Tuesday, 23 April 2013

Sadowsky Preamp

Request, and unusually for the site, this layout has been done by our very own Geiri who asked to post it here so everyone can share it, so thanks Geiri! :o)

Info about the original:

The Sadowsky Outboard Bass Preamp/DI Pedal contains the same famous circuitry built into every Sadowsky bass. Housed in a small footpedal box for use on the floor, it measures just 4.5" x 4.5" x 2.25" and weighs 1.5 pounds. Just plug your bass into the box and then go from the box to your amp, and/or direct to the board.

Controls consist of volume, treble boost and bass boost. The Preamp/DI Pedal is perfect for vintage basses where installation of an onboard preamp would affect the instrument's original condition and resale value. The Preamp/DI pedal is recommended for all passive basses, basses with active pickups, and instruments that have active electronics that can be bypassed. It also works great with all upright bass pickups.







135 comments:

  1. Thank you very much Geiri! I'm pretty sure I have to start hoarding 2N5457s.... they're getting way too expensive.

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    1. You're welcome! I couldn't have done it so nicely without Marks help. You should get as much of them as you can. I've got hundreds of J201 which are my most used JFETs but I'm definitely gonna stock up on 2N5457 as well!

      Hope the layout works!

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    3. Professional Troll?

      Cock!!!

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    4. Ha ha. Yes I was going to delete it but I decided he wasn't making anyone else on here look stupid, only himself, so thought I'd leave it :o)

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    5. Yea man! First I got confused reading the layout here, but I went to another page in this site such as build guide, offboard wiring, etc. And tada! I get confused no more
      Sorry for bad English, I'm from Indonesia!

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    6. Total Confusing Guitar FX Layouts

      You got that right !

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  2. Maybe I'm blind, but I can't seem to find D1 on the diagram. Is it missing?

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    1. It was a 1N4001 parallel protection diode between supply and ground but Geiri removed it and must have forgot to take it out of the notes

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    2. Ah yes that's true! Will fix it!

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  3. I am way excited for this! Thanks!

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  4. I am way excited for this! Thanks!

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  5. Go Geiri! Can we expect some more?

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    1. Haha maybe! I like doing this but I think I'll just start off smaller and work my way up. Mark gave me a bunch of tips that are very useful. Let's see if I can find something that isn't here but still within my ability.

      Cheers!

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  6. Great looking job, Geiri! I'd love to see more layouts from you posted here!

    I just got DIYLC a couple weeks ago and have been having lots of fun doing layouts. I'm really starting to get the hang of it but then I see how Mark uses links and whatnot and realize I still have a lot to learn!

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  7. Hey looks and sounds good - is there a schematic available for this anywhere? I think I'm going to try fitting this into a 1590A.

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  8. Just a note about this circuit.... This was meant to be installed in a bass, thus the 500k pot on the input simulates the bass volume knob. If you're building this into a stompbox, I would probably put the level control on the other end, where it's buffered. Just my two cents.

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  9. can i use a 9.1v zener instead?

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    1. I think so. I actually question if those zeners are necessary in a pedal. They look like they're doing some kind of static protection, which would make a lot of sense mounted in a guitar, but on a stompbox, I'm not too sure.

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  10. It would be easy to create a the control of middles???
    regards
    DL

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    1. Replace the 750 ohm resistor with a pot. The Fender Twin Reverb has a 10K in that slot, so that might work.

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  11. where is the input, ouput, switch etc wired? anyone know how to mod it out to be more like the one in the video with DI?

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  12. is this still not verified?

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  13. I built it and it seems to work. Only the bass pot lugs are reversed. And that little beast has lots of gain, I still need to figure out how to use it as an onboard preamp

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    1. Thanks Robin, I'll get Geiri to correct the bass lugs.

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    2. Hi is the current layout the right one for the bass lugs? What did you mean by the reversed lugs?

      I get this annoying noise like a wind blowing, only with the bass pot. When it's zero, there's no noise, but as I turn up there's the noise. All my joints are healthy and good.

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  14. Hi, is there a schematic somewhere?

