Handmade Music Clubhouse

Cigar Box Guitar Headquarters - CBG HQ

If the box is big enough, this should work just fine!  Will I have feedback issues with the pickup wires?  Any other troubleshooting I have neglected?

(Good god, look what's happened to me . . .)

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Should be okay. A metal mint tin is a good Faraday shield, just be sure to tie your ground (and nothing else!) to the tin.
Curious about doing this myself and interested in what others have to say. I have a lunchbox that I'd like to try and do the same thing with. Build a guitar and amp all in one, plus have a standard jack "out" for going into any self standing amp. Haven't tried the Minty out yet though. Anyone have any experience with these guys'?
One rather important thing to keep in mind - building the amp part inside the guitar is not an issue. A preamp is, after all, an amplifier, and they are built into the guitar all the time. Observe good shielding practice, and you'll be in good shape. What you CAN'T put in the guitar is the speaker, unless it is completely isolated mechanically and acoustically from the vibratory portion of the guitar. Otherwise, you are going to be building an acoustic feedback generation system the likes of which Jimi Hendrix himself couldn't control.
Interesting points Dave - would the speaker have to be in a "box-within-a-box" so to speak? Never looked at one close enough to know, but is this what they have to do for these "beginner" guitars we see, that have a built in amp and speaker?
Hi, I have mounted a mini amp and speakers in 4 CBGs so far. This one had a preamp aswell as a mini amp

With the preamp on you do get feedback with the magnetic pups and the piezo if you crank up the volume too much. With the preamp bypassed the bridge mag pup can be played on full volume. Neck mag pup and piezo are also OK until you get to the top of the volume. I made a friend one using telecaster pups

These had no problems with feedback at all (the neck pup was a fairly low output). All the onboard miniamps I use have no overdrive - I once tried to use a LM386 chip smokey amp circuit but it was hopeless with loads of feedback. My last effort was a 3/4 size CBG for my son with a bridge magpup and piezos around the bridge area. For a speaker I used a 5 Watt speaker from a surround sound TV set. No problems with feedback at all. Regards, David
Those First Act guitars with the amp and speaker built in are solid-body electrics - a bit more isolated than on a CBG. Looking at the examples Mr. Lloyd has provided, the speakers are mounted to the back of the box, not the front vibrating surface (where some folks, myself included, would be prone to mounting speakers), and as such are more mechanically isolated from the front where the pickups are; since they are built to be opened, the front and back are not solidly coupled, further reducing the sources of feedback. And as he mentions, the hotter they go, the more feedback is introduced - and those aren't very big speakers, very little mass to add to the vibration. It would be interesting to hook up an oscilloscope to the speakers and the pickups and see if they are in phase with each other, or 180 degrees out-of-phase (that would also cancel some feedback, along with a bit of apparent output power). Still, that they function as well as they do is encouraging. Heck, play around with different configurations and see what you come up with. I'm not a big fan of feedback, and try to eliminate as much a possible, but that's just me.

And Mr. Lloyd - what kind of boxes are those? That wood is really rich-looking, I love the color.
Hi, One of the easiest methods of having on board amp/speakers is to use one of the Kemo 3.5W amplifier modules which I buy in the UK from Maplins
http://www.maplin.co.uk/Module.aspx?moduleno=37734 doing a quick google search they sell it on Amazon.com for $9.95
http://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&f... The technical specs are Specifications: Output: maximum 3.5W music power Operating voltage: 4.5-12Vdc Loudspeaker connection: 4-16Ω Input sensitivity: > 80mV Frequency response: approx. 40-20,000 Hz Dimensions: approx. 40 x 40 x 12mm (I use a 9V battery.) Here is one on a recent build

Thank you Dave Kroening for your posts - it is nice to get a proper scientific explanation as to why there is less feedback with this layout (please call me David - when people call me Mr Lloyd I think they mean my Dad ;o) ) In my case it was pure luck rather than science. I opted to stick the speakers on the back so that it wouldn't affect the sound too much if played acoustically. Regarding the type of box in the previous posting - They are plywood 35mm photoslide boxes. In the UK I find it difficult to get hold of large cigar boxes and these type come up fairly often on ebay UK. I am really interested how you find the Minty amp as it is based on a LM386 chip which caused feedback problems when I tried to used one (although on that occasion I had wired the chip with overdrive) Regards, David
David Lloyd -

I haven't used the Minty Amp specifically, but I have used the LM386 amplifier chip configured for more bass output for a bass headphone practice amp, and on a few projects where the amp is separate from the guitar. I have used a 9V battery, and a 12V full-wave rectified, big capacitor filtered plug-in supply, and haven't had any trouble with noise or feedback - but I either built the amp in a small metal enclosure tied to the power supply ground, or used grounded metal shielding around the amp section. This most likely isn't completely necessary in all cases, I just do it out of force of habit. As I recall, the LM386 is fairly responsive in the lower frequency ranges, and may have picked up on the resonant frequency of your enclosure (acoustic cavities, like the enclosed area of a guitar, have resonant frequencies, even if we don't know what they are), and proceeded to give itself a good shaking. That particular amp / speaker / guitar combination may have been in phase with each other, and if so, the resultant vibrations would reinforce each other and become stronger, and continue to feed that increasing signal back into the amplifier, until the system becomes overwhelmed with feedback. If you still have that guitar, reversing the speaker polarity might make it more stable. I don't think a LM386 based amp system, in and of itself, is necessarily any more prone to feedback than any other amplifier, it just has a bit more punch than some, and that would contribute to increased feedback in a guitar with onboard speakers (pointing at the soundboard).
forgive me if this is hijacking the thread, but i have read the discussion and having just built my first ruby amp (386 based) am experiencing problems with my piezo pickup cbgs - it is fine with my strat, but when i plug in a piezo pickup cbg i get a very loud noise like an overdriven hum

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