How can I combine 2 different types of pickups in one jack?- created 01-12-2009

kuun, murray - 01/12/2009.08:07:07

I'm making an acoustic archtop to which I am adding 2 pickups. The first is a piezo disc which one sticks on under the bridge area. The second will be a floating type archtop pickup.

I have closed the body and have already stuck on the first pickup. I'll fit the second one when it arrives after the guitar is complete.

I know almost zero about electronics. Can the 2 pickups be attached to one output jack? Or do I have to have 2 jacks? Neither of the pickups requires a pre-amp evidently. If this is possible, would the sound come "blended" from both pickups or would one have to have a selector switch of sorts?

The reason for 2 pickups. I had the disc piezo pickup in stock and at the time of closing the body I thought it may be an idea to put it in anyway as it cannot be done after the body is closed. But I'm not sure that this pickup would give the traditional jazz sound so I thought I had better order a jazz floating pickup as well in case the piezo sounded lousy.

Am I likely to have feedback problems? If so, how are they overcome?

Two pickups like that cannot be combined at the jack like that, not without active electronics- a preamp. And that piezo pickup should have a preamp, no matter what you were told. A preamp would solve all of your questions, you need a preamp that has blending capabilities. That can be done with a switch, or a blend pot that gives gradual combining of the two. Adding a preamp to an archtop can be quite a challenge, because there's nowhere to put it along with a battery.

There is another way. Although you do need a blending preamp to combine the pickups, it does not have to be internal to the instrument. You can install a stereo jack with the floating pickup to the tip and the piezo disk to the ring (both pickups connected to the ground). You can connect an external blending preamp with a stereo plug and get both pickups that way, but if you plug in a normal mono cable, you will get only the floating pickup. That is the way I have my cittern wired, and it works well. I also have a disk piezo and I used a Pick-Up-The-World under-bridge pickup as my primary pickup. If you are clever the preamp can be built into a small box which plugs into the end of your instrument

My Parker p-38 works much as Jim described. If I plug in a regular cable I get only a mono signal and must switch form pickup to the other with a switch on the guitar. If I plug in a stereo splitter I can then run the electric line out to an amp and the acoustic line out into the PA. It works nicely

Yes, that's right but please take note that both of the pickups in your Parker are active- that means they are both run through a preamp, which is the right way to do it.

A lot of this is tootechnical for me to understand. Of course, I suppose, I could just fit 2 jacks and use whichever one I "feel" like using at that time

Hey, people who should know better combine these signals passively all the time and get away with it. Try it and see if you can live with the sound you get. A stereo output jack and a stereo cord can separate the signals to a simple "splitter box" that has two separate mono jacks (or a "Y" cord). Or you can take a mono 1/4" cord and plug it in half way to connect to the ring and all the way in to connect to the tip. It's unconventional and not terribly reliable but if that's what you want it's there for the taking.

The technical side is a perfect opportunity to ask more questions and search for terms in the library or try your luck on wikipedia. The concepts are dead simple, it's just the jargon that you have to wade through.

I built a solid body guitar a long time ago with a Piezo bridge and nothing else. It sounded like <a href="http://www.box.net/shared/alxzxclm1n">this...</a> If you like that sound then you don't need a preamp. If you hate that sound than you do need one.

<a href="http://www.box.net/shared/j7rszbkc65">Here </a>is another clip of that guitar. It's the first guitar you hear. The hammer on guitar at the end is my old Tele.

Later I added some P-90 pickups to that guitar and a blend pot and it was not very easy to dial in a good blended tone. I ended using two outputs and a small mixer for that rig.

Murray, I wouldn't install two jacks. I choose to install one jack and a three way switch or blend pot (on the fingerrest?) that will give you three sound choices by hand. To go or not with a preamp depends on what kind of sound do you expect and your music style. The sound Clint shared is pretty the same I have in some experiments with piezos without a preamp, and I think is useful, especially if you have a neck humbucker that will give a much warmer and bassy sound in complement

Using a blend pot with two pickups, one active and one not, is a mess. And using a blend pot with a piezo passively and a magnetic is no better, doesn't work well

How about mixing passively with some really big resistors to make up some of the difference in impedances, I haven't tried it but I see that Graphtech sells a 1Meg volume control kit. http://www.graphtech.com/products.html?ProductID=10&CurrencyID=2

Any resistors you add to a passive circuit will affect the volume and tone, usually in a negative way

I've used the passive approach successfully with a pre-amplified piezo mixed with magnetic pickups. There are many compromises involved, including loss of signal level in addition to potential changes in tone. Further, it doesn't work well with certain configurations of the rest of the wiring. The negatives tend to make some people view the approach as "completely unacceptable," while others might be willing to accept the compromises.

I would definitely not do any passive mixing with an unbuffered (unpreamplified) piezo signal.

I would propose passive mixing as a "plan B" if you just can't work up the elements to go properly active, which is the "technically correct" approach.