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    1. http://theernie.com/?page_id=669

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  15. Could someone confirm the connections and components for Pot Middles?

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  16. 10K would be way too high for the mid control. The circuit is low impedance...bass and treble are 25k instead of 250k in a Fender, so the mid should be a 1k pot, or at most a 2k. 10k would quickly decouple the tone controls and you'd end up with a loud, midrange mess, and no control over bass and treble.

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    1. Thank you, I forgot about the divide by ten impedance trick!

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    2. In my tests about 5k is the most you would ever want to go. Any higher than that and the whole ciruit gets really loud.

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  17. Congratulations! is very good, just try it, and this really well, I have only one problem with the bass control, and I see a 1uf cap is in truth electrolytic 1uf and is not? Sorry for my English! I write from Argentina!

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  19. Built this one for a friend's birthday and found some mistakes: Vol 2 sould be vol 3 and treble 1 should be treble 3.

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  20. How would one install this onboard a bass guitar instead?

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  21. Hi I built this and added a mid range control. Check out my demo here https://www.youtube.com/watch?v=kRYZs09B2Wc

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    1. Hi Simon, i have just bulid this preamp today and getting the same bass pot problem as you mentioned above, do you know how to fix it? Thanks for your help.!

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    2. Hi Simon, how did you wire the midrange control pot? I mean how did you connect the three pot logs into the circuit board? Thank

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    3. Hey Unknown, I just redid the board and it worked again. I changed all the pots and checked all solder joints but it didn't work first time. Second time it worked!

      Nipponbass - if I'm not wrong, take the top end of the 750ohm resistor and solder it to lug 3, and the bottom end to lug 2. Lug 1 will be ground. If the sweep is reversed just swap lug 1 and 3 around. This was too long ago I can't remember sorry!

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  22. Hello all, just built this preamp as a stompbox, it works very well, the sound is very full. My only problem with subparagraph, is it too much. I applied kondenstatory electrolytic 4.7 uF and 47uF instead of 50uF 5uF and whether this could be the reason? I ask you for help. Thank you and best regards - Mark

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  23. How can I increase the high cut when I roll down the control pot?
    Thanks to all!

    paolo

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  25. How do you wire the XLR out to this schematic? Great stuff!!!

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  26. since they never got around to updating the correct treble and bass control wiring to the vero posted at the top of this page, here's the correct wiring . I also wired the volume control at the output rather than at the input for lower noise:

    http://johnkvintageguitars.homestead.com/Effects/others/Sadowsky/SadowskyBassPreamp.png

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  27. and here's a vero that's one column narrower (17x12) and it's more like the pedal version since it has the 330K pull down (anti-pop) resistor on the the input.

    http://johnkvintageguitars.homestead.com/Effects/others/Sadowsky/0001-SadowskyBassPreamp.png

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    1. Great stuff...
      I currently play an active bass but considering purchasing a passive bass too (jazz config)
      Can you reccommend this circuit for a passive bass as a pedal?

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  28. IMO, it works even better with passive basses and I believe that's what it was originally intended for.

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  29. Hi everyone,
    I built this circuit and it sounds good but my problem is when i maximize the treble
    and the tone pot of my bass i got a unwanted noise, I already checked the wiring connection and the components and it seems to be correct.

    Could anyone help me how to eliminate the hum, I will appreciate all your comments and suggestions. Thanks

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  30. John Kallas, thank you for your layout, it works ok, but I have not tested too loud yet.

    Elmer Labe in layout to the top of the page is the error:
    - "treable 3 & bass 1" should be marked as "treable 1 & bass 1"
    - "treable 1" should be "treable3"
    As in the layout of John, and This is the cause of the noise (in my case it was)

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    1. I really appreciate your reply Tomek ,
      but i already did that thanks to John Kallas for his correction.
      I am confused of my capacitor if this would be wrong.
      can i see your actual PCB?

