Thursday, 15 March 2012

Klon Centaur - Bare Bones

[Updated 4th July 2014 - correction to treble control resistors]

This is an easier build and is perfect for someone who wants the Klon tones without having to mess around buying charge pumps and curing squeals.  This came from a thread on FSB where earthtonesaudio wrote the following:

The charge pump in the Klon seems a bit unnecessary to me. The only logical reason it should be used is to keep op-amp U2 from clipping.
But here's the thing. When the gain pot is at maximum, the only signal hitting U2A has already been clipped by the diodes, so a typical Ge diode will limit the signal going to U2A to under 1V p-p. For this signal U2A has a gain of about 8.3. Granted, this would clip a TL072 with a 9V single supply. BUT, if you used a rail-rail op-amp, then you'd get no clipping.
That would ensure no signal coming from the distortion stage could cause clipping in U2A, even if you used +9V and 0V as the rails.

From U2A the signal goes into the tone section, where the maximum treble boost gives a gain of about 8.2 to the highest frequencies. Again referring to the situation where the gain pot is at max, that means the signal coming from U2A into U2B is about 5V (.6V p-p signal times U2A's gain of 8.3), so U2B will try to make the highest frequencies into a 40V p-p signal. The power supply can't reproduce anything (even with a rail-rail op-amp) greater than 27V, so the op-amp clips.

Another useful scenario to analyze is when the gain is set to minimum. For high frequencies, the maximum gain from lug 1 of the lower half of the dual gang Gain pot to the output of U2B is 266. An average guitar signal (especially if boosted) can easily make a .1V p-p signal, which would cause op-amp U2B to clip if the gain was set to minimum, and the treble at maximum. Of course, before the signal gets to the that lug of the gain pot, it is attenuated by the input voltage divider as well as the network at the output of U1A.

Anyway, my point is that there is some op-amp clipping possible in the Klon at normal settings, even when using the charge pump. To me, the whole point of using a charge pump is to avoid op-amp clipping. But the Klon uses a charge pump and still clips the op-amps. So why not just ditch the charge pump and use op-amps that sound better when distorted (or will operate at their rails to minimize the amount of time they spend in clipping)?

For those people that would like to fit a Klon into a smaller package (though that is of course limited by the dual gang pot and other hardware), or those who just want to use fewer of the Earth's resources in their pedal building, I think it would be nice to have a Klon alternative which operates from a single supply, with no charge pump.

And mictester very kindly produced a schematic based on the discussion.  Thankfully there's some very clever people on FSB to keep us busy!

Youtube demo:


56 comments:

  1. I built this and it works and sounds great, but there is a volume drop when the effect is active. Its about half of what the clean signal puts out. I've double checked and all the part values seem correct. Any ideas?

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    Replies
    1. Is it louder with the gain at minimum?

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    2. No, the gain pot has no effect on the output level.

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    3. Any chance it could be a bad volume pot? I'm going to swap it out later this week just to make sure.
      Thanks again.

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    4. Possibly, it could be that too much of the signal is being dumped to ground, but most of the time with something like this there's a microscopic bridge somewhere that needs sorting, either on the board, or offboard wiring.

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  2. Whelp, of course you were right. The tone knob was being grounded somewhere off board. It works great now! The knobs are very interactive. Thanks for your help!

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  3. are there any differences tonally between this one and the one with the charge pump?

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  4. Hi mark i have 2 q maby you can help me with.
    1 the dual gang pot pin out. Is the pot closest to the shaft 1-1 and so on and the second one 2-1 and so on or reverse.
    2 how do you wire the position volume 2 to output and the switch, is it 2 wires from one hole or is it first to switch and then output jack or separet wires?
    Hope you understand what i mean

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    Replies
    1. 1) It doesn't matter which one order you use the pot lugs, as long as the main 1-2-3 numbering as as per the diagram here:

      http://4.bp.blogspot.com/-Eu1vuXVH3UM/TzGNIkeLuAI/AAAAAAAAAlM/h7re0CGH6A8/s1600/Pot20numbering.jpg

      2) Again either way is fine, some people prefer 2 wires, some prefer daisy chaining, but as long as they are all physically connected it doesn't matter which way you do it. Personally I'd daisy chain but it's up to you

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    2. Ok thanks then those 2 things where correct
      2 more then
      Were do i put the - of the power jack? The + goes to the board and iv connected the - to the 2 of the stereo input jack. Should it go to ground?
      And do i connect the ground on the output jack to the ground of the input?
      Hopefully its one of this things beacuse if not its the circiut

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    3. Every point of ground needs connecting together. Ground on the board, DC adapter, input/output sleeves and stomp switch.

