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Old 30th September 2012, 04:39 PM   #21
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Le Monstre, a DC powered amp, is covered in a good paper at the link above. The google translation adds some humor to the read!
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Old 30th September 2012, 04:49 PM   #22
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Quote:
Originally Posted by Tachyon View Post
Hifimediy T1-M TK2050 9 - 24V

Hifimediy T1-M TK2050 9 - 24V
This website has a neat selection of products. Seems like a good place get some toys. May experiment with my own power supply on one of their amps.
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Old 30th September 2012, 05:04 PM   #23
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Quote:
Originally Posted by Rundmaus View Post
DC-DC converters invariably work internally as DC-AC-DC converters* (it's physics )
I'm not sure what DC to DC converters are commercially available,
but is very easy to step up DC voltage with an inductor, transistor, diode and a cap - there is no conversion to AC.
But these are generally noisy - and create tons of EMI.
Plus the toroid core will need to be big enough so that it stays clear of saturation.
A capacitive doubling circuit will do it too - without an inductor.
.
.

A few comments concerning the use of any lead acid batteries

- they should be kept in an explosion case (marine supply stores typically sell these)
- fuse the battery outside the case (don't want a the spark from a fuse igniting hydrogen gas).
- Most (not all) lead acid batteries are charged from a constant current source.
- Below 1.75 V per cell and the cell may be damaged - fully charged cell 2.1v.

Maybe find audio equipment that can run directly off of DC.
Where the amp is in a separate case from the power supply,
One of the Musical Fidelity integrated amps comes to mind, but there are others.
.
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Old 30th September 2012, 05:21 PM   #24
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A few more comments

Wheel chair batteries - are actually designed for deep charge and discharge cycles.
They are a much higher quality battery than a Car or marine battery.
Exide is an actual manufacturer of lead acid batteries.

Data sheets should be available to show what the charge and discharge curves look like.
Very importantly, understand how to charge up the battery - data sheets should spec what is required (Not necessarily show the circuit)
Again, this is nearly always done with a constant current source.

4 batteries in series is pretty well the max since above 48 Vdc becomes lethal.

With 6 cells per battery - and the range of each cell is 1.75 v to 2.1v
That would give you voltage rails that would range from +/- 21 to 25.2 v.
I'm sure there is plenty of equipment that could run off of that.
.

Last edited by Uunderhill; 30th September 2012 at 05:25 PM.
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Old 4th October 2012, 07:38 PM   #25
krasnal is offline krasnal  United Kingdom
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Hi,

At the begining employ battery to supply any electronic equipment seems to be good idea; purest dc power supply ever. Hovever having more than one battery you have to keep in mind, those discharge cycle will be different. You may find out difference up to 1 volt between two 12 volt batteries (I learnt it hard way). So far i got good experience using batteries to supply preams and DACs and for those applications I can recommend them.
P.S. If you want to supply op-amps from batteries I would recommend batteries made for rc cars. They are 7.8 volts, so that give you some margin for voltage adjustment

Regarding power amp power supply; try to add some caps to your power supply. If ie. you got 10000uF, then add 1x1000uF, 1x100uF, 1x10uF, 1x1uF and 100n. I know it looks like overkill, but it works.
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Old 10th October 2012, 09:24 AM   #26
AndrewT is offline AndrewT  Scotland
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Location: Scottish Borders
all batteries are using chemical reactions to deliver the current.
That current comes from the random reaction times and must result in some noise. It cannot be avoided.

You should not willy nilly jump on the first or any battery and assume it is better than the main supply.

Many battery types are very noisy.
Some battery types are very quiet.
Select accordingly.
__________________
regards Andrew T.
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Old 10th October 2012, 05:15 PM   #27
krasnal is offline krasnal  United Kingdom
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the only batteries I would use is lead-acid or gel batteries

Regards,

Michal
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Old 19th October 2012, 12:17 AM   #28
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Quote:
Originally Posted by AndrewT View Post
all batteries are using chemical reactions to deliver the current.
That current comes from the random reaction times and must result in some noise. It cannot be avoided.

You should not willy nilly jump on the first or any battery and assume it is better than the main supply.

Many battery types are very noisy.
Some battery types are very quiet.
Select accordingly.
Resistance causes noise

Recall the thermal noise from a resistor is Vn = SQRT(4kTBR)

So a battery, with a low internal impedance, is probably a figure to look at.
For lead acid, a low internal impedance is probably an indicator that the battery has good plates.

For a wheel chair battery Zint ~ 21 m ohms.

Unfortunately as a battery ages, its internal impedance rises.
.
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Old 19th October 2012, 02:36 AM   #29
Yooper is offline Yooper  United States
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A good source for low voltage DC/DC power is Wall Industries.
Their DCHB150-12S24 can boost from an input between (8.5V to 18V) to 24VDC in a pretty small package..2.2" x 2.2" x 0.5". Isolated too.
Plus, the 92% conversion is outstanding.
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Old 19th October 2012, 12:29 PM   #30
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recall, v(t) = - L di / dt

So a DC to DC conversion will need an inductor and a transistor switch.
However, switching an inductor creates all sorts of noise.

For audio, I suggest using the voltage straight off the batteries.
Again, make sure there is an appropriate fuse outside the battery case.
.
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