      Here's my actual components;

      http://i.imgur.com/lCFLG6j.jpg

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    2. I had at home only cheap capacitors, maybe I replace them for some time.
      http://zapodaj.net/9012e4434d49f.jpg.html

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    3. It looks like the only defetence is the 470nf capacitor ,, I'll try to replace a ceramic instead using maylar if this can solve my problem ..
      Thanks a lot Tomek

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    4. Elmer, where did you put a potentiometer? at the Input or output?
      I have at the output, when I had at the input then was a lot of noise and drive.
      I still got little drive, but I've tested only on guitar tube amp, on headphone amp is ok.

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    5. I'm talking about volume pot :)

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    6. I put my volume pot at the output,
      my only problem is the treble pot it has hum when it reach to average to maximun resistance of potentiometer .
      I had a bad fellings of my bass tone pot too.

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    7. I have the same thing with my when I connect to the guitar amplifier, on headphone amplifier (mxr clone) is great. I have not tested on the bass amplifier.
      It is a preamp, maybe I try to connect to some audio amp.

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    8. And when I be ordering parts, I replace caps on better.

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    9. Well , good luck to both of us ill do my best .
      I hope someone can manage to help us to solve this problem :D

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    10. you will want the volume pot at the begining of the circuit. Hot bass pickups can clip this circuit quite easily. Also battery life will be better since you are would only amplify what you need rather than amplifying the whole signal only to cut it down at the end.

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  31. I've followed John's second layout (17x12) and it works like a charm.
    I've tested it in a little PA system (stagepas 400i) and the sound is very good.

    https://lh6.googleusercontent.com/-GAaWun6IABo/Uv-S1PxKtqI/AAAAAAAAAEU/-FCRE0TumTk/w1245-h827-no/P1160181.JPG
    https://lh6.googleusercontent.com/-FxfkPURiWdE/Uv-S_S__eaI/AAAAAAAAAEc/17a8KcraEGc/w1245-h827-no/P1160182.JPG

    I would have liked to install a symetrical output (xlr) but it seems to be difficult...(?)

    However, thanks John, mark, and all of you who post, almost daily, this little gifts...!

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    1. what about ure treble pot,
      Is there any unwanted noise ?

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    2. sorry for the late...
      no unwanted noise at all.
      oh! I've omitted to say that I've used A20K pots for bass and treble. (my retailer didn't have 25k...)

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  33. I just built this to spec above, and I'm having a few issues.


    First, when I don't use a high end power supply, such as a Voodoo Labs Pedal Power 2 Plus, I get an insane amount of what sounds like space reverb echo octave up. It's absolutely insane. The more I turn the treble and volume knobs, the more it acts up. Bass knob does nothing.

    When plugged in to a good power supply (voodoo labs PP 2+), the sounds are gone, but the treble control doesn't work until around 2 o'clock, and when it kicks in, it sounds like it is going to blow the speakers right out of my cabinet. The bass knob doesn't seem to do much at all, nor does the volume for that matter. I've done a bunch of builds off here with no problem, so I'm coming to here to see if anyone has any idea.

    Thanks!

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    1. there must be an error in your build somewhere. mine works great with either my bench top lab power supply or a cheap wall wart with none of the issues that you're describing.

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    2. So, I just opened the pedal back up. I touched up a few solders that may have been cold and messed with the veto a little in case something was touching and now it seems to work.

      The issue now, is that the treble pot is backwards. Meaning when the pot is turned all the way, it is no treble, and then as i back off, more and more treble comes in. Completely backwards.

      The schematic has board to Treble 3 to Bass 1, does this need to be reversed or something?

      Thanks!

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  34. hi everyone,
    i allready try to build John's second layout, and im confused what's wrong, it didn't works at all,

    btw sory for my bad english, because i am from indonesia.

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  35. So, I just opened the pedal back up. I touched up a few solders that may have been cold and messed with the veto a little in case something was touching and now it seems to work.

    The issue now, is that the treble pot is backwards. Meaning when the pot is turned all the way, it is no treble, and then as i back off, more and more treble comes in. Completely backwards.

    The schematic has board to Treble 3 to Bass 1, does this need to be reversed or something?

    Thanks!

