Noise free 12v psu for Headphone amps/DACS

[405line]

Hello all,
Go find one of these portable/emergency power packs to cleanly, that is lead-acid power a 12v headphone amp or dac, in practice it usefully buffers the incoming psu to give "clean" battery power while float charging or you can run off battery only for hours/days, I believe this particular device has 2, 6v/5ah completely sealed lead acid batteries wired in series and has 2, 12v cigarette lighter sockets built in, I used one to perfection (I cannot find a more suitable term, really) when I found the class A mod I tried was coupling smps noise onto the output of my mini dac modded with opa627. I found it makes for a perfect?, completely noise free psu if 12v is all you need. I believe it will likely improve the sound as well as there are now no PSU related artifacts. Just thought I,d pass on a left of center idea.....p.s you will obviously need a car type cigarette lighter male jack to DC jack or whatever lead and if you see what looks identical for a £10 or so cheaper elsewhere.........
MAKE SURE YOU GET THE VERSION WITH THE BUILT IN 12v LEAD ACID BATTERY THAT POWERS THE BUILT IN 200W 12V TO 240VAC INVERTER "WIRELESSLY"

www.maplin.co.uk/module.aspx?moduleno=225153

[Deleted]

I do not see the point in using these devices for hifi.

1: If you plan to use 12V battery power for the low impedance from the battery I can assure you this is ruined already when using the cigarette lighter because of the wiring, fuse and connections you will be making.
2: it's a bit heavy for portable use.
3: The AC coming out of these devices is anythhing but a nice, clean and stable sinewave with LOTS of harmonics and garbage.
4. When using the 12V while it is connected to the mains chances are a lot of the mains garbage is passed though and the internal SMPS used to charge the battery is likely to give you even more RFI common mode garbage making it NOT clean power but heavily poluted power.

IMHO you can use these devices for anything BUT hifi gear.
Just my view on it.

[405line]

Hello, I am certainly not suggesting that you use the mains output as it is very ruff and not actually a sine wave, I just suggested you use the internal 12v power supply that is pure dc battery and it is certainly better than the supplied smps. The current draw on most headphone amps is modest and yes you could solder up all the internal connections and fit a higher rated fuse if you wished to do so, you could also hard-wire the output bypassing the cigarette lighter. All as I can say is that it works well and is silent in use as you are not actually switching the device "on", the twin ciggy lighter sockets are directly wired to the internal batteries, no switches just an auto "blade" type 25A! fuse for safety and it is designed too be portable which could also be of use. It's just a safe way to try out battery power...gives an excellent sound, honestly I did not know mp3 etc could sound so good. For the record I disconnected and reconnected the charger to the device which is not directly mains powered but does requires a 12vdc@300ma(min) power pack DC jack input to slow charge the internal batteries and I could not hear any additional noise when it was connected so I am satisfied that without going to further extremes this seems the best overall solution..for me at least...try you might like. Once again you can just use the internal 12v DC batteries to silently power your DAC or Headphone amp. I will assume this will be effectively an unregulated power source but as everyone knows lead-acid cells can generate very high currents due their very low internal resistance (try to start a car with a 12v dry cell) and this will mean that the actual voltage is unlikely to vary much when lightly loaded with a DAC or modest headphone amps.
Thanks for reading.

[rowuk]

Um, the lead acid batteries are actually not that low impedance. If you want to get a really good battery pack, the best that I have found are the LiPo batteries that are used for model airplane competition. Like these:

www.rfcafe.com/references/electrical/battery-li-poly.htm

Battery does not mean necessarily low noise or better performance than a solid power supply.

[xerxes]

I used a 24v SLA with my WNA headphone amp for a while. At Rick's suggestion I added some electrolytic capacitors on the output to lower the impedence. It sounded fine, but I got fed up with mucking about charging the battery and I eventually replaced the battery pack with a decent mains linear power supply which sounds just as good.

[mrarroyo]

Well, I have been using the Red Wine Audio products for over 18 months and I love what they do with the music!

www.redwineaudio.com/products/

[405line]

Hello all, yeah, a lead acid cell acts as a the power/RF filter in a car, if you disconnect the battery from your car while it is running you will likely blow up the electronics, it has extremely low internal resistance as it can deliver several tens if not hundreds of amps, more importantly for delicate electronics enthusiasts it has an equivalent capacitance of THOUSANDS OF FARADS, YES THAT'S CORRECT, THOUSANDS OF FARADS OF EQUIVALENT CAPACITANCE:This was taken from a premium battery charger FAQ "Because of the construction of lead acid batteries, the equivalent electrical capacitance is in the range of several tens of thousands of Farads. For this reason, specifying a ripple component of output voltage on a battery charger when it is connected to a battery is somewhat futile because of the tremendous voltage-filtering characteristic of the battery’s equivalent electrical capacitance."

