Workhorse said:
No one except you is saying for switching at 850kHz...........
250kHz is optimum!
For analogue modulators (and from efficiency point of view) I agree -- but for all-digital noise-shaping modulators (like the Zetex chipset) higher sampling rates give higher SNR, obviously at the cost of decreased efficiency.
It is possible to make a 95% efficient class-D amp switching at these rates using 100V MOSFETs with very fast switching low Trr/Qrr body diodes like the IRF6645, but the diodes get worse very rapidly above 100V:
Device Vdd Ron Qgd Trr/Qrr@If Package
IRFB4227 200V 20mohm 23nC 100ns/430nC@46A TO-220
IRF6641 200V 51mohm 9.5nC 85ns/320nC@5.5A DirectFET
IRF6775 150V 47mohm 6.6nC 62ns/164nC@5.6A DirectFET
IRF6645 100V 28mohm 4.8nC 31ns/40nC@3.4A DirectFET
A full bridge using 100V FETs has a theoretical absolute maximum output power (100V peak voltage) of 1250W/4ohms, but by the time allowance is made for supply regulation, overshoot, and maximum modulation depth this is probably down to about 800W/4ohms. For 2000W/4ohms (127V peak) 150V FETs are barely adequate, probably in practice 200V FETs are needed.
So if anyone knows of any 150V/200V FETs with lower Trr/Qrr than the IR devices please post details...
Ian
thylantyr said:Useless ramblings
Go buy one of these amplifiers and do some tests.
Once you have data from testing the amplifier, then you
have something to talk about.
You don't need to test one to spot the issues with their claimed fantastic new design, unless they've found a way of breaking the laws of physics or have found new exotic switching devices made out of unobtanium...
Speculation and discussion is free, buying a QSC PL380 costs £2700.
Ian
iand said:
You don't need to test one to spot the issues with their claimed fantastic new design, unless they've found a way of breaking the laws of physics or have found new exotic switching devices made out of unobtanium...
Speculation and discussion is free, buying a QSC PL380 costs £2700.
Ian
I can analyze amplifiers too, and I do, but the reality is that
people need to have tests dones otherwise you may look foolish
if your guesses are not on target
I've read some early reports on this amplifier used in a concert settting driving subwoofers and the feedback was excellent. This
person had experience with old Crown Macrotech and the new
IT8000 for reference.
But this end user testimony is no different than someone looking at the guts and forming a conclusion, it's all an opinon.
I don't want to nit pick, but if you are going to judge an
amplifier, it's best to write down the claims first.
QSC PL380 published specs;
http://www.qscaudio.com/products/amps/powerlight3/PL3_FullRange.pdf
MAXIMUM OUTPUT POWER
8 ohms, both channels driven, 1kHz, 1% clipping = 1500
8 ohms, both channels driven, 20-20kHz, THD = 1450 0.25%
4 ohms, both channels driven, 1kHz, 1% clipping = 2500
4 ohms, both channels driven, 20-20kHz, THD = 2500 20-10kHz, 0.35%
ohms, both channels driven, 20-20kHz, THD = 1500 at 20kHz, 0.35%
2 ohms, both channels driven, 1kHz, 1% clipping = 4000
Comments:
1. Did you read all the 'IF' scenarios in the product specifications?
2. Did you analyze the guts and factor these specificaitons into
your speculation evaluation ?
2. Did you test the amplifier and comply with those restrictions?
You can read the rest of the document.
amplifier, it's best to write down the claims first.
QSC PL380 published specs;
http://www.qscaudio.com/products/amps/powerlight3/PL3_FullRange.pdf
MAXIMUM OUTPUT POWER
8 ohms, both channels driven, 1kHz, 1% clipping = 1500
8 ohms, both channels driven, 20-20kHz, THD = 1450 0.25%
4 ohms, both channels driven, 1kHz, 1% clipping = 2500
4 ohms, both channels driven, 20-20kHz, THD = 2500 20-10kHz, 0.35%
ohms, both channels driven, 20-20kHz, THD = 1500 at 20kHz, 0.35%
2 ohms, both channels driven, 1kHz, 1% clipping = 4000
Comments:
1. Did you read all the 'IF' scenarios in the product specifications?
2. Did you analyze the guts and factor these specificaitons into
your speculation evaluation ?
2. Did you test the amplifier and comply with those restrictions?
You can read the rest of the document.
Yes I read all the detailed documentation about the PL380 (and understood it, it's my job).
The idea of using a single HV MOSFET switching pair looks attractive, but unless QSC have some "secret sauce" to keep the current out of the slow body diodes (and there's no evidence of this) it's not going to have high efficiency -- this was what my original questions were about.