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    1. I mentioned that the treble pot was backwards earlier but they never corrected the posted layout.
      here's how it should be wired:

      http://johnkvintageguitars.homestead.com/Effects/others/Sadowsky/SadowskyBassPreamp.png

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    3. Hi john, thanks for your great work, how can I increase the Hi cut when I roll down the treble pot? Maybe change the 100n cap on treble 2 to 200n
      regards
      Paolo

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    4. there is NO hi cut on the Sadowsky. both the bass and treble controls are boost only. flat is with them set at their minimum (fully CCW). if you want less highs you have to roll the tone knob on your bass down.

      the original's owner's manual is here: http://www.sadowsky.com/support/owners_manuals/Sadowsky_DI.pdf

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    5. Ah..ok! thanks john, I have it on board mounted, it sounds very nice but the high are ok near the full CCW and I like to have also a darker sound.
      thanks a lot!
      Paolo

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  36. I really want this as a D.I. What do I need to do to make this an XLR out. Thanks!

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  37. Does anyone have an actual schematic of this pre? Id love to etch my own board for this to put inside my bass. THANKS!

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  38. Hi, I just build this preamp and it sounds interesting.
    But I think the output volume is too low. I need to adjust full volume on my speaker just to get a fair volume.
    What's the matter? Should I use buffer in the input of the preamp?

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    1. mine has plenty of output.
      first check your voltages at the drains of the Jfets. they should be at around 4.5V. if they're not, you'll probably have low volume issues.

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    2. Hi John
      I followed your layout and it sounded fantastic. Thank you. One more thing, how to add a mid control? I mean how to connect the mid pot's lugs into the circuit board? Thank you.

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    3. since the bass and treble controls are BOOST ONLY on this preamp, it's not just a matter of adding a pot. you'd have to add an additional amplifier circuit to have a boost for a mid control. with the bass and treble controls fully counterclockwise, this preamp is flat. increasing them makes it scooped in the midrange and just adding a mid pot would only make it even more scooped which, IMO, would not be beneficial at all.

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    4. Thanks John! That was a fast response :-D

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    5. Thank you John!
      I'll try to check on this and I hope it'll get better. :)

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    6. Hi John,
      here what I've got for both of the FET:
      FET 1: Drain 7.92V, Source 0.512V, Gate 0.739V
      FET 2: Drain 7.89V, Source 0.525V, Gate 0.74V
      It's normal that they have similar voltage for both of them because they have the same source of biasing voltage. Or maybe I did wrong on the biasing?

      Another one, I changed the zener diode to zener 9V size. I thought it's fine because the supply is just 9V. But anyway, is it the problem?

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  40. Schematic Here
    http://theernie.com/?page_id=669

    I made it from the vero and built one. Sounds great. A few optional mods there too.

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  41. Great sounding little preamp. But you can switch the bass pot to a 10 k pot without problems. The circuit doesn't do anything beneath 7 or 8k (therefor a 25k lin pot is unusable. Reacts only up to 9 o'clock).

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  42. I'm going to build this circuit but I want to use it as a pedal. If so, where should I benefit more from the volume, input or output, how does the original go? I will be running my bass passive.
    Also, the 5uf(4.7) output cap, does it really have to be electrolytic, or is it 4.7 uf metal film way to big for this build?

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    1. Well it's a lot easier to find a 4.7uf electro cap than a metal film, and I imagine they used an electro on the original so you may as well just take the easy route.

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    3. Ei Charles, and regarding the volume pot, where is it on the original?
      Also, If it goes on the output, why a 100k pot, isn't 10 or 25k enough to keep impedance low?

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    4. The posted layout is the pedal version! And as you can see volume is a 500k log pot at the input.

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  44. I put the volume at the output on mine since it has less noise that way. with it at the input (like the schematic) it's running at full tilt and the circuit noise is quite noticeable when the input volume is low.

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  45. Do you use a filtered power source? I read something written buy the guys behind Sadowsky that this pedal should use one of their power adaptors because it is well regulated and filtered. I know that fet based circuits are very sensitive to noise.They work like antennas.
    So, you used the volume on the end, what pot value did you use, 100k? I don't understand the use of 100k pot at the end since it's low impedance output, shouldn't there be something like10k or 25k pot instead?

