I have no idea what the power systems are like at your work place. It should be rather obvious, however, that in a typical domestic environment there are all manner of wideband-noise producing devices and appliances connected to the household A.C. wiring, from air-conditioning and furnace blowers, to refrigerator compressor and washing machine motors, to Triac and SCR based light dimmers, to various and sundry switched-mode power supplies in nearly everything else. I really don't see how anyone could suggest that high-frequency garbage isn't very common on household A.C. lines. None of which even includes the ultrasonic ringing of the audio equipment power transformers themselves due to their leakage inductance forming an LC tanks circuit with the parasitic capacitance connected to the secondary winding. I haven't even touched on ground line common-mode noise. No, I think that the job of voltage regulators and the amplification circuit PSRR are not as trivial as merely rejecting 100Hz/120Hz ripple. If only, that were so.
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I build my own 220V mains regenerator to feed my cd player, and it lower the noise floor from the mains , now you can hear more sound what is on the cd what was not heard before. (cd player was a sony sacd 555ES ), if you look at the schematic of the cd player, it uses a special transformer and many high qualified electronic regulators , but stil for high end it was not enough
That was why I used the example of a large phase controlled power supply, This power supply has 2 SCR controlled full wave bridge rectifiers feeding and inter phase inductor followed by a CLC filter. The fundamental is 600Hz the rise time when the SCR's switch is 4 us giving a dv/dt of 200V/us. This sort of fast rise time signal on the output of the rectifier makes any mains born noise from light dimmers look trivial yet the output noise is dominated by the fundamental.
To illustrate the importance of design practice, this power supply has large circulating currents in the frame, being aware of this and taking appropriate measures made sure they stayed within the frame rather than being transferred into the building frame or onto the output.
Just have to throw in that batteries aren't as perfect as many believe. They aren't so quiet, especially if you draw current from them. Their performance varies widely, depending on type and (if rechargable) state of charge. The LM317, with the right circuitry and layout, can outperform most batteries within certain limits. Using a pre and post regulator can bring any ripple down below the noise of the supply, though its rarely necessary. It's also important to bypass rectifiers and kill the RF they tend to generate. Very subtle errors in layout sabotage many, if not most, linear power supplies.
Conrad
Conrad
Presumably, the noise of batteries goes up as they discharge. Haven built two headphone amplifiers with a goal of low noise, one with batteries and the other with a low noise power supply, I found that it a lot easier to get low noise with batteries. (I'm still working on the later.) However, depending on use, the batteries only last a couple of weeks, before needing to be replaced. I use alkaline, but lead acid is a good choice for rechargeable.
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If you look at the datasheet of the LM317/337 than the line transient response show that a pulse on the input of the regulator , the half of the amplitude of the pulse is at the output , so the half of the amplitude of the noise and spikes at the input is present at the output, much different than the rippel reduktion
surely batterys getting discharged will have quite a load sensitive voltage output.
one can use a regulator in order to make up for this effect to some degree, but usualy prehaps a better idea is to use a large enugh battery.
pre-amp and voltage gain stage f an amplifier would suposedly quite happy with a battery power source. Output stages surely will have problems.
for sure the many of the AC line nises are not present in the battery to start with , i think of that as a nice advantage.
one can use a regulator in order to make up for this effect to some degree, but usualy prehaps a better idea is to use a large enugh battery.
pre-amp and voltage gain stage f an amplifier would suposedly quite happy with a battery power source. Output stages surely will have problems.
for sure the many of the AC line nises are not present in the battery to start with , i think of that as a nice advantage.
Abe Lincoln once said, "You can take some of the ripple out of all of the circuits, and you can..." Well, you get the idea.
And big capacitors have their own problems. If you look inside a well-designed commercial audiophile preamp (I consider Connie Johnsons to be well-designed) you will not see wazoos or even banks or battalions of big fat noisy electrolytic capacitors.
What seems to be reasonable these days is to knock initial noise down on the "dirty" rail into the sub 100 millivolt level using passive components, and then run the dirt through a low noise voltage control device (like an LDO regulator) so you end up with a "clean" rail in the sub 100 microvolt range. See Jung's twelve year journey along those rails as a reference. And then after you have a clean rail you depend on the spectacular PSRR (power supply rejection ratio) of modern parts to kill the last little bit of cr@p you couldn't regulate. At that point you could be way more than 120db below the noise of the AC line. And you better be because on a big system you can hear that hum.
