clipping and slew rate limiting are quite different phenomena.
Clipping whether mild or severe is very common.
Slew rate limiting is very uncommon.
Clipping whether mild or severe is very common.
Slew rate limiting is very uncommon.
I built two monoblock 25W LM1875 amplifiers with 2,000uf (2x1000uf) per rail - they sound absolutely fantastic. Putting 22,000uF is seriously testing the law of diminishing returns.....
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Sometimes I run prototype amps off a regulated bench supply before putting them in a case with a linear unregulated supply - mostly Class AB. I've never noticed any degradation in the treble clarity, or the mid-range when using an unregulated supply. I have perceived a difference in the bass where regulated bench supply was subjectively better. Since moving to a pcb design with the power rail caps on-board and relatively close to the power transistors I've found no difference at all. My TGM8 amplifier, operating with simple linear power supply, unregulated, sounds so good it has convinced me that I could make no further improvement in it's performance with a regulated supply (or any other changes for that matter).
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I've used different speakers, for initial testing I used B&W 2.5-way floor standers and also PMC FB1 floor standers.
generally low impedance and medicore or low efficiency speakers show the difference.
those make the rails sag more, and you need the rail voltages pinned to get the most out of the system.
those make the rails sag more, and you need the rail voltages pinned to get the most out of the system.
I'm sharing my experience with a non-inverting LM1875 gainclone I built and I am quite happy with its sound signature.
1. Firstly I built it with standard LM317/337 regulated power supply with a 22uF bypassed adj. resistor and output 220uF Elna silmic on the pins. It sounded harsh and unbearable, even after some burn-in.
2. I removed the regulators and put it on unregulated voltage. My filtering capacitors were 4400uF Siemens LL capacitors. I was able to increase the output voltage as the regulated one, because I had many taps on the power transformer's secondary. I got acceptable, listenable, nice sound without loosing details or dynamics.
3. Nirvana came to me from the innocent looking LM1875 after transforming the power supply filtering into choke input. I inserted 200mH chokes before the capacitors and made sure critical idle current was drawn using a dissipating resistor. I increased my output voltage further from the secondaries taps, because choke inputs lowers it with an approx. factor of 0.9 as opposed to 1,41 from a cap input filter.
I never went to capacitor input again. The sound was cleaner, smoother and more detailed.
The irony is, the amplifier circuitry is in a small chip. The power supply can be 100 times larger than it and still determines the sound quality by a huge factor.
1. Firstly I built it with standard LM317/337 regulated power supply with a 22uF bypassed adj. resistor and output 220uF Elna silmic on the pins. It sounded harsh and unbearable, even after some burn-in.
2. I removed the regulators and put it on unregulated voltage. My filtering capacitors were 4400uF Siemens LL capacitors. I was able to increase the output voltage as the regulated one, because I had many taps on the power transformer's secondary. I got acceptable, listenable, nice sound without loosing details or dynamics.
3. Nirvana came to me from the innocent looking LM1875 after transforming the power supply filtering into choke input. I inserted 200mH chokes before the capacitors and made sure critical idle current was drawn using a dissipating resistor. I increased my output voltage further from the secondaries taps, because choke inputs lowers it with an approx. factor of 0.9 as opposed to 1,41 from a cap input filter.
I never went to capacitor input again. The sound was cleaner, smoother and more detailed.
The irony is, the amplifier circuitry is in a small chip. The power supply can be 100 times larger than it and still determines the sound quality by a huge factor.
the key point of a regulated powersupply is to get closer to the maximum supply voltage.
if you go unregulated you account for the main line fluctuation, and as the load increases /the amplifier draws more current/ the rails start to fall a bit.
so, with an unregulated supply you begin with a few volts less of a suply voltage, to make sure if the main line has a ripple you don't fry anything.
in my country for example, the 230 voltage is standard, with a maximum +-10% variation.
that means it can be ANYTHING from 207 volt to 253 volt.
just an example, your amp needs a rail voltage on the secundary of the transformer to be 23 volt. just for the sake of ease. means, you need 10:1 windings.
this can varry between -accounting the main line fluctuation- from 20.7 to 25.3 volts.
so, you risk of getting your stuff burned.
to avoid it, you choose a transformator with 11:1 ratio, even if the main line goes up to the 253 volt maximum, you will have 23 volts then.
