Efficient amp?

root fifth · #1 02-17-2011, 07:41 PM

I have seen this as the answer to a couple of post on here about people wanting to play out doors without power,or busking and what not.It seems to allways come up to use a efficeint amp and a battery or a battery pack.So how do you tell how efficeint your amp is or what amp would be more efficeint? Thanks for any help!

T-Bird · #2 02-17-2011, 11:20 PM

Hi.

In short, output power vs. input power is the efficiency.

Tube amps (regardless of the class of operation) are generally the least efficient, ~35%
SS
Class A/B ~50%
Class G&H ~60%
Class D ~90%

So it's a low power class D, pereferably with SMPS (Switch Mode Power Supply), one would look if a busking amp is the main requirement.

Regards
Sam

root fifth · #3 02-18-2011, 03:15 AM

SMPS? not real for sure what a switch mode power supply is?Busking is not the main requirement but we do like to go to outdoor jams and have from time to time played in a park or downtown.So i am looking for somthing to fill the nich for that!Also when you say low power are you talking about wattage?

root fifth · #4 02-18-2011, 03:22 AM

Ok i just googled that and i dont think the avarage power pack has that LOL.

T-Bird · #5 02-18-2011, 04:15 AM

Hi.

Quote:

Originally Posted by root fifth

Also when you say low power are you talking about wattage?

I assume that by busking, You mean something where you won't be able to use mains voltage, but you have to rely on (lead) batteries. One way or another. The lower the power draw ie. wattage of the rig, more you'll get out of one charge.

A small(ish) horn loaded enclosure like those on BFM site will help in building an efficient rig.

Regards
Sam

root fifth · #6 02-18-2011, 03:17 PM

Yes i am talking about using batteries only.

seamonkey · #7 02-18-2011, 03:41 PM

Car amps, class-d and otherwise, will have an SMPS to raise the voltage so you can get more current and thus more power through a 8, 4,2, or even 1 ohm speaker.

12V through an 8 ohm speaker would be 18W
Google ohms law. It's a law that is enforced in cars.

root fifth · #8 02-18-2011, 04:53 PM

Seamonkey dont take this wrong but what does all that car info have to do with playing my amp off of batteries?I would use a converter to go to 110 or just use a powerpack that has a built in converter.I due have a minor understanding of ohms laws but dont see how that will help me find the efficiency of different amps.Like i said dont take this wrong you cought me off gaurd with the car talk!

root fifth · #9 02-18-2011, 04:57 PM

Over all goal is smaller combo running off of a power pack or a battery to boost my acoustic bass guitar in outdoor places with out power outlets.Want to be as light weight as possible!(As least as light as you can get dragging bass,amp,battery,and ?)LOL

GrowlerBox · #10 02-18-2011, 09:57 PM

Quote:

Originally Posted by root fifth

Seamonkey dont take this wrong but what does all that car info have to do with playing my amp off of batteries?I would use a converter to go to 110 or just use a powerpack that has a built in converter.I due have a minor understanding of ohms laws but dont see how that will help me find the efficiency of different amps.Like i said dont take this wrong you cought me off gaurd with the car talk!

I think he's referring to the fact that loud car stereo systems manage it on a 12V car battery.

will33 · #11 02-18-2011, 10:11 PM

You guys technical lingo is above my paygrade. I'm also not a Carvin endorser or anything but are you looking for something like this?

http://www.carvinguitars.com/product...ct=S400&cid=10

Rechargeable battery power, tiny little mixer/preamp with a 110+tweet, maybe two?

Kind of a little restaraunt/coffeehouse little does it all rig, maybe a UB rig with ext. cab?

Exploiter8 · #12 02-18-2011, 10:34 PM

What converter are you using? I haven't really looked into them, but the one I have on my DieHard PowerPak gives a buzz/hum.

Just wondering,
X8

T-Bird · #13 02-18-2011, 10:35 PM

Hi.

Quote:

Originally Posted by root fifth

Seamonkey dont take this wrong but what does all that car info have to do with playing my amp off of batteries?I would use a converter to go to 110 or just use a powerpack that has a built in converter.I due have a minor understanding of ohms laws but dont see how that will help me find the efficiency of different amps.Like i said dont take this wrong you cought me off gaurd with the car talk!

He mentioned the car amplification since the kind of an amp that You're asking for, doesn't exist without at least some level of DIY involved. Not below $1K or so anyway

.

Low rail-voltage class D amp modules are rare, and expensive (finding a suitable PS for those pumps the price even higher), so a car amp is a logical choice.

The most energy You can safely draw from a regular lead-acid "car" battery for a longer period of time, is often 10% of it's capacity, often less for the dry ones. That, for example, means that from a 55AH battery (common in batt-packs?), the max draw is 5.5A. With (assumed) 12V that calculates as 66 available watts. Combine that with a regular class A/B amp, and You'll get max 33W. Combine it with class D amp and You'll get about 60W.

In this calculation, I didn't take the batt-pack (~80%) efficiency into account.

Regards
Sam

James Judson · #14 02-18-2011, 11:03 PM

I have seen nothing in the runs on batteries amp that has near enough horse power (watts) to drive a bass guitar enough to keep up with acoustic instruments. I have owned three marshal, peavey, pignose ams that are useless. Guitars (barely), bass (not even close). My suggestion is a Guitarone (you know the mexican bass), they are tuned different and two strings are plucked at a time giving more output. Or an upright (double bass) so much for light and easy. Or make your self a gut bucket (wash tub bass), will cost you about 20 bux at the hardware store and you'll draw a lot of attention to yourselves.

I did see another alternative at an outdoor jam once (Seattle Center, Folk Life Festival). This guy had taken a typical hand kart, mounted a car battery on the bottom and a power converter (12v DC to 110v AC) and stacked a semi small bass amp on top. The whole thing was semi portable and kept up with acoustic musicians quite well. If your handy enough to put one of these together your considerations are:

1. How much current does my bass amp need (its listed right next to the power cord imput measured in amps)
2. What is the converter rated at. (I would double the number you just saw on the back of your amp).
3. Get the biggest battery you can afford or care to lug around.

And there ya go. Only other consideration is charging that battery (overnight trickle charger might cost 25 to 50 bux). If this is all greek to you a boat or RV dealer deals with this stuff all the time and should be helpful.

Let us know if you find a solution that works for ya.

YMMV

root fifth · #15 02-19-2011, 08:31 AM

Well James Judson that is pretty much the plan i wasnt going to use a cart.I was thinking more like hand dolly.I havent read about multiple people having any luck with battery powered amps out side of the breif case and thats to much money for me.Also i plan on using a marine batt and i can use my trickle charger that i already have for the recharging. Tbird I am just asking about how to tell amp efficeincy.I plan on just using a combo like i mentioned above. Thanks all!

root fifth · #16 02-20-2011, 06:59 PM

BUMP!

Rick Auricchio · #17 02-21-2011, 11:05 AM

Quote:

Originally Posted by root fifth

I would use a converter to go to 110...

First, you will lose even more efficiency in the inverter. I don't have figures, but they certainly aren't 100% efficient. You would do better finding an amp that runs at 12v and skip the waste of the conversion.

Second, many inverters are designed to power appliances, computers, chargers, etc. Not audio equipment. They don't produce clean sine-wave AC power because these devices don't care. But many amps will be noisy with that type of power.

root fifth · #18 02-21-2011, 03:48 PM

Hmm sounds like i might be S.O.L