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Old 6th February 2008, 06:12 PM   #11
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Quote:
Originally posted by JohnW
Hi Jan,

I believe what Eva was alluding to was the fact that Mr Sanchez was asking such basic Class D / SMPS design questions that this only served to highlight his lack of basic understand of the technology.

Reading back though the "Questions" posted as Pierre; same are at such a basic fundamental level that they should never have been asked by a competent designer already SELLING SMPS!

I fully support Eva on this subject, as a Class D / SMPS designer I can read between the lines of Eva's postings and see that she has a great deal of experience within the subject - which is why we are both mortified at the question ask by Mr Sanchez, with this in consideration it’s terrifying to consider that he was / is selling SMPS that are connected directly to the mains supply.

Ok, in laymen’s terms, it’s akin to a car designer producing a car then asking how the brake servo should work – would you be concerned??? – Maybe not if you don’t know what the brake servo is…

With the greatest respect,

JohnW

John,

I know what you are saying. But I think it is wrong to tell other people not to buy things because you or somebody else think the designer is not smart enough. Hell, if we go that way, 3/4 of the audio industry would collapse overnight!

Do you tell people not to buy Chip amps because the designer doesn't know ohms' law from spilled milk?

As for safety, as long as a product does have the required safety markers, you can't do anything, really.

Jan Didden
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Old 6th February 2008, 06:57 PM   #12
JohnW is offline JohnW  Hong Kong
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Hi Jan,

3/4 you say – wow I admire your diplomacy…

Now that I better understand your objections to Eva’s post, I’ve re-read her post and don’t quite see Eva “telling other people not to buy things” but rather for people to draw there own conclusion - with the supporting facts however.

Well, not much more to say rather then that whole sordid incident is very very sad, and just displays the very worst side and fears of great public forums like this. Its one of the reasons I post very little these days… maybe that just sum's up why this kind of behaviour ultimately damages the whole DIY community – prevents “professionals” from releasing there IP / know-how for the fear if it being commercialised by deceiving 3rd party’s who bring little to the table in return.

JohnW
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Old 6th February 2008, 07:37 PM   #13
iand is offline iand  United Kingdom
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I should say I'm not exactly naive in this area, my profession is electronics and I've been looking at both class-D and SMPS design for many years, but haven't actually needed to build anything until now (new lightweight high-power PA for the band).

I could design and build both amp and SMPS myself (yes I'm well aware of all the analogue design issues, this is easy stuff compared to what I do at work :-) but I don't really have the time, and if I can buy modules or amps ready-made I will so I can concentrate on the bits where I can't buy what I want but can build them (compact line array speakers and subs).

From this point of view CAD Audio in Denmark looked very attractive, 4x2000W/4ohm modules and suitable SMPS would cost about 1300 euros, but I've read bad things about them on this forum and have had great difficulty getting information out of them.

Unfortunately they're still the only choice for modules and SMPS at this power level, nobody else sells such high-power modules and SMPS (Powersoft have the 2x1400/4 Digimod 3000 PFC module but will only sell to volume OEMs).

Coldamp looked like the next best bet (I'd need a lot of modules though!) but I'm rapidly going off the idea -- especially regarding SMPS safety...

If I can't get suitable modules I'll probably end up buying ready-made class-D pro amps, but these are a lot more expensive obviously -- at least 2600euros for 2 2x2000W amps such as these:

Powersoft Digam K4 or D7000 -- *very* expensive!!!
CAD audio DPA4800 http://cadaudio.dk/dpa4800.htm -- no!!!
D-amp 4000HVI http://www.d-amp.com/serie_hvi.htm
PKN XD4000 http://www.pknc.com/

Anyone got any other suggestions, preferably for modules, or failing that, pro amps?

Ian

P.S. Final version of Zetex DDFA digital modulator chip tapes out this week, we've managed to get output jitter down to about 3ps :-)

P.P.S. If you think that's small, our 1GHz 14b DAC has 250fs...

P.P.P.S. Our next generation RF DAC should be less than 25fs...
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Old 6th February 2008, 08:54 PM   #14
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Hi Ian.
Could you please be a bit more specific about your needs.

Do You intend to drive low impedance speakers? If so how low?

How important is it to keep the weight down at a minimum?

Here´s a brand new Class D module NCD 4 but no SMPS from them , but
it is said that Hypex will bring one to the market.

http://www.newclassd.com/

Then there is the QSC PLX2 amps which I guess is linear amps with SMPS and e.g. the PLX 1804 at 2x900 W in 4 ohms weighs in at 5.9 kg.

BK Electronics has sold this Class D amp with SMPS for some years but I don´t know much about it.
http://www.bkelec.com/HiFi/ClassD/ClassD.htm
They also sell the Citronic range of PA amps but they seems to be conventional ones.

We have the Swedish Lab gruppen (bought by Tannoy) with their solutions for low weight amplification.

http://www.labgruppen.com/

And ther are many new examples of Class D technology being used for PA amps...

I have laid my eyes on the Mackie amps M2000 etc with their class H technology. May be modded for a good sub amp!
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Old 6th February 2008, 09:06 PM   #15
Eva is offline Eva  Spain
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You don't seem to be considering UcD, which is an exemplary design, particularly regarding EMI control, as most other modules for sale are full of uncontrolled ringing propagating freely through the wiring.