A smoothing capacitor (micro-farads) is actually acting as a battery...think about it.

You can get a float charger that will keep the battery at around 13.2-13.4v indefinitely, I just got one today from US and it is working perfectly on my set-up you don' not need extra smoothing circuits (see above) as the float charger is regulated anyway, you could use and ordinary charger and a timer. You can connect this to the 4mm plugs on the front.

Not sure about this, however if the polarity protection diode takes 0.7v from the input voltage (@12v reg) then halves it using a virtual ground to op amps with +/- and the regulator only sees half the input voltage then some of these dacs may be running a little near the margins for my liking as they try to regulate 5v from @5.75v and likewise for op-amps etc.I would have to surmise that the extra voltage is really handy and ensure at least a 12v "working" voltage.

Thanks for reading.

[Deleted]

a lead acid cell acts as a the power/RF filter in a car, if you disconnect the battery from your car while it is running you will likely blow up the electronics,

Not quite... it acts as a rechargeable battery storing energy put into it by the generator.
IF you take the battery out while the car is running AND there is little current drawn (lamps are off e.t.c.) in some cases some electronics may go belly up.
This is because the battery acts like a zener with a capacitor in parallel and the generator and rectifier can produce high voltage peaks which some parts may not like.
Modern day car electronics must be able to withstand these peaks b.t.w. and this is specified in guidelines and standards.
Automotive standards are about the most severe to meet for above reasons.
Car batteries have a tendency to go open circuit sometimes, quite suddenly and if this would destroy the cars electronics there would be many law suits against car manufacturers

For RF a battery is a lousy low-Ohmic resistance b.t.w. because of it's internal structure.
Electronics get their HF/RF low Ohmic resistance from the small decoupling caps mounted near the PS pins of IC's. NOT by the power supplies huge caps nor by a battery.

When connecting a float charger to a battery you introduce CM RF and other groundloop problems again which one wants to avoid.
The fact that they often cannot be detected or have negative impact says something about how it all connects and interacts with each other.

The internal resistance of a battery is not that rediculously low, certainly not with smaller batteries as those that are found in said gear.
10 to 50mOhm is not that stunningly low and can be bettered by low ESR capacitors.
When starting a car lots of current is needed BUT the voltage may drop considerably which is no problem for a starter motor.

Every wire in series with the battery is an extra inductance increasing the internal resistance for higher frequencies.
a diode in series with everything destroys all you have tried to accomplish as the dynamic resistance of it is about 1/40*the current drawn.

Low PS impedance comes from big reservoir caps and voltage regulators CLOSE to the circuit and for RF the small caps close to the IC's NOT from anything in front of it, this only needs to replenish the drawn power from the reservoir caps fast enough.
No matter how people think it works or believe it works.

[405line]

Goodness, what more can one say about a hundred year old battery?
A lead acid battery is to all intents and purposes the best "reasonable" PSU if you do not require the sort of voltage or current for a powerful amplifier as far as I can tell, the fact that most PSU switched or linear have a (1-5A usually) current rating tells you that they must have more internal resistance than the said battery, yes they are small but they are still rated to @20 amps you could use a larger type for even less I.R if you wished to do so.

Batteries are a silent source of power unless you want to get into sub-atomics, thermionic noise etc....!!!

[405line]

12v@25A=0.48 from a very small lead acid battery requires the source PSU to have an ohmic resistance of about 0.48 ohms that seems small to me.
I think most high end audio engineers would disagree with you to a certain extent,
an oversized PSU is always a very good place to start of with.

[Deleted]

an oversized PSU is always a very good place to start of with.

I agree with you on that.

Your logic concerning internal resistance, however, is quite 'basic' and IRL has little to do with a proper power supply I am afraid.

Internal resistance of a power supply is determined by how well the regulator performs.
(NOT talking about power amps but HP amps and digital circuitery and preamps)
Meaning how 'constant' the regulator circuit can maintain the output voltage under different load currents and at which frequency.
The powersupply resistance (at a certain frequency) can be calculated by the voltage drop under a certain load.
A good regulator does not vary it's output voltage under different loads as where batteries always do as they have no regulation, however small that may be under these circumstances.

One can even create a negative resistance (as happens in some JLH regulators) which means that with a certain current increase the voltage of the regulator doesn't drop but INCREASES in voltage.

THAT is where the powersupply internal resistance comes from, not from how low Ohmic the path between the reservoir cap and 'the powerplant' is.
As long as the latter part is capable to keep the reservoir caps as full as is needed for proper regulation it is O.K. on the internal resistance part.

