Two channel Guitar case amplifier

[marcipicus]

I want to make an electric guitar  case with a built in amplifier for convenience when travelling. I would like to know if it would be possible to make a two channel amplifier using the various amp emulator pedals, specifically the english channel and BSIAB2 for clean and dirty respectively. I would very much appreciate i if someone could tell me everything i would have to do to get this to work. ie. Power amp to drive speaker, power supply ing d cells etc.

Thanks in advance to anyone who can help

[Mark Hammer]

Short answer, yes.

Considerations:

1) Is there space for the speaker, including enough depth?
2) Will things rattle around inside the case when you play loud enough?
3) Will there be an easy way for you to secure the speaker, the circuit, and the power supply, and an easy way for you to get at it to service/mod/change battery
4) Will the speaker be a good match to the "enclosure" the case provides, or will it sound boxey?
5) Will the combined weight of case, guitar, amp be the sort of thing you want to drag around?
6) Will it be possible to protect the controls (pots, switches) from getting hit or bent and damaging them?
7) Will it be possible to protect the back of the speaker cone from anything piercing it or otherwise damaging it?

Overall, the answer is that it can work, but you will need to plan well, and start off with the "right" case.  Sticking in two amp-emulator circuits will be the very least of your worries.

[marcipicus]

If i do this project i'm going to do it from scratch so any of those details can be hammered out before starting. Also when i was talking about travelling i meant going to someones place for a week not backpacking so the weight factor won't come in to play (i'm making it out of solid poplar so the case itself will be a heavy bastard).  The only thing i'm wondering about is number 4. Since i don't know much about speakers i would like to know what i would need for it not to sound "boxy" as you put it. Room for the speaker to breathe i guess?

Although you have brought up some good questions about the practicality of my idea i was wondering more about the technical side of putting all the elements (emulators, power supply, speaker, Power amp if necessary) together in one package.

[remmelt]

perhaps leave the case open when you play, so you have kind of an open-back cab?

[Mark Hammer]

I just finished a 2W battery powered amp last night that is surprisingly loud.  Very simple 2 op-amp input stage and Baxandall (cut/boost) tone controls.  Runs off 8 C-cells in two 4-packs.  The electronics for the whole thing could easily fit in a 1590BB or comparable sized plastic box (also 1590 but different suffix), and the battery pack could easily be an 8-pack of penlights, though with shorter lifespan.

With a closed back cabinet for the 6" speaker this thing is loud!

I'm not sure what sort of volume you had in mind but bear in mind that 2W is, in theory, only half as loud as 20W into the same speaker.  Make yourself a 5W amp and you can have some serious portable power.  It is possible to get fairly slimline rechargeable 12V gel or sealed lead-acid batteries that would easily power a 5W setup run full tilt for an hour or two before recharging.

Practical issues...

To avoid boxiness, there are a few generic strategies:
1) Physical - design the case AS cabinet so that the space for the speaker/s (and no one said it HAD to be just one) is designed for the speaker properties.  That could involve a sealed cabinet, a ported one, two small sealed cabinets, acoustic padding, etc.  Of course what limits this is that the box has to accommodate a guitar too.  Fortunately the end of the case nearest the headstock has enough room for such things.

2) Electronic - resonant filter can easily be used to compensate for the resonances of the box and make for a more amp-like sound.  You can also consider revoicing the tone stack or putting in a little preset EQ between preamp and amp.

3) Happy-go-lucky - Accept the resonances of the speaker and case as simply part of its unique sound rather than aiming for a specific amp sound.  That was good enough for the folks that had a Silvertone amp/case and it *might* be good enough for you.

Packaging  Consider doing this.  The electronics get mounted in a 1590BB.  The chassis is attached to the guitar case by polting it from the outside of the case to the inside of the chassis.  The "cover plate" side is what you see when you open the guitar case up.  The mounting bolts that protrude through the guitar case into the chassis can also serve double duty as your mounting bolts for the circuit board inside the chassis.  Protection of the controls can be achieved by simply mounting them on the outside edges of the chassis, rather than facing up as they might on a normal stompbox.

One of the things you'll need to do is find away to dissipate heat away form the power amp chip.  You can do this by thermally coupling it to one side of the aluminum chassis.

Gotta run for a bus.  If anything more comes to mind I'll chime in tomorrow.