I made this as a result of a discussion in another forum, but I'm posting it here to amuse y'all.

It is a cheap (Oz$12) stethoscope with a silicone rubber extension and the head replaced with a piece of 6mm thin-wall aluminium tubing. You plug it in the jack socket of yer electric and stick the earpieces in yer ears. It doesn't amplify much, but it cuts out external sounds to some extent, and gives a somewhat cavernous resonance to the tone, which isn't as bright and stringy like a typical solidbody electric tone, quite pleasant, in fact. - Reverb and treble cut. It works better on some guitars than others, it was pretty good on my prewar pressed metal Rick 59 lap steel, for instance, well enough to practice technique. The downside is that anything brushing against the tube makes a lot of noise, not unlike scratchy pots on an amp.

It is still a work in progress, but the argument behind the design is that a stethoscope works due air vibrating in the tube, so if it is connected to a cavity in the guitar, eg the electronics cavity, it should transmit the sound from it.
Last edited by Tony Done at Jun 7, 2017,
I have used an ordinary stethoscope on acoustic guitars for many years.  I used a clamp to attach it to the top near the soundhole, being the only place you can use a clamp.  You get the sound right out of the wood, it's an amazing quality.

Oh, don't give me ideas.

It works pretty well, but I'm having trouble with discomfort from the ear pieces. The tone is the kind of thing you would have to hear to appreciate, it isn't like the unamplified sound, and the volume drops off strongly after about the 15th fret, 1st string. I shortened the tube yesterday, and I think it made an improvement to both volume and tone.

EDIT Except for the stethoscope, which I bought, the design concept was pretty much dictated by what I had on hand in the workshop.
Last edited by Tony Done at Jun 8, 2017,
Quote by Tony Done

I didn't think to try it with the original head on an acoustic, as you say, attachment is a consideration. Have you tried it on an electric? I I did and it worked somewhat, but this method of attachment is easier.

I haven't tried it on an electric...never thought there'd be enough volume.  I don't have the steth anymore but when I used it on an acoustic i did so with a mini C clamp at the soundhole, only place to do it with my simple method.  The sound is amazing, almost like pressing your ear on the wood while playing, not easy to do.
One thing you might try is using the tube method in a pin hole instead of a bridge pin.
I got one of those cheap lapel mics for my violin. The little mic itself out of the alligator clip holder is only about the size of the erasure on the end of a pencil. It has a small wire that goes a few feet to a little box with a battery, line level amp, and volume control, continuing on to a 1/4" male TS plug.

The mic would be just about the right size for inserting into the end of a rubber tube...
Quote by reverb66
I'm pretty sure the Bible requires that you play through a tube amp in Texas.
Quote by Tony Done

Good idea, I could easily jury-rig that as I have some brass tube that could be substituted for a pin.

The other thing I've tried for increased player satisfaction is sound ports. They have a small but significant effect on (greater) brightness

I'm considering a sound port on my Silvertone archtop.  The tone of the guitar is very good but the player can't hear it well.  The port will be a small f - hole in keeping with the ones on top.