HF is much more difficult for a feedbackloop then LF (audio is LF) is.
In digital and fast opamp circuitery a low internal resistance is of essence and does NOT come from reservoir caps, does NOT come from regulators but is determined by the small 10-100nF decoupling caps interacting with the inductance of coppertraces and PS wiring I might add.
Failing to create a low internal resistance for HF can seriously cmpromise SQ and cause unwanted oscilations which may not be audible by itself but can have audible consequences.

I am curious to find which (high end) audio engineers have valid reasons to disagree with this electronics/audio engineer (me) about this part.

NOT saying that your way of powering is a bad thing at all and batteries cannot or should not be used.
Merely saying batteries are not 'the holy grail' although it may have proven to you and /or others that it is.
But that is another (subjective) matter.

PS... is your nickname derived from televison or are you a quad 405 fan ?

[405line]

Digital multimeter reading a rock solid floated 13.34v.No switching or 100hz humming noise, no power coupling noise from the class A opa627 opamps i'm using for dac amplification. You have to float the battery it will self regulate on float charge to balance. That's enough for me.

[Deleted]

Well... like I always say.
each of us acts to their own 'audioreligion'.
If it's good enough for you, then that's what it is.

Technically feeding something from a battery has it's perks.
Connecting it to a (floating) charger, especially switchmode simply makes it loose it's technical advantage as ground loops and common mode currents are back in play making the benefits disappear again.

[Deleted]

Frans

Not quite audio but sounds like you could answer a question I have never got a trustworthy answer to. When recharging a car battery is it necessary to disconnect it from the car? I read years ago, when alternators were only starting to get popular, that it was.

Thanks

Syd

[Deleted]

I see no reason to disconnect it when the car contact is switched off and the lights are off too.

...but I am no expert on this matter.

[jkeny]

Try A123 LiFePO4 3.3V batteries - <8mOhm internal impedance, 70A current output continuous (120A bursts - 4 in series will start a car), low noise, very portable

[Deleted]

But you will need a special charger that charges the 4 individual cells...
the 'fun' part of said device is the price (charger, 12V power supply and emergency 230V generator for a LOW price)
and a life expectancy of about 5-10 years if kept under charge.

If a charger is connected during operation CM signals and groundloops are possible again and the purpose of 'clean power' is defeated again, which should be unacceptable for purists that want that clean power and have to use very short and thick wiring to maintain that low impedance (the decoupling caps around the parts take care of the real decoupling)

there is ONLY clean power when used without it being on any type of charger during use and thus must be physically disconnected.

Especially LiFePO4 as charge currents are 10A and come from switchmode power supplies.
One really should see what CM signals eminate from these devices and which currents run through the shields of interlinks when used.

Actually I am curious as I can only find data/graphs about charging/discharging and resistance (down to 2mOhm) when used as a DC powersource. (bike's model airplanes, cars)
I wonder how well it holds up at higher frequencies where low impedance matters most ?
Worth a study isn't it ?

[Deleted]

I see no reason to disconnect it when the car contact is switched off and the lights are off too....but I am no expert on this matter.

Thanks Frans

Syd

[jkeny]

Jan 30, 2011 8:16:01 GMT @solderdude said:

But you will need a special charger that charges the 4 individual cells...

OR 4 very easy to make CC/CV DIY trickle chargers using only LM317 & TL443 active devices.

the 'fun' part of said device is the price (charger, 12V power supply and emergency 230V generator for a LOW price)
and a life expectancy of about 5-10 years if kept under charge.

If a charger is connected during operation CM signals and groundloops are possible again and the purpose of 'clean power' is defeated again, which should be unacceptable for purists that want that clean power and have to use very short and thick wiring to maintain that low impedance (the decoupling caps around the parts take care of the real decoupling)

there is ONLY clean power when used without it being on any type of charger during use and thus must be physically disconnected.

Especially LiFePO4 as charge currents are 10A and come from switchmode power supplies.
One really should see what CM signals eminate from these devices and which currents run through the shields of interlinks when used.

See above

Actually I am curious as I can only find data/graphs about charging/discharging and resistance (down to 2mOhm) when used as a DC powersource. (bike's model airplanes, cars)
I wonder how well it holds up at higher frequencies where low impedance matters most ?
Worth a study isn't it ?

Have a look at this study - it reports impedance dropping at higher freqs www.google.ie/url?sa=t&source=web&cd=1&sqi=2&ved=0CBQQFjAA&url=http%3A%2F%2Fwww.lifebatt.com%2Fsandiareport.pdf&ei=rnhFTdzIL4-7hAejn9GyAQ&usg=AFQjCNEq9smR3E3xfBW5J9XWb8p8ff4fEw&sig2=AzELRJL7swmiDEz6i7VdEg

[405line]

Hello ,if you float the battery then current balances out to stabilize the float voltage to give you silent battery power. I am not sure what the impedance at high frequencies does an this is essentially a DC/0hz transmission.What you need is a float charger not a trickle charger unless it has a float mode to reduce the voltage/current applied after charging to @13.2-13.4v otherwise when the battery charges to above 14.4v and stays at or above that voltage for over 12 hours say the battery will start to gas and loose its water.