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  5. Thanks a lot. Now iv checked my wiring and im sure it is like it should. But my problem is in the circiut i think, in bypass i have no guitar out and in on mode therse no guitar singnal either, but when i use the pots you here an increase in hum so something is being amplified but without the guitar, the tone knob work as well you can hear it filtering from a bass hum to a trebele hum, this is an step forward i found a bridge befor removing that it was copletly dead.
    Any ideas? Thanks again

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    Replies
    1. Hello,

      If you have no guitar out in bypass, the problem is in your switch. Can be the witing (most probable)or the switch itself being defective.

      Until you get sound in bypass, the problem is in the switch / wiring. After you can hear your clean guitar on bypass, we'll be able to trace the problem, but first the wiring has to be ok.

      In bypass, no signal goes trough the circuit, just jacks, direct wires and switch.

      Anyway, always check your circuit's working BEFORE you solder the switch, will save you lots of time.

      BR

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    2. Well thanks for the answer but i dont think you are right one this one. Beacuse its wired through the board first in a buffer en then out to switch then to output jack. Normaly i would wire it with a 3dpt but this isva 2dpt and input jack goes direct to board then out trough board to switch and then back in again. But talking to you i just realized i have to first fix that singnal gets trough the board an buffer. I will fix that and then see? What do you think? Iv done 50 or so pedals but dosent help me now:)
      Tanks

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    3. Hi Jens,

      Yeah, you're right, I was sure that this one was the true bypass one. Sorry about that.

      Well, if you get no sound in bypass (buffered), the signal goes (basic) like this:

      Input jack -> 10k Resistor -> 100nf cap -> Ic Pin3 -> IC Pin2 -> 4,7uf cap -> 560R resistor -> Switch 4( two wires) -> Switch 5 -> Output jack (you can complete if any doubt with the Klon buffer layout in this blog, dual opamp version).

      The fact that you don't get any sound in bypass nor with the effect engaged makes me think that the error is in this part of the circuit, including jacks and switch. Double check the components and surrounding ones, I bet the problem is there.

      Anythinh more, you're welcome to ask.

      BR

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    4. Well i do have a copule of questions if you dont mind :)
      I can see the signal path you talked about. What woulde be the best way to trace the problem? Should i use the multimeter, im not realy shure how to ? Should use ohm when cheking connection trough resistors? What would i use to check the caps?
      I was realy thurough (sorry for the english here) so im quite shure all components are in the right place and all the cuts an jumpers. Iv checked the connections horrizantal on the board whit the signal diod thing so i know that those are ok.
      And i couldt find any bridges where there shouldt be


      Why dose the pots work at all? As i talked about before, therese an increase in hum when using the gain pots and there is an filtering effect when using the tone pot.? Its like that part works but dosent get fed any guitar signal. Ok
      Thanks

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    5. http://www.geofex.com/FX_images/audioprb.gif

      and this may help:

      http://www.diystompboxes.com/smfforum/index.php?topic=79707.0

      Make an audio probe like this, plug a cable into your amp and the audio probe into the other end of the cable, and with your guitar plugged into the Klon. Then you trace through the circuit from the start following the schematic, and find out where the sound dies.

      So for instance, at the start of the circuit (after the first input cap) you know you're going to be able to hear the guitar through the amp because the audio probe is bypassing the majority of the circuit and essentially connecting the guitar straight to the amp. As you move through the circuit you should hear the sound start to change as the pedal effects the signal, and as I said there will come a point where the sound dies completely. That will show you where the problem arises.

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    6. Few words to add. If a visual check (cold solder, loose component, misplaced ones) doesn't seem evident, you have to check voltages.

      Checking voltages on the IC's or trannies can also give some valuable information. Two days ago my Big Muff just built, showed a very low output. A voltage measure on the trannies, showed me very low curent on Q4's collector -> Just checked the collector resistor (direct from 9 volts) and it was loose at one side. I had checked it 20 times and couldn't see it at sight. A drop of solder, and problem solved, sometimes the problem is just in front of us, but we don't see it.

