Frankenstein Guitar Amp Build

This is called the "Frankenstein Amplifier" because I had a couple of amp cabinets with speakers and no working amplifiers, plus some other bits and pieces that were just waiting to be reduced and combined.

I wired a Crate GX15 into 3 separate speakers instead of 1, and turned a pair of old computer speakers into an overdriven 2nd channel.

Step 1: Gluing and Compressing the Plywood Speaker Panel

I had plenty of 3 ply wood lying around, but this wasn't quite up to the task of handling 5 speakers with heavy magnets in them.

So I cut identically sized pieces, spread a thin layer of wood glue between them, and (as you can see in the pic) clamped the hell out of them! Once dry and trimmed to size, the profile was seamless.

Comments

[yudithkarimi]

its very hard

[JuCo]

dang... i was working on this exact instructable, but my soldering iron broke. (cheap little piece of junk) mine has a 6" pignose speaker from one of those 7-100's, the amp and a 6" from some cheapy practice amp and 2 little radio speakers that give a nice ratty overdrive. the only difference was that i was gonna give an on/off for each circuit, though, (pignose speaker, no name speaker, and radio speakers.) because they each had an interesting tone and then i could mix them however i wanted or play them individually. you did great job, though.

[IronManMC]

I've never broken a soldering iron. I own both cheapies and a pro soldering station (Weller WTCPL 60 watt controlled output) that I bought CHEAP.). My favorite is a plain vanilla iron (blue handle) I bought at Heathkit. I've used this for decades, and the tip just won't tarnish.

I buy soldering irons for specific purposes, such as microtip very low wattage for surface mount, etc. that's the trick to good soldering. Use JUST enough wattage.

I keep all of my soldering tools so clean, my Mom the clean freak could eat off it. Keep a small wet sponge nearby, and wipe the tip frequently. I'm not that concerned about the irons. A clean iron makes much better joints.


-Mike Curtis

[kyismaster]

might as well buy a 50- 100 dollar solder, little 10 dollar ones are worthless, mines is $300 +, works like a champ.

[IronManMC]

I'm an electronics engineer, and I smell SMOKE!

Solid state amplifiers (I didn't see any tubes) have a specific output impedance. If your speakers are LESS than this, the power amp will overheat and destroy itself. If you wired your speakers in parallel, they're probably too low, unless they're unusually high impedance (16 ohms). The formula for parallel impedance is 1/((1/sp1)+ (1/sp2)+(1/sp3)).

If any (or all) are 4 ohms, wire them in series.

to amps (-)---(-)-sp1-(+)---(-)-sp2-(+)---(-)-sp3-(+)----to amp's (+)

The impedance of series wired speakers is the sum of all (sp1+sp2+sp3)

If your amp output is tube, then you MUST use the specified impedance OR LOWER. Too high and you'll arc the power tubes, and probably the plate transformer.

You can also use series-parallel. connect 2 speaker pairs in parallel, then connect the two sets in series. Four 8 ohm speakers connected thusly have a total combined impedance of 8 ohms.

I generally don't recommend mixing speaker impedances. The lower impedance receives WAYYY more power. And yes speakers blow out, too.

-Mike Curtis

[maxkracht]

How did you wire up the speakers? If memory serves, the champ runs at 4 ohms, the crate speaker says 4 ohms, and the other speaker?? I could be missing something, but I don't see how you could have matched the amps impedance with that setup. Sorry if I am underestimating you, but if you didn't get the impedance right your setup is either going to be inefficient/weak or on the verge of blowing a transformer or the voicecoil on a speaker. If i'm right, i would recommend just using one of those speakers and leave the rest in there for appearance... no one would know the difference and your amp will probably sound better/louder/etc.

[J3PPiSH]

Nice!

[iamtoats]

Nice. I have a Crate MX15R. Even though I have other nice amps, I will never give this up because of it's awesome spring reverb, and pedal friendlyness.