Need Battery driven Guitar AMP

[trialabc]

   I am new to here and new in making guitar amps. I wanna make a guitar amp that can be used outside, where you can't possibly find a plug to plug in. As a result, I don't know how to start off.

  Feel free to comment. Thanks.

[J M Fahey]

Hi trialabc
This place is all about that.
Start by searching here "Ruby", "LM386", "Scarface" and you'll find enough to keep you busy.
That amp is less than 1 watt, but with a good speaker it rocks.
Good Luck.

[trialabc]

Thank you J M Fahey, I will try to study those! Thanks a lot!

[joecool85]

Thank you J M Fahey, I will try to study those! Thanks a lot!

This page has the schematics and layouts for the Ruby and Little Gem.

http://runoffgroove.com/articles.html

I love my Little Gem and have built 3 others for friends and family.

[rowdy_riemer]

I just built a Little Gem Mk II for my son. It is housed in an old school intercom speaker cab along with the 8 inch speaker that came with my Valveking Royal 8. It uses a 9 volt battery right now, but I'll replace that with 8 C or D batteries. There is no volume knob, tone control, or power switch. Just plug in the cable to turn it on. When I have the volume cranked(via knob on the guitar) and I pick hard, the amp sounds like it is cutting out. Perhaps the two lm386's are wanting more current than  a nine volt battery will supply. Even if that isn't the problem, it probably makes sense to use larger batteries. ROG rocks!!!

[trialabc]

I have "read through" the schematic of Little Gem and Ruby, it seems that they all use a 9V battery. I am wondering if I can use other voltages like 6V or 12V since this may affects the performance of the amplifier.

[joecool85]

I have "read through" the schematic of Little Gem and Ruby, it seems that they all use a 9V battery. I am wondering if I can use other voltages like 6V or 12V since this may affects the performance of the amplifier.

They can indeed use other voltages.  The LM386 is comfortable in many voltage ranges.  I have used it down to 4.5v (my pocket amp runs on 3xAA) and up to 12v.  Some say that there is more headroom for clean playing with higher voltage, I didn't notice a big difference.  So I normally use 3xAA for 4.5v or a 9v battery, more dependent on the case I'm putting it in than anything else.

[Brymus]

12v is the safe max V for the 386 chip.
I have however had good results running them at 18v with a heatsink on the chip.
I also have run two of them BTL mode at 18v and its quite impressive at that point.
I would use the highest output 386 the 386LM-4 or the 386-D and run them at 12V with at least AA batteries. C size being optimal if you have the room.
Two 386LM-4 chips in BTL mode at 12V will give you close to 3 watts ouput more than enough for a practice amp.
Use a breadboard and experiment for yourself,have fun.

[joecool85]

12v is the safe max V for the 386 chip.
I have however had good results running them at 18v with a heatsink on the chip.
I also have run two of them BTL mode at 18v and its quite impressive at that point.
I would use the highest output 386 the 386LM-4 or the 386-D and run them at 12V with at least AA batteries. C size being optimal if you have the room.
Two 386LM-4 chips in BTL mode at 12V will give you close to 3 watts ouput more than enough for a practice amp.
Use a breadboard and experiment for yourself,have fun.

BTL mode = bridged?

If so, do you mean like this:

[Brymus]

Yes thats exactly what I mean.
You should note that the ROG work/specs were using the 386 that only puts out a 1/2 watt at 9v ,hence 1 watt BTL,for the Little GemMKII .
The 386LM-4/386BD is 1 watt at 9v (I believe it's been awhile)
Download the data sheets and folllow the graphs ,You can get a good idea where 18V
will put you output wise.
I would stop at 12V though just to save having heat issues and chip failure.
16V seemed pretty stable (again if my memeory serves)I shoulda took notes...
But if your really adventurous you can use some heat sinks and run them at 18V.

[rowdy_riemer]

Since I built my Little Gem MkII with sockets, I might give the 386LM-4/386BD a shot.

[trialabc]

Oops! I think i have somehow mislead you guys. I should have stated more clearer.

Yes, I do want to make an amp that is supplied by battery. However I have two more constraints, which I think is the most troublesome part :

1. It is suppose used in an open area. e.g. not inside a house.

2. It should be able to play for at least 4 hours.

Since I have no idea in this area, I would still try to make RUBY or LittleGem first.

[joecool85]

Oops! I think i have somehow mislead you guys. I should have stated more clearer.

Yes, I do want to make an amp that is supplied by battery. However I have two more constraints, which I think is the most troublesome part :

1. It is suppose used in an open area. e.g. not inside a house.

2. It should be able to play for at least 4 hours.

Since I have no idea in this area, I would still try to make RUBY or LittleGem first.

Well, a little gem will still play outside, just won't be that loud.  I have a 250w car amp I'd let go for $20 plus shipping.  It would run on a 12v car battery for a couple hours, or if you only used one channel you should get 3-4 hours.

[rowdy_riemer]

You might consider a TDA2040 based amp. I've run a TDA2040 at 12v and it was much louder than a ruby(if I remember right). It no doubt used more current, but with a car battery, no prob. (btw, I've got a project that's been on hold forever to use a TDA2040 for a car PA system, so my wife can yell at bad drivers.) You can do something like this: http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=59&Itemid=200 . You'll need a preamp circuit, but that shouldn't be a big deal.

[trialabc]

I was planning to build a RUBY for my first trial. However, I could not find MPS102, nor could I find 2N5457 in stores. Does anyone know what other components I may use instead?