New amp build

[Chuck Bouwens]

Planning a new amp. A two speaker set up with parts from Gitty. Does anyone know if there is anything to be gained by wiring two 9 volt batteries in parallel? More amperage to drive the two speakers, longer playing time or would this damage the amps circuit board? 

[Ted Crocker]

According to OHMs Law, the total amperage will be half that of a single 9 volt battery when wired parallel. I'm not sure of the total voltage.   Wired in series, both will be double, but that could harm the circuit with too much voltage.  I say stick with one battery.  Good luck!

EDIT:  As an aside, also according to OHMs law, if you wire the speakers in parallel it will effectively double the output wattage of the amp circuit.  For example, 2 8 ohm speakers parallel in a 2 watt amp will be the same as a 4 watt speaker in a 4 watt amp.

[Wayfinder]

I dunno about Ohms law; my math stinketh.  However, this site on batteries explains both serial and parallel connection.

https://www.batterystuff.com/kb/articles/battery-articles/battery-b...

According to that site, running batteries in parallel retains the same voltage but doubles the amps, which is what I'd always heard.

[BrianQ.]

That’s about right about the amperage, Wayfinder? Chuck, a rechargeable battery is something to think about, you can easily find lithium based batteries with higher amperage ratings. This way, you’ll go through less batteries? 

[Wayfinder]

If your amp board requires around 5v  (or if 5v won't blow the parts out)... a portable cell phone recharger battery is a wonderful thing.   It uses a USB cord as recharger, but you can also then use a USB cord as a power cord (just solder) a USB receiver into the power leads of your circuit board).

Those cell phone rechargers can provide 5 volts of power at between 2 and 3 amps and store up to 20,000 mA of total power.  They're inexpensive, small, relatively light weight (fit easily inside a cigar box or other portable amp).  So long as your amp circuit board doesn't draw more than 5v or 3A, these things are gold. 

When purchasing them (off Amazon or wherever) look at three things:   the power (some only have 1A power, some 2.1A, some 3.1A).  Then check the over all mA rating.  Some are 3,000... 5,000... 10,000... 20,000+.  Then check the customer ratings to make sure the product actually works.  I've purchased several of them, ranging from "lipstick chargeres" (about 2000 ma and 2.1A charge... really easy to carry around), to a solar-based self-charging 15,000 mA model.   they are just dandy for 5 volt (or thereabout)  sound boards.  And if the voltage is too much (you need 1 o r 2v instead of 5v), you can always insert a cheap voltage converter into the circuit (under $10 on ebay).   I even managed to buy a 12v version for powering equipment; that's enough to power some decent-size amplifiers (I've powered 10" power amps with that killer little battery).  And it's about 1/5th the size of a "scooter battery".

For the person who needs long playing time, here's a 25,800 mAh monster:

https://tinyurl.com/y9dh4bll

There are lots available if you look under EXTERNAL CELL PHONE CHARGER.  There are lower-power, cheaper units that work just fine.  Great little power devices  for us CBG amp players... and they'll last 3-5 year or so.

-- Wayfinder