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Toroidal vs SMPS for Class D Modules

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#1
What are the Pros and Cons of the different power supplies to these modules? I don't understand the real world performance differences and would like to start the discussion. I have read that toroidal will increase the module output and provide higher continuous power. I have also read that toroidal reduces the overall output of the modules. The basis for my question is twofold:

- The Hypex NC252 data sheet, 3.4 line 2 on page 6 spec's the continuous output power as 50 Wrms with a note it's typically 1/5 peak output.
- Manufacturers spec's using the two different power supply's with the same module indicate considerable differences I want to better understand.

Thanks, hope to get some useful information.
 

egellings

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#2
The modules are pretty supply invariant. A stiff toroid supply with no voltage regulation or SMPS which has it will likely not make an audible difference.
 
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Thread Starter #3
OK, but does no "audible difference " equate to no pros or cons between the two or have nothing to do with the differences in measured output?
 
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Thread Starter #5
I understand. There certainly are reasons designers/manufacturers are using toroidal/linear supplies to modules that were designed with SMPS on the module. I want to know why? It's early but hope this discussion gets more input as the day goes on. Meanwhile I'll email ATI and ask them why they don't use SMPS and how their design benefits me as a consumer.

It sure costs more to design, supply proprietary modules, add a toroidal/linear power supply and ship a larger/heavier product. There must be tangible reasons beyond the typical marketing gobble-de-gook.
 
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Doodski

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#6
PWM has the advantage of smaller space req'd, lighter weight, tighter regulation and of course DC-to-DC operation.
 

egellings

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#7
It's possible for small measured differences in two devices to not be audible, or just barely so. Both the xfmr and the SMPS can work equally well. Pros & cons would be price, complexity and weight of the selected device. Xfmr is simple in design, very reliable, generates little if any HF hash, (diode reverse recovery, maybe) but is heavy, and has limited voltage regulation characteristics. SMPS gets you light weight, voltage regulation, but HF hash and reduced reliability since it has more parts in it that could fail. As for sonics, if the DC is clean and steady, the choice does not matter if listener beliefs do not intrude. SMPS may also be cheaper than a XFMR, since a handful of silicon and other small bits is cheaper than a good sized chunk of iron wound with copper.
 
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Doodski

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#8
It's possible for small measured differences in two devices to not be audible, or just barely so. Both the xfmr and the SMPS can work equally well. Pros & cons would be price, complexity and weight of the selected device. Xfmr is simple in design, very reliable, generates little if any HF hash, (diode reverse recovery, maybe) but is heavy, and has limited voltage regulation characteristics. SMPS get you light weight, voltage regulation, but HF hash and reduced reliability since it has more parts in it that could fail. As for sonics, if the DC is clean and steady, the choice does not matter.
I specialized in car audio mechatronics for several years in the heyday of car audio class AB amps and the DC-DC conversion was done veryyy well. I repaired small and very large monster amps and had no issues with PWM DC power supply purity.
 

egellings

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#9
Well designed and implemented SMPS properly used in their end application can have excellent MTBF.
 
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Thread Starter #10
I appreciate all the input, but still not clear about my orginal question of whether a toroidal/linear supply gets more continuous and/or peak than SMPS on the same module.
 
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#11
What you're actually asking about is linear vs SMPS, not toroidal vs SMPS (linear supplies don't have to use toroidal transformers).

The answer is - it depends on whichever is rated for more output. You can get increasing amounts of power in whichever style you prefer.
 

egellings

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#12
SMPS is generally used for high power applications where high efficiency and low heat generation are desired. For low power or high noise sensitivity ones, such as a preamplifier, it makes sense to use linear supplies. They're simpler and don't generate HF hash. Diode turn-off ringing can be easily damped with appropriately designed snubbers, whereas switchmode noise is more difficult to eliminate.
 

boXem | audio

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#13
I appreciate all the input, but still not clear about my orginal question of whether a toroidal/linear supply gets more continuous and/or peak than SMPS on the same module.
Power supplies, whatever their type, have an ability to deliver voltage and current. The one with the best capability will allow the module to deliver it's best, be it the good ol' toroid or an SMPS.

PS {not to you): most smps are not regulated and properly designed amplifiers do not really care about power supply noise
 

egellings

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#14
Most SWPS I have encountered do have voltage regulation. Something in the design of the supply has to control On time of the switch to get a desired DCV at the output terminals.
 

boXem | audio

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#15
Most SWPS I have encountered do have voltage regulation. Something in the design of the supply has to control On time of the switch to get a desired DCV at the output terminals.
For audio power amplifiers, using a regulated SMPS is not without issues.
To quote @Armand:
Regulated SMPS'es that try to keep the voltage constant on the output (by using feedback) can introduce modulated noise on the power rails if the feedback control loop is not fast enough (which it typically not is.)
The perfect power supply is of course one that keeps the rail voltages 100% constant regardless of how many amps drawn with a bandwith of at least 20kHz, but that would be very expensive and not really pay off. Especially not on todays class D amplifiers with a lot of feedback that just corrects everything anyway.. On power amplifiers without feedback it is a totally different story.
 

egellings

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#16
That would also hold for linear feedback type regulators. The regulators (both kinds) have output caps which slows their response to large transients. High frequency garbage is, however, a problem. I think there are power amps out that that are switchmode through and through. I've never tried one, though.
 
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