Electric Viola - Done! (Almost)

[Eric Knapp]

Well, here's the first musical instrument I've made. It's a 5-string electric viola for my music-major daughter. The body and bridge are maple, the fingerboard and tailpiece are Macassar Ebony. I made everything except for the pickup, the tuning pegs, and the chin rest. She wanted a chin rest that is the same as the one on her acoustic viola. I'll post better photos once I've had a chance to take some.

I have a question about the pickup. The last photo shows what I'm trying out first. It's a piezo made to go under the bridge of an acoustic guitar. The instrument sounds amazingly good, even my picky daughter is impressed. And that low F string is really loud and full, just what she wanted. However, we're getting a lot of buzzing and humming in the amp. Nothing is shielded and I'm wondering what we can do. This pickup was cheap and one solution is to try different ones if there's nothing I can do about this one. I'm very ignorant about the electronics of instruments.

Thanks,

-Eric

[Barry Daniels]

I think you need a pre-amp between the piezo pickup and the amp.

[Eric Knapp]

You need a pre-amp between the pickup and the amp.

I forgot to mention that we are using a preamp. It doesn’t make a difference with the buzzing. We have an acoustic guitar amp with inputs designed for piezo pickups. It sounds great with and without the preamp but the buzz is always there. If we hold the lead from the pickup the buzz is reduced greatly but is still there.

-Eric

[Alan Carruth]

It will help a lot if you use a normal bridge, or, at least make some cutouts that follow similar practice. The flexibility of the bridge acts as a filter for sound in different ranges, and can make a real impact on the tone coming from the pickup.

In a normal violin it's the sound from the bass foot of the bridge that drives the top for the most part. The bridge pivots around the top of the sound post, which is near the treble foot, acting as a bell crank to convert the sideways motion of the bow into a vertical force that can drive the top. I used a small piezo element under the bass foot on the electric violin I made and got a pretty decent sound. With the pickup running all the way across, and thus under both feet of the bridge, you may be getting some cancellation of the sound.

The cutouts in the bridge have another function as well; adding damping. If you're familiar with the 'quality factor' measurement of damping, you may know that the 'Q' value gives the proportion of energy dissipated per cycle of vibration. A Q of 100 means that 1/100 of the energy is 'lost', while a Q of 30 signifies a loss of 1/30th per cycle, more than three times as fast. This works to some extent in reverse as well. That is, when you're trying to get the string moving with the bow you can only pump in energy at a certain rate, expressed as a percentage. Strings have very high Q values, which goes along with the well defined pitch of the sound they make. A string mounted on a rigid bridge can only accept energy from the bow at a low rate: it takes a relatively long time to get it going, and the bow tends to 'skate'. It also takes it a long time to wind down after you do get it going. Fiddlers don't appreciate either of these things in general, since it makes it hard to play quickly. With a solid body design you don't have too many places that can absorb sound and reduce the Q value, and the main one is the bridge.

[Eric Knapp]

It will help a lot if you use a normal bridge, or, at least make some cutouts that follow similar practice. The flexibility of the bridge acts as a filter for sound in different ranges, and can make a real impact on the tone coming from the pickup.

The instrument sounds great right now. It sounds much closer to an acoustic viola than an electric guitar does to an acoustic guitar. I could not find a 5-string viola bridge so I made that one. I will probably add some cutouts to see the effects on tone.

The issue is a hum that sounds like a ground loop problem. How do guitars with piezo pickups solve this?

-Eric

[Alan Carruth]

Shielding. The pickups themselves are normally shielded, Check the ground.

[Bob Francis]

Nice Eric

[Jim McConkey]

Congratulations, Eric! I hate to say I even remember when you started on this "a while back." Glad you brought it to fruition and it meets with your daughter's approval!

[Eric Knapp]

Nice Eric

Thank you, Bob. A labor of love that got my butt moving.

-Eric

[Eric Knapp]

Congratulations, Eric! I hate to say I even remember when you started on this "a while back." Glad you brought it to fruition and it meets with your daughter's approval!

Thank you, Jim. I'm so glad she approves! The stress of worrying about that was pretty high. This was the first instrument and I sincerely hope it's not the last. After having a heart attack this week I have even more motivation.

-Eric

[Karl Wicklund]

Eric,
You had a heart attack this week? How are you?

[Eric Knapp]

Eric,
You had a heart attack this week? How are you?

Yes, I had a major heart attack this week and survived. I called 911 in time and now have two stents and a story to tell. Overall, I’m doing very well, thanks for asking. I’m sure glad I got this viola done before my daughter leaves for school tomorrow. I will be out of the shop for a bit, understandably, but I’m recovering faster than I realized was possible. I’m very grateful for that. On to the next build!

-Eric

[Alan Carruth]

Wow!

Best of luck on a speedy recovery.

[Karl Wicklund]

Wow is right. Glad to hear you’re recovering well.

[Jim McConkey]

I hope your recovery is fast and complete! That is a scary ordeal and I'm glad you survived intact!

[Bob Francis]

Best to you and thank goodness for a quick reaction from the 911 folks.
Feel better soon.

[Ken Nagy]

Dude, that's nice advice for all of us! Don't procrastinate. That is surely a wake-up call.

Hoping you have a great recovery. You must be doing really well if you are already playing with toys! My dad had a bypass, and lived to be 93. That was probably before they had stents.

[Teresa Wiggins]

Very cool!