Voltage regulation for busking amp and effects

[Ben79]

Hi all,

I've built the Tiny Giant which I'm intending to use as a busking amp (do you guys say busking in the US? It means playing in the street, usually for money in case you don't).  I already have a 5000mAh LiPo 14.5v battery and charger to power it with but I'm wondering if I can also use that to power some pedals.

My question is, would it be better to either....

A. Use a second regulator from the 12v output of the Tiny Giant down to 9v.

B. Use a regulator to go straight from the 14.5v to 9v. 

C. Just buy another battery, a 3 cell one that puts out 11v and regulate that to 9v. 

I'm currently leaning towards C because I think it'll last ages.  The pedals are all fuzz and one wah so the current draw will be low and a 1300mAh is gonna last a LONG time, right?

Thanks for any help.

[anotherjim]

I'd lean toward C.
But there's D -  Put a 9v out on your 14.5v and then make another one. Take both with you (option C still means taking 2 power packs). Then you have backup.
If the pedals are low current, the power loss in the 9v regulator off 14.5v shouldn't hurt.

[PRR]

I would skip (bypass) the TG's regulator. A 14.5V battery is well within the limits for the power chip (and TL0), since it is really a car chip and many cars charge well over 14V. The reg is there because the intended use was with a 19V laptop supply, which is a bit over the chip's rating.

A basic no-LED fuzz or wah is a couple mA. A 1,000mAh battery gives you about 2 weeks of non-stop play time. I think your butt will get sore long-long before the battery drains.

Don't over-complicate.

[amptramp]

I wonder about this - the TDA7240 amplifier is designed for car radio service.  Do you really need to drop the voltage from 14.5?  The specsheet test data assumes a supply of 14.4 volts.  The chip is rated for an absolute maximum of 18 volts.  You could use a regulator for 9 volt pedals.

I see PRR beat me to it.

[Ben79]

Thanks guys, that's helpful.

So if my fuzzes are drawing little in the way of current, would I be significantly adding to the drain on my 14.5v battery by using a regulator to drop it to 9?

Are there any other options?

A one battery solution would be ideal as I'm considering housing the whole lot in one enclosure....


 

[anotherjim]

If the fuzzes draw as much as 10mA, you waste about 55mW in the 9v regulator off 14.4v. I don't think you will notice that.

A 78xx series regulator takes little extra current (a few mA at most?). What it does do is lose the extra voltage across its in and out pins. 5.5v here. The load current passes thru these pins. Power (watts) is volts x amps. Can you see how I got 55mw?
Now, if your pedals took 1A (they should be nowhere near that much), that's 5.5w lost in the regulator and that is significant power wasted from the battery - and a hot regulator.

If you can get a 78L09 regulator, it will shut down at current over, if I remember right, a sustained 100mA; which will save you from severe battery drain should something bad happen.

[deadastronaut]

OT, but i love that enclosure...very cool.

[Chris S]

I did option B. I have a Vox Da5 I amp powered off a 12v battery. I'm powering a tube reamer and a power hungry looper.

[anotherjim]

I'm sure there was a time you buy console cases like that from Maplin & such. Blue Hammerite coated steel with an Ali' top panel. But the steel part still RLF! Only ABS cases nowadays it seems.

[amptramp]

If you have a surplus store nearby, you can usually find a lot of electronics chassis/enclosures for a reasonable price.  Just replace the aluminum front panel with a cheap piece of aluminum (baking sheets work well) and drill the appropriate holes and all will be well.

[Ben79]

Many thanks everyone, you've answered my question and I've learned something.

I'm gonna go straight in to the TG with the battery and run a 9v regulator for the fuzz circuits.  It's a 5000mAh battery and it's made for RC cars so it really IS 5000mAh so I'm hoping to get a couple of hours out of it.

Should be working on this later in the week.  I'll post up the results in a new thread.