Hi
I going to try a 12v car battery to temporarily power my DAC and read somewhere on the forum (can't find it now) that it may be beneficial to use capacitor bypassing to improve this power supply.
Anyone got any thoughts on what may be required - i.e. schematic, capacitor type/capacitance required, capacitor location etc.
Thanks for any replies.
I going to try a 12v car battery to temporarily power my DAC and read somewhere on the forum (can't find it now) that it may be beneficial to use capacitor bypassing to improve this power supply.
Anyone got any thoughts on what may be required - i.e. schematic, capacitor type/capacitance required, capacitor location etc.
Thanks for any replies.
If there is a reasoning behind this, I'd like to know.
It may be that a lead-acid battery generates some noise above DC and the cap shunts... I'd do a search and see what people are saying.
If ur DAC runs the 12v battery power into regulators first, then that idea is likely moot.
It may be that a lead-acid battery generates some noise above DC and the cap shunts... I'd do a search and see what people are saying.
If ur DAC runs the 12v battery power into regulators first, then that idea is likely moot.
I don't know what the impedance of a flooded LA battery looks like at the plates, but in any case, that's not what you get at the terminals, which for a car starting battery could be as much as ten inches apart, already a problem in itself. You may as well use added capacitors and assume that and their leads/ circuit traces define the supply impedance above a couple hundred Hertz. Maybe you might want to worry about even lower frequencies.
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Try it.
The car battery intrinsically is a huge capacitor by virtue of its construction.
You would only need to try smaller caps to see if there would be any improvement to the HF response - they are pennies.
Extremists work in factors of x100 or so, so adding 220uF as close as possible to the output devices might be a starting point, then maybe 2.2uF. Bypassing with anything smaller after that might be a bit extreme.
The car battery intrinsically is a huge capacitor by virtue of its construction.
You would only need to try smaller caps to see if there would be any improvement to the HF response - they are pennies.
Extremists work in factors of x100 or so, so adding 220uF as close as possible to the output devices might be a starting point, then maybe 2.2uF. Bypassing with anything smaller after that might be a bit extreme.
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If the DAC board is already designed to be supplied by a wall wart or similar, the most important thing to add would be a fuse close to the battery. Suitable input bypass and regulators would already be present.
Here is a paper about battery noise but I don't think lead acid batteries were covered.
I was surprised just how much quieter a nicad was than a Lm317 regulator.
http://tf.nist.gov/general/pdf/1133.pdf
I was surprised just how much quieter a nicad was than a Lm317 regulator.
http://tf.nist.gov/general/pdf/1133.pdf
Interesting experiment but the batteries tested were
(beyond being Old tech ) AA's !
Widely varying battery types, not only in size/chemistry but More significantly in capacity.
Even back in '95 some Nicads could output 40 amps for the duration of their full charge (no mean feat that) while another brand, in similar size, would have trouble matching the output of a AA alkaline.
A flawed or near sighted test at best imo.
(beyond being Old tech ) AA's !
Widely varying battery types, not only in size/chemistry but More significantly in capacity.
Even back in '95 some Nicads could output 40 amps for the duration of their full charge (no mean feat that) while another brand, in similar size, would have trouble matching the output of a AA alkaline.
A flawed or near sighted test at best imo.
OK, I've found the thread where I read it awhile back, but rereading it perhaps I've interpreted it wrongly?🙂😕
From here:http://www.diyaudio.com/forums/power-supplies/214471-anyone-listened-li-ion-batteries-2.html#post3225541
"Since no battery of anything other than ridiculous size has a near-zero impedance, no battery will ever be a "perfect" source of DC power for an AC circuit. At the very least some capacitor bypassing will be necessary. That's just basic electronics.
The only gain of a pure battery supply would be isolation from noisy AC power sources and ground loops, maybe... Lots more trouble than it'd be worth, to me.
Frankly, I'd be using lead-acid car batteries if it came to that. Cheaper and reasonably low impedance."
From here:http://www.diyaudio.com/forums/power-supplies/214471-anyone-listened-li-ion-batteries-2.html#post3225541
"Since no battery of anything other than ridiculous size has a near-zero impedance, no battery will ever be a "perfect" source of DC power for an AC circuit. At the very least some capacitor bypassing will be necessary. That's just basic electronics.
The only gain of a pure battery supply would be isolation from noisy AC power sources and ground loops, maybe... Lots more trouble than it'd be worth, to me.
Frankly, I'd be using lead-acid car batteries if it came to that. Cheaper and reasonably low impedance."
The battery will have very low noise, but the impedance is actually in the milli-Ohms. The impedance also changes with charge. A film or ceramic cap will lower the impedance.
FWIW, an active regulator like the Jung or Salas shunt has impedance in the micro-Ohms.
FWIW, an active regulator like the Jung or Salas shunt has impedance in the micro-Ohms.
marcus1 does your DAC board come with a voltage regulator, or does it operate all parts from and '12VDC' supply (if so then does the board have 12VDC filtering on it) ?
Actually I got it wrong; it's for an old Perpetual Technolgies P-1A D/D processor, not the PT P-3A DAC (that takes 9VAC);
The P-1A normally uses a walwart (that I can't find) and I guess there are numerous voltage regulators onboard.
I'll try the battery by itself and then try some caps near the plug and see if I can hear any difference (probably not 😀 but worth a go)!
The P-1A normally uses a walwart (that I can't find) and I guess there are numerous voltage regulators onboard.
I'll try the battery by itself and then try some caps near the plug and see if I can hear any difference (probably not 😀 but worth a go)!
No it is not.
It produces electricity by chemical reaction.
That produces noise and has output impedance.
It's also lots of parallel plates - which is a capacitor.
Add in the electrolyte and it's very close to a huge electrolytic.
In an electrolytic capacitor the electrolyte is a conductor; an extremely thin layer of metal oxide on one of the plates provides the insulator.
??? What noise does a battery exhibit by way of chemical reactions?
To my mind it is best to think of a battery as a voltage source with an equivalent LCR type network in series to characterise the actual voltage presented at the physical terminals. The form of LCR network can get quite complex and include non-linear components to adequately represent realtime behaviour across a range of operating current levels and time.
The noise generated by the batteries in the pdf listed eariler was at worst -200 decibels...I don't think any filtering would be worth the effort. Though the OP should use some kind of reg to bring the voltage down to 9V the device needs. Note if he was connecing some kind of charger to battery while he was using it then some kind of filter would be a good idea...just to be on the safe side.
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^LOL...while lead acid was not listed in the paper I doubt it would be noiser than the 7809 to get 9v the OP needs.
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