Tuesday 11 December 2012

Analogguru SDD-3000 Preamp

Requested by a few people, this is the pre-amp section of the rack mounted Korg SDD-3000 digital delay.  One for the U2 fans who want to try to get a bit closer to The Edge's tone.

This one based on Analogguru's schematic with a simplified 9V supply.






23 comments:

  1. These have an incredible amount of dB gain. I use it as a boost and if I go more than 10% it is way too much. This and the Boss Fet preamp are my best clean boosts.

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    1. Hmmmm... Master volume control to use this as an overdrive...
      +m

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    2. Yep, probably a useful mod. Output goes to 100K log volume pot, Volume 1 goes to ground, Volume 2 is then the output to the switch

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    3. Original Korg SDD3000 has an input and output attenuators. I can't see them here. That's the reason why boosts so much, almost like fuzz.

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  2. I dropped Mark an email....

    Master volume is a good idea, but as the clipping makes this pretty bad sounding distortion, i'd suggest 20K or 25K pot log for volume - 100K log for master volume.

    Once one particular fix is committed, then this should be tagged :)
    +m

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    1. Modded version added and tagged. Cheers matey

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  3. Fantastic !

    Thanks a lot for this one.
    I will work on that i soon as I have make some easier project .

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  4. The original circuit ran at 15v, in fact the guy who makes the sdd-3kp runs his as 15v too. This circuit doesnt look like its stepping up to 15v, so wont the tone suffer ?

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    1. You can refer to this thread:
      http://www.freestompboxes.org/viewtopic.php?f=13&t=2895

      AG states, that only difference is with lower maximum headroom.
      +m

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  5. Built this circuit and it sounds great. I was wondering, I found a a labeled 9v power supply thats behaving badly and outputting 15v. Would this circuit in its current configuration run ok at 15v? I know the original one did, but since this is a trimmed down version of the original, I dont know if the opamps would suffer or such. My caps are all rated high enough,

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    1. Yes that should be no problem, both ICs can take 15V. The only reason I think that Analogguru did this version of the circuit at 9V is because it can then be daisy chained with all your other 9V effects, or a battery of course. The original circuit was actually +/-15V though and so a 30V swing, so this still won't have quite as much headroom but the differences won't be great. And congratulations on the 400th verified layout :o)

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  6. Question about +15V
    I expect to build soon this pedal.
    I have found a schematic from analogguru regarding a symmetrical Voltage multiplier, but I am absolutely not sure what a veroboard layout for such thing could look that, and how I should have to link it with the preamp Veroboard ?

    What means exactly +15V and -15V. In all the veroboard I can see, we speak only of +9V and Ground.
    does it mean I should just use the +15V on the +9V Rail from the preamp, and ignore the -15V (not connected ??)

    for my information as newbie, pleas help me to understand (even If I will build first the +9V version as it is)

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    1. Analogguru's schematic is designed to be run with just a 9V supply, you don't have to worry about the bipolar voltages. You could use a 15V adapter if you want which should give you slightly more headroom, but he did this scheme in the first place so it could be run off a 9V battery.

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  7. Thanks.
    I have noticed that Analogguru schematic is made for +9V with different choice of diodes in comparison with -/+ 15V version.
    My question was more regarding the Voltage multiplier alone, to better understand this schema and learn something.
    is this -15V/+15V equivalent to ground/+30V ?
    I mean, it is not a "simple" votlage multiplier, isn't it ?
    (What could be a Veroboard fur such schema ?)

    Once again, Thanks. I will build the +9V Version

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    1. Yes +/-15V is a 30V swing and so the equivalent of 0 to 30V. With +/-15V, it references to ground, whereas in most effect pedals that use a simple 9V supply, a half voltage reference is created (vbias 4.5V) which in this circuit is done with the two 22K resistors at the right hand channel of IC1. More voltage will give you more headroom, but Analogguru suggested that the difference wasn't great.

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  8. could work also a preamp for piezo acoustic guitar?

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  9. swanky sound

    to less noisy
    replace 4p7 cap to 47 p, 10p to 100 p

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  10. Hello,sorry for the question but i'm a beginner in diy stompboxes.
    I've just populated the veroboard with components and approacing to wiring,but i don't understand where is the output from the board.
    I know that the Master 2 goes to 3pdt output then to the tip of output jack and i think the board output goes to Volume 3 but....where is it? :-D
    Thanks to anyone who responde to my question.

    Cheers,

    Luca.

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    1. Volume pot's lug 3 is not connected. The Master pot's lug 2 is the output - which you take to your bypass switch.
      +m

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    2. Many thanks mirosol!

      I'm finished to wiring just now,directly to in/out jack without 3pdt/led for test,but unfortunately doesn't work..:-D..tomorrow while i'm less tired and more refreshed i'll check up what i mistaken.

      Thanks again,

      Luca.

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    3. Yep,i've powered with 9v battery and it's really ok...i don't know if the dc jack is faulty.

      But more probably if i thinking very well the problem was myself,if i correctly remember yesterday i wrongly inverted the in/out jack of guitar/amp. :-O x-D

      Now i will try the JRC4558DD if produce a little bit of extra drive respect the D version.

      Finally this layout is verified also from me,many thanks to all.
      Cheers,

      Luca.

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  11. If i'm removing the diodes, can i turn this into a clean preamp?

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    1. It could possibly be a bit cleaner but I'm not sure how much affect those diodes will have anyway. The diodes are following a buffer and so it's not like the signal is going to be particularly high when it hits them, and it's after the diode that the opamps act as amplifiers. So yes you could try it, but you may also want to decrease the value of the 330K resistor at the top left to reduce the gain from the last stage.

      Basically you may need to experiment a bit with the stages to get it reacting as you like.

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