Monday, 5 May 2014

JHS Little Black Buffer

Traced from gutshots on the blog forum posted by hahafender, thanks for the pics buddy :o).  Some of the traces on the unused side of the opamp weren't visible but the left hand side is a generic opamp buffer and that's the important bit.  I think the resistors used on the other side we're just used as suggested by the IC manufacturers to do to unused channels.  Not sure why he didn't just use a TL071 and so not require the 2 additional resistors, but I suppose that does make it at least appear further removed from the common opamp circuit that we've seen lots of times before.

Info about the original:
This may be the greatest weapon you didn’t know you needed.

For those of us who are a little “pedal happy” there can be some downfall to our tone. When running a pedal board with more than one or two effects, something called “capacitance” happens. This natural problem happens due to the amount of cable or line that your signal has to travel through, not to mention bad switching systems in certain pedals. The result is a very audible amount of high-end loss, weak signal, flabby bass and uncharacteristic pickup behavior in guitars. Another problem is the assumption that all “true bypass” is good. This isn’t true and actually can be worse than imagined.

This is where the “Little Black Buffer” steps in providing the perfect input impedance to your rig and giving you the final result of clear, natural tone that sounds like you're plugged straight into your amp no matter how many pedals you use.








58 comments:

  1. Hm... What's the purpose of the rightmost two 2M2 resistors? As I see the complete right side of the opamp is doing nothing.

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    1. The manufacturers recommend that to avoid noise from unused channels you should connect the non inverting input to a reference voltage, and link the inverting input and output. A much easier way to avoid noise from an unused channel is to use a single channel opamp :o)

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    2. help me .. i made the modded version and there is no signal..help me with the wiring

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    3. do you have some images where i can see how to wiring the modded version??.. thankkss

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    4. There was an error on the modded one which is why I removed it. I think you should be able to fix it by putting a cut between pins 3 & 6 where there is currently a gap, and then taking a 1M resistor over the top of the IC horizontally on the 4th row of the vero from the far left hand hole to the far right hand hole (and so connecting pins 3 and 6 with a 1M resistor. Give that a try and see if it fires up.

      I couldn't show the wiring in any way that would be easier than the way you see it now. Wire the input jack to the input connection shown on the board, output jack to output connection, ground to ground, 9V to 9V. And that's it.

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    5. hello its me again i just made the original version and there is no signal too..help about the resistors..there are 1/4, 1/2 and 1 watt. and also i put a cap 10u to 63V ....help me how can i to make this works..thanks..

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  2. Where is the best place to use this buffer at? In front of all my pedals or I assume at the very end of my pedals?

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    1. first pedal in your chain

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    2. Unless you have a fuzz or wha pedal that doesn't respond well to a buffered signal - these pedals should be first in the chain. In such cases place the buffer after these pedals.

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  3. Perhaps the other half of the opamp is for a buffered reference voltage?

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    1. That would definitely have made better use of it, but if that were the case then the two 2M2 resistors on the input side of the board wouldn't have been required.

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    2. I've added an "improved" modded version to the post. That is the way I would prefer to build it I reckon.

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    3. i'll be building the first one... i'd give the second a shot but i don't have 47uf caps lying around anywhere. but maybe i'll get to it soon. would be cool if someone built the second version to see how it sounds!

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    4. They will almost certainly sound identical. Buffering vref makes better use of the second channel but it isn't going to make an audible difference IMO. The extra filter caps means the second should be less noisy, but I've never heard a noisy opamp buffer anyway so again I can't see it making too much difference. Basically the second method is something I would prefer to do with the unused channel, but the main difference is two less resistors :o)

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    5. ahhhh okay cool. good to know

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  4. Hi Mark,
    I tried to build this (the second version) last night without success. I noticed you are missing a cut under the IC which I added to my build, this gave me a very quiet signal, much less volume than unity . I also replaced the chip several times with no improvement. Looking at the klon buffer, it seems the resistor values are very different for what seems to be a similar circuit. How sure are we of the resistor values in particular?
    Cheers
    Dave

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    1. Hi Dave. No the cut shouldn't be there. That connects the non inverting input of the buffer to the vbias voltage divider as it should. Make a solder bridge over the cut and post the voltages you're getting.

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    2. Ah ok, I'll stick it back then. That means by build has something else going on then because it didn't work before I made the cut, I got no signal at all. Id love to post voltages but I accidentally left my multimeter on and its now out of battery! ARGH!
      Cheers for the reply
      Dave

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    3. Let us know the voltages when you get a new battery in it. I can tell the layout is good by just looking at it, it's a classic generic buffer, so there must be a problem somewhere. Did you socket the IC?

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    4. I did, I think your layout is spot on, I reckon I have a faulty component somewhere. I'll report back when I debug.

