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Toroidal vs SMPS for Class D Modules

JonfromCB

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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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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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JonfromCB

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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?
 

Doodski

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I'm confused a bit. Toroids are used in both linear and PWM power supplies.
 
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JonfromCB

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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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egellings

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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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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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Well designed and implemented SMPS properly used in their end application can have excellent MTBF.
 
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JonfromCB

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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.
 

howard416

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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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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

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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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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

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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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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.
 

Johnplayerson

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A toroidal or transformer based power supply will be near bullet proof, and more reliable. A typical 500va toroidal transformer weighs around 11 pounds and will not necessarily be bulky or add to much weight so to speak. It will of course increase the cost to produce for manufacturers, who can spit out an entire SMPS amplifier case and all, for less then the oem bulk cost of buying hundreds of transformers. It will also increase the cost to ship. SMPS is 10 fold more profitable for manufacturers at the minimum.

500 va would be more then enough to power the new hypex modules. Such a transformer would easily be capable of peaks of 500 watt PER CHANNEL. Given this the major excuse not to use them is that the manufacturer would be 10 times less profitable doing the same amplifier with a transformer. New tech in SMPS has always been profit driven and is the main reason why transformers have been withdrawn by manufacturers, in favor of making their own smps modules. In order to ensure you buy in on their huge profits they sell you on , efficiency, weight, cooler running etc, most of which means little to actual audio reproduction in a 500 or less watt per channel amplifier.

When transformer amplifiers were the mainstream, one would find overbuilt units, and what they referred to as underrated units. The underrated units would point to the musical nature of power, and acknowledge that one could use a smaller transformer in many cases. as it would only have to supply peaks for short durations. Classic pro amplifiers like the crest ca series implemented transformer under rating, yet were known to be among the best for long term reliability, and able to survive two ohm abuse.

When gobs and gobs of cash in this magnitude is on the line, you can be sure to hear a lot of snake oil and bs about SMPS.
 
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Doodski

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500 va would be more then enough to power the new hypex modules. Such a transformer would easily be capable of peaks of 500 watt PER CHANNEL
That sounds like a small transformer for a huge power output. How do you figure this? :D
SMPS is 10 fold more profitable for manufacturers at the minimum.
How do you get these figures? :D It's a huge difference in cost so I am intrigued.
 

Chris M

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https://de.m.wikipedia.org/wiki/Transformator, https://www.thel-audioworld.de/module/Netzteil/Infos.htm, and other.

Depending on the design and construction, transformers can briefly deliver a multiple of their rated power. Power supply units based on this can, if designed accordingly, also briefly output higher power than the nominal power.
As far as I know, this ability is not as pronounced or non-existent in smps. I'm not saying linear power supplies are better than smps or vice versa. It always depends on the design of the power supply and the application, in this case the corresponding amplifier and its design.

For further basic knowledge, but also the translation, you are welcome to use Google, maybe Doug Self has also written something about it.

There are statements that amplifiers should also sound different depending on the power supply (for example https://www.diy-hifi-forum.eu/forum...-Vorstellung-LJM-L20-5-Amp&p=326357&viewfull=). I don't know to what extent this is double-blindly secured, i.e. ASR-proof. I myself form :)oops:) I can also hear differences...
 

Johnplayerson

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That sounds like a small transformer for a huge power output. How do you figure this? :D

How do you get these figures? :D It's a huge difference in cost so I am intrigued.
For one simply add up the costs. SMPS is comprised of nothing but transistors, diodes, smaller value capacitors etc. As my favorite man Randy Slone, has said, when he worked at Heathkit back in the day, they were not allowed to bend over to pick up any components dropped, while working on the production line. At the end of the day all dropped components would be swept up, and dropped into grab bags to sell to hobby electronic shops. It cost more money to bend over to pick up a dropped component, then it was worth. I have always said SMPS is like replacing a transformer supply, with one of these worthless grab bags. Mr Slone himself said entire amplifiers could be made less then the wholesale oem cost of a torodal transformer.

When SMPS was invented, they changed the way power amplifiers were rated. Power was now rated as a 22ms burst, despite the fact 500ms burst would be required to mimic a complete audio signal, and 3 seconds full burst would be required for EDM bass. Today most SMPS are measured this way, and you can find WIlliston Audio labs using the AMP DYNO, to measure thousands of amplifiers, this exact same way. AS such I have always said we are using measuring specifications of power , that do not even reproduce an audio signal.

If you check Yorkville sounds ratings for toroidal amps, you will note they were one of the few manufacturer, to also add the burst ratings. Almost any toroidal amplifier, using the same measuring tactics, currently used to measure smps power, would easily double their current and actual specifications, and this is after the fact, that many of these high powered pro amplifiers used under rated transformers to begin with.

Transformers are specified out at CONSTANT power. So a 500va transformer should run a 500 watt heater if need be, on a constant full burn at 500 watts indefinitely. The dynamic nature of music, has average power of the transformer like this, way down at just a few hundred watts at most. as such a transformer of 500va should be able to easily handle twice it's VA rating, when used for music. However if one is actually going to consider a 22 ms burst, power worth measuring, It would probably peak out 4 times higher.
 
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