The "Forum Amp" design thread

[Tubebass]

I just (finally!) got mine built, worked great right off. I set mine up to run off either the 19.5v laptop supply or 12 volt battery, using a 2.1mm power jack for the 19.5v input and a 2.5mm for the 12v (so that the 19.5 can't accidentally get plugged into the 12 v input). Both jacks are set up with tip=negative. The 19.5 is wired to the power pads on the PCB as designed. The LM338 has its output pin lifted from the board. The 12v jack positive goes to the pad where the 338's output pin would normally go. The 338's output is wired to the break contact on the 12v jack so that if nothing is inserted in the 12 volt jack, the output of the 338 goes thru the jack and back to the board. Works like a charm!

[add4]

I realize the project is already done and i'm a bit late for saying that, but how impossible would it be to design a super precise and dynamic, easy to carry amp? (think AER, enricksen, polytone,...)
My perfect design would be : light and easy to carry (aer compact 60 is GREAT for that), combo, clean sound only, as flat as possible, para eq 3 bands (can be a normal eq if that's too much work), lots of dynamics, lots of precision, large frequency response, no effects (or a very small and subtle reverb (equinox?)). Volume should be enough to play with a reasonable drummer and 2-3 others bandmates in researshals/small clubs/gigs.
I am certain that some people here have references for getting cabinets, chassis, faceplates, speakers, ...
It would be nice to try to make a complete amp kit from the collaboration of people in this forum.

Just in case some of you like the idea.. i'm just starting the diy thing and i'm not able to design that at the moment, but i think the idea would be nice.

[armstrom]

http://www.lunchboxamp.com/

It could be done DIY too, but the challenge is coming up with a lightweight combo of speaker and cabinet that doesn't sound like a practice amp. (I'm assuming you DON'T want the practice amp sound). Keep in mind that the lunchbox amps are small, but not as light as you would expect from looking at them.
-Matt

[Ben N]

The Tiny Giant would do fine for that if you gave it a generous power supply, paired it with an efficient speaker, and maybe filled out the front end with a tonestack and clipping.

[fatfoohy]

what is the current draw of this amplifier?

[waltk]

what is the current draw of this amplifier?

When you first turn it on, it spikes up to a little over 1 amp (1.14a in a quick test I just did).  Then it settles down to 70ma with no signal through it.  When you're playing the current draw depends on how much current is being output to the speaker - but even at very high volume, it doesn't draw much more than 1 amp.

[fatfoohy]

Awesome thanks! Im planning on using a 12 volt scooter battery to make this into a backpack amp

[fatfoohy]

are there supposed to be any jumpers on this board? I put one under the IC holder, I built this amp, and it is totally not working correctly, the only time it will work right is one sweet spot on the knobs of my guitar, it does it on multiple instruments

[Taylor]

No, there are no jumpers. Any part that needs to be filled is labeled, so don't put in any parts that it doesn't tell you to put in.

The things you might be thinking are for jumpers are called vias. They connect the top copper layer and the bottom copper layer. Don't put anything in them or do anything with them, they're just part of the PCB design.

The build/debug thread for this project is here:

http://www.diystompboxes.com/smfforum/index.php?topic=89687.0

[meffcio]

[Wrong topic. Please delete this post]