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    5. Like Dave above, I couldn't get the modified version to work either. No signal at all. Built the regular version and it worked first try using the same socketed IC as I did on the modified... Not really sure what's going on with the modified...

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  5. can i retrofit this on a volume pedal? taking the output from this to lug 1 of the pot lug 2 to output of volume pedal and lug 3 to ground? if so what value do you think is best for the pot? 50K? 100K?

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    1. The pot lug numbering would depend on which direction the pedal actuation rotates the pot, but yes there's no problem in doing what you suggest. For a pot value if you opt for 100K log that should let the full range of frequencies through and not filter out any low end.

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    2. I guess the typical wiring for most rocker pedals.. also thinking about 100K log.. Thank you!

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  6. Hi there!
    I found only 2M resistors (closest to 2M2). Will the pedal work with the resistors I have?

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  7. Built the none modded layout... Worked perfectly! VERIFIED!!

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  8. Where is the second/modded version? Or is this it?

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    1. A couple of people have had issues with it, and although I can't see what the problem could be, I decided that the original one was the important one for this thread rather than my take on the circuit. I may add it as another buffer at some point but I'll build it first myself to verify next time I'm sat in front of an iron.

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  9. If you bring the led out of the board like this, do you still need the 2k2 resistor?

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    1. If I have room I will put the LED resistor on the board, so if you see a connection saying LED+ then you don't have to add an additional resistor offboard. That wire goes to the anode, and the cathode goes straight to the stomp switch

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    2. thanks man. sorry if you've answered a hundred times.

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    3. Hi !
      I'm a noob, but I try to understand what's going on.
      If I follow the 9v path on the board, the LED resistor is the 470R, right ?
      Isn't that low ? I usually go with 2K2 for a LED. Does something happen to the 9 volts that I don't understand ? or can I use à 2K2 if I don't have a 470R ?

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  10. i made two times the original version and doesnt work.......

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  11. Also if I am not using a stomp switch and have it on all the time how should it be wired??

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    1. Input jack to input, output jack to to output. Both sleeves to ground.
      +m

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  12. I built one the other day and all i get is a squeal sound , any ideas? i double check my layout and it all looks good. Bad IC chip?

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  13. Would a TL082 be an ok IC replacement?

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  14. Hey guys, how is this schematic? can you guys vouch for it?

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    1. yes, it works well.... satisfaction guaranteed just around the corner ;)

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  15. Hey I'm new at this. Do I put the components on the same side as the cuts? I feel like if I make the cuts on the copper side then put everything on the opposite side that the components won't be in the right spot according to the cuts.

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    1. noooooo!!!!!!

      just read this first!!

      http://tagboardeffects.blogspot.gr/2012/04/vero-build-guide.html

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    2. Ahhh I knew there was something so simple that I was missing!! Thanks!

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  16. Can I use a 100nj cap instead of a 100nf?

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    1. nj? The 'n' is relevant to the actual capacitance of the capacitor - the 'j' is there to denote the tolerance of the cap - in this case 5%. That means it will be within 5% of 100nf.

      So technically that cap you have should read 100nf j. NF denoting the nanofarad range, and j denoting the tolerance.

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    2. Check this out http://www.sentex.ca/~mec1995/gadgets/caps/capcodes.gif

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  17. Does anyone have a picture of this circuit completed that I can look at?

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  18. I'm having a hard time completing this. I can't figure out how everything connects as far as the led, jacks, and power jack. It would be awesome to see a pic so I can see exactly how everything connects.

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  19. jason go to site links and read the off board wiring

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  20. Anybody else got a pop when this buffer is in a loop ? .. ok .. what I mean is... when testing I put this buffer in a tbp loop pedal , to hear if there was an audible difference vs the unbuffered signal. I got the "common" pop of the 3pdt. Tried pull down on input and no dice, the pop was still there. And in another test... I built a blues breaker, all wired up with it's own 3pdt... all is good.. but with this buffer before the bb (as is, in line before the bb, no on/off of any kind) I got the pop again. With the bb I tried lowering the input pull down from 2M2 to 1M and in a seperate test put a 100K pulldown on the output. The pop kinda reduced, but never really go away. Is this a common thing with this or any other buffer ? Can this be fixed or should I try an other buffer ?

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  21. This has made the pedals after it pop loudly. I didn't add the led. any ideas?

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    1. Try adding 220K resistor from output to ground.
      +m

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  22. So if I attach the input to the unused opamp, and have it setup the exact same as the other opamp, do I essentially have their buffered splitter?

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  23. the led i used (ultrabright 8000mcd)was very bright with the 470R resistor, used a 4,7 k instead.

    anyways nice & easy build, Thx for the layout

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