Adding Volume to Piezo Preamp

[jaylow]

Hello Everyone! This is my first post.

I saw a post here about adding a piezo pickup to a strat and it inspired me to do the same to my own strat. After some reading and research, I realize that I need to add a preamp in order to get an appropriate sound from it. Don Tillman's preamp seems to be the popular choice for a preamp.

I'd like to be able to control the volume at the same time. How can I go about altering the schematic so that I can get volume control? Is it possible to add a volume pot between the piezo and preamp and if so, what value pot should I use? Or is there something I can do to the preamp so that I can adjust the volume?

I look forward to hearing your responses. Thanks for the help everyone!

[newey]

jaylow-

Hello and Welcome to G-Nutz 2!

The post you reference was JohnH's, using a cheap piezo buzzer element to convert a Strat. And now I can't seem to find that post to link to it.

But as I recall, John provided a diagram of the buffer circuit he used, and I thought it had a volume control on it.

I don't think adding a passive volume control before the buffer is the best solution. Probably better to add one to the buffer circuit itself.

If you can post a link to Tillman's circuit, we can evaluate adding a volume pot to it. I'm sure it can be easily incorporated.

JohnH hissownself will no doubt chime in as well.

[newey]

I found JohnH's post:

guitarnuts2.proboards.com/index.cgi?action=display&board=schem&thread=3718&page=1

His circuit, now that I look at it, is more involved since it incorporates mixing of the magnetic signals with the piezo signal. It has Vol, tone and mix controls.

[jaylow]

Haha yes, that was the post I drew my inspiration from.

Anyway, here's a link to the schematic: www.till.com/articles/GuitarPreamp/

[JohnH]

Hi jaylow - you can add a volume control after the preamp, as on the last diagram on the first post of this thread:

guitarnuts2.proboards.com/index.cgi?board=schem&action=display&thread=3150

Until you try something out though, you won't know how much gain you need, and whether the tone will need tweaking. My piezo thread has the story.

cheers

John

[jaylow]

Just to confirm, that last circuit on your thread there would be a suitable starting point me to use?

[JohnH]

yes its a good basis for a gain stage. It will drive a guitar amp or most line inputs. maybe change the output cap from 330nF up to say, 2.2uF to get max low end if you are driving a line input. Also, omit C6 to get about x3 gain, or add it in to get significantly more gain.

I suggest starting however, by mounting your piezo, plug it directly into a guitar amp input or non-tru bypass stomp box and find out how it sounds. The tone and level that you get will inform the right preamp design.

J