Some have said I have a basic grasp of what I am reporting...I say you do not need to complicate things with ground loops etc a battery
will probably do more to stop ground loops than cause it. What is this CM thing is that common mode noise which is noise on both live and neutral in an AC distribution system?
Common mode noise is the electrical noise on all power lines with respect to ground. Differential mode noise is the electrical noise on one line with respect to another line.

I fail to see the relevance if that is what you are talking about.

Most battery chargers are double insulated and do not have an earth connection in the first instance and the ones that do mostly will have a metal case and that is just a safety earth due to the metal casing possibly becoming live....unless as an in earthed laptop PSU some bright spark has decided to connect the AC electrical ground to the laptop DC 0v line which can and does cause that nasty static noise that disappears when you go onto battery power you can solve this best by getting a 2 pin (unearthed) psu for your laptop.

A battery/float charger is not generally rocket science, it is essentially a mains step down transformer, the secondary of the transformer produces isolated, floated and balanced AC with a suitable voltage (floating but not the same floating as the battery, this time it means that the output AC voltage has no reference to ground or distribution earth and will be clean and free from noise as it will have also become balanced and fully floating due to transformer action) this is then connected to diodes to be rectified and to produce a full wave rectified output, some use diode bridges, some use a center tapped secondary and use 2 diodes, that for the most part is that....however if you have spent the required funds you will also have some voltage and current circuitry to limit the output voltage and or current of the charger because as the battery charges its relative resistance increases and the voltage across the battery will eventually become too high and cook the battery under charge.

A float charger limits the voltage in a well documented way with a voltage and or current regulator to keep the voltage across the battery from becoming too high after being fully charged, the lead acid (definitely) or other wet cell technology (perhaps) also has the effect of filtering the noise and ripple voltage from the connected charger that's it.
Unconventional thinking I know.

If you want to swat up on wet batteries some of this info may be useful.

batterytender.com/resources/float-charging.htm

batterytender.com/resources/frequently-asked-questions

www.stealth316.com/misc/deltran-battery-charger-algorithm-graphs.pdf

P.S There are many sites that essentially say the same thing the main thrust is
"A battery as like a voltage stabilizer or filter to the pulsating DC
produced by the alternator."
Not really relevant to this discussion but it continues... "Disconnecting a battery while the engine is running can destroy the electronic components, e.g., computers, radio stereo, alarm system, etc., or the charging system. Just say NO! if anyone suggests this."

Please do not get to wrapped up with the car alternator argument
it is only meant to demonstrate the filtering and stabilizing effect of lead acid cells.

Glad to have stirred up some debate.

[gommer]

Disconnecting a battery in a car with running motor can indeed cause havoc, but this is completely unrelated to what's beeing discussed here.

The reason it can be catastrophic is linked to how the voltage regulation works in an alternator. The stator is regultated with a current that produces the voltage wanted on the rotor (or vica versa, i would'nt know exactly). An alternator has a rotating set of coils and a fixed set of coils. When a magnetic field is generated on the stator and the rotor rotates around it, then the alternator starts producing power (current) and the voltage is regulated by influencing the magnetic field. If you disconnect the battery suddenly, then the feedback loop of the voltage regulation isn't fast enough and you can have a voltage spike of up to 80V. This is called a load dump.
Some car electronics are prepared for this, but not all.

Cheers, Marc

[Deleted]

Have a look at this study - it reports impedance dropping at higher freqs

Wow 100Hz that's a real high freq.
I was more talking about 1kHz and up (to compare it to 'normal' regulators and 10kHz and up for the better types. and 100kHz and up for comparison to super regs or add ons.
These values are of importance the DC to 100Hz region is more important for powering motors and actuators in high drain applications, yes also in audio.

Time issues prevent me from investigating it myself in the lab, but may do so in the future to shed some light if you are interested.

If you have already made up your mind I won't bother.
The high-face is probably locally HF decoupled in many critical places anyway and a stable PS like Alex suggested or the battery will NOT make things worse as it was already designed to be fed from extremely crappy PS (USB port)

[Deleted]

I fail to see the relevance if that is what you are talking about.

That just might be caused by a certain lack of knowledge on this matter.

[405line]

My voltmeter is reading 13.34vdc on load, with float charger attached and my little dac sounds wonderful and clear which after all is the whole point of me doing this, it is a very simple thing.

[405line]

Hello, go on then enlighten me and everyone else, explain the CM and ground loop problems, don't just snipe explain the mechanism to me please, I am all ears mate, I don't pretend to know it all and if something is to be learned then I will learn it, if it is unsafe etc please advise.
Cheers