Maybe if the long-term thermally limited power is relatively small they don't care that the power loss is 15-20% instead of 5%, it's still less than a conventional amp.
But their publicity blurb presents this solution as some kind of major breakthrough, when it doesn't seem to be anything of the sort -- it's just another way of making a not-especially-cool class-D amp like many of the others that are around...
Ian
The idea of using a single HV MOSFET switching pair looks attractive, but unless QSC have some "secret sauce" to keep the current out of the slow body diodes (and there's no evidence of this) it's not going to have high efficiency -- this was what my original questions were about.
Maybe if the long-term thermally limited power is relatively small they don't care that the power loss is 15-20% instead of 5%, it's still less than a conventional amp.
But their publicity blurb presents this solution as some kind of major breakthrough, when it doesn't seem to be anything of the sort -- it's just another way of making a not-especially-cool class-D amp like many of the others that are around...
Ian
But their publicity blurb presents this solution as some kind of major breakthrough
QSC is mild compared to other manufacturers with bigger
marketing departments 
I can find flaws with any manufacturer, but it's all a game of
compromises because you want your business to stay in
business.
QSC has some great amps, perhaps others not so great.
You can download QSC schematics of most of their amps here.
http://www.qscaudio.com/support/technical_support/schems1.htm
Certain older products are impressive. PL6.0, PL9.0 PFC's
are favorites amongst the audio fantatics who want mad
power, enough power to raise the dead at cemetaries.
I'm not sure which PL amp this is, but the internals have
very nice heatsinking and plenty of it, plus IIRC, four
fans in the rear.
http://home.pacbell.net/lordpk/proamps/QSC_PL.jpg
PL9.0 was sine wave tested by someone on the pro forum.
117VAC, 1% THD, 4 ohms/ch.
@20hz = 3152w/ch
@1khz = 3293w/ch
@20kz = 4804w/ch
It's rated for 2 ohm/ch, but not tested in that configuration.
It's PFC, it will do well in sagging AC input
These are good scores considering the pro industry doesn't
really rate their amplifiers on continuous sine waves. Their
test methods offer more generous ratings.
Lab Gruppen FP6400 was also tested, same situation.
117VAC, 1% THD, 4 ohms/ch.
@20hz = 1327w/ch 1010w/ch
@1khz = 2310w/ch 1784w/ch
@20kz = 648w/ch 718
note: bold = 96VAC input test.
The only reason I listed the FP6400 is to establish a reference as
people think FP series 'can do no wrong' and they rate this
amp for 6kw, not to mention is cost much more than the
new PL380. Lab has introduced FP+ series, perhaps they
improved the design. :heh:
Even if the PL380 didn't meet published specs, don't worry,
not many pro amps do. ... you can only analyze them for
what they do and then look at the price tag, then recalculate
the new dollar per watt.
QSC is mild compared to other manufacturers with bigger
marketing departments
I can find flaws with any manufacturer, but it's all a game of
compromises because you want your business to stay in
business.
QSC has some great amps, perhaps others not so great.
You can download QSC schematics of most of their amps here.
http://www.qscaudio.com/support/technical_support/schems1.htm
Certain older products are impressive. PL6.0, PL9.0 PFC's
are favorites amongst the audio fantatics who want mad
power, enough power to raise the dead at cemetaries.
I'm not sure which PL amp this is, but the internals have
very nice heatsinking and plenty of it, plus IIRC, four
fans in the rear.
http://home.pacbell.net/lordpk/proamps/QSC_PL.jpg
PL9.0 was sine wave tested by someone on the pro forum.
117VAC, 1% THD, 4 ohms/ch.
@20hz = 3152w/ch
@1khz = 3293w/ch
@20kz = 4804w/ch
It's rated for 2 ohm/ch, but not tested in that configuration.
It's PFC, it will do well in sagging AC input
These are good scores considering the pro industry doesn't
really rate their amplifiers on continuous sine waves. Their
test methods offer more generous ratings.
Lab Gruppen FP6400 was also tested, same situation.
117VAC, 1% THD, 4 ohms/ch.
@20hz = 1327w/ch 1010w/ch
@1khz = 2310w/ch 1784w/ch
@20kz = 648w/ch 718
note: bold = 96VAC input test.
The only reason I listed the FP6400 is to establish a reference as
people think FP series 'can do no wrong' and they rate this
amp for 6kw, not to mention is cost much more than the
new PL380. Lab has introduced FP+ series, perhaps they
improved the design. :heh:
Even if the PL380 didn't meet published specs, don't worry,
not many pro amps do.
