Using Batteries For Odd Voltages

[phaeton]

I'm looking at a small (simple (beginner)) circuit that I intend to
build. It is a portable guitar amplifier, designed for use with
headphones (think Sony Walkman) or even a small speaker (think
Pignose).

In any event, the circuit calls for 12V DC, which is pretty simple to
wrest from a standard universal wall-wart, but for the sake of
portability, batteries are the key. There is such a thing as a 12V
battery i've seen (i think it's an "N" battery) but since it's just a
little larger than a AAA, i'm going to guess that it will go dead
quickly (not a lot of total mass). I also haven't been able to dig up
a holder for it anywhere...

I know that i could use 8 AAs, or 8 AAAs, or a 9V and 2 AAs, but that
all seems excessive or otherwise strange. There's a lot of ways to do
this, but what would be the universal *best* method to acquire 12V from
smaller batteries (not really interested in strapping a Sears DieHard
to my belt, especially since i have a nice little tube amp that weighs
less )

How about 2 9V batteries with a voltage regulator circuit? Would that
be wasteful or otherwise silly?

Thanks!

 

[phaeton]

Thanks to everyone who's responded. Yes I should have posted a URL to
the schematic:

http://www.generalguitargadgets.com/richardo/practiceamp/craig.gif

Or maybe some more info like what OpAmp it uses, wattage and such. I'm
sorry i didn't include that before. I'm sure that it will work on 9V,
and probably would be ok with 18V. I just thought that 12V is somewhat
of an odd requirement for something portable. Of course, the circuit
is a pretty old design (iirc 1970s) and i was too young to remember
what battery choices we had then :-D It's probably even closely based
on the datasheet for the LM383

Roger- I don't do street performances at this time. The tube amp
plugs into the wall directly. I was going to use this small practice
amp as a "disposable amp" project for testing homemade effects pedals
and such. I would hate to mis-wire something in a stompbox and damage
my Reverend :-( It would also be useful to have a small portable amp
like this- something i could even keep in the guitar case itself. I
also intend to make a second amp on breadboard or pegboard with IC
sockets just for experimenting with.

Robert- That amp design looks interesting too! I actually just
ordered a bunch of TDA2002 (replacement for the LM383) and some LM386s
from Jameco. Futurlec is awesome but they take forever to ship. The
LM386 is typically 1/2W, and the LM383 amp is 8W. My tube amp is
switchable between 5W and 15W.

Rich- I haven't built it yet, no. But I intend to. ;-) Thanks for
the tip on similarities between mic pre's and guitar pre's. I had a
feeling that an amp is an amp is an amp (more or less). I figured i
could stack batteries like that, but i've never seen 9V batteries
stacked, or dissimilar types or sizes stacked like that before in
manufactured equipment. I assumed there's gotta be a reason for it

 

[phaeton]

Roger Johansson wrote:

"phaeton" <blahbleh666@hotmail.com> wrote:

I was going to use this small practice
amp as a "disposable amp" project for testing homemade effects
pedals
and such. I would hate to mis-wire something in a stompbox and
damage
my Reverend :-(

To protect the input of a power amp you can put two diodes in
antiparallel over its input.

True that it would protect the input of the amp, it's also a standard
waveform clipping setup- it may introduce distortion (which may or may
not be desirable ) but even for gits and grins i'd like to build this
small practice amp :-D

It would also be useful to have a small portable amp

For headphones you can probably use common op-amps, like the TL071
series. A TL072 for stereo.

Or no amp at all. You probably use some guitar effects boxes before
the
amp, and most of them have output power enough to drive earphones

None of the commercial effects boxes will drive headphones...

directly. There are schematics for thousands of guitar effects on the
web, and they are suitable as beginner projects in electronics. Check
out
geofex.com, for example.

Yep! Along with generalguitargadgets.com

Futurlec is awesome but they take forever to ship.

That is interesting.
Have you tried them or do you base that on some information?

Yes, my initial investment in parts (i bought one each of all their
value packs) was from futurlec.
It was just over 2.5 weeks between the time i placed my order and the
parts shipped. Most everyone i talked to in #electronics on
irc.freenode.net said their experience was similar. However, that's my
ONLY complaint. Otherwise, they were very inexpensive, courteous, and
all the parts i received were packed well, organized and marked well,
and appeared to be brand new and good quality.

I would buy from them again, but sometimes i want stuff a tad sooner,
so i go to Jameco ;-)

Anyways, you (and everyone else in this thread) have been very helpful.
thanks!

-phaeton

 

[phaeton]

If they sent the stuff halfway around the globe by ship I think 2.5
weeks
total shipment time is very acceptable.

Actually, I placed the order, and it didn't get packed and shipped for
2.5 weeks.

It then took another week to travel halway around the world. The week
for travel time is acceptable, sure. It's just that they sat on the
order for a while after I placed it.

But hey, everything else about the transaction was excellent. For
things that I don't need in a hurry (read: If i plan ahead a little
better) I'll happily order from them.

-phaeton

 

[phaeton]

Roger sez:
# That is very irritating. I hate when that happens.
# The company should tell all customers about such delays at their web
# site, so the customers know about it before even considering placing
an
# order.

Definately. I wish i had known that up front, and if i did i would
still have ordered from them, it's just that the first couple of weeks
of it sitting in "Order Submitted" status and being left in the dark
was starting to make me a little bit nervous... ;-)

Roger says again:
# Maybe they are not storing all the products they say they have in
store,
# so it takes time to get the stuff from their sub-contractors. That is
# often the real cause for delays.

That's my guess too. Again, some notification on the website ("May
delay order shipment by 3-4 business days") would be nice. I don't
think Futurlec is trying to be malicious or deceitful, they've just got
a rather sparse website. To their credit, it looks great and works
great in every web browser i've hit it with. Jameco's website used to
be slow as molasses, then they revamped it and for awhile there i
couldn't do anything at all with it using Firefox. They've since
improved the compatibility and it's 100% functional, though
occasionally the forms get all jumbled up and ugly. Everything works
now, so that's good enough.