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Boss GT-6B as a temporary pre-amp

Discussion in 'Amps, Mics & Pickups [DB]' started by musicman1586, Aug 14, 2012.

  1. musicman1586


    May 24, 2012
    Hey everyone, so got my first upright bass about two weeks ago (Christopher DB102T since I figure someone will ask). Got it for a fantastic price with a lot of accesories including a pickup. Have been doing a lot of research on bass related topics over the past few months so I've read up on the fact that many piezos need a preamp of roughly 1megaohm input impedance to really sound worthwhile, and mine definitely does need something because plugging it in sounds horrible right now. I play electric bass (amongst quite a number of other string instruments) and I might have the opportunity to pick up a Boss GT-6B for really cheap here in a few weeks. Reading up on the specs it has an input impedance of 1MOhm, so any reason that I couldn't use this multi-effect unit as a preamp for a while? Don't foresee myself seriously playing live as a doubler any time in the near future, so I don't have a need to be amplified. I do have a need for something like the Boss, so I figure it would be nice to know if I could use it for the upright as it would make a dual-investment just in case some of my buddies want to get together and jam regardless of my poor intonation.
    Here's the info from Boss if you need it by chance: http://www.bossus.com/gear/productdetails.php?ProductId=239

    Also on another, possibly important, note, as it might also be the source of the poor sound I am getting, I can't really figure out what the pickup on the bass is, doesn't look like anything else I've come across on the market. It is just a small silver disc mounted to the middle of the bridge (not in the wings or under the foot or anything, just smack dab in the middle) and it leads out to a rather short thin cable which ends in a male 1/4". The cable is short enough though that I surely am going to need to female-female coupler to be able to send it to a longer cord, or to a close-by preamp, as when plugged in I'm right up against my amp. It honestly looks like it might be a homemade radioshack pick-up, figured I'd ask though as it might sound familiar to someone. Heh, makes me realize how little I know about instrument electronics.

    Thanks everyone, been lurking here on the forums for a long time, the search button is my best friend, but couldn't bring anything up regarding using a multi-effect unit as a preamp.
  2. moles


    Jan 24, 2007
    Winnipeg, MB
    I used the GT-10B for a short bit as a preamp/processor with my K&K RAB+ pickup. I sort of MacGyver'd it into giving me two inputs so I could run it dual channel.
    It sounded fine - not a*great* preamp out there for DB, but if like you say one needs it anyway for BG gigs, it'll do just fine.

    IIRC the buffer in the GT-6B sounds about the same - I had one for a short while, but it was a few years ago.

    That pickup sounds like it might be an issue. Even if it's not homemade, it sounds like it's basically half of a Fishman BP-100, which is a pretty bright pickup at the best of times (even on the basses that it sounds great on). Something like a Bassmax or Underwood or Rev Solo 2 that fits in the bridge wing will give you a warmer sound right off the hop, pre or no pre. There are lots of other options out there too, so reading through the Amps and Pickups forum would be a smart move...[EDIT - not to imply that you haven't already done some reading on it all... ;) ]
  3. It sound like your pickup is a piezo disk. These often have a lower output (might be enough depending on the mounting of it) and a high output impedance. So even the 1 MOhms might not get the optimum out of it. But using a 1 MOhms input impedance effect unit is a relatively cheap solution (specially if you already own one).

    You might want to compare your pickup with another one. At least try bowing also, the amplified bowed sound might sound unacceptable with some pickups.

    Have a look at FDecks quick 'n' dirty impedance buffers or the mint box buffer. Easy to build, you can select your own input impedance resistor to match your pickup and use almost any amplifier with the box. Or buy a HPFpre from FDeck (10 MOhms input impedance, good for piezo disks), cheap for what you will get and no soldering needed.
  4. playbass0410


    Feb 8, 2008
    I had the Fishman platinum with 10MOhms for a piezo pickup and just by accident I once used my old GT10-B for the DB.......

    .... the Fishman never ever got to amplify my DB and went to ebay.

    Anyway the GT-10B has a much better sound than the GT6B I also had for years. But yes - give it a try!
  5. You can even change the input resistor, if you know where to look for it. It depends a bit on the first semiconductor (JFET or JFET-OPamp), but generally it is no problem to remove the 1 MOhms resistor replacing it with a 10 MOhm (and you even can switch the old one in parallel for almost the same impedance as before).

    The FDecks HPFpre, quick 'n' dirty and mint box are good because they don't change the sound. Any preamp with an equalizer does colour the sound in some way (more or less and even if you don't want that).
    I think the Fishman was made to compensate for the BP100 pickup sound colouring, so has some colour built-in.

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