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Looking for portable amp on tight budget

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Re: Looking for portable amp on tight budget

PostPosted: Fri Sep 18, 2020 8:24 pm
by zan1976
Sam I appreciate the answer :thumbup:
but don't understand how you got to it, the logic behind it :wtf:.

If you or someone could explain how I can estimate these things for myself, for different setups. Did you get to those numbers by seeing a certain spec in the speaker and console or was it out of experience? I don't even understand how to google these things! :headbang:

Perhaps a suggestion for battery and inverter?

Thanks again for taking the time guys, it is much appreciated!

Re: Looking for portable amp on tight budget

PostPosted: Fri Sep 18, 2020 9:19 pm
by Folderol
It is actually very difficult to give a definitive answer.

The makers don't give enough information. From the battery life point of view the amplifier 'class' makes a lot of difference. Class B is better than A, and D is much better still.

Also your playing style will make a lot of difference. Something like single clean guitar, will draw much less average current than 'wall of sound' backing, and it is the average that is the issue. Batteries have no problem at all with short high peak loads.

Re: Looking for portable amp on tight budget

PostPosted: Fri Sep 18, 2020 10:38 pm
by Mike Stranks
Let's have a look at Sam's numbers again:

They'll probably draw about 60 watts or so, so about 1/4A at 240V, that converts to roughly 5A at 12V so a 20 AH sealed lead acid battery, run down to 50% (the inverter will shut down when the voltage drops to 10V which represents, very roughly, 50% charge being used) would give you about 2 hours. But it's impossible to calculate with any accuracy and you may get three hours, or maybe only one....

He's estimated that the two items you've specified will require about 60 watts. (He's guessing because you can't find any information about such things for the Ibiza anywhere.)

Watts = Amps x Voltage. So 60 watts at 240 volts is 0.25 amps

but you'll have a 12-volt battery supply so this time the equation is 60 = ? x 12. Thus the ? is 5 amps.

A typical Leisure battery will be 100ah - that's 100 amp-hours. So in theory you can draw 5 amps for 20 hours.

But as Sam has pointed out you can't drain a battery flat. He's suggested 50% which gives you 10 hours.

BUT these are simplified theoretical figures. We don't know the actual current requirements in watts that the kit you're thinking of buying will have. Also the current-draw will be variable depending on the style, volume etc of the music. Then there;s the power requirements of the inverter. That itself will use some power in its operation/conversion processes. Most inverters have a cut-off to stop you draining the battery. The voltage at which they'll shut-down also has an impact on how long you can power the kit.

So it's not a precise science unless we have a lot more information. But the figures above give you a very approximate way of calculating some numbers. :)

Re: Looking for portable amp on tight budget

PostPosted: Sat Sep 19, 2020 12:33 am
by zan1976
Wow, that's very helpful Mike. Much appreciated!

By the way,
Mike Stranks wrote:. We don't know the actual current requirements in watts that the kit you're thinking of buying will have.

I won't be buying a kit, I already own the two items I linked previously:

Ibiza speaker
https://www.amazon.co.uk/Ibiza-SLK10-Active-Loudspeaker-25/dp/B009G176P6

and yamaha mixer
https://www.amazon.co.uk/Ibiza-SLK10-Active-Loudspeaker-25/dp/B009G176P6

I also have 2 of these:
https://www.dbtechnologies.com/en/products/b-hype/b-hype-10/

and another ibiza:
https://www.amazon.co.uk/ibiza-sound-XTK10A-Active-Speaker/dp/B00SG1123E

but none of these is portable, hence the battery.

Does anyone have any models in mind (battery, inverter) or what specs I should look out for them?

Re: Looking for portable amp on tight budget

PostPosted: Sat Sep 19, 2020 9:12 am
by Folderol
The B-Hype 10 specifies that it is class D, (while the others don't say) so that's definitely the one to go for, as I mentioned before.
It will draw very little power at low volume or standby.

You posted the wrong link for the mixer! However I doubt it will draw very much power.

Re: Looking for portable amp on tight budget

PostPosted: Sat Sep 19, 2020 10:33 am
by Sam Spoons
Foldy and Mike have covered it and the power consumption of 60 watts was indeed a guess* but an educated one based on some research I did a few years ago. But, it is only a guess and could be significantly off the mark (as my 1-3 hours comment suggests). The only way you'll know for sure is to measure it. The easiest way to measure is to buy one of these https://www.amazon.co.uk/230V-250V-Monitor-Consumption-Calculator-Analyzer/dp/B07FZZ17ZY/ref=sr_1_1_sspa?adgrpid=57342046710&dchild=1&gclid=EAIaIQobChMIqOjTuvT06wIV2ZrVCh34IQXVEAAYASAAEgJivfD_BwE&hvadid=259047051519&hvdev=c&hvlocphy=2826&hvnetw=s&hvqmt=b&hvrand=7754486017890663600&hvtargid=kwd-296081052919&hydadcr=28152_1821060&keywords=mains+power+meter&qid=1600507879&sr=8-1-spons&tag=googhydr-21&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEzQVg0RVAxMTlRRDJXJmVuY3J5cHRlZElkPUEwMTg3ODk4MkZPRVVVNTVFNEZHUyZlbmNyeXB0ZWRBZElkPUEwMDkzMTY3MkdUVDQ1MUsxOEtPJndpZGdldE5hbWU9c3BfYXRmJmFjdGlvbj1jbGlja1JlZGlyZWN0JmRvTm90TG9nQ2xpY2s9dHJ1ZQ==, plug the mixer and speaker into it and play while watching the display.