but.. when everything is normal, you gona get only 20,9 volts...
and if the main line sags down to 207 volts, it will only be 18,8 volts..
and even further, when the amplifier has to drive a current demanding load, this voltage will go down even further.
but why not go with a regulated supply, then you can make sure tthat in any case, from 207 to 230 volt main line voltage, you have a 23 volt output. even if the amplifier is pushed hard.
and here things get a bit more interesting, generally a fast acting regulator is a good idea to have. if the regulator is slower than the current demand change of the amplifer, you made things just worse as the rails will be jumping up and down a lot.
allso, one must account the precision of the regulation vs the load on the regulator.
and the regulator does not mean you do not have to have a decent bank of capacitors as buffer/tank in between the regulator and the amplifier.
so done right the regulators make sure you can supply your chipamp with the maximum operating voltage they can handle, and generally they do give a better sonic experience.
i allso have to add, i had the best experience driving amplifiers from battery power.
clean dc is clean dc.
if you go unregulated you account for the main line fluctuation, and as the load increases /the amplifier draws more current/ the rails start to fall a bit.
so, with an unregulated supply you begin with a few volts less of a suply voltage, to make sure if the main line has a ripple you don't fry anything.
in my country for example, the 230 voltage is standard, with a maximum +-10% variation.
that means it can be ANYTHING from 207 volt to 253 volt.
just an example, your amp needs a rail voltage on the secundary of the transformer to be 23 volt. just for the sake of ease. means, you need 10:1 windings.
this can varry between -accounting the main line fluctuation- from 20.7 to 25.3 volts.
so, you risk of getting your stuff burned.
to avoid it, you choose a transformator with 11:1 ratio, even if the main line goes up to the 253 volt maximum, you will have 23 volts then.
but.. when everything is normal, you gona get only 20,9 volts...
and if the main line sags down to 207 volts, it will only be 18,8 volts..
and even further, when the amplifier has to drive a current demanding load, this voltage will go down even further.
but why not go with a regulated supply, then you can make sure tthat in any case, from 207 to 230 volt main line voltage, you have a 23 volt output. even if the amplifier is pushed hard.
and here things get a bit more interesting, generally a fast acting regulator is a good idea to have. if the regulator is slower than the current demand change of the amplifer, you made things just worse as the rails will be jumping up and down a lot.
allso, one must account the precision of the regulation vs the load on the regulator.
and the regulator does not mean you do not have to have a decent bank of capacitors as buffer/tank in between the regulator and the amplifier.
so done right the regulators make sure you can supply your chipamp with the maximum operating voltage they can handle, and generally they do give a better sonic experience.
i allso have to add, i had the best experience driving amplifiers from battery power.
clean dc is clean dc.
I have salvaged a lot of transformers from old amps.
Problem is that they have too high output voltage for a chipamp.
Regulating down from 50-0-50 to 25-0-25 for instance?
Problem is that they have too high output voltage for a chipamp.
Regulating down from 50-0-50 to 25-0-25 for instance?
absolutely possible, but keep in mind you gona dissipate a ton of heat, it will be verry lossy and from no point of view i would ever consider it as an option.
what kind of transformers are they? maybe you could just undo some turns on the 2ndary, to get the voltage you need, its a more sensible approach...
what kind of transformers are they? maybe you could just undo some turns on the 2ndary, to get the voltage you need, its a more sensible approach...
Yes that's as good idea.
Transformers are mainly from Denons and Nads.
Gonna see if I can unwind them a little.
Transformers are mainly from Denons and Nads.
Gonna see if I can unwind them a little.
if.. i where you i would leave some headroom to account to regulator losses, and some losses for noise suppression. most probably i hazard i would measure the voltage with AC line filter components in place. even a regulated powersupply makes good use of AC line filtering.
and this is how a simple amplifier with a nadfull of components can grow it self to a more complex unit. one must allso keep in mind problems can not be solved with just throwing in additional components, however.. if a "unit" is split up to multiple subunits, and all of them have a minimal parts count, the while big unit may end up using a lot. and in that case, its not just throwing "stuff" at it. work backwards, the drivers tell what cabinets and crossover you need for the speaker to work, speakers will tell what kindof amplifier you need, the amplifier will tell what kindof powersupply you need, and so on.
and this is how a simple amplifier with a nadfull of components can grow it self to a more complex unit. one must allso keep in mind problems can not be solved with just throwing in additional components, however.. if a "unit" is split up to multiple subunits, and all of them have a minimal parts count, the while big unit may end up using a lot. and in that case, its not just throwing "stuff" at it. work backwards, the drivers tell what cabinets and crossover you need for the speaker to work, speakers will tell what kindof amplifier you need, the amplifier will tell what kindof powersupply you need, and so on.
