Using distortion pedal with homemade piezo pickup

TheKevil · #1 01-05-2010, 10:10 PM

Hey guys. I have a pair of homemade piezo pickups... One under the bridge foot and one for a slap pickup. I'm wanting to play my db with a distortion pedal to add an extra grungy flair to my slap for heavier gigs. I get a horrible amount of low end feed back. I tried the same setup with a bass guitar and all was ok... I have turned my amp way up clean and j don't have any hum or static at all other than the normal you get when you turn the highs all the way up. Any suggestions from any of you diy guys out there? Is it just normal with the way piezos pick up straight vibration instead of magnetism like bass guitar pickups work?

MR PC · #2 01-06-2010, 02:39 AM

That's a big question for your very first post!

The low end feed back...well you might start by troubleshooting that problem before going any further with your quest for grunge. First of all, piezo pickups are totally different beasts than magnetic pickups. 2nd, piezo pu's under the bridge foot are a sure recipe for feedback at high volume levels. 3rd, blending the signal for the slap pu and body pu is tricky business, usually more successful with individual inputs rather than sharing one.

Isolate each pu individually to sort out which piezo transducer is causing the low end feedback. I'd guess it's the body mounted one. Once you isolate that problem you might consider trying a different placement and/or using a eq pedal to tame it.

You might find that having separate channels for each pickup will give you more control in blending in the distortion effect with the clean sound. Either a 2 channel amp or small mixer will work for this.....Stanley Clarke used to run a separate line to to a small tube amp for his distortion/grunge sound on the old Framus EUB he was using. Of course he had plenty of minions to tote his gear and twiddle his knobs in those School Days of old!

TheKevil · #3 01-06-2010, 02:58 AM

Thanks for the reply. That's helpful.... So... To solve my problem, the first thing to try would be to separate the pickups to have their own inputs.... Then play with the eq of the body pu to try to get rid of the feedback. Now, wouldn't that affect the overall sound of my setup? If I take the bass out of what the pickup is transmitting out, won't it not give any bass to my amp itself? Or would the amp be able to compensate in some way? Also, if I get a small mixer, I would be able to use the individual channel eq settings instead of a pedal, right?

TheKevil · #4 01-06-2010, 03:21 AM

Btw.... This is my first db... I needed to start playing shows quick, and had no money to buy expensive pu's to convert to an eub, so I started researching online on how to make one. I tried lots of stuff... I actually had an account here a couple months ago and I used it to ask questions about specifics when building the pu. For some reason, I wasn't able to log in. I recreated the account with the same screen name, so I guess it got deleted somehow. Anyway, I experimented with different types of cable and made this thing I use now. I even wired in a volume pot to control the master volume for both pu's. So I grew quickly, so my big questions come quickly too. Haha. Thanks again for the help. I am going to do all that tomorrow.

TheKevil · #5 01-06-2010, 07:56 AM

Umm... It's electric now and it's a double bass, so it's both now. I suppose since it's not like a electric bass guitar in upright form, it's more in the realm of a modified db. I always thought that was also considered an eub...

TheKevil · #6 01-06-2010, 01:22 PM

Can anyone else offer a second opinion? I think what Mr. PC says may indeed work, but I don't want to go pick up a mixer if it's not gonna make any difference... I know I'm not the first person to try to use distortion with piezo pickups.

MR PC · #7 01-06-2010, 02:41 PM

You need to be sure that whatever you plug your piezo pu into isn't loading the signal. The input impedance of whatever you plug into is critical to the sound. 1 megaohm (or more) input is ideal. Anything less than 500K ohm, and your pu will sound thin, boomy, scratchy, undynamic, ect. Basically like sh**. The guy from Primus (Les Claypool) uses distortion all the time on upright, as do many others. Though I don't use the type of sound myself, I admire guys like him who are crazy enough to explore it.

