Newb here, want to build little SS amp

[demym]

Hi there, i'm new to this forum, and rather new to electronics; till january 2009 i have been exploring mainly stompboxes, and i have successfully built some of them: a BSIAB2, a Tillman JFET preamp, a Carvin Legacy JFET emulation and a Dr.Boogey (MesaBoogie Rectifier JFET emulation);

I would now like to explore the power amp part of this fantastic hobby; but i am really afraid about high voltages, and so on...

I have a Roland Microcube (which i like very much), and i've seen the ROG LittleGem and Ruby projects (and also i tried to build a Ruby, but it doesn't sound right to me... maybe something wrong with my wiring);

But, mainly, i have some questions:

1) for battery powered amps, i've understood that only the LM386 will do the job, is that right ?
2) for mains powered amps, do i always need a trasformer and some heatsinks ??
3) what's the max power i can obtain for a battery powered amp (say, using 9V) ?


Sorry for the many and not ordered questions..... Just want to clarify a bit.


Thanks in advance.

Demy

[rowdy_riemer]

1) for battery powered amps, i've understood that only the LM386 will do the job, is that right ?

I haven't tried any other chips for battery powered amps, but I know there are others that work. If you want to power the amp with a little nine volt battery,
you might should stick with the LM386. It all depends on the current requirement and how heavy you want the amplifier to be. Some of the amp chips used in car radios
or any chip that'll work with a 12V or lower supply would likely be fine with battery power. I'm sure others will have several good suggestions. When considering a chip, figure what the current requirement is, and make sure you use batteries that will supply the needed current.

2) for mains powered amps, do i always need a trasformer and some heatsinks ??

Transformers - YES. heatsinks - depeneds. Even if you wanted a 120V supply, you would want a transformer for safety considerations. Now, using a transformer might mean using a walwart. For small amps, wall warts that supply enough current will work fine. Also, ATX power supplys from dead computers make great 12v supplies.

For heatsinks, that depends on how much power the amp chip dissapates. You can use the datasheet to figure this out by looking at the chip's thermal resistance.

3) what's the max power i can obtain for a battery powered amp (say, using 9V) ?

That depends on a given batteries internal impedance, which will vary between batteries. I do not think you'll get much power from a 9V. I'm considering investigating this further. I've had ok results with 9v's for Ruby's. It seems that with my Little Gem MkII, the amp did better with D cells than with  a 9 V. I'm considering measuring the current through the LGMII using a 9v and D cells to see if the 9V is being loaded down significantly.

[demym]

Thanks !

I would like, in particular, to build a 50/70W guitar power amp (for powering my vooduvalve preamp) that uses a normal, say, marshall 4x12 speaker.

Is this possible using an IC (main powered, obviously) ? I mean, would the circuit be very difficult or some specific IC would provide the same simple schematic as in the LM386 amp circuit ?

I've read about many TDA20xx, but i'm a little confused about which TDA would do the job.

To build a poweramp for guitar (and already having a preamp as my rocktron) should i look for specific guitar poweramp or any poweramp (as the hifi ones and car radio ones i've seen) would be fine ?

Last question: would my already built stompboxes (BSIAB2, CarvinLegacy JFET emulation, Dr.Boogey, or even the Tillman JFET preamp) work as a preamp for such a kind of poweramp ?

I'm from Italy and we have 220V mains.


Thanks once again; i think i will make many other questions in the beginning, so please be patient.

Have a nice time

[rowdy_riemer]

For your power requirements, you should try an LM3886. There's a lot of good info on this site about those. Also, see http://chipamp.com/lm3886.shtml . Using effects as a preamp should work fine. I've used my Dr. Boogey and other effects as a preamp on my Crate GFX 212  by plugging them into the effects loop to bypass the amps built-in preamp. It works fine.  I've also done this with my Digitech RP-70. Actually, just for the hell of it, I've plugged my guitar directly into the effects loop, and it was plenty loud enough. In fact, there is no technical reason not to consider most effects to be preamps depending on how you define the term. BTW, what did you think of the Dr. Boogey? To me, the bass response is somewhat lacking. Perhaps that's due to a bad solder job on my part  , but I wonder if anyone else has a similar opinion.

[demym]

I like very much DrBoogey, but i've built it without the tonestack, as i don't like to many knobs, so i was trying to associate another kind of tonestack. I've breadboarded a tone+contour pots (i think those are the AMZ presence control), and will try others as well, with max 3 pots.

I hear the sound  of the boogey (without the TS) as well equilibrated, at the moment. Also, had luck, cause i built it on veroboard and didn't have oscillations problems.. I don't usually play mesas, so i can't speak for the similarity with those.

My carvin legacy emu has way much bass, btw...

Will look at the LM3886 schem, thanks very much !

[rowdy_riemer]

Since you have already built a ruby, you might enter it into this contest, http://www.ssguitar.com/index.php?topic=1456.0 , and you might win what you need for a higher powered amp. :tu: