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Inexpensive impedance matching device

woodyng2

woodyng2

Oct 4, 2015
9,141
24,068
Silver Coast Portugal
#1
Hello technical folks. :)
I bought a Tune semihollow body bass guitar that has piezo-only pickup.
It has an 18 volt preamp, with a lot of internal adjustments, as well as 3-band cut/boost eq. The signal is super hot, and i have managed to tame it by adjusting all 9 of the internal trimpots downward.
It initially sounded terrible through my Markbass amp, but is somewhat better now.
I’ve tried a TC Bodyrez pedal to declack the piezo sound, and it had a very subtle effect. (Probably going to be returned.)
I’ve been told that what Really needs to be addressed is the impedance mismatch.
So i am looking for recommendations for a good quality, low frills pedal to accomplish this.
Unfortunately there appears to be a bunch of them on the market,with descriptions that I don’t fully comprehend.
Considering I don’t need a full preamp with tone shaping capabilities,would something like an IMP-2 work?
Or one of many Radial brand models?
 
Last edited:
#6
amper said:
What impedance mismatch? If your bass has an onboard preamp, then it will have a low output impedance and should work fine with virtually anything.
Click to expand...
I don’t really know,this was from some internet pundit’s dissertation when i said my piezo sounded unpleasant and clacky. He pretty much insisted that a piezo pickup into an amp was a really bad mismatch of impedance,and was the source of my problem.
I gave all the i formation on a facebook forum that i gave with my post here.
 
#7
woodyng2 said:
I don’t really know,this was from some internet pundit’s dissertation when i said my piezo sounded unpleasant and clacky. He pretty much insisted that a piezo pickup into an amp was a really bad mismatch of impedance,and was the source of my problem.
I gave all the i formation on a facebook forum that i gave with my post here.
Click to expand...
A piezo straight into an amp does do that, but the preamp is designed to fix that. The preamp on my acoustic is a harsh mess too, I don't play it much, though so I never worried about fixing it.
 
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#8
woodyng2 said:
I don’t really know,this was from some internet pundit’s dissertation when i said my piezo sounded unpleasant and clacky. He pretty much insisted that a piezo pickup into an amp was a really bad mismatch of impedance,and was the source of my problem.
I gave all the i formation on a facebook forum that i gave with my post here.
Click to expand...

Impedance problems with piezo pickups are only a problem with passive piezo pickups, which have an inherently very high output impedance, and so require a preamp with a very high input impedance, something on the order of about 5 Mohm or 10 Mohm, in comparison with the typical 1 Mohm input impedance of most MI amplifiers.

Any instrument with an onboard preamp will not have the same issues. However, you may find that a preamp specifically designed for piezo pickups gives you more tonal control. I might suggest the Tech21NYC SansAmp Para Driver DI v2 or the Fishman Platinum PRO EQ/DI.
 
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#9
amper said:
Impedance problems with piezo pickups are only a problem with passive piezo pickups, which have an inherently very high output impedance, and so require a preamp with a very high input impedance, something on the order of about 5 Mohm or 10 Mohm, in comparison with the typical 1 Mohm input impedance of most MI amplifiers.

Any instrument with an onboard preamp will not have the same issues. However, you may find that a preamp specifically designed for piezo pickups gives you more tonal control. I might suggest the Tech21NYC SansAmp Para Driver DI v2 or the Fishman Platinum PRO EQ/DI.
Click to expand...
Thanks for the explanation...i was wondering about that since the bass has quite an extensive preamp inside already. I really like tech21 products,so will look into that product.
 
#10
cheapbasslovin said:
A piezo straight into an amp does do that, but the preamp is designed to fix that. The preamp on my acoustic is a harsh mess too, I don't play it much, though so I never worried about fixing it.
Click to expand...
That’s kind of a shame,though,isn’t it?
I really love this bass,and want to be able to play it live, and record with it.
2E63D894-4C9C-4D5E-8907-E5D6A847AC35.jpeg
 
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#13
Does the preamp look similar to that on this page:

https://www.tuneguitars.com/wb5-2wn

4c18ca_19ef4250d64d44098c905540ac228b3f.webp


If so, I doubt the issue is an impedance mismatch. Tune has been makign electronics for quite a while, and they have a rather good reputation (at least here in Japan). It would be very unlikely that they'd not matched the pre-amp's input impedance with the saddles. Having said that - the Tune basses often have quite a "hot" output.

I wonder whether simply turning down all the trim-pots at the same time, you've not also maxed-out the "low-cut" adjustment, which would take a lot of the bottom end out of your tone & make the top-end sound quacky. If you didn't get a manual with the bass, I'd suggest checking for the individual effects of each trim-pot one at a time.

Let us know how it goes - I'd be curious to know, in case i ever come across one of these :) Actually - in any case, if you could share a pic of what the electronics look like, if you deide to have another look - that would be helpful :) Not much info out on this on the net!
 
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#15
woodyng2 said:
Hello technical folks. :)
I bought a Tune semihollow body bass guitar that has piezo-only pickup.
It has an 18 volt preamp, with a lot of internal adjustments, as well as 3-band cut/boost eq. The signal is super hot, and i have managed to tame it by adjusting all 9 of the internal trimpots downward.
It initially sounded terrible through my Markbass amp, but is somewhat better now.
I’ve tried a TC Bodyrez pedal to declack the piezo sound, and it had a very subtle effect. (Probably going to be returned.)
I’ve been told that what Really needs to be addressed is the impedance mismatch.
So i am looking for recommendations for a good quality, low frills pedal to accomplish this.
Unfortunately there appears to be a bunch of them on the market,with descriptions that I don’t fully comprehend.
Considering I don’t need a full preamp with tone shaping capabilities,would something like an IMP-2 work?
Or one of many Radial brand models?
Click to expand...
I disagree with what you've been told. As mentioned above you might have impedance mismatch between the piezo and the pre(amp) but not from the preamp to the amp.

The fact that the signal is super hot depends on the preamp too.

Not everybody likes piezos since they sound pretty different from magnetic pickups. It might just not really be your cup of tea.

Take a look at this review of a completely different bass which nonetheless offers a magnetic and a piezo pickup.
You'll clearly hear a huge difference between the two.

 
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#18
Sounds like you should learn exactly how your preamp works, what the trims all do, what the output impedance is. Could be all those electronics are for tone shaping and not buffering. My experience with piezos is that the buffering is the important thing and after that you may need to boost low bass and cut high mids a little. A few times I think my NS Designs NXT sounds like crap and then I will remember to set the high z input on my outboard pre and I then am good.
 
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