Tone control for Active Pickup Blender

[jayedgar]

I am building a new "guitar" from an old mandolin-banjo and a slightly newer cheap electric guitar. The woodworking part is nearly finished and the guitar has come out better than expected.

So why not add some microphones? I bought a cheap lipstick mag mic and a pair of Belkin piezo mics from Hongkong.

When scanning the web I found JohnH:s Active Pickup Blender or Volume Module and built both blender and volume module.

guitarnuts2.proboards.com/index.cgi?board=schem&action=display&thread=4595.

Small, simple and well working when fed into my Line 6 POD 2.0!

Now I am looking for a tone control for this setup. I know how to solder if I have a good schematic, but lack the knowledge to figure out anything on my own.

Is there somebody here who could help me out?

Regards

Peter

[JohnH]

Hi jayedgar, welcome to GN2, and I'm glad to hear those modules are working!

There would be lots of ways to get some tone control, but what sort of control do you want? eg, just a treble roll off?, or bass and treble boost and cut?

If you can work with just the treble roll off, then a few components could probaly be slipped in between modules without needing further active stages.

Others please chip in, since I dont have an off the shelf design

John

[newey]

Jayedgar-

Hello and Welcome to G-Nutz2!

I edited your post to fix the link to JohnH's active blender/pre.

Sorry, but I don't have a clue on adding a tone control, apart from what John said.

[jayedgar]

Hi, mates!

Thanks for speedy answers and help.

I am looking for as simple solution as possible. i.e. treble roll of.

Should anyone have other suggestions, you are also welcome.

Regards

Peter

[JohnH]

I think a simple treble roll-off tone control could be done with a pot, resistor and capacitor, between the blend and volume modules. I will consider some values and wiring.

But have you tested your basic system yet? Do the mag pickups and piezos work togther in a balanced way, or is one much louder? (id expect the piezo mics to need a boost to match the mag pu)

cheers
John

[JohnH]

Here is how a simple treble roll-off could work. basically like a guitar tone control, with an extra resistor.

Its placed between the mix and volume modules:



The maximum roll off is determined by the 33k resistor R and the 0.1uF capacitor C, and as shown, it will roll off above about 1800hz under the control of the pot. The pot can be a 250k log pot, and you'll probably find most of the action is down the low end. Or try a 100k log, and maybe cut the track at 10 if its still cutting a bit of treble at maximum.

If you want the roll-off to start at a lower frequency, increase the cap, say to 0.18uF to roll off above 1000 hz.

On the volume mix module, you can leave off r4.

John

[jayedgar]

Hi John, thanks a lot. I will add that to my crude lab setup.

On your question about balance: I was aware of that a piezo normally needs a preamp, but, having none at hand, I tried without.

To my surprise and satisfaction the balance is fine.

I think it is due to that there is a "mechanical" amp in my system. I tried different places for the piezos, and the best result was to have both of then glued to the banjo skin close to the bridge. There is a lot of movement in the banjo skin (at least compared to a guitar) so my theory is that the skin gives a much stronger signal in the piezos than in a guitar.

If you are interested I have a few pictures of my project on:

www.aspe.se/Fars/Gitarrbygge.html

Regards!

[JohnH]

Very interesting indeed, and a nice web page.

So its got a guitar neck and banjo body comstruction? I think I want one!

I picked up a banjo once, and I was amazed at how loud they are, so it makes sense about how the piezos are getting a good signal

Good project.

cheers
John

btw so did you write it in Swedish, and then when I clicked the transliate button, is that an automatic process? or did you have to write it twice? It was quite clear and understandable.

[jayedgar]

Hi mate, it must have been an automatic process.
But I have thought of writing in english, but it doesnt seem necessary, then.

[jayedgar]

Maybe this is not appropriate on this forum; but I checked your website, and you seem to have a nice place!

I visited Melbourne/Sydney a few years ago and fell in love with your country, especially Sydney, the second most beautiful city I´ve been to (Stockholm is a wee bit better).

Is that a Tilley hat you are wearing?

Regards from some 50 degrees colder

[JohnH]

Thanks, and yes thats the hat. Made in Canada, and not common down here

[jayedgar]

Yippee! It works!

There is a little hum, but I think that is due to the crude lab setup, and will disappear when I do the final assembly inside the banjo, well shielded.

I had some trouble to get it right, but when I made an systematic approach, using a 200k log pot (turned so I got a slow slope in the beginning) and a 100nF capacitor it worked fine.

Should anyone use your sketch, they should be aware that there is a small ambiguity regarding the R4 that can be omitted. In the sketch you say the in the mix unit; in the text you say in the volume unit, the latter is correct (at least it works for me).

(On Tilley hats: they are rare in Europe as well, I ordered mine on the web from Canada)

So now I can go on and finish the woodworking. Should anyone be interested in my project, I will update my site from time to time, and write in English.

Regards/ Peter

[JohnH]

Im glad it works, congrats.

I did intend it to be the mix module where R4 can be omitted, but it will work with or without it in either module. Its small function is to control a small pop that you might get when you first plug it, by keeping the output side of the ouput capacitor at ground. i adjusted the text above.

John

[jayedgar]

Thanks again John.

I have one small question: I will mount the caps and jack through the holes in the aluminum frame. That means that the frame and subsequently the strings will be grounded. Is that a problem?

I have updated my website www.aspe.se/Fars/Gitarrbygge.html on this project and written it in English. Should anyone look at it, please bear in mind that English is not my mother tongue.....

Regards /Peter

[JohnH]

I would that should be fine. Grounding the frame and the strings should be a good idea for noise

[jayedgar]

Put it all together today, plugged it in to the amp - not a sound - not even hums or cracks. Back to the lab, multimeter and soldering iron. Guess shortcut somewhere

It turned out to be the signal and ground in the output jack that had been bent together. So I finalized the inside, and could test my banjolintar to my great satisfaction. It sounds really good, with very different sounds from the mag and the piezo. The blender works fine, as well as the volume control and the tone control. There is no humming or hissing or any other unwanted sounds. So now I can stow away my electric tools.....

Thanks for the help!

(my website is uptodate with pictures aso)