Class-D designers that ask elementary electronics questions in public forums during commercial product development are likely to produce that kind of RF generators. Examples are not hard to find.
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Old 6th February 2008, 09:29 PM   #16
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Here we go again. Lightweight amplification isn´t too hard to find these days!

Mackie FRS series:

http://www.mackie.com/products/frsseries/splash.html
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Old 6th February 2008, 09:36 PM   #17
iand is offline iand  United Kingdom
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Quote:
Originally posted by The golden mean
Hi Ian.
Could you please be a bit more specific about your needs.

Do You intend to drive low impedance speakers? If so how low?

How important is it to keep the weight down at a minimum?

Here´s a brand new Class D module NCD 4 but no SMPS from them , but
it is said that Hypex will bring one to the market.

http://www.newclassd.com/

Then there is the QSC PLX2 amps which I guess is linear amps with SMPS and e.g. the PLX 1804 at 2x900 W in 4 ohms weighs in at 5.9 kg.
Load will be 4 channels x 4ohms (2 parallel 1200Wrms/8ohm speakers per amp, main and sub) on each amp, so I'm looking for at least 4x2000W/4ohms (we play in some pretty big venues sometimes).

This doesn't have to be continuous rms power simultaneously on all channels but needs to be there for at least a few seconds, so relying on capacitor storage isn't enough. The PSU needs to be able to supply maybe 6kW short term, 1-2kW long-term is fine -- this is the same basis the PL380 is rated on.

SMPS is pretty much essential -- our existing amp rack is much lower power than this and is a 2-man lift. 8kw of amps with linear supplies would be a fork-lift truck job...

I know about the NewClassD and Hypex modules but they're a bit feeble and expensive in £ per watt at these power levels. A pair of bridged ZapPulse 2.3SE would do 2000W/4ohms with the maximum +/-80V supply for about 200 euros per channel, but the SMPS problem remains.

Most of the class-D module makers are aiming at the lower-power high-end audio market, only CAD Audio seem to fit the high-power PA market -- but as I said I have major reservations about them.

However I don't see any other choice for modules and SMPS right now -- 1100 euros for CAD Audio modules, or 2200 euros for PKN Controls ready-built amps (2x XD4000 @ 9kg each).

Known (but dodgy?) Danish supplier vs. unknown Hungarian supplier (no comments from anybody either way) -- what a choice...

Ian

P.S. At least the PKN amps look professionally built inside (unlike the CAD Audio and D-amp ones which look rather amateurish) and have full EEC EMC/safety certification.
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Old 6th February 2008, 09:42 PM   #18
iand is offline iand  United Kingdom
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Quote:
Originally posted by The golden mean
Here we go again. Lightweight amplification isn´t too hard to find these days!

Mackie FRS series:

http://www.mackie.com/products/frsseries/splash.html
4 of these in a rack weigh about 100lbs, I don't call that lightweight :-)

High-end manufacturers like Powersoft and Lab Gruppen (and now QSC) do make nice lightweight high-power amps, but at a not-so-nice heavyweight price (2xQSC PL380 = 8000 euros)

Ian
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Old 6th February 2008, 09:54 PM   #19
Eva is offline Eva  Spain
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I happen to be developing the kind of technology that you are asking for. I can assure you that doing it right is not easy at all, and there is not much people in the world capable of making that kind of circuits work cool, EMI quiet and flawlessly, so the high price is actually not that high.

The SMPS issue is not that hard to solve because there are plenty of companies producing off-the-shelf modules that may be paralleled and stacked. For example, units with 48V outputs are pretty standard as they are used for telecom. Surplus bargains are found at times in places such as eBay.
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Old 6th February 2008, 10:39 PM   #20
iand is offline iand  United Kingdom
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Quote:
Originally posted by Eva
I happen to be developing the kind of technology that you are asking for. I can assure you that doing it right is not easy at all, and there is not much people in the world capable of making that kind of circuits work cool, EMI quiet and flawlessly, so the high price is actually not that high.

The SMPS issue is not that hard to solve because there are plenty of companies producing off-the-shelf modules that may be paralleled and stacked. For example, units with 48V outputs are pretty standard as they are used for telecom. Surplus bargains are found at times in places such as eBay.
Obviously it's not *easy* (I'm very well aware of this) or everyone would do it! But given sufficient knowledge about fast switching MOS/IGBT/diodes, gate drivers, parasitic inductance and mutual coupling, current return paths, magnetic field radiation and so on it's not at all impossible -- we deal with equally (sometimes more) difficult problems daily but on a much smaller scale.

It's just as hard switching 20mA in 20ps cleanly into a load as it is switching 20A in 20nS. And if you think noise and crosstalk in a big class-D amp is difficult to deal with, try keeping analogue clock jitter at the sub-picosecond level on the same piece of silicon as millions of noisy digital gates with noise radiating off the bond wires and sneaking across the silicon... :-)

But all this does need a completely different skill set to conventional amplifier design, and -- as you say -- not many people have this.

There are plenty of 48V telecom PSUs around but they're usually designed to deal with relatively constant loads, and can go haywire when confronted with the rapidly varying and reactive load of a class-D amplifier.

Companies who know how to design decent SMPS could of course knock out a decent one for PA application in no time -- but they don't because there's no big market. Companies who know how to design traditional audio amplifiers don't usually know how to design SMPS, as can be seen by looking at some of the examples on sale now...

Ian
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