Q: Make an amplifier battery powered?

[a.busker]

Hi. I want to purchase a really nice acoustic amp, for street performance.
I've tried all the various busker amps available, the Crate Taxi, the
Fender Amp-Can, but unfortunately they're not good enough for the sort of
stuff I want to do. There's the AER Compact Mobile, which is good enough,
but far too expensive IMO.

I'm considering the Roland AC-60

http://www.roland.com/products/en/AC-60/index.html

Unfortunately, it's not battery powered.

Is my only option, therefore, to carry around a big car battery and an
inverter?

Somebody told me that on some amps you can get technician to bypass the
power supply, so you can run it off batteries. Is that plausible?

 

[Clifford Heath]

Hi. I want to purchase a really nice acoustic amp, for street
performance.
Somebody told me that on some amps you can get technician to bypass the
power supply, so you can run it off batteries. Is that plausible?

Not really unless the amp has a low output or a 1 ohm speaker system.
12 volts isn't enough to produce the power levels you'll need.

Auto subwoofer amps use a step-up power supply. I have one here
extracted from a 400W car subwoofer amp. The power supply MOSFETs
had been blown up by some ignorant modifications to the amp, but
that wasn't hard to fix. It uses a TL494 SMPS chip, as many computer
power supplies used to. Anyhow, the two pairs of output MOSFETs in
the SMPS drive a toroidal transformer in push-pull, with two secondary
windings of 2:1 ratio, which produces an output after rectification
of +-25 volts from a 13.8 volt input.

I suspect that the amp you like differs only from the ones you don't
simply by the quality of the speakers - nothing to do with the amp at
all. Consider buying a speaker you like, and driving it from a car sub
amp on your battery.

Clifford Heath.

 

[a.busker]

Terryc wrote:

draw.

Well, one that runs directly off the battery would be best as you are
saving the losses of converting 12V to 240V, then back down again inside
the amp.

Is it the sort of thing that's plausible though? What kind of technical
difficulties are there in getting an converted to run on DC? I wouldn't
have the faintest idea.

No idea, but I'll bet it cost him a lot in replacement batteries. The
advantage of deep discharge lead acid batteries is that if treated
properly, they last a decade easily. The disadvantage is the weight and
the fact that they were ot designed to play ball games with.

Another approach might be to outline exactly what is wrong with each of
the amplifiers that you have tried and see what polite suggestions are
returned.

Well seeing as you asked.....

I'm a classical guitarist, and as such I'm aiming for clarity of sound.

I've tried four amps in my time as a street performer: the Ashton BSK158 (15
watt output), Fender Amp Can (10 W), Roland Microcube (5W) and the Crate
Taxi 30 (30 watt).

The Crate is the latest and clearly the most powerful. But even that, when I
get to a level of volume that I can be heard 10 metres away in a crowded
shopping strip, with all sorts of audio interference, including hundreds of
people talking in the immediate vicinity, spruikers, piped music ... then
the sound becomes muddy. It's especially noticeable when I'm strumming with
my thumb and picking with my fingers at the same time.

I met another classical guitarist busker in Sydney who actually had a good
sound. Though he had a big 200 watt + JBL powered speaker plugged into a
car battery via an inverter.

Then there were these other guys I kept running into in Melbourne, who had a
slightly more portable option. They were using the AER Compact 60, a nice
portable 60w PA accoustic amp, also plugged into big batteries via
inverters. Perfectly clear sound they got.

http://www.aer-amps.de/Sites/sites_ENG/productpages/compact60.htm

The Roland AC-60 is almost the same thing as the AER Compact 60, except at
$800 it's half the price. It has a few stupid design flaws admittedly (for
e.g, instead of a kettle plug, it's got a stupid power cord permanantly
hanging off the back of it, just ready to unfurl and fall off when you
really need to carry it somewhere quickly).

But the only real problem with either the Compact or the AC-60, is the issue
of having to carry around a big stupid battery and inverter, because you're
losing power converting DC to AC, and then back again. It's just
inefficient, labor intensive, and wrong.

 

[a.busker]

a.busker wrote:

I've tried four amps in my time as a street performer: the Ashton BSK158
(15 watt output), Fender Amp Can (10 W), Roland Microcube (5W) and the
Crate Taxi 30 (30 watt).

Oh I should add that all these amps come battery powered.

 

[Phil Allison]

" a.WHINGER "

But the only real problem with either the Compact or the AC-60, is the
issue
of having to carry around a big stupid battery and inverter, because
you're
losing power converting DC to AC, and then back again. It's just
inefficient, labor intensive, and wrong.

** You really are a COLOSSALLY arrogant, know nothing wanker !!!!!

Jaycar have very compact inverters for under $50 with >90 % efficiency and
low standby consumption ( cat M15102) - it weighs under 1kg.

They also have a 12 volt, 18 AH SLA battery for $65 ( cat SB2490 ) - it
weighs just over 6 kg.

So all up weight = 7 kg.

Operating time = about 5-6 hours.

Many amps that run from a 12 volt battery have DC-DC inverters INSIDE
them - you ASS.



....... Phil

 

[-=Spudley=-]

" a.WHINGER "




** You really are a COLOSSALLY arrogant, know nothing wanker !!!!!

Sounds like the POT calling the KETTLE Black,. again.

 

[hempster]

Hi. I want to purchase a really nice acoustic amp, for street performance.
I've tried all the various busker amps available, the Crate Taxi, the
Fender Amp-Can, but unfortunately they're not good enough for the sort of
stuff I want to do. There's the AER Compact Mobile, which is good enough,
but far too expensive IMO.

I'm considering the Roland AC-60

http://www.roland.com/products/en/AC-60/index.html

Unfortunately, it's not battery powered.

Is my only option, therefore, to carry around a big car battery and an
inverter?

Somebody told me that on some amps you can get technician to bypass the
power supply, so you can run it off batteries. Is that plausible?

check out this @ Ebay

http://cgi.ebay.ca/400W-Battery-Pow...ryZ10171QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

 

[ian field]

Terryc wrote:

But the only real problem with either the Compact or the AC-60, is the
issue
of having to carry around a big stupid battery and inverter, because
you're
losing power converting DC to AC, and then back again. It's just
inefficient, labor intensive, and wrong.

For the sort of power demanded there probably isn't much alternative to a
big heavy battery (except maybe a portable generator).

Many buskers adapt car audio equipment to suit their needs, often a stereo
graphic equaliser/BTL booster is easy to modify to fit the job, although
hard core customisers who like their "1 note honking bass" use low voltage
inverters with split rails (about +50V & -50V) and in car power amplifiers
designed for this use. The obvious advantage of the setup is that the
voltage isn't being transformed up only to be transformed down again so the
conversion losses are minimised.

 

[ian field]

Sounds like the POT calling the KETTLE Black,. again.

Philthy never learned any better having been raised by dingoes!