Stratocaster Ammeter Modification

[maxcalibur]

Hi,

This is my first post/thread but this seemed like a good community to come to for this question!

I have modified my strat with an "Ultra Strat" mod from www.1728.com/guitar2.htm

Since then, I have aquired an old fashioned looking analogue ammeter and a voltmeter in the same style. I want to cut out a hole for one of these in the body of my guitar and insert it. Then I wanted to wire it into the guitar so that the needle jumps as I play.

I wanted to know firstly if this is possible and if so how to do it. Secondly, what order of magnitude of current flows through the circuit of a guitar?
Lastly, if this whole idea isn't possible, does anyone have any ideas on how to achieve a similar effect once I have installed the ammeter/voltmeter?

Thanks a lot!

[newey]

MC-

Hello and welcome!

this seemed like a good community to come to for this question!

Flattery will get you everywhere. ;D

Some might say, why do this, since it's strictly cosmetic? But we're guitar nutz, too, we understand.

You've been watching too much "Spinal Tap". So have we, and this mod has been previously discussed in connection with the "Spinal Tap guitar" which sports exactly this ammeter mod.

EDIT:

[JohnH]

Welcome to the forum. Unfortunately theres not enough signal generated by the pickups to run a meter dramatically, and it will also load the pickups such that tone will be spoilt. You can try it for a test, on your most sensitive ac volt setting, and you may get a small twitch of the meter.

However, if you like the idea, a couple of JFET transistors or an opamp, in a suitable circuit with a battery, will give you a boosted output, that should make the needle jump about, and also have a high input impedance so as not to load the signal.

John

[newey]

I found the prior discussion, which is in the middle of an unrelated discussion. But Sumgai said:

kuzi,
Quote:

Quote:
...Oh and I heard that the 'rev counter' on that spinal tap guitar actually reacts to the strength of picking on the strings- not very accurately, but still...

how would one wire that - that might be fun to play with

Simple! It's nothing more than an analog VU meter, often found on recording equipment and some of the (slightly) more expensive mixing boards. One simply captures the value of highest voltage generated at the pickup, prevents it from dropping back down quite so quickly with a capacitor, and then delivers the voltage measured on the capacitor to a meter. QED. The trick is to keep the cap from interfering with the tone of the pup. For that, an active system will probably be the easiest way to go.

Now an updated version, such as a LED bar graph extending all the way from the bridge to the neck, that'd be uber-cool! ;D



sumgai

So, apparently the Spinal Tap one is a VU meter, not an ammeter, but he also notes the need for an active power supply, as JohnH indicates above.

EDIT: I should also mention that the UltraStrat mod you did from is by our member Wolf, who visits here often. The website you link to is his. He would probably appreciate an email, or a PM here, as to how you like the mod.

[sumgai]

Let me amplify my long-ago post.

A VU-meter is volt meter at heart. As John points out, volt meters do require some juice to drive them, but they can be made to be very sensitive, on the order of microvolts if necessary.

Moreover, an ammeter is actually a volt meter in disguise. A shunt resistor inside of the casing is what turns amps into volts, so once again, it can be very sensitive when needed.

But the real issue is what will such an "add-on" do to the tone? John's correct, it won't be pretty. Which of course means an active circuit is in order to isolate the output tones from the meter driving circuit.

HTH




sumgai

[wolf]

Surprisingly, the "metered" guitar was not exclusive to Spinal Tap. OLP made this model a few years ago:



Sadly, that guitar was discontinnued and I believe even OLP is no longer in business. (I thought they made some good inexpensive guitars.)

[maxcalibur]

Thanks for the quick and enthusiastic responses. I can see this was the right community to come to! (More flattery there).

I had no idea about the Spinal Tap guitar. I'm not sure if it almost put me off the whole idea for a second, but decided that it didn't!

I will talk to my friend who is doing an electrical engineering degree about VU meters and op amps in an active circuit. Does anyone know where there would be some reference wiring diagrams for this kind of thing?

Tell me if I can't bring up another subject in here, but i also have another guitar project on the go. I'm building a mini amp into a second hand guitar i acquired. It's a strat style guitar with two single coils and a humbucker at the bridge. I'm thinking of putting the speaker of the mini amp into the place where the two single coils are and removing them completely. This guitar doesn't need to have a superb sound quality as it will just be used for bedroom use by my girlfriend but does anyone think that sacrificing two single coils for the speaker to be put in a convenient place is worth it? Otherwise I will have to cut a cavity into the bottom of the body to insert the speaker.

Thanks again everyone!

[newey]

does anyone think that sacrificing two single coils for the speaker to be put in a convenient place is worth it?

What does your girlfriend think? There are plenty of players who like a single HB Strat. I have one I built and I like it a lot, but it doesn't much sound like a Strat. That was part of the point in building it.

This guitar doesn't need to have a superb sound quality as it will just be used for bedroom use by my girlfriend

If you and your girlfriend both play, neither of you should need to suffer mini-amp sound quality. Can't you negotiate a Marshall stack for the bedroom? ;D ;D

[maxcalibur]

Yeah, I've read that a lot of players having a guitar with the single HB setup and no complaints.

The reason I'm making this guitar is because my girlfriend is only just starting to play and doesn't have a guitar of her own. I already have my own Strat and 50 watt Marshall AVT so thats not the problem! We don't actually live together. We're at different universities and she doesnt have much room so I'm building this so after the summer she has her own guitar just for her to mess around on and no need for an amp or cables in her small room.

[torind2000]

why not just get her a second hand acoustic?

[Teleblooz]

Jun 1, 2009 10:00:59 GMT -5 torind2000 said:

why not just get her a second hand acoustic?

Or a small practice amp? There's some decent inexpensive ones out there.

[maxcalibur]

I thought this was Guitar Nuts!

I actually want to make this modification, as well as do something a bit more meaningful than buy a second hand acoustic.

Also, with regards to a small practice amp, the guitar will still have the normal output if an amp is to be used.

[newey]

Max-

No one's trying to discourage you from doing the mod, just pointing out some practicalities.

I think it would work fine as you have proposed, with the speaker under the strings. The one member we had who did a similar mod put the speaker below the bridge. That might sound better since the player's arm/hand won't be partially blocking the speaker.

The prior one was Keebo's meager attempt. You might pick up some tips in that thread.

[catweazle]

Hi Max
Go for it - I put a tiny amp into my first electric way back in the 70s. It was a single chip that ran on a 9v battery and powered a 2.5" speaker mounted on the scratch plate between bridge & neck pups. Output was 1/4 watt tops but that's surprisingly loud. The project made cover article in Everyday Electronics (UK hobby mag). I should have a copy somewhere but I'm sure the chip is now obsolete -plenty others around though.

3 or 4 years ago, I made a prototype amp for a guy who'd built a folding guitar (busker's dream - neck folded in-over & body sort of telescoped). His mate had made him a copy of (I think) a Marshall front end, but it sounded feeble & drained the battery so fast it (the battery) ran warm! I devised a cunning system whereby the electronics would power the (2) internal speakers OR could be used as a pre-amp with distortion OR could be used to play ipod etc. through the guitar speakers. The next stage was to have been to make a stereo effects version with vibrato or Leslie panning between the two speakers. I may still have some details 'filed away' somewhere.

Finally to the original query - like the others have said, even a sensitive meter will soak up all the guitar signal. A 100uA meter movement typically has an impedance of 1K. But a single fet transistor can boost that to lots of kilohms or more and would probably run OK with a single AA cell. I could breadboard a hookup if anyone would like a circuit to follow...