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Old 1st March 2007, 08:22 PM   #1
fotios is offline fotios  Greece
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Default Which is the better power supply for a preamplifier?

Do not search without reason. See the photograph below; four Lead Acid rechargeable batteries (each of 12V / 7Ah, from those that are used in UPS or alarm units) can offer a split power supply of +/- 24Volts without any ripple noise. With such supply can operate for 3 to 4 hours a preamplifier who consumes 150 W approximately. Afterwards the batteries it should recharged with a 1 hour fast charger. What a story and this, ha? It concerns however those that seek the absolute solution. Moreover it costs as much as one good stabilized power supply. I believe however that the benefits that it offers this solution are very much compared to the labour that it requires.
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Old 1st March 2007, 08:23 PM   #2
fotios is offline fotios  Greece
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Here is the proof. See in the oscilogram the noise floor of my discrete preamp module output; and with the input opened! (not shorted to ground). The output noise is just about 73 ėVolts!
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Old 1st March 2007, 08:33 PM   #3
AndrewT is offline AndrewT  Scotland
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Hi,
I have seen other sites compare batteries to active PSUs and always the batteries came out looking pretty poorly.
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Old 1st March 2007, 10:41 PM   #4
fotios is offline fotios  Greece
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Quote:
Originally posted by AndrewT
Hi,
I have seen other sites compare batteries to active PSUs and always the batteries came out looking pretty poorly.
Personally me, and for a given preamplifier without input select relays, without screens and Leds or anything other consume current without significant reason, the numbers that i wrote they are confirmed. On the other hand, were not lost by the market the batteries of bigger capacity. Those that you see in photo, are a gift from a friend to me. I will very soon try the new NiMH that has enormous capacity concerning their size. Come now, here we are ready to make a car that moved exclusively with NiMH batteries laid in his bottom, and with independent drive in each wheel with 4 electric motors. A preamplifier we mightn't move?
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Old 2nd March 2007, 12:05 AM   #5
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Default Re: Which is the better power supply for a preamplifier?

Quote:
Originally posted by fotios

...a preamplifier who consumes 150 W approximately.


150W for a preamp?...
I tend to use fairly high rails and high current for the preamps I build, but I find it difficult to use more than a third of that.
Incidentally, the use of batteries in audio circuits hardly qualifies as news--it's been done for years. The merits (or lack thereof) are already known.

Grey
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Old 2nd March 2007, 12:18 AM   #6
Leolabs is offline Leolabs  Malaysia
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How to assure that both rails have the equal discharge rate during usage????
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Old 2nd March 2007, 12:49 AM   #7
fotios is offline fotios  Greece
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Default Re: Re: Which is the better power supply for a preamplifier?

Quote:
Originally posted by GRollins



150W for a preamp?...
I tend to use fairly high rails and high current for the preamps I build, but I find it difficult to use more than a third of that.
Incidentally, the use of batteries in audio circuits hardly qualifies as news--it's been done for years. The merits (or lack thereof) are already known.

Grey
I do not know for your own preamplifiers, however mine it consumes what precisely i write. The designing moreover differ radically from one circuitry to another. As for the second part of your reply, i do not claim no innovation neither i discovered the wheel. You wondered how much new DIY fans enter in this site? It shouldn't we say certain things to them, that him we know (how many know moreover as you what mean ripple) be it we remembered also him certain times? In any case i could not understand why the batteries can be harmful for the audio circuits? Such something you don't say? (or lack thereof).I would be compelled to you if informed me on this subject as i have complete ignorance about this.
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Fotios Anagnostou
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Old 2nd March 2007, 01:03 AM   #8
fotios is offline fotios  Greece
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Quote:
Originally posted by Leolabs
How to assure that both rails have the equal discharge rate during usage????
Good question. As long as sure it can you are, that the power supply of a bought preamplifier has precisely symmetric supply, in other words the same precisely voltage in the positive and in the negative rail. If it presents a small leak one of the electrolytic capacitors of power supply? If LM317 or the LM337 is in the same state as they were regulated initially?
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Old 2nd March 2007, 02:00 AM   #9
fotios is offline fotios  Greece
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Default in order to close this subject here

I want to make a clarification. Sure the subject of supplying by batteries is more encyclopaedic. I write this in order to it does not take error conclusions some new person in the audio constructions. Moreover and me i use electric power supply from the mains in my preamplifier. Experimental i only use from time to time the batteries because they are not practices. What that has importance however, is this oscilogram shows the complete absence of noise in output, in order to we conceive how many it influences the ripple of power supply the sound quality. Also when the batteries begin to discharge, while the appliance still operates, is decreased dramatically his sound quality. The circuit is designed and measured in order to operate with constant supply voltage. When it falls under a limit, as we say from +/- 26 Volts in +/- 24 Volts together it falls also the transient response while are increased all kinds of distortion. These with regard to other preamplifiers. Mine has a limit at +/- 20 Volts so it begins to distort or it presents D.C. offset at output. In any case the experiments do not harm. All these in order to us close this subject here.
Fotios Anagnostou
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Old 2nd March 2007, 03:42 AM   #10
Gopher is offline Gopher  United Kingdom
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It seems to me the major problem with conventional active power supplies is the wideband RFI generated by the sharp current pulses and diode switching noise of capacitor smoothed diode bridge circuits.

Batteries do not suffer from this problem but can have higher transient noise levels than active PSUs when called on to supply current.

Is not the simple answer to regulate battery power supplies with high performance low noise regulators?

Gopher
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