Anyway, if you work on getting a good clean sound first, adding the distortion will be the icing on the cake. You might find that using just one body pu works best if you can put your distortion pedal in the effects loop of your mixer/amp and blend it in to your liking. With a second channel for the fingerboard pu, you can adjust the volume of whatever it is that you like about that. Using a small mixer for all of this could simplify things. Borrow one and experiment, this ain't rocket science, good luck!

fdeck · #8 01-06-2010, 06:01 PM

If the bass sounds good without the distortion pedal, then putting the pedal in your amp's effects loop will avoid changing hour your pickup is loaded.

But a potential problem is that a distortion pedal is basically a circuit with a lot of gain, and a lot of gain is what causes feedback.

TheKevil · #9 01-06-2010, 10:04 PM

My clean sound is fine. The pickup produces no hum at all. I can get good sounds messing with my eq settings with my setup... Anything from psychobilly to country to rap to arco. It's just adding that distortion. And I thought at first, maybe it's just the way bass distortion is, but that didn't happen when I plugged a bass guitar into the same pedal. It sounded heavy and awesome with no feedback. And I plugged it through the effects loop circuit And I get the same problem. Just gotta try that mixer idea... I found a used yamaha 8 channel one for like 60 at my music store I go to. Not small, but I have credit there and that's all they got. Sucks being a starving artist. Haha. Hence all the diy stuff.

fdeck · #10 01-06-2010, 10:38 PM

Quote:

Originally Posted by TheKevil

My clean sound is fine. The pickup produces no hum at all. I can get good sounds messing with my eq settings with my setup... Anything from psychobilly to country to rap to arco. It's just adding that distortion. And I thought at first, maybe it's just the way bass distortion is, but that didn't happen when I plugged a bass guitar into the same pedal. It sounded heavy and awesome with no feedback. And I plugged it through the effects loop circuit And I get the same problem. Just gotta try that mixer idea... I found a used yamaha 8 channel one for like 60 at my music store I go to. Not small, but I have credit there and that's all they got. Sucks being a starving artist. Haha. Hence all the diy stuff.

If there is a feedback problem, I would expect it to occur on the upright but not the bass guitar.

TheKevil · #11 01-06-2010, 11:22 PM

Right... But is there any way to fix that feedback problem... That's the question.

TheKevil · #12 01-06-2010, 11:40 PM

Oi... Now there's a crunch... even when bypassed or on clean... when i play through my zoom. Haha... There's distortion, but no feedback though as long as I keep it set to clean. I also broke the ceramic on one of my transducers in the process of hooking it up to it's own jack. Hooray for another radio shack trip tomorrow. And my effects loop on the amp seems to sound crunchy also... But it may just be making the pedal's problem sound worse. Fun times in San Antonio.

MR PC · #13 01-07-2010, 02:02 AM

Quote:

Originally Posted by TheKevil

Right... But is there any way to fix that feedback problem... That's the question.

This little magic box might be the answer to that problem, it works very well. Many folks in the around here are using it. Search the threads for "fdeck HPF".

http://personalpages.tds.net/~fdeck/bass/hpfpre.htm

TheKevil · #14 01-07-2010, 11:31 AM

Thanks. That may be helpful. Hopefully that box could do the trick. Fdeck, I sent you an email about your box... You're the maker... Think it will help me?

julio.gamiz · #15 01-07-2010, 11:37 AM

Maybe you should try filling up the f-holes.

sevenyearsdown · #16 01-07-2010, 11:42 AM

or just get a decent preamp.

MR PC · #17 01-07-2010, 12:32 PM

The fdeck HPF is an excellent buffer/preamp (10meg input). Coupled with the very good tube pre on the SVT Pro (listed in The Kevil's profile) there, would be plenty plenty of options with eq.

TheKevil · #18 01-07-2010, 07:25 PM

Awesome. Got a new piezo from radio shack and made that second pickup. I plugged both into a small amp that I borrowed from a friend that had high and low inputs. The sound is amazing... Never knew what difference that made. Sounds like my bass acoustically, just louder.... Not as much bass as before. Amazing new difference. It's not as loud, I don't think, but it's ok. I don't crank all the way up ever anyway. Still gets feedback with distortion, but I'm gonna have to tame both pickups to take care of that.