... you can only analyze them forwhat they do and then look at the price tag, then recalculate
the new dollar per watt.
I was really expecting this amplifier to be more "high tech".
I always expect new amplifiers to hit the market to be
better than ever, but it may not be the case. Business is business, it's there to make money and put excitement into
your life.
A PFC-style power supply with pseudo-regulated output wouldn't have hurt anybody. They used this technology in other amplifiers but it seems that they weren't able to achieve the degree of reliability expected in a touring amplifier. Why?
QSC has developed PFC amplifiers before. They were eventually
discontinued. A little bird told me the failure rates were 10%
leaving the factory. The theory is the power semiconductors
used at the time [long time ago] were the best, but perhaps
not good enough for that ambitious design. From a business
point of view, it makes sense to put the design back on the shelf.
But, there are many of these amplifiers in the field working great.
It's that random moment that may cause the semiconductor
to blow, people speculate this is caused by 'dirty AC' transients.
/whatever.
The users that have these PFC amps running claim to this day,
it's the best amplifier they have ever used. QSC also offers
a transistor upgrade kit as semiconductors have made advances.
Why not re-introduce these true behemoths ? I don't know
why, it's business, it's there to make money.
What will make you more money, the PL380 guts or
the PL guts?
http://home.pacbell.net/lordpk/proamps/QSC_PL.jpg
For example, I have developed a PFC capable of 5KW day and night at 230V input in my home lab with far less resources (now I'm going through the hell of adding a "green" low idle power mode).
DIY projects and making a business of your DIY hobbies can
clash. I've tried in along time ago. Try to market your product,
mass produce it, support it, and see if you can turn a profit.
Easier said than done.
People in DIY loudspeakers can make great loudspeakers
for a fraction of the cost of commercial loudspeakers, then
why don't they start a business ? Same thing, it's not easy.
I always expect new amplifiers to hit the market to be
better than ever, but it may not be the case. Business is business, it's there to make money and put excitement into
your life.
A PFC-style power supply with pseudo-regulated output wouldn't have hurt anybody. They used this technology in other amplifiers but it seems that they weren't able to achieve the degree of reliability expected in a touring amplifier. Why?
QSC has developed PFC amplifiers before. They were eventually
discontinued. A little bird told me the failure rates were 10%
leaving the factory. The theory is the power semiconductors
used at the time [long time ago] were the best, but perhaps
not good enough for that ambitious design. From a business
point of view, it makes sense to put the design back on the shelf.
But, there are many of these amplifiers in the field working great.
It's that random moment that may cause the semiconductor
to blow, people speculate this is caused by 'dirty AC' transients.
/whatever.
The users that have these PFC amps running claim to this day,
it's the best amplifier they have ever used. QSC also offers
a transistor upgrade kit as semiconductors have made advances.
Why not re-introduce these true behemoths ? I don't know
why, it's business, it's there to make money.
What will make you more money, the PL380 guts or
the PL guts?
http://home.pacbell.net/lordpk/proamps/QSC_PL.jpg
For example, I have developed a PFC capable of 5KW day and night at 230V input in my home lab with far less resources (now I'm going through the hell of adding a "green" low idle power mode).
DIY projects and making a business of your DIY hobbies can
clash. I've tried in along time ago. Try to market your product,
mass produce it, support it, and see if you can turn a profit.
Easier said than done.
People in DIY loudspeakers can make great loudspeakers
for a fraction of the cost of commercial loudspeakers, then
why don't they start a business ? Same thing, it's not easy.
PL380 v IT8000 v 9001 Pro v PLX3402 Smackdown
http://srforums.prosoundweb.com/index.php/m/229083/0/?srch=IT8000#msg_229083
http://srforums.prosoundweb.com/index.php/m/229083/0/?srch=IT8000#msg_229083
Observations:
Room temperature 26C, relative humidity 54%, RMS voltage (later converted to watts) was measured with a Fluke Scopemeter on battery power, max RMS voltage decided on when the output stopped increasing with increasing input or the sine wave got ugly, i.e. results are somewhat subjective. The red LED's proved pretty accurate on all amps tested, although the PL380 seemed to illuminate about 1dB prior to heavy limiting. The other amps began significant limiting as soon as the red LED illuminated. The 50ms bursts are more than twice the duration of a kick drum hit, thus I think it's a pretty conservative test. All of the following should be taken with a grain of salt as I'm no amp guru, but the fact that each amp was tested and judged in the same manner makes comparison between them possible to some extent. Where's JR when you need him?
PLX3402
Bridged mode, 4 ohm resistive load. 120v 60Hz power source on a 20 amp breaker. The breaker tripped a couple of times during testing, but I've never had a PLX3402 trip a 120v, 20 amp breaker in actual use, bridged or otherwise, regardless of load.
The sine waves looked very good at all frequencies tested.
Continuous loops of 1kHz sine 50ms on / 50ms off produced 120v RMS at onset of limiting. Single 50ms sine bursts are reported in the following table driven at the onset of limiting. This thing is a HF beast. Keep in mind this is a single channel bridged setup while the other amps are being measured and loaded on both channels in stereo mode.
I-T8000
Stereo mode, both channels driven into 4 ohm resistive loads, left channel output measured. 120v 60Hz power source on a 20 amp breaker. It was obvious that the amp would have been happier and probably could have developed more power if more current or voltage were available to it. My application for the I-T8000 has been two Danley TH115 per channel or the low bandpass of four EAW KF730 cabinets per channel. In both cases this is a nominal 4 ohm load per channel. I have fed these amps 120v via a 20 amp breaker in both applications and never had a breaker trip. Testing with these sine wave signals is a different matter and I tripped the breaker quite often. It was obvious that the voltage was sagging when the amp was approaching full output, which I'm sure biased the results negatively. These amps need either a 120v, 30 amp or 208v/240v, 20 amp power source to yield their full output into 4 ohm (or lower) loads at full output. I've seen the red LED's (indicating limiting) on these amps on occasion at loud rock shows while driving two TH115's per channel.
Both 10kHz and 20kHz sine waves looked a little weird even before limiting. I was unable to test a continuous loop of a 1kHz sine 50ms on / 50ms off due to the power issue mentioned above. Single 50ms sine bursts are reported in the following table with both channels driven to the onset of limiting.
QSC PL380
Stereo mode, both channels driven into 4 ohm resistive loads, left channel output measured. 120v 60Hz power source on a 20 amp breaker. In this case the amp did not need more power as it only tripped the breaker once during testing (during the continuous loop). With the I-T8000 the lights in my house dimmed with each 50ms burst at each frequency tested and caused frequent walks to the laundry room to reset the breaker. Neither the PL380 nor any of the other amps did this. Granted the other amps are not as powerful, but the burst power of the PL380 is within a dB (or less), yet seems to use much less power. I substituted a PL380 at a pretty loud rock show for one of the I-T8000's and had one I-T8000 and one PL380 driving two TH115's per channel for a total of 8 subs. Both amps intermittently engaged their -10dB LED's during the loudest portions of the show and both worked perfectly. The I-T8000's fans run much louder and faster than the PL380 during testing, but with all the noise at a show, you'll never notice a difference in actual use.
The sine waves looked very good at all frequencies. The limiter was the best of the bunch as far as keeping the sine shape while reducing output. I have no idea what the limiter sounds like nor what the amp sounds like on the mid/high bandpass of my KF730's yet. I'm quite hopeful based on what I saw on the scope. TBA.
Continuous loops of 1kHz sine 50ms on / 50ms off produced 84v RMS at the onset of limiting. Single 50ms sine bursts are reported in the following table with both channels driven to the onset of limiting. This thing has excellent dynamic headroom into 4 ohms and is a smart engineering compromise over continuous power ratings given the nature of music.
Smaart measurements of the PL380 under load and with the HP filters are available here.
Crest 9001
Stereo mode, both channels driven into 4 ohm resistive loads, left channel output measured. 120v 60Hz power source on a 20 amp breaker. This amp behaved exactly like the PL380 in that it seemed happy with the power source as it only tripped the breaker once during testing (during the continuous loop). The 9001 wins the loudest, fastest fan award. At 110lb it is also a tad heavy to move about. Pin 3 positive still bugs me.
The sine waves looked very good at all frequencies.
Continuous loop of 1kHz sine 50ms on / 50ms off produced 85v RMS at the onset of limiting. Single 50ms sine bursts are reported in the following table with both channels driven to the onset of limiting. This amp also has good dynamic headroom into 4 ohms. It is interesting that the 20Hz result is higher than the 50Hz result - I repeated both measurements several times to be sure. The I-T8000 was a little stronger at 20Hz compared to 50Hz as well.
Single 50ms bursts:
dBW is referenced to 1 watt and rounded to the nearest whole number to illustrate how little volume difference there is between what appear to be rather large differences in wattages.
