I've been building a few projects that use DC SMPS plug pack (wall wart) for the power supply. Some are for TPA3116D2 or similar power amps and others are for op amp based circuits that use TLE2426 or ESP P43 as rail splitters.
Is there any benefits of using filter capacitors etc between the SMPS power supply and the amp module or are the caps on the amp module is all that is needed? I searched around and haven't found any additional circuits between the power supply and the amp module.
I only ask as when I built Class AB amps I put effort into the power supply such as CRC, by pass caps etc and same with op amp circuits circuits using regulators. I now keep away from 240V for various reasons and hence the move over to DC SMPS supplies.
Am I over thinking this as I've had no issues with the projects I've mentioned running via DC? Just curious.
Is there any benefits of using filter capacitors etc between the SMPS power supply and the amp module or are the caps on the amp module is all that is needed? I searched around and haven't found any additional circuits between the power supply and the amp module.
I only ask as when I built Class AB amps I put effort into the power supply such as CRC, by pass caps etc and same with op amp circuits circuits using regulators. I now keep away from 240V for various reasons and hence the move over to DC SMPS supplies.
Am I over thinking this as I've had no issues with the projects I've mentioned running via DC? Just curious.
I wouldn't try anything until you first measure what the ripple/noise is like as measured at the amp and then make an informed decision based on what you see.
The noise seen on SMPS rails can be difficult to suppress by simply adding caps, and on some occasions they may do more harm than good if any wiring inductance is brought into play. Carefully chosen L-C filters can be effective but need to be chosen with care to suit the conditions in use.
The noise seen on SMPS rails can be difficult to suppress by simply adding caps, and on some occasions they may do more harm than good if any wiring inductance is brought into play. Carefully chosen L-C filters can be effective but need to be chosen with care to suit the conditions in use.
What you want is a stable supply voltage for your amplifier. Not hysterically noise-free but a voltage that does not deviate much from nominal when the amplifier suddenly demands a lot of current. That requires some decoupling capacitance.
Almost all amplifier boards have some decoupling capacitance on-board, at least enough to prevent them from oscillating. Due to the price and size, the on-board decoupling capacitance is often a minimum. And, an amplifier is a very dynamic load.
The SMPS you normally buy are meant for LED lighting or general purpose use. The capacitance at the output determines the output ripple and is enough for a ripple suited for general purposes - but not necessarily for an amplifier. Another parameter is the SMPS reaction time where a faster reaction time means a quicker return to nominal voltage which is what we want for amplifiers. Unfortunately, general purpose use often imply a rather static load and the SMPS are designed for that.
While decoupling capacitors make rapid energy available for the amplifier, it is the reaction speed of the SMPS that is important to re-fill the decoupling capacitors. And to complicate matters, the reaction speed of an SMPS tend to reduce with more capacitance at the output but depends on the design of the SMPS.
Confusing. Most consumer SMPS need some extra capacitance for decoupling of an amplifier. But it depends on the SMPS, power of the amplifier and how much is already available on-board. I typically use 2200uF-10000uF.
What you can do if you have an oscilloscope is to connect the actual SMPS to the amplifier and play some music with a heavy and dominant bass (like hip-hop). When you look at the supply voltage with the oscilloscope you can see the voltage swings mainly caused by the bass. Then you add decoupling capacitance as long as the voltage swing reduces.
Almost all amplifier boards have some decoupling capacitance on-board, at least enough to prevent them from oscillating. Due to the price and size, the on-board decoupling capacitance is often a minimum. And, an amplifier is a very dynamic load.
The SMPS you normally buy are meant for LED lighting or general purpose use. The capacitance at the output determines the output ripple and is enough for a ripple suited for general purposes - but not necessarily for an amplifier. Another parameter is the SMPS reaction time where a faster reaction time means a quicker return to nominal voltage which is what we want for amplifiers. Unfortunately, general purpose use often imply a rather static load and the SMPS are designed for that.
While decoupling capacitors make rapid energy available for the amplifier, it is the reaction speed of the SMPS that is important to re-fill the decoupling capacitors. And to complicate matters, the reaction speed of an SMPS tend to reduce with more capacitance at the output but depends on the design of the SMPS.
Confusing. Most consumer SMPS need some extra capacitance for decoupling of an amplifier. But it depends on the SMPS, power of the amplifier and how much is already available on-board. I typically use 2200uF-10000uF.
What you can do if you have an oscilloscope is to connect the actual SMPS to the amplifier and play some music with a heavy and dominant bass (like hip-hop). When you look at the supply voltage with the oscilloscope you can see the voltage swings mainly caused by the bass. Then you add decoupling capacitance as long as the voltage swing reduces.
I tested a few wall-warts once, and found a huge amount of variation in them. Some produced very little ripple and needed no extra filtering, while some exhibited massive amounts of ripple, including common-mode, requiring a common-mode filter and large capacitor to get something resembling DC out of them.
So, if you want the amp to work with any wall wart, including cheap crap, then you may well need a filter of some sort, but you need to measure to be sure what's going on.
So, if you want the amp to work with any wall wart, including cheap crap, then you may well need a filter of some sort, but you need to measure to be sure what's going on.
Thanks for the replies. I'm unable to measure the ripple etc so I will leave well enough alone. For anything that requires a better power supply I can use an AC plug pack followed by a regulated circuit (similar to ESP P05x).
Regulated DC linear plug packs are hard to find these days hence the use of SMPS.
Regulated DC linear plug packs are hard to find these days hence the use of SMPS.
Putting big caps on the output can cause power up overloads and the SMPS goes into protect mode.
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