Good News: This works a treat on modest power units running the latest op amps from Analog Devices, Burr Brown, and National Semi. Bad News: On a class A amp you typically have pretty much 0 db PSRR. I once built a circuit that had -20 db PSRR -- I AMPLIFIED THE HUM! (I recommend avoiding that approach.)
And big capacitors have their own problems. If you look inside a well-designed commercial audiophile preamp (I consider Connie Johnsons to be well-designed) you will not see wazoos or even banks or battalions of big fat noisy electrolytic capacitors.
What seems to be reasonable these days is to knock initial noise down on the "dirty" rail into the sub 100 millivolt level using passive components, and then run the dirt through a low noise voltage control device (like an LDO regulator) so you end up with a "clean" rail in the sub 100 microvolt range. See Jung's twelve year journey along those rails as a reference. And then after you have a clean rail you depend on the spectacular PSRR (power supply rejection ratio) of modern parts to kill the last little bit of cr@p you couldn't regulate. At that point you could be way more than 120db below the noise of the AC line. And you better be because on a big system you can hear that hum.
Good News: This works a treat on modest power units running the latest op amps from Analog Devices, Burr Brown, and National Semi. Bad News: On a class A amp you typically have pretty much 0 db PSRR. I once built a circuit that had -20 db PSRR -- I AMPLIFIED THE HUM! (I recommend avoiding that approach.)
I think the best PSU for audio is a battery followed by a capacitor multiplier, a darlington with the base with a resistor to the plus and a 100uF to minus which removed all the noise . And you have no hum interference from the mains.
Many expensive equipment have the tranformer and PSU outside the box or it is sealed with mu metal ( Spectral ) to avoid interference with the mains.
Many expensive equipment have the tranformer and PSU outside the box or it is sealed with mu metal ( Spectral ) to avoid interference with the mains.
completely ignores the "fact" that all batteries have a finite life.
In my opinion that makes batteries the worst PSU by far.
lifecycle was not included, target was less noise.
other than that You are absolute right.
SLA is cheap nowdays, at least the ones made for alarm systems.
12 V @ 6 AH.
I bet it would take a LOT of time to draint hat with a pre-amp or a voltage gain stage.
If the amplifier is off, a circuit can charge it from mains.
I would think SLA has a high life cycle if its drained only a bit and then recharged and kept thatway.
other than that You are absolute right.
SLA is cheap nowdays, at least the ones made for alarm systems.
12 V @ 6 AH.
I bet it would take a LOT of time to draint hat with a pre-amp or a voltage gain stage.
If the amplifier is off, a circuit can charge it from mains.
I would think SLA has a high life cycle if its drained only a bit and then recharged and kept thatway.
I think my question fits into this thread:
How much capacitance is proper?
I'm a rank amateur to electronics. I'm collecting all of the parts to assemble an SET amp with a separate PS. I'm using an LC filter after the rectifier tubes & from there providing separate LC's to each channel (a la Lundahl).
I've read everything I can find about sizing of the LC components & have wound up with two ranges of cap sizes. The RCA handbook has led me to use a 6uf cap after the first choke of 4.5H & 25uf caps after the two channel's 4.5H chokes.
The other indicated sizing is for 110uf after the first choke & 230uf after the other two. The output will be 350vdc & 250mA.
I enjoy reading DIY Audio & learn a great deal from it. Mainly, that there is more than one way to skin a cat.
How much capacitance is proper?
I'm a rank amateur to electronics. I'm collecting all of the parts to assemble an SET amp with a separate PS. I'm using an LC filter after the rectifier tubes & from there providing separate LC's to each channel (a la Lundahl).
I've read everything I can find about sizing of the LC components & have wound up with two ranges of cap sizes. The RCA handbook has led me to use a 6uf cap after the first choke of 4.5H & 25uf caps after the two channel's 4.5H chokes.
The other indicated sizing is for 110uf after the first choke & 230uf after the other two. The output will be 350vdc & 250mA.
I enjoy reading DIY Audio & learn a great deal from it. Mainly, that there is more than one way to skin a cat.
Some years ago , I build a PSU which was not connected with the mains noise, after the diode bridge you have the capacitor follwed by a electronic switch ( FET) and after that a second capacitor , when the diode bridge is conducting the switch is of, and when the mains is not connected anymore the switch is on, this is followed by LM317 and a capacitor multiplier, the same for the negative part of the PSU..
I could not measure a different in noise when de switch was always on
I could not measure a different in noise when de switch was always on
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