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  47. i connects the 10K and 750R resistors to ground.

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    1. I have built John's version 0001, and I am having issues. I am new to all of this and need some clarification on a few things. On the left side of the layout it says Bass2&3 and on the right side it says Treb1,Bass1. Are the connections made in the same manner, and how are they connected.
      Thank You,

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    2. Hey Martin. The Bass 2&3 connection is easy to do - just take a wire to the Bass 3 lug, and then strip a bit a bit more wire so you can also make a connection to the lug just next to it, Bass 2. Basically it means that connection is joined between both lugs. They do not need to be separate wires.

      Same goes for the Treble 3 & Bass 1 connection - you could take one wire to the Treble 3 lug, then take a wire from the Treble 3 lug to Bass 1. Whatever is more convenient. They just need to be connected together.

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    3. Charles ,
      Thank you for the reply. I'll give it a shot tomorrow.

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  48. I've just deleted the comment cause I've just realized that... :)
    Thanks for being helpful.
    Do you know what is the function of the 100k resistor on the output to ground?is it an anti-pop res, or is it part of the circuit?

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  49. This is the technical information I've found regarding this pedal, specially because I was wondering about the input and output impedance:

    "Frequency Response: 5Hz to 50KHz
    Power Source: AC Adapter / One 9Volt Battery
    Battery Life: 90 Hours
    Bass Control: +13db Boost @ 40 Hz
    Treble Control: +13db Boost @ 4 KHz
    Total Harmonic Distortion: 0.1% @ 1 KHz
    Input Impedence: 330K Ohms
    Output ImpedenceL 600K Ohms (XLR), 1K (Tuner Out), 10K (1/4" out)"

    Therefore, this makes me believe that 1: There's a 330k pulldown resistor on the input; 2: The volume pot should be on the output and it should be a 10k pot leaving no place to that 100k pulldown( it would increase its output impedance) resistor on the output as showed on the layout.
    does this make any sense?

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  50. Nevermind, I've just found that the 500kvolume pot on input with the 1M input resistor forms an +- 330 input impedance and that there's a 10k resistor before the final 1k resistor on the output.
    All makes sense now.

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  51. Yesterday i built JK's pedal version. However, i found it start distorting a little in the low end when turning up the bass pot.
    I suppose the distortion comes from the preamp and not my amp, since it distorts quite the same at different output volume levels of the preamp... but im not really sure.

    Anyone else has the same 'effect'?

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  52. I've tested mine today as well. I've used the volume pot on the input and this beast distors like hell specially when the bass pot starts going up. Segfredo, where did you put your volume pot?

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  53. I have the volume pot at the output. I actually have almost no headroom on the bass pot. I don't believe that is per design. Also did a little test with a resistor in front of the circuit to simulate the bass volume roller back a bit. That seemed to help a little

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  54. I moved my pot to the output as well. Since I don't have a 100k pot UI have a put the 500k that was used at the input. I'll be waiting for a 100k log pot to arrive. By the way, did you check the video that Simon Tan has put on youtube? His clone sounds good, it sounds as it should , no boost in volume or distortion of any kind. I'm trying to get in touch with him to see if he can help.

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  55. I also have almost no headroom for the volume pot.

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  56. Yep, the bass boosts very fast

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  57. I've built this one for my passive jazz bass. I use the two volume knobs mostly for tone nuances instead of volume. Its safe to say i mostly play with full output on my bass (both pickups 100% and sometimes the bridge pickup rolled back a bit).
    Therefore, would it be a good option to add an input (trim)pot to tune the preamp for my bass?
    And if so, should i loose the 330K resitor?


    I used JKs pedal-version: http://johnkvintageguitars.homestead.com/Effects/others/Sadowsky/SadowskyBassPreamp.png

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  58. So that sort of works ;)
    I've put a 100K trimmer where the volume pot is on Geiri's on-board version.
    So basically i have two volume pots.
    Then i dimed all pots and gradually turned back the trimpot till i had no more audible clipping.
    At this point i still had a lot more output volume then my direct signal.
    I left the 330K resistor, but i guess that basically just changes the sweep of the trimpot a bit.

