Hi There,
I've purchased a Nelson Pass F4 amp kit and just recieved it.
I went ahead and purchased 2 X 24V+- 350w SMPS units online. my question is, can i filter the SMPS DC output using a CRC power filter board like the one below (bypass the AC to DC conversion). and is it worth it?
Also, I've read somewhere that CRC filter configuration is supirior than just using filter capacitors, can someone help me understand why.
Thanks in advance. 🙂
I've purchased a Nelson Pass F4 amp kit and just recieved it.
I went ahead and purchased 2 X 24V+- 350w SMPS units online. my question is, can i filter the SMPS DC output using a CRC power filter board like the one below (bypass the AC to DC conversion). and is it worth it?
Also, I've read somewhere that CRC filter configuration is supirior than just using filter capacitors, can someone help me understand why.
Thanks in advance. 🙂
Putting that much capacitance at the output of most SMPS would be courting trouble, and may cause the power supply to go into protective "hiccup" mode during startup as it attempts to charge that massive capacitor bank.
Keep in mind that the switching power supply has a closed feedback loop (generally with several kHz bandwidth) and will respond quickly to load changes inside its loop bandwidth - this includes bass. The refresh rate for an SMPS is much faster than that of a conventional line transformer supply - 60-100kHz or more vs. 50-60Hz, so there is no sag between line half-cycles as there is with a standard mains-frequency power supply, meaning there is no need for a massive capacitor bank to prop up the supply voltage between line half-cycles.
A more sane approach would be to use about 1000 microfarads of local bypass right at the amplifier boards and let the SMPS do due diligence to respond to sudden changes in load. Remember that most of the amplifier power will be expended in powering the woofers, as they eat the most power supplying the bass portion of the audio spectrum due to their inefficiency in moving air at that frequency. The bass frequency portion of the audio spectrum is well within the loop bandwidth of a well-designed SMPS, so it should be able to respond to sudden demands for bass energy with little disturbance to the output voltage.
Keep in mind that the switching power supply has a closed feedback loop (generally with several kHz bandwidth) and will respond quickly to load changes inside its loop bandwidth - this includes bass. The refresh rate for an SMPS is much faster than that of a conventional line transformer supply - 60-100kHz or more vs. 50-60Hz, so there is no sag between line half-cycles as there is with a standard mains-frequency power supply, meaning there is no need for a massive capacitor bank to prop up the supply voltage between line half-cycles.
A more sane approach would be to use about 1000 microfarads of local bypass right at the amplifier boards and let the SMPS do due diligence to respond to sudden changes in load. Remember that most of the amplifier power will be expended in powering the woofers, as they eat the most power supplying the bass portion of the audio spectrum due to their inefficiency in moving air at that frequency. The bass frequency portion of the audio spectrum is well within the loop bandwidth of a well-designed SMPS, so it should be able to respond to sudden demands for bass energy with little disturbance to the output voltage.
@wrenchone that's interesting, i understand what you mean. do capacitors exclusively improve response to load or do they perform any other function?
also, why do most people insist on using toroidal transformers instead of SMPS in audio applications. the way you describe it, it seems SMPS is a better choice than a transformer.
also, why do most people insist on using toroidal transformers instead of SMPS in audio applications. the way you describe it, it seems SMPS is a better choice than a transformer.
You need a pretty monstrous capacitor bank with line-frequency type power supplies (including ones using toroidal transformers). First off, they run open loop, so there is no correction for any sudden load change. Second, keep in mind that the capacitor bank only gets refreshed by the the AC line once each 1/2 cycle, or 8-10 ms, so you need a hugeish capacitor bank to prop up the supply rail between half cycles and to supply power demands that occur between half cycles without excessive voltage droop. An SMPS is regulated and responds to load demands by pumping out more energy, and it responds much faster, generally having a bandwidth of several kHz for a well-designed supply.
Edit - line frequency supplies are used a lot because they are easier to comprehend, and generally, they "just work" without a lot of fiddling around....
Edit - line frequency supplies are used a lot because they are easier to comprehend, and generally, they "just work" without a lot of fiddling around....
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The SMPS runs at such a high frequency you dont need massive caps on the output.
Most SMSP will just go into protect mode.
Put smaller caps on output if you feel you really need them.
Plus, any SMPS worth its salt has closed-loop regulation with a bandwidth of few kilohertz or so that will correct output variations induced by a sudden load change.
I am curious about this topic, and recall this quote I read: “was never impressed with the Pascal modules' performance. For one thing,low frequency tone bursts at high power (think kick drum) showed a several hundred millisecond droop in power after the initial few cycles due to their use of a power factor corected power supply and inadequate primary storage capacitance. Hopefully, what Roland has done with that array of add-on filter caps is to shore up primary storage.”
Hi.
For me, this CRC board is really for linear power supply use.
I bought the same when the DIY Audio Store was out of stock for their universal PSU board.
I use it after a toroidal transformer and 2 rectifiers in a M2x.
After SMPS, it should be a different design (board from Ship of Theseus comes to mind, but that for a +36v supply after smps, not +24v and -24v. And it performs others functions also)
Regards
For me, this CRC board is really for linear power supply use.
I bought the same when the DIY Audio Store was out of stock for their universal PSU board.
I use it after a toroidal transformer and 2 rectifiers in a M2x.
After SMPS, it should be a different design (board from Ship of Theseus comes to mind, but that for a +36v supply after smps, not +24v and -24v. And it performs others functions also)
Regards