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Modification: 2 vol's to - Volume-blend in 18volt EMGs

Discussion in 'Pickups & Electronics [BG]' started by TL5, Jun 28, 2005.

  1. TL5


    Jun 27, 2005
    Can it be done?

    If so what is required?
  2. wire the pickups to the blend pot, then from the blend pot to the volume, then to the jack

    i dont know exactly, but i dont see why it wouldnt work . . .
  3. TL5


    Jun 27, 2005
    I sent an email to EMG tech support. I just got the reply:

    You'll have to replace the EQ with either the BQC or BQS System. We do not sell the components separately to make a Control into a System.

    You can find online Dealers back at our site, and diagrams are supplied with each EMG active EQ.

    That seems odd, why would I have replace the EQ section?
  4. Do you have a preamp or is it just active pickups ?
  5. BruceWane


    Oct 31, 2002
    Houston, TX
    Are you using an EMG preamp, or EMG pickups, or both?

    Blend pots are tricky things. Their internal design causes some problems. Without a buffer to isolate the pickups from each other, a blend pot allows their impedences interact - one pickup will tend to put a load on the other, varying with the position of the blend control. So you end up with somewhat strange results; the pickups sound will change. In other words, your neck pickup might sound one way when you're at 60/40, then sound different when you're at 70/30 or 40/60. The overall result is that the taper as you fade from one pickup to the other seems very "chunky", not smooth at all. In one entire range you get very little change in tone, then you just barely touch the blend and you get a LOT of change.

    EMG doesn't say specifically that the blend in their BTC and BTS systems are buffered, but it looks like they are. The blend pot in these systems has a circuit board that is powered. And I can see that the EMG systems with blend pots use a 50k master volume, while the vol-vol schematics specify 25K volume pots, so there is definitely something else going on in the circuit.

    I can tell you that, in my experience, they do work flawlessly. MUCH better than any passive blend I've used.

    But if you want to try a passive blend, www.allparts.com does carry a 25K blend pot.

    If you do try the passive blend, be very careful soldering the ground to the pot casing. Do not overheat the pot. These things tend to be a lot more sensitive to heat than regular tone/vol pots. If you're pretty good at soldering, be careful and it'll be OK. If you're maybe not so good at soldering, I'd connect the ground to the washer instead.

    I've heard you can get passive blend pots to work pretty well, but you have to play around with various pot values for both the blend and the master volume to find what interacts with the impedance of the pickups best.

    I've got two basses with "fussy" blend pots right now, and I'm considering going to a vol-vol setup with a push-pull switch on one of the pots so I can easily "mute" the bass without altering whatever pickup balance I've got dialed in. Either that or a concentric pot for vol-vol, with a master volume after that.
  6. TL5


    Jun 27, 2005
    More research, A couple things.

    The bass is a Shecter Stiletto Studio 5 fretless. The PUPS are labled EMG hz, unless I'm mistaken that's EMG's passive PUPS. However, It does require two 9volt batteries, SO I'm guessing that it is passive PUPS with an active EQ.

    I pulled the back cover to take a look last night, both volume pots are labled 500K. This further convinces me that the PUPS themselves are passive and that there's nothing special in the volume part of the circuitry. I'm thinking I should be able to replace one of the volumes with the 500K blend pot, then use the other existing volume as a master volume.

    I plan to have a good tech here in Nashville take a peek at it before I proceed.
    What do you think? Does my reasoning make sense?
  7. David Wilson

    David Wilson Administrator Administrator Supporting Member

    Oct 14, 2002
    Lower Westchester, NY
    Yes, EMG HZ are passive. You should be able to replace with one vol pot and one blend pot no problem.
  8. Mark Gollihur

    Mark Gollihur Supporting Member Commercial User

    Jul 19, 2000
    Mullica Hill, NJ
    Owner/President, Gollihur Music LLC
    Maybe it's different with the HZ's, since they're not active P/ups... when I inquired with them several years ago asking the same question for my 6-string PBC with dual EMG (actives) they actually sent me the pot set I needed to do the conversion - free of charge. Though I wonder, since I've hosted that EMG 18v page for like, forever, if maybe that was a small gesture of thanks. :)

    EMG has always been good to me, both with excellent products AND service, which is why I never hesitate to recommend them.

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