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Hard to believe... (scratchy pots)

Discussion in 'Effects [BG]' started by pauliebass, Aug 3, 2012.


  1. I was just told by a stompbox builder that it doesn't make a difference if the volume pot is scratchy. I don't know about you guys, but if I buy a new pedal, I want the knobs to not make noises when I turn them. Is this being unreasonable?
     
  2. CptRevell

    CptRevell

    Aug 15, 2011
    Maryland
    I personally would frown on pots being scratchy right out of the gate, but I have heard similar sayings.

    I personally haven't had any problems with scratchy pots on pedals however.
     
  3. JehuJava

    JehuJava Bass Frequency Technician

    Oct 15, 2002
    Oakland, CA
    Why would this be even remotely acceptable? Hey I just bought a brand new car with a dent...the dent doesn't affect anything so I'm good to go?

    Sure a scratchy pot is nothing more than scratchy pot. But it sure speaks volumes about a builder's work ethic, quality control, and probably his or her customer service.

    And yes pun intended
     
  4. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
    Some volume controls are scratchy by design like on a Zvex SHO. It's not ideal but it can't always be avoided in certain topologies.
     
  5. Does zvex explain that the volume will be scratchy by design?
     
  6. JehuJava

    JehuJava Bass Frequency Technician

    Oct 15, 2002
    Oakland, CA
    What makes it scratchy by design? Not familiar with the pedal.
     
  7. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    Yes, it's written on the face of the pedal ("Crackle OK").

    The deal is that the knob controls the amount of voltage going to a transistor, whereas most volume knobs are just passive attenuators.
     
  8. That's really cool for zvex to write that on the face, but I'm not talking about that pedal.
     
  9. Growly Lytes

    Growly Lytes

    Dec 4, 2009
    Downunder Oz
    Bass player
    Bro does that go for poweramps also ? The controls on Poweramps arent really for volume but for the amount of volts coming into it ?
     
  10. xander8280

    xander8280

    Dec 29, 2011
    I only dont like it if they're so scratchy and dirty that they have dead spots in the pot:/
     
  11. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    No, the volume knobs on power amps are passive attenuators, situated between a fixed-gain input buffer and the main power gain section.
     
  12. johnk_10

    johnk_10 vintage bass nut Supporting Member Commercial User

    Feb 16, 2008
    Thousand Oaks, CA
    John K Custom Basses
    the Zvex pedals that do that (as well as others that use the same type of circuit) are scratchy because they are changing the transistor bias to the drive stage. it's completely normal and my early model Fulltone '68 does the same thing when you adjust the bias knob. my super duper 2n1 does it (it has Twin SHO's) and it doesn't bother me at all.
     
  13. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    From a PM, the pedal in question is a Dr. Scientist The Elements. Anyone here know if that specific pedal has a "crackle OK" type of vol pot like the SHO, or a normal not-supposed-to-be-scratchy vol pot?
     
  14. This is the email response the dealer got from the manufacturer:

    To be honest, scratchy pots are just part of guitar pedals.. that's really normal. In my opinion it's not worth replacing a scratchy pot, especially a volume control that is shifting a DC level, it's normal to hear scratchiness and is really only a problem if the person is constantly turning the knob up and down...
     
  15. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
    This unfortunately is the scratchy kind of volume control. Anytime there is DC on a pot, it's scratchy time.

    Maybe it could be redesigned but it may not function the same.
     
  16. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
    I wouldn't let it bother me. Especially after the designer told me how it functioned. Now, if I was designing a circuit I would try to avoid this type if gain control but to be honest, in the guitar world at least, the scratchy pot is more forgiven because of the popularity of Zvex and all of the clones.
     
  17. I wish there would be a warning about that in the literature. One thing I have to say is that this is one of the most amazing sounding pedals I've ever used. I don't see it ever leaving my board. That's why I'm a little peeved about the pot... But if that's the way it is supposed to be...
     
  18. father of fires

    father of fires Commercial User

    Nov 29, 2006
    BALTIMORE CITY
    Chief of Medicine at Damnation Audio
    It should have been mentioned in the manual at least.

    I hear it's an excellent pedal.
     
  19. Wasn't the guy just talking about the knob's function? Meaning, that a scratchy pot works just as good as a silent one?
     
  20. bongomania

    bongomania Gold Supporting Member Commercial User

    Oct 17, 2005
    PDX, OR
    owner, OVNIFX and OVNILabs
    I still have doubts about the meaning of that email. On the one hand it does mention changing DC levels, but OTOH he fibs and says scratchy pots are normal for guitar pedals. Clean, undamaged pots, in almost every usage other than changing the bias of a transistor, do not make scratchy noises. A brand new pedal should have clean undamaged pots.

    Also, scratchy pots cannot always be assumed to work just as well as non-scratchy ones. If we were just talking about scratchiness from a tiny amount of dirt or corrosion, which IS totally normal after a pedal has been used for some time, then sure--no big deal. But a brand new one that's scratchy might be faulty, and will only get worse over time.

    I know the comment about DC suggests this is a "crackle OK" vol pot, but those are just a TINY minority among volume pots--they are not "normal for guitar pedals". Plus, if this were a "crackle OK" vol pot, then why did the email say it just wouldn't be worth the cost to replace? After all, with that bias control there would be no point at all in replacing the pot even if it cost the builder nothing, since the crackle is not from anything wrong with the pot.

    I know if it was a pedal I had sold, and if a customer had a complaint like this, I would be calculating my cost: an hour of labor (depending on ease of access to the pot), plus about $10 for Priority mail one way, plus a couple bucks for parts, plus the customer might expect not to have pay for shipping the pedal in for the repair, since it's a new item, so that's another 10. So all told this scratchy pot could look like a loss of maybe $40 to the builder, depending on how they value their labor. So then the builder has to decide whether to eat that cost in the name of good customer service.

    To be clear, I am not saying anything bad about the builder! I am only saying their email was vague and contradictory, so IMO we shouldn't blow this off as an open-and-shut case.
     
    Driven Crane likes this.

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