      My debug method:

      1. Reflow all solder. I do this everytime I finish a board. Reflow all components joining close solders in just one, takes a couple of minutes, and saves lots of time.

      2. Measure voltages on IC, trannies or other critical components.

      3. If the previous steps don't work it leads to a misplaced component, a forgotten one (yes, is not difficult sometimes to forget a cap or a resistor) or a defective one. At this point you can only use a sound probe or a signal injector..... or rebuild the board.

      BR

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    7. Thanks guys i will start be resolder and use an audio probe ill get back on e iv done that
      Thanks again

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    8. Ok i buildt an audio probe (great tool) found the problem bad connection at ic pin 2. No it works great, thanks to javicap and mark

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    9. Gratz Jens, enjoy now your Klon, one of the most awesome overdrives you can find :)

      BR

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  6. This comment has been removed by the author.

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  7. This thing sounds fantastic. Quick question for anyone who's built this. With the gain at minimum and volume at max I'm getting pretty much unity gain with the bypassed signal and the tone works fine. Seems like there should be a bit of a volume bump though.

    On another note I build this into an old DS-1 shell. This is going on my touring board and I love the idea of a stock looking shi**y boss DS1 sounding awesome.

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  8. This is pot which i need?

    http://www.taydaelectronics.com/100k-ohm-linear-dual-taper-potentiometer.html

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  9. So D1 is OA91 and D2 is 1N277?

    Where i can get those?

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    Replies
    1. No, it's giving 2 alternatives - for D1 & D2, you can use OA91 or 1N277.

      You can also use 1N34A's, which you can get from Tayda.

      Ian

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    2. And 1N34a would be similar to OA91 or 1N277?

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    3. Yes, they all have a very similar forward voltage drop so the results will be similar

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  10. Switch is not mentioned.
    http://www.taydaelectronics.com/mini-toggle-switch-dpdt-on-on.html

    This one?

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    Replies
    1. What switch do you mean? The one shown at the bottom of the layout is the stomp switch. This is a buffered bypass effect and so you don't use conventional 3PDT true bypass wiring, and you can get away with just using a DPDT stomp.

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    2. I mean this switch on layout. So for this layout i need only this one?

      http://www.taydaelectronics.com/2pdt-stomp-foot-pedal-switch-solder-lugs.html

      Or this one?

      http://www.taydaelectronics.com/2pdt-stomp-foot-pedal-switch-solder-lugs-2.html

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    3. You'll need the latching one:

      http://www.taydaelectronics.com/2pdt-stomp-foot-pedal-switch-solder-lugs.html

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  11. I have little problems with that. Bypass is working. When Klon is ON i can hear guitar quieter than on bypass, tone pot is working but it makes a lot of noise. Gain pot doesn't work at all.

    Is it a good way to wire it?
    http://oi42.tinypic.com/1zdpvd0.jpg

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    Replies
    1. Hmmm.. Seems like you got it wrong. Think of the dual pot as two normal, single pots. Gain1-1 means the 1st lug of the first pot. Gain1-2 is the lug 2 and Gain1-3 is the third.

      Try wiring it like this...
      http://mirosol.kapsi.fi/varasto/crap/DualPotLugs.JPG
      +m

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  12. Hi,

    I want to use this circuit, but without the ability to change my tone. Is it possible to remove the potentiometer and use resistors instead? If so, where do they have to be placed?

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  13. Replies
    1. Not if you use the TLC2262, that can only have a 16V swing maximum. If you use 2 x TL072s then it should be ok, but it may not sound as good without the rail to rail opamp.

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  14. What part is responsible for the bass tones?

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  15. Is there any IC comparable to the TL072 and the TLC2262? Or are these pretty common, and something I should have some of?

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  16. I'm a bit confused by the diagram. I'm trying to wire this up, but don't know what to do with "Output Jack & Sw5" and "Volume 2 and Sw6". Do I put two wires in the board, or go to the jack and then the switch, or the switch and then the jack? Just need some help wiring the switch altogether. Thank you! This is my first vero attempt. So far, so good.

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    Replies
    1. 2 wires if you like, or daisy chain from the first connection into the second. It doesn't matter as long as the connections are made between them all.

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    2. Thank you. Got it up and running. Sounds great! I am wondering about the breakup and fuzz when the volume and gain are turned all the way up, though. I get a lot of breaking up of the sound and fizzle at this setting. Is this normal, or do I have a problem? I got my diodes from a cheap supplier and I am afraid they might be of lower quality and may be contributing to this.
      Thanks again!

