Acoustic guitar with 2 pickups, but no internal mixer: what to do to make it mono?
 

Hey guys

I just wrote about a custom Taylor Dan Crary guitar which has two pickups installed. One goes to the left, one to the right stereo channel.

One pickup is for the strings, the other for the body sounds (ie. percussion).

The current owner used a Y-cable to split the stereo signal into a separate left and right mono output, then plugged each output into his mixer, and there he could decide how the signals would be mixed.

I'm a street busker traveling with minimal luggage, and I need to keep my gear as little as possible. I have two inputs on my little PA system, one for my microphone, the other one for my guitar. I don't want to carry around an additional mixer. So I need a way to mix those two signals together into a single mono channel.

I have no idea about acoustic engineering, but I think it should be possible somehow to build a simple adapter which has:

- at one end a male 1/4" TRS stereo signal (to receive the two pickups' individual signals)
- and then merges it into a 1/4" female TRS mono at the other end

Preferably, it would offer a little control dial/knob so I could manually choose the wanted ratio.

I have a friend who knows to solder audio cables and such, he just doesn't know a lot about guitar gear, so it would be great to get some advice from you guys.

Another way to go could be the installation of a small mixer into the guitar's body. I don't like the huge plastic elements and displays of many modern guitar mixers; in fact, the Taylor's unobtrusive three little knobs are most appealing to me (while the Dan Crary in question doesn't have any of these at all).

http://i0.wp.com/acousticguitar.com/...size=750%2C500

So maybe there is even a small mixer that allows for what I need which would only have a single knob on the outside of the guitar body (I don't care too much where it would be... possibly directly next to the stereo output)?

Any help is highly appreciated. Thanks a lot.
Josua

Assuming both pickups are active and have buffered outputs, you could simply use a 4.7K resistor from each to a common tie point as your mono output.

If you want adjust-ability, try a 10K pot and wire each end of the pot to each pickup, and the center wiper becomes your mono output.

Thanks for posting an idea.

My friend understands the first part, but is unsure about this:

> If you want adjust-ability, try a 10K pot and wire each end of the pot to each pickup, and the center wiper becomes your mono output.

Can you explain a bit more in detail, please?

Use a 10K linear pot.

Connect one of the outside terminals of the pot to the output from your first active pickup (on the TIP connection of the jack).

Connect the other outside terminal of the pot to the output from your second active pickup (on the RING connection of the jack).

The center connection of the pot then becomes your mono output which you can send to your amp. The pot will serve as a blend/balance control for the two pickups.

Thanks a lot for the more thorough explanations. :-)

Meanwhile, I have experimented with my friend a bit.

We first tried to follow these instructions here: https://qscprod.force.com/selfhelppo...-to-mono-input. But that didn't work out (sound was very, very low and bad quality). Not sure whether we did everything right?

After that, we have created a guitar cable with a male stereo jack on one side, then inside the cable, the left and right channels are combined (by simply soldering them together), and on the other side of the cable, there is a male mono jack.

https://i.ibb.co/8xWx1NT/Window-and-...otal-pages.jpg

As I don't have the Dan Crary guitar with me, we have simply tested it by connecting the stereo jack to a radio, and the mono jack to an active speaker. When panning to the very left or right on the radio side, either the left or the right stereo channel can be heard through the speaker. It seems to work pretty well (we couldn't distinguish sound quality by ear from a standard mono cable, although we couldn't turn up the volume too much because of sleeping kids). So the first goal (combining stereo into mono) seems to be achieved.

Question so far: is there any issue with our approach? I read somewhere about two channels "canceling themselves out" by just soldering them together.

If the two pickups of the Dan Crary guitar deliver roughly the same volume, then this would work pretty well. I'm unsure by the way whether the pickups are active or passive. The K&K Pure Mini seems to be passive (see https://www.kksound.com/products/puremini.php), while for the hexadecimal pickup I don't have any further information; I just wrote an email to the seller though.

After this first success, we wanted to experiment a little more. My idea was: if the two pickups do not deliver same volume, we only need to be able to lower the volume of the louder one so it matches the less loud one.

We took a 10k potentiometer, and created another cable that has a female mono jack on one side, a male mono jack on the other side, and a potentiometer between.

https://i.ibb.co/fG1r0jV/image.png

The proof of concept works: we can change the volume of the audio signal using the potentiometer's knob. (The change of volume is not really "linear" when rotating the knob, but it works just fine. Maybe a higher quality potentiometer would improve the experience even a bit.)

We could now combine the two ideas, so that the potentiometer would affect one channel (the left or the right one, depending which one is connected to the louder preamp) of the stereo jack. Afterwards, both channels could be soldered, and leave through the mono jack.

We are unsure though whether this will work with passive audio signals (we don't have any equipment here to test that). I will just have to test it with the Dan Crary guitar some day soon.

If it doesn't work: is there a potentiometer-like thing that works on passive audio sources? Or is there a resistor that I could just add to the louder channel (I suppose there exist resistors with different "strengths", so I would just need to find the one that fits best)?

THANKS A LOT FOR YOUR SUPPORT. :-)

Geez that sounds like a lot of work.. get a blender preamp detar makes them several different companies make them I use a Felix but also have Detar.

Seems like this would fill your needs.

https://www.radialeng.com/product/mix-blender

https://www.radialeng.com/wp-content...b-768x1047.png

~Bob

Get a 3’ TRS cable and a Baggs MixPro. It’ll sum both signals to mono and give you adjustable gain for both. You just wear it on your beltclip and it runs on 9volt.

Another option is the Schatten Mini-Pre 2 Dual Channel preamp.