Electric Violin, Piezo Pickup

[Robert300]

Hi,

 

I'm in the beginnings of researching and maybe getting an electric violin.  It has a Realist pickup with a stated impedance of 10M ohms.  The last few days I've been reading about needing a DI box to insure proper loading of the pickup.  I'm a bit confused because the DI boxes specifically targeted towards piezo pickups makes a big deal about the input impedance of the DI being 4 or 10Mg. ohms.   Yet this pickup says its 10M ohms.   I thought the input impedance of the DI had to be significantly higher than the piezo that was connecting to it....?

 

It also seems that it's not an exact science with a lot of trial and error.  I just like to know what I'm going to be potentially dealing with as far as what's needed.  I have a guitar,HD500 to amp effects loop setup now and it works great.... just looking to get into the violin.

 

I just remembered that the HD500 has the 3.5Mg Ohm setting available.  What are the chances that I could just plug the violin into the aux in port and configure a patch to be 3.5Mg ohms.   If these DI boxes are being sold as a solution for a electric violin and are (for the most part) providing 4Mg Ohms, maybe I don't event need a DI...  just use the aux in port with an acoustic setting and go from there... (?)

 

Thanks,.

Bob

 

 

 

 

[Charlie_Watt]

Piezo pickups require a preamplifier to convert the high impedance to low. 

[pfsmith0]

Piezo pickups are capacitive and don't have a "real" impedance per se (it's "imaginary" in the mathematical sense in that it has a 90 degree phase shift) . What they mean is you should plug it into something with a 10Meg input impedance. You can certainly use something with less impedance but you'll start losing low frequencies. With a violin that may not be much of a problem since you only go down to G whereas guitars go ~1.5 octaves lower. I imagine you can use the HD500 3.5M input impedance but you'll probably need to use several FX blocks as gain to get the signal level up.

[BlueViolince]

IIRC, passive piezo pickups prefer a 10:1 ratio with input impedance. I.E., use a 1meg input load. I go straight in the hd500 with my Barbera 5-string violin pickup. It gives me the best s/n ratio and tone.

[Robert300]

The piezo in the violin I'm looking at is 10Mg ohms. If I need a 10:1 impedance ratio I would need to plug into something that had a rated impedance of 100Mg ohms if in fact I had to have a 10:1 ratio...  The higher end DI boxes from Radial offer 4mg and 10mg.   So either there is no box on the market that offers 100MG impedance.... OR ... I really don't need a 10:1 ratio and and it would work fine with a 1:1 ratio....   Radial makes a big deal about this new Firefly DI at 4mb ohms impedance being able to handle all types of acoustic intruments ... specificially piezo transducers.....  thus my confusion...

[Charlie_Watt]

All piezo equipped guitars I own have their own piezo amplifier.  Is there an amplifier designed for your pickup?

[Robert300]

http://www.electricviolinshop.com/violins/realist-violins/realist-violin-rv5pe-shadow-3653.html

 

http://www.davidgage.com/store/product_info.php?cPath=21&products_id=30

 

"The output level directly from the pickup is unusually high, and as a result the signal to noise ratio is also very high, so no pre-amp or other active, battery powered gear is necessary. Just plug it in! The copper foil sandwich construction is the third key element in the system. It provides total shielding to eliminate hum from light fixtures and other electrical or radio interference. It is flexible enough to conform to the curve of the top of the instrument, so that the full pressure of the bridge is concentrated evenly onto the piezo surface."

 

I think this is where I'm getting confused...  Even if the signal has been bumped up... its stil rated at 10mg ohms and from everything I'm reading says that the device you are plugging into has to be a significantly higher impedance to allow for good frequency transfer... if there is a mismatch it will roll off the high frequencies...

 

..... which gets back to the POD...  there is a 1mg and a 3.5mg ohm setting.... (along with all the other lower settings and "auto")  None of these settings come close to the 10mg impedance of the violins pickup...  There was a response that the POD can handle any input... but if the port on the POD does not adapt to the equipment as far as an impedance value... then are we saying that the impedance settings in the POD don't really change the impedance but rather "model" the sound differently for each setting and that is what lets the user dial in the sound that they want?    If that is the case that's fine... I'm just having problems understanding...  If that is the case then there is still an impedance mismatch ... but it is removed from the perception of the listener because now its wrapped up in the modelling.... (?)

 

I have to put a call in to Realist because if they would just say that their website was a misprint and the impedance of the pickup is 1mg ohms and not 10mg ohms that would clear up a lot of my confusion.   Then using the 3.5mg ohm setting on the POD would make sense to me...  1mg ohms pickup  : 3.5mg ohms upstream device (POD).

 

Thanks. 

[Robert300]

Is there an amplifier designed for your pickup?

 

Sorry I didn't answer this...   The Electric Violin Shop sells acoustic amps for the violins they sell... which is frustrating because most or all of them don't list their input impedance in their specs.  The LR Baggs Venue DI Acoustic Guitar Preamp lists its input impedance as 10mg ohms which is the same as the Realist pickup.  So that would be a 1:1 impedance ratio... which goes against the convention of the upstream device having a much higher impedance.

 

Ultimately what I want to do is to use the violin with the HD500 going into my amp out one output of the POD and use the other output and go into an L2t.   If I have to get a DI box for the impedance that's fine....  What Im not understanding is the stated best practice with regards to lower impedance to higher impedance,... the stated impedance of the Realist pickup at 10mg ohms,..... and the stated impedance values in all these upstream devices whether it be the POD, Radials DI boxes, LR Baggs .. or whatever...   because I'm left with a 10mg pickup impedance going into a 10mg impedance or lower upstream device ....  and that flies in the face of everything I'm reading about what the ratio should be.

[GeiGit]

My violin is also passiv and works great with 1M-Ohm setting on aux input and on guitar input. The sound is great an better than it was before with the built-in preamp.

You don't need an preamp, or a DI between HD500 an violin. :)

All the low frequencies are good and the output-signal is as high, as a normal passive Les Paul with two humbuckers or my active JTV59. All you need is your violin and the HD500 and a XLR-cable to your L2t. :D

[BlueViolince]

GeiGit, what kind of signal chain are you using with your violin? I like the Hiway into a 112 field coil.

[pfsmith0]

Piezo pickups are capacitive in nature, not resistive. If yours really DOES have a 10M output impedance then they're doing something really crazy and unusual, but I doubt that's the case. Resistors larger then 10M are very, very specialized and expensive and noisy and not audio-friendly. That's why you'll never find a DI with anything larger than a 10M input impedance. As I mentioned before, as the input resistance goes down, a piezo will lose more & more low frequency response. But the lowest note on your violin is about 1.5 octaves higher than a guitar, which is the same as saying your lowest note is x3 the frequency of a guitar's lowest note. This leads me to believe that you will be fine going from a 10M ohm to a 3.5M ohm input resistance, which is ALSO ~x3. I would not hesitate.

[Robert300]

Thank you for all of that.   I was going through my pedals and realized the Joe Meek Floor Q compressor/preamp pedal has an input impedance of 6.8Mg ohms.  The nice thing is you can turn the compressor function off if you want and just use the preamp function which gives a clean 20db, from a class A circuit.

 

So worse case I can use the 6,8Mg ohm input on the compressor with a little clean bump from the preamp to get it into the HD500.  But is sounds like I don't need it anyway!  I spent days researching this.  I did get an answer back from Radial ....

 

 

"Hi Bob, any device that has a 10meg input impedance will work with a piezo pick up."