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    3. You may want to do the regular checks. Fizzle and fuzz are not descriptions I would describe with the sound of this pedal. Might try it with a different amp too. I have noticed a big difference in the sound of this pedal with different amps.

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    4. You can get some opamp clipping with the Bare Bones Klon at max settings, what opamp did you use for IC2?

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    5. Same result on different amps. IC2 is a TLC2262 and D1 and D2 are both 1N277, as per the build sheet. I had a feeling it was just clipping, but I don't have a lot of experience with this in a pedal. Just wanted to check in with you on it. It sounds awesome at slightly lower settings, but when pushing the gain and volume to max, it does begin to break up and lose sustain.

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    6. Ok, just checked it over again and gave it a good listen. When the gain is turned from approx 90-100%, it sounds good, but if I hit a string and let it ring out, as it fades and gets more quiet, the sound will pop, fizzle and break up, almost like a gate that can't get a fix on the threshold. It also seems to modulate a little as it rings out, with little swells in the volume. I can also turn the gain up, then without hitting a string, back the gain off until I hear the "gate" open and I can hear my pickups.

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  18. Hi folks. This is my first post, and I just want to thank the folks running the show here. What an incredible resource this site is!

    Anyways, I'm absolutely stumped on this build. I've triple-checked every value, reflowed everything, i have continuity through each IC leg through the sockets under the board, and done the switch a couple of times, but nothing.

    I've used an audio probe and it's got signal up to and on IC1-3 (when bypassed), but nothing on IC1-2.

    Here are my IC voltages for IC1:
    1 = 1.24, 2 = 1.23, 3 = 1.13, 4 =0, 5 = 2.26, 6 = 2.21, 7 = 1.09, 8 = .59

    Any help would be greatly appreciated, as I'd love to get this one wrapped up.

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    Replies
    1. Well if you're only getting 0.59V on pin 8 that is a definitely problem. Check placement and soldering of the link because that should be fed directly from the 9V row.

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    2. SUCCESS! Thank you so much! The link was just a hair too short and wasn't poking through the bottom of the board.

      I learned quite a bit about troubleshooting with this particular build, so thanks very much!

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  19. this. sounds. so. good! And worked first try (well, after missing the two wires to sw4)

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  20. In my opinion this circuit is not optimised, you can hear it in the demo video, the highest gain setting is not fuzzy and distorted enough compared to a real Klon. By doing this "mod" to get down to 9V, the second IC's gain is reduced considerably, which affects the amount of distortion and overall gain of the circuit. I'm not sure if it's a loss of feedback to the first gain stage, or just less clipping from the make up gain/summing op amp stage or both, but there is a definite loss of gain when you do the "9 volt mod." Just look up some Youtube demos for reference, or play a real Klon if you have one.

    My recommendation if you want more (and more like the stock Klon) gain, to chaing the 390 pF cap to 165 nF and the 422K resistor to 1 MegaOhm.

    This will adjust the feedback in the "gain" op amp path, while maintaining the correct Lowpass Filter value to give you more level into the clipping diodes. You can adjust these two parts higher or lower for different amounts of clipping, but they need to be in the same ratio to keep the tone correct. You can google op amp theory pages for the formula.

    I haven't compared it back to back to a 1:1 Klone build yet, but to my ears this is a better way to build the "mini klone." I know a lot of folks use this as a clean or mild grit boost, but I like having plenty of gain on tap. I don't know if 1 Meg + 165 pF is too much? gain or not, that's why I would say to adjust it to your own taste. I find that the gain knob has a nice sweep this way from clean to fuzzy.

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  21. Sorry that was a typo I meant:

    My recommendation if you want more (and more like the stock Klon) gain, to chaing the 390 pF cap to 165 pF** and the 422K resistor to 1 MegaOhm.

    **pF!!! not nF

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    Replies
    1. I have settled on 300 pF and 560K as ideal values. The 1M was a bit over the top with gain. However, I would still recommend building the standard Klon with the charge pump in tact. When you've got the gain all the way down to the clean boost setting, this bare-bones build does not really get that far past unity gain with the volume maxed. There's plenty of juice on tap with the gain turned up a bit. But still the lack of big clean boost is a bit disappointing. Go with the stock circuit, I say.

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