    I still like to know why i seem to be one of the few with this 'problem'

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    1. And that is because there should be a 500K at the input instead of a 100K ofcourse...

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  59. So, something is really wrong with this layout. To me it makes no sense and I think that now we can this vero a better version. That Volume pot on the input makes no sense and it doesn't let the preamp work as it should. Lets consider these two things and get to a conclusion:

    1:The onboard version is 1M input impedance and 1k output impedance.
    2: The pedal version is 330k input impedance and 10k output impedance.
    So, what has changed between the two? It seems more obvious now than it did before. The volume pot should be 10k ( 10x higher than the 1k output resistor) and since it uses truebypass switching it should have something like a 470/500k resistor from input to ground that together with the first 1M resistor forms a 330k input impedance.
    Bearing this in mind: I've just wired a 10k Log Pot on the output, and since pedal is always on with no switching I've left the pulldown resistor out.
    Try it and see if it doesn't sound as it should!?
    Mine now does!

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    1. I believe the volume on the input works great, specially if you will be using basses with different output levels.
      If you want it at the output you can put a fixed resistor here instead of the input pot
      In my case a 330K resistor instead of a 500K pot was too small and seemed to be the cause for the my clipping problem
      My own logic sense tells me you should put the remaining 170K before the 100n to get the same behaviour as a 500k pot at about 65%

      I decided to keep both volume controls... because i can ;)

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  60. Hi... Today i build this.. But sound nothing, i thing my fet's is broken.... And i used this circuit. http://johnkvintageguitars.homestead.com/Effects/others/Sadowsky/SadowskyBassPreamp.png. Is that correct... ???? Please somebody explain

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  61. Anjang, Check for solder joints.
    Seg, If it works for your needs, great. This is a simples jfet preamp circuit and it works as any other of the same kind. The input inpedance is high enough so you can take basically anything you throw at it. The volume and "overloading" it's the nature of the beast. Just go to the Sadowsky site and do some investigation and you'll soon find that things are way simpler.

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    1. I have built John's version 0001, and I am having issues. I am new to all of this and need some clarification on a few things. On the left side of the layout it says Bass2&3 and on the right side it says Treb1,Bass1. Are the connections made in the same manner, and how are they connected.
      Thank You,

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  63. Hi, thank you for sharing! I did the following mods:

    - replaced the 100k resistor to ground with a 10k log pot for volume control
    - added a 10k input resistor (no input volume pot) for RF rejection and better stability (I see a 10k input resistor in a lot of commercial FET-input-based pedal schematic)
    - added a 2.2M pulldown resistor at the input to remove clicks when engaging (true bypass wiring)

    It sounds fantastic, it doesn't distort and it is ultra-quiet!

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    1. I think the 100k res on the ouput should stay there. I think it is part of the circuit.

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  64. Can this be voiced to suit an acoustic guitar?

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  65. Hi, can I use this pedal and then my marshall speaker guitar simulator straight to the mixer to play my bass live?

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  67. Just built this, sounds fine though a little noisy.

    Even when set flat its much much louder than my passive bass usually is, so I'm thinking of adding a trim pot; but just to complicate things I'm going to change my pickups to EMGs soon so I'm thinking I may need a trim pot on the input and output to keep the level sensible and prevent clipping.

    Any suggestions what values of trim pots I should use?

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  68. Built it, sounds good.

    Wondering if anyone can assist me with adding the DI/Balanced output?

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    1. hi, when I switch the power on. There is signal but immediately the signal attenuates an becomes barely audible. can anyone suggest what might be the problem? Thanks.

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  69. Hello. I made several pre Sadowsky. Correct calls, correct components and well made welds. With 2N5457 25v 10mA, it has too much noise, and some distortion. With 2N5457 25v 1mA, the noise decreases, but still enough. Increasing the treble becomes unbearable. Please can you help me. Thank you. Sorry for the bad Inglês.Cmpts

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  71. Hello all,
    Is there a chance to make this on-board?
    I want to replace my bass electronics, and I don't want to spend much money,

    Thank you :)

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  72. will this work well with a 12v ps?

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