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Class D Switching Power Amplifiers and Power D/A conversion

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Old 13th March 2009, 03:29 PM   #21
Eva is offline Eva  Spain
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Any switching circuit employing any trick to allow the current from an inductor to charge parasitic capacitances, thus preventing them from being charged by the switching devices with the associated losses, could be considered resonant.
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Old 13th March 2009, 04:19 PM   #22
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Default Re: Re: PKN XD-4000

Quote:
Originally posted by iand


Do you have any measurements for bass frequencies (e.g. 45Hz) instead of 1kHz?

Ian

Yes, I would need to see this also, as I dont really need 2kw @ 1khz.



Could you also measure power output/consumption in 2.66 ohms stereo @ 45hz.

That would be a realistic environment for me.
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Old 13th March 2009, 06:23 PM   #23
iand is offline iand  United Kingdom
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Quote:
Originally posted by Eva
Any switching circuit employing any trick to allow the current from an inductor to charge parasitic capacitances, thus preventing them from being charged by the switching devices with the associated losses, could be considered resonant.
As normally defined, a true resonant SMPS has an LC tank with significant energy storage from one cycle to the next, which normally means having a high-current low-loss resonating capacitor (usually ceramic or polypropylene) and a high-AC-current low-loss resonating inductor (usually wound with Litz wire) to store enough energy and still keep the losses down.

Using inductor current (small inductor eg. printed) to charge and discharge parasitic capacitance on each edge is normally termed quasi-resonant or resonant-transition because there's no cycle-to-cycle energy storage -- also referred to as ZVS/ZCS depending on how the switching loss is reduced.

Most of the amps quoted by workhorse seem to be quasi-resonant ZCS/ZVS by this definition, with the possible exception of the Crown (and PKN).

But as Eva said, all of them can be said to be resonant in one sense, and different people have different definitions.

(yes I understand about all the different types of SMPS, we probably don't want to go there on this forum :-)

If you want the highest possible power density and output power then a resonant supply has the edge if you run it at a high enough frequency (MHz?); this isn't usually the case in class-D SMPS, so I'm curious about what PKN do and why.

Of course Peter doesn't have to tell us, but I suspect giving some information away is fairly safe given the increased difficulty of making a reliable resonant supply -- it's not something that can be copied easily except by someone who really knows what they're doing, and if they know this much they could design their own...

Ian
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Old 13th March 2009, 08:06 PM   #24
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Quote:
Originally posted by iand



Most of the amps quoted by workhorse seem to be quasi-resonant ZCS/ZVS by this definition, with the possible exception of the Crown (and PKN).

Ian
Why crown is an exception?


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Old 13th March 2009, 10:31 PM   #25
iand is offline iand  United Kingdom
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Quote:
Originally posted by Workhorse


Why crown is an exception?


Because it's the only one you mentioned with an added resonating capacitor, without this you've only got the switch parasitics which don't store much energy.

Ian
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Old 20th May 2009, 02:55 PM   #26
fb is offline fb  Australia
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Iand, did you ever investigate these amps any more?

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Old 20th May 2009, 04:00 PM   #27
iand is offline iand  United Kingdom
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Iand, did you ever investigate these amps any more?

There was more discussion on the speakerplans forum here

http://www.speakerplans.com/forum/a-...766_page6.html

but nothing further since March -- though we did find out that the PKN uses an LLC resonant SMPS, not a quasi-resonant one.

Personally I'm now waiting to try out a Peavey IPR 6000, due here in a couple of months -- don't know what they'll cost in the UK but street price in the USA is said to be around $600 for 2x2000/4 or 2x3000/2...
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Old 20th May 2009, 11:16 PM   #28
fb is offline fb  Australia
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Thanks for that, guess I'll have to wait for some reviews on those too
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Old 21st May 2009, 08:25 AM   #29
iand is offline iand  United Kingdom
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Thanks for that, guess I'll have to wait for some reviews on those too
I expect real detailed reviews will appear soon in the trade press -- Peavey's announcement of the IPR amps has raised a lot of interest in the pro sound world, unlike PKN they're a well-known PA manufacturer (thought maybe not with absolutely the highest reputation) who will be aiming to sell a lot of them.

If they deliver what they promise then these could blow a big hole in the high-price high-power class-D amplifier market -- because I know what these really cost to build (especially in China), and this bears no resemblance to the current market prices.

Prices are high now because people are willing to pay them -- and of course companies have to recoup the R&D cost needed to develop the amps, which is obviously way higher than a linear amplifier. So all high-power class-D amplifiers are expensive, nobody in the market right now wants to drop the prices and see their revenues plummet.

Peavey are effectively breaking this cartel by entering the market with pricing much closer to production cost (with a decent margin, of course) in the hope that they'll sell far more amplifiers on the back of this -- the volumes in the sub-$1000 market are much higher than in the $2000+ market which is where most similar amps are right now.

$600 "street price" -- which probably means lower from the cheapest suppliers -- for a 2x2000/4 2x3000/2 amp with inbuilt crossovers is *really* going to put the cat among the pigeons unless it's total rubbish -- OK maybe it won't sustain this power into 2 ohms, so use it into 4 ohms and still get 4kW for very little money...
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Old 29th July 2009, 12:53 AM   #30
fb is offline fb  Australia
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Still waiting on the Peavey IPRs....

Meanwhile - I noticed PKN now offer an even larger amp - XD-6000, 2x3650W@4ohm


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