OCD - how do you work around impedance problems?

Discussion in 'Effects, Pedals, Strings & Things' started by SpinalTap, Sep 11, 2008.

  1. SpinalTap

    SpinalTap Member

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    hi - im new to the forum and have searched for a thread
    with a solution on how to keep the punchy mids on the ocd, and not
    the more toppy - loose of midrange - sound it gets when you have a buffer
    or buffered pedal after it. Especially with a volume pedal after - where i do
    need a buffer before runnin back to the amp.
    Does anyone else have that issue ?
    Id really appreciate any good ideas here - thanks.
     
  2. charless

    charless Member

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    My solution was to put an MXR 10-band EQ later on in the chain to cut out the highs and boost the mids and the OCD (v3) sounds fine now. The EQ acts as a buffer as it boosts the signal. You have to cut the 8K and 16K to fix the problem. You can boost the mids around 1K and 2K if you want also, I do but mainly because I have a Deluxe Reverb and I want more warm mids out of the amp.

    BTW .. I tried a little test -> the SparkleDrive got toppy and thin also with buffers in the chain, I thought it was only the OCD but maybe because the OCD is so dynamic and touch sensitive it responds more severly to buffers than a more compressed pedal like a tubescreamer. Not sure.

    If you can try to eliminate all buffers before the OCD .. usually much better cause you will need a buffer down the chain so if you have to buffer somewhere (like me) do it after (EQ, compressor), not before. Right now I am waiting for a Retro Sonic Phaser to replace my EXH Phase 90. The Retro Sonic is TB so I want that instead of the EXH Phase 90 in front of my OCD.
     
  3. Sikor

    Sikor Member

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    I had more problems with buffer before OCD (made OCD sound trebly and thin), than after.
     
  4. StompBoxBlues

    StompBoxBlues Member

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    Are there specific pedals that when ON (i.e. not the bypass buffer) tend to make this problem? Like vibes, or choruses?

    Also, I am not 100% sure after reading the OP, do you own an OCD and have heard this problem, or are you researching before buying one?
    I wonder because I have the latest (4 I think) version, haven't heard the problem with mine, and am under the impression this issue is fixed in the current OCD...if you have one, which version is it?
     
  5. charless

    charless Member

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    I would like to know also, as I have OCD v4 and would swap it with the v3 if I knew it could get along better with other pedals.
     
  6. novawind

    novawind Member

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    I have a v3 and haven't noticed any tonal differences about where my buffered pedals go. Maybe my ears aren't sensitive enough.
     
  7. SpinalTap

    SpinalTap Member

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    Thanks for the replys -
    I have OCD V3 and 4 and today i tried a little test where i plugged a long cable
    between the OCD and a buffered delay and then the OCD reacted more like
    when its the only pedal in the chain.
    The output impedance of the OCD is something like 2kohm which is a little higher than most other pedals so maybe somthing like a "capacity" box
    between OCD and buffer could do the trick.
    That is probably also why it sounds a little "darker/thicker" when its the only
    pedal.
    Does this make any sense ?
    Both V3 and 4 reacts more or less the same on impedance - same in and out
    i guess.
    I think - like most others here - that its one of the all time ODs but it sounds
    better without buffers IMHO.
     
  8. StompBoxBlues

    StompBoxBlues Member

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    I built (and posted a few weeks ago a number of the readings I got) a simple input and output impedance measuring device. I still have the readings, and on my V4 OCD I measured 283k Input impedance, and 66k (the output impedance was harder to measure with the pot I was using but ought to be in the ballpark) for output impedance.

    Generally, rule of thumb I read in Andertons book, you want 10 times the input impedance on the next pedal in line. So you want like 660k input on the next pedal...if off and buffered (if TB it won't matter til it hits a buffered pedal).

    SO, to give examples that I also measured...some other OD pedals, and
    some other types

    Pedal Input impedance output impedance
    OCD 283k 66k

    Zendrive 333k 25k
    Bad Monkey 530k 1.33k
    TS-9 346k 1.7k (this measured about the same when off and just buffer was on)

    So, a bad monkey would be a interesting pedal to try after the OCD?
    For other than OD types, I see from my list (you can probably still find all my readings in my original post)

    Boss CH-1 chorus (when off or on) 668k 1k
    VS liquid chorus (might be same on H2O) 586k 1.35k out.

    According to the rule of thumb, a TB (but when on) vibe would not be a good thing to use direct after OCD as they typically (Mojo vibe and deja mini vibe) run about only 60k in, 40k out.

    Also fuzzes would be bad, as they are around the same.

    This is all theory, but I think you hit the nail on the head about the output impedance. That most likely is the problem, but the good news, putting a pedal with a high input impedance right after the OCD might help, it shouldn't have any bad effects by anything further down the line. Just make sure the output impedance of the pedal just after the OCD doesn't have a high output impedance?
     
  9. DreamTheaterRules

    DreamTheaterRules Former Lyricist for Calhoun Tubbs Silver Supporting Member

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  10. fr8_trane

    fr8_trane Member

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    I copied this from an old thread about this issue. I believe this is AMZ-FX's response.

    [FONT=&quot]"The output of the OCD is an unbuffered volume pot... 100k or 500k depending on which version that you have. The pedal following the OCD will put a load on the volume pot and reduce the overall signal volume, significantly or not depending on the input impedance of the second pedal. A buffered input pedal will not put much load on it and the signal will come through stronger than if the pedal has a lower input Z. The volume drop/boost will be more noticeable with the 500k version than the 100k. This same problem applies to any other pedal with a volume pot on the output. The Fuzzface should produce a similar response..."[/FONT]

    As it relates to your experiment. It looks like the output impedance may be variable based on where you set the volume knob. Give it a test and let us know.
     
  11. Shakermaker

    Shakermaker Member

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    I think StompBoxBlues has hit the nail on the head. Your problem is not 'buffers' in general, but the input impedance of the next thing in line. If you like the sound of the OCD plugged straight into the amp I'd throw a Boss pedal after it, the specs state they have a 1 Meg input impedance (althought StompBoxBlues has it a little less at 668k.)

    From experience, I stick a Boss pedal after my Sun Face for best results (better, for example, than a TS9.)
     
  12. StompBoxBlues

    StompBoxBlues Member

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    I plan on testing a lot more pedals (all of mine actually) just to have an idea. I'm pretty confident on the Boss CH-1, and as you mention about impedance I noticed it varies on the few Boss pedals I checked. The GE-7 for example tested at 890k (almost a meg) in, and 10k output.

    I think you're right, I should do this after my Sunface too.
    By the way, my Sunface (I think it is called Sun lion..not sure but it is the one with the face knob in the middle) tested at 53k input, 46k output impedance, just FYI. Fulltone '69 came in at 45k input, 12k out.
     
  13. Mike Duncan

    Mike Duncan Staff Member

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    My v3 seems to get along fine with everything.
     
  14. SpinalTap

    SpinalTap Member

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    Mike - I didn`t mean to impose that there`s something wrong with the OCD -
    its just that in my setup it causes " problems" - im sure it works great for everyone else -
     

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