Quote from: joecool85 on May 04, 2006, 08:37:13 AM
How much got fried this time?

The chip. I smelled that smell of burned plastic again. It wasn't as violent as the end of the 4780 but it's just as dead. I'm going to cut the perf away just leaving the PS part and try my rescued LM4780 board again there. I'm using an insulating pad on it and strapping down the chip instead of bolting direct so hopefully the heatsink will not be charged. I'm gonna do the same thing to the subamp. I've got to tighten up and stop screwing up everything. I'm a legendary half-asser.

RDV

I'm about done with non-insulated versions of chipamps.

I forgot that I had an insulator around my speaker jack for the original perfboard chipamp guitar-amp I built and fried it last night by touching the metal plug casing to to the heatsink and grounding it out. SNAP!! What a sick feeling. I'm gonna insulate them from now on or I'm not gonna even plug them in.

I'm gonna cut the chipamp part of the perf off and use the rectifier section on another chipamp. I'll post anything positive.

RDV

In a similar vein, I've ordered a Dr. Boogie PCB which I'm going to build as soon as it comes in to try as a front end for the LM3886 amp. It's been described as sounding best with a bright SS amp. Hopefully it will make a kick-a$$ second channel.

RDV

It seems that you(I) are not allowed to download or view attachments on this board.

A common shortcut is to find an acoustic amp that you like and sort of copy the dimensions for your own cabinet. I sort of like the little Marshall one though I believe it has 2 8" drivers and a horn.

I'm considering building an acoustic amp also so maybe we'll be comparing notes and stuff. My idea is to use 2 10" drivers and a good horn, almost like building a small PA with an emphasis on mids and highs.

I'll be biamping mine using two different chipamps, an LM4780(running in parallel) for the lows/mids and an LM1875 for the highs. It'll use an active crossover similar to what I used on my subwoofer project(only with a much different X-over point).

I also plan to use a fairly simple preamp consisting of just one channel with a graphic EQ. I may also try a Bass/Treble EQ also but haven't made up my mind yet. For effects I'll just use a preamp out/poweramp in to use as an effects loop.

RDV

Cool, I don't think that a Velleman kit will be the way to go, but YMMV of course.

I would pick out some speakers and design a cabinet around them. What are you thinking as far as drivers go?

RDV

There'll be no flaming here, this is a friendly place.

To help you we need to know a few things.
How much soldering experience do you have?
How much money are you willing to spend?
Do you want to do this because you think it will cheaper? It won't be.
How old are you? Because I'm a little unwilling to to get a pre-teen or teen to fool with mains power?

I'll gladly answer any questions you have to the best of my ability.

Velleman does have some kits that would be decent guitar amps but the lower power ones(like Joecool mentioned) won't get it done.

Just tell us what you want to accomplish and we'll try to help.

RDV

Actually my singer's got an old ART Mp-1 which I'm gonna see if he'll let me borrow to check how the whole genre works with a chipamp. I'm pretty sure the Behringer's a clone of that. The tube runs pretty cold(low voltage) so I don't imagine it's too spectacular. We used to use the MP-1 to jump up the gain from the Mackie board to run a sub-amp which worked pretty well. I'll get it from him this weekend as we're going back to the same studio we recorded the other stuff in to knock off a couple of tunes before whatever happens to him legal-system-wise.

RDV

http://www.musiciansfriend.com/product/Live/Sound/Signal/Processors?sku=182491

This one models all kinds of different preamps for only $10 more! Vocals, acoustic or electric guitars, and more. This one may become mine!

RDV

Quote from: teemuk on April 26, 2006, 02:49:28 PM
One thing you should also consider is that acoustic amps are usually equipped with some kind of an "anti-feedbacking" circuit. Those hollow-body guitars tend to get really crazy when you stand too close to an amp - even at very low volumes.

Not so bad with one of those rubber things in the soundhole. This is where a good graphic would shine. The more bands the better to pinpoint the FB frequency.

RDV

That Behringer preamp would work well as an acoustic preamp as long as the guitar has a decent EQ built in. If not, a graphic EQ might work well.

RDV

For clean headroom, power is how you achieve it, but 70 true watts will make a nice acoustic amp with careful speaker choices.

RDV

I dragged the PCB out of the trash and had a good look at it and I believe I may have shorted a couple of pins(there's 27 of them) partially so I carefully pryed up all the long side pins a bit and cleaned all the flux away and checked for continuity from the supply rails to the proper pins. I think I just jumped the gun when I tested the board by not cleaning up the board and stuff. I'm gonna test it again soon after I install some connectors so I don't have to do all that unsoldering and resoldering. I may also replace the bypass caps on the negative rails as they may have been damaged when the chip smoked.

It seems I'll never learn to be more patient. The thing may still not work, but there's a lot better chance that it will now.

RDV

Design and build your cabinet 1st I say. Just leave a good sized place for your electronics. A transformer needs some room as to not be too close to your other components. A good way to go for something like this would be to biamp. An example would be using an LM3886/LM1875 combo along with an active crossover.

RDV

I've PM'd him on DIYaudio w/no answer and his site says he's down till the end of the month.