source of the JFETS (the ones going to the 2 4k7Ω resistors)to 1uf (non polarised) to let all of the low end through (I'm a bassist) and used a 4M7Ω for the input resistor as I'd run out of 2M2, but realistically, anything over 1M is good there.

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  60. Built this according to the layout but I was not pleased by the way the pot acted. I prefer the dry signal to go through all the way always and only mix in the wet. So, board output to lug 2 AND output jack. Then "return" to lug 3. DO NOT attach ground to lug 1, this will, well, ground your output. Also switched all caps to 330n for bass use,

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    1. believe it or not you don't need to change the input and output caps on this for bass, the stock 100nF is fine and you're bypass signal and engaged dry signal will be exactly the same

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  61. Built today with a pair of 2N5457's (turned around to keep the pin out correct)

    As many have said, if there is a HUGE volume drop/the bass disappears in the middle position then, chances are, the pedal in the send/return loop is out of phase of the clean signal. I had this issue on some pedal but not others (as expected). To fix this I added an LPB1 circuit between 'return' and the pot on a DPDT switch (the LPB1 inverts the phase) This way, it the volume drops massively in the middle position, flick the switch putting the LPB1 into the wet signal path et voilà!

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    1. hey man. even easier, just use 2N5458's instead of 2N5457's and you'll have no volume drop in the middle.

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    2. Nope. You are both wrong. First, the LPB does not invert phase. The volume drop you are experiencing is due to pedal in the loop inverting the phase. If LPB was to invert phase, the drop in middle position (where positive and negative phase cancel each other out - causing the drop in level) would not be present. And no, different JFET type will not affect the phase cancelling at all. Those FETs are just buffers to decouple/couple parts of the signal and act as impedance transformers. As buffers are, you could stick any NPN/N-Channel BJT/JFET/MOSFET in there and there would be no audible difference whatsoever.

      To cure the issue, you'd want to use insulated jack for the return and use DPDT switch to simply swap the + and - leads. Or just not use this particular circuit to blend pedals that invert phase. I do recall i'd drawn a layout for a blender with phase switch, but don't remember where that would be.

      This will get the job done: http://tagboardeffects.blogspot.fi/2015/01/hpf-technology-hpf-pre-2.html
      Just build that between the return jack and split board return wire. Plus you'll get a rather sharp low frequency cutter which may come in handy.

      Either way - Sorry, but both of your solutions are wrong and do not address the issue as all.
      +m

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    3. Hey Miro. The first time I built one of these years ago in a rat I had a volume drop when the pot was in the middle, but when I switched the FETs to 2N5458 or could be 2N5457 I'll have to check the volume drop disappeared and there was smoother transition and blend. Maybe there was something else going on before the swap, but I do remember that the swap fixed the issues cause I ordered around 500 of the same FETs mostly for use in this blend. Fucking odd.

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  62. I added a note to the post about the phase inversion issue, as it seems that half of the comments are about this well known issue.
    +m

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  63. The issue I had, and still have, is that a rat does not invert signal yet this circuit does not provide anything near a proper clean blend. My solution is to isolate the power supplies and outputs for each half with small 1:1 TRW brand audio transformers. Cleans it up a little but the fact the blend pot causes voltage division cannot be avoided. Still quite lossy. A separate volume control for each side fixes this, but requires the use of an lpb1 or other boost and output isolation to avoid feedback down the wet or dry signal chains. Not really fun after all is said and done.

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  64. (For some reason none of my browsers let me click on the "reply", so..)

    Zach: My bet is on that there was something else at play with yours. You could try on different FETs. By electronics theory there should no audible difference.

    apotheodaimon: Sounds like impedance mismatch issue to me. But this circuit will not be the best performing camper for many circuits. I know for a fact that it plays really well with fuzz face style circuits...
    +m

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    1. When you're right you're right. Unfortunately, there's no way to know what was going on since it was so long ago. My attitude is if it works right now, it sounds good, and most importantly it works right.

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  65. Hey everybody! I have a Deluxe Electric Mistress that sucks tone, and I thought putting it in the loop of one of these might be a good idea. Any thoughts?

    Thanks!
    Chuck French

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  66. Would a 500k Lin pot work on this?
    Thanks,
    -Yari

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  67. This comment has been removed by the author.

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  68. I want to implement this into a xesign for eurorack, which uses +12v. Do I need to change resistor values?

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