Hello All,
I am shopping for a switching Meanwell power supply or similar dual, plus 24 volts, minus 24 volts.
The goal is to get rid of the power line harmonics caused by the bridge rectifier. (60hZ, 120hZ 180hZ and on up)
It seems that many of the recently on the market amplifiers are much quieter than they were just a few years ago. Are these power supplies available on the market?
Thanks DT
I am shopping for a switching Meanwell power supply or similar dual, plus 24 volts, minus 24 volts.
The goal is to get rid of the power line harmonics caused by the bridge rectifier. (60hZ, 120hZ 180hZ and on up)
It seems that many of the recently on the market amplifiers are much quieter than they were just a few years ago. Are these power supplies available on the market?
Thanks DT
I'm not aware of any ±24 V supply from Mean Well (or other major manufacturers) that's suitable for a chip amp. I have used the Mean Well RPS-series with good results, though. Just get two of them and put them in series. The only catch there is that you want a supply that's capable of delivering the full output current required of the amp. You'll want around 24/(4*sqrt(2)) = 4.2 A per channel for 4 Ω operation if you want to avoid having the SMPS shut down on a deep bass thump. You may be able to skimp a little and aim for 24/(4*2) = 3 A per channel. So I'd say the RPS-200-24 would be a minimum for a stereo amp.
I've seen a couple of Modulus-86 amps built using that supply with good results.
Tom
I've seen a couple of Modulus-86 amps built using that supply with good results.
Tom
I am planning on building a headphone amp. Trying to keep things as simple as possible, design-wise. I can buy a 120VAC -> 24VDC (1A) wall wart, but it's unregulated. The chip I'll be using can accept up to 25V DC. However, do you need to have a regulated power supply for a chip amp? If so, what can happen if you don't?
You don't necessarily need a regulated power supply for a chip amp as long as you can guarantee by design that the voltage applied to the amp will not exceed the absolute maximum specified in the data sheet. That said, many chip amps benefit from a regulated supply (or other means of improving the PSRR). A headphone amp would be a good case for a regulated supply as the current draw is relatively low.
You may find that a chip amp is a bit too noisy for headphone use - unless you're talking very inefficient planar types of headphones. With IEMs you'll likely have audible hiss.
Tom
You may find that a chip amp is a bit too noisy for headphone use - unless you're talking very inefficient planar types of headphones. With IEMs you'll likely have audible hiss.
Tom
Hmm… interesting. You mention inefficient planar headphones. I happen to own a pair of Drop+HiFiMan X4’s I absolutely love… however, a pair of cheaper Sony’s I bought from Target sound twice as loud at the exact same volume, but I don’t like the sound anywhere near as much. The Sony’s are only 1 Ohm lower, yet 7dB higher (sensitivity). Is the dB what you’re referring to, as efficiency?
I don’t like IEM’s (like earbuds)… don’t like ANYTHING in my ears. Much prefer on/over ear headphones.
I don’t like IEM’s (like earbuds)… don’t like ANYTHING in my ears. Much prefer on/over ear headphones.
Agreed. Last year I built a 3886-based headphone amp to power 16- to 44-Ω 'phones. The 3886 is absolutely loafing along into these loads. Bass integrity is much improved with the regulated supply. And the difference is much more audible with headphones vs speakers.
With the 3886's mandatory high-gain use, noise was my concern as well. My 44Ω cans are 108dB SPL / V. Comfortably-loud levels for me are with less than 1/2V RMS drive. Background hiss is just audible but not offensive.
During this time I've also built/optimized several other amps (Class A and AB) to drive these loads. I have to say that, all else being equivalent (power supply, grounding, good layout, etc.), much to my surprise, a well-executed LM3886 amp has proved to be hard to beat for driving low-Z headphones of any kind..