* As were several other assumptions I made.

Re: Looking for portable amp on tight budget

PostPosted: Sat Sep 19, 2020 12:21 pm
by zan1976
Apologies, this is the mixer, for what it's worth.

https://m.thomann.de/gb/behringer_xenyx_802.htm?sid=a38d8d3594d4a7819bf9e48718f6a689

I know the dbs are better, but they are not very convenient to use, they are used in another production.

Any suggestions on the battery and the inverter or what specs I should look out for? I will probably be using them in summer camping too, if that's in any way important.

Re: Looking for portable amp on tight budget

PostPosted: Sat Sep 19, 2020 3:29 pm
by Mike Stranks
Well the good news is that Behringer publish decent Tech Specs for that mixer!

According to them, the power-supply pulls 13 watts...

As Mr Spoons says the only way you're going to get any idea of what the amp pulls is to use one of those nifty plug-in meters.

Ah! So you also want to use the battery/inverter set-up when camping. If you want to use it to power things other than the amp/mixer we're into load calculations again as inverters are rated by the load they can handle.

You might find this: https://www.tlc-direct.co.uk/Technical/DataSheets/Skytronic/Guide_to_Inverters.pdf useful. Personally, I've run audio from a modified sine-wave inverter with no problems, but others may have a different view.

and this: https://www.tlc-direct.co.uk/Main_Index/Transformer_Index/Inverters/index.html?ad_position=&source=adwords&ad_id=109759574237&placement=&kw=%2b12v%20%2binverter&network=g&matchtype=b&ad_type=&product_id=&product_partition_id=&campaign=ROAS_Distribution&version=finalurl_v3&gclid=CjwKCAjw2Jb7BRBHEiwAXTR4je2NRJIbitleGQDuWSwqXqmlKerft3QfkOdKglqGzXBLBs0TD1ui5hoCnWcQAvD_BwE might be of some use. I've bought lots of stuff from TLC - always helpful and efficient IME.

Are you in the UK or somewhere else?

Re: Looking for portable amp on tight budget

PostPosted: Sat Sep 19, 2020 4:05 pm
by Sam Spoons
I have both modified sine wave and pure sine wave inverters and have had mixed results with the modified sine wave jobs, they have worked fine on some kit* but the first Li-Ion 'power generator' I bought off Amazon created a lot of noise used with my XR-12 and TC VoiceSolo speakers. I have since bought the pure sine wave version I linked to up-thread which works fine.

* My modded Epiphone Valve Junior seems perfectly happy with a SLA battery and 300 watt modified sine wave inverter.

Re: Looking for portable amp on tight budget

PostPosted: Sat Sep 19, 2020 4:21 pm
by Folderol
The greatest risk from modified sine inverters is with transformer type PSUs. These will suffer damage, mostly through overheating which will shorten their life. How much will depend on the transformer quality and ventilation. Smaller encapsulated types will be worst affected. The usual result is internal insulation breakdown causing shorts, then rapid complete failure.

Re: Looking for portable amp on tight budget

PostPosted: Sat Sep 19, 2020 9:19 pm
by zan1976
So the inverter should be pure sine, got it. Any tips or suggestions on the battery?

Mike Stranks wrote:Are you in the UK or somewhere else?
I'm in Greece.

Re: Looking for portable amp on tight budget

PostPosted: Sat Sep 19, 2020 9:33 pm
by Sam Spoons
A leisure batter will be good but heavy, a used car battery will be ok and cheap but also heavy, a lower capacity* sealed lead acid battery will be much lighter and not too expensive but needs a special charger.

By the time you have bought a pure sine wave inverter the cost is going up to around £100 in the UK. Li-Ion based kit is much lighter and more efficient so I'd be buying an all in one 'power generator' similar to the one I linked to if portability is important. Otherwise, as your speaker almost certainly has a SMPSU a cheap modified sine wave inverter and a cast off car battery will get you going for well under £40.

* SLA batteries are used for car booster packs, computer UPS, golf carts and kids ride on toys usually 7-20 AH, leisure and car starter batteries are usually 80-120 AH.