PLX3402 [bridged mode];
20hz = 2704W
50hz = 2916W
200hz = 3136W
1khz = 4900W
5khz = 5184W
10khz = 5476W
20khz = 5775W
Crown IT-8000 [stereo mode];
20hz = 3481W
50hz = 2916W
200hz = 3364W
1khz = 4356W
5khz = 4225W
10khz = 4356W
20khz = 4356W
QSC PL380 [stereo mode];
20hz = 2601W
50hz = 2704W
200hz = 2704W
1khz = 3249W
5khz = 3721W
10khz = 4096W
20khz = 3844W
Crest 9001 Pro [stereo mode];
20hz = 2601W
50hz = 2209W
200hz = 2304W
1khz = 2500W
5khz = 2500W
10khz = 2601W
20khz = 2601W
There's no denying the PL380 is an attractive product that delivers what the spec says (I wouldn't expect any less from QSC), it's just not the leap forward that the publicity suggests -- the fact that other companies are worse is no excuse...
I'd also be interested to know how/whether it's legally sellable in places like Europe where PFC is almost mandatory on such high-power equipment due to tight limits on current harmonic distortion. Similar (or higher) power rating amps from companies like Powersoft include PFC for exactly this reason, as well as to reduce the rms current draw which is what blows fuses and trips breakers.
PFC reliability is no excuse nowadays, there's no reason this should be any less reliable than a non-PFC switchmode supply given robust design and the availability of rugged switching devices nowadays. As I said, many SMPS designs in amplifiers (but not all) are not up to scratch compared to the state of the art.
Ian
I'd also be interested to know how/whether it's legally sellable in places like Europe where PFC is almost mandatory on such high-power equipment due to tight limits on current harmonic distortion. Similar (or higher) power rating amps from companies like Powersoft include PFC for exactly this reason, as well as to reduce the rms current draw which is what blows fuses and trips breakers.
PFC reliability is no excuse nowadays, there's no reason this should be any less reliable than a non-PFC switchmode supply given robust design and the availability of rugged switching devices nowadays. As I said, many SMPS designs in amplifiers (but not all) are not up to scratch compared to the state of the art.
Ian
I looked up EN61000-3-2 which limits mains current harmonics in the EU...
http://www.epsma.org/pdf/PFC Guide_November 2002.pdf
...and found that there is an exemption (no limit) for "professional equipment with input power over 1kW" -- where "professional equipment" is defined as:
"for use in trades, professions or industries and which is not intended for sale to the general public. The designation shall be specified by the manufacturer."
I wonder if this is a loophole exploited by high-power PA manufacturers? They could claim "it says "Professional Audio Amplifier" on the label so it's exempt". On the other hand these amps are clearly on sale to the general public regardless of what the label says and whether their profession is audio or not.
If they did this it would mean that amps under 1kW would have to have PFC but amps over 1kW wouldn't, which is clearly ridiculous!
Or are they just ignoring the problem in the hope that nobody notices?
Does anyone know the real legal position on this?
Ian
http://www.epsma.org/pdf/PFC Guide_November 2002.pdf
...and found that there is an exemption (no limit) for "professional equipment with input power over 1kW" -- where "professional equipment" is defined as:
"for use in trades, professions or industries and which is not intended for sale to the general public. The designation shall be specified by the manufacturer."
I wonder if this is a loophole exploited by high-power PA manufacturers? They could claim "it says "Professional Audio Amplifier" on the label so it's exempt". On the other hand these amps are clearly on sale to the general public regardless of what the label says and whether their profession is audio or not.
If they did this it would mean that amps under 1kW would have to have PFC but amps over 1kW wouldn't, which is clearly ridiculous!
Or are they just ignoring the problem in the hope that nobody notices?
Does anyone know the real legal position on this?
Ian
Well, this gets more and more interesting...
I found a review of the Camco Vortex 6 which mentions EN61000-3-2
http://www.ashly.com/brochure/camco/vortex_prod-partnertest.pdf
and it says that this "does not stipulate a limitation of the harmonics contained in the mains current for consumers for professional uses with more than 1kW of power consumption under nominal conditions i.e. for power amps loaded with bandwidth-limited pink noise and an averaged output power of 1/8 of their sine power."
It also says that this does not apply to the Vortex 6 because "under the given conditions it already draws more than 1kW nominal power from the mains" (it's a class-H amplifier with SMPS without PFC).
Now the PL380 is a class-D amp with claimed overall efficiency of 85%, so at 1/8 power it's probably *just* over the 1kW limit with 2 ohm loads -- but not at 4 ohms.
I suspect all the high-power amp manufacturers are steering very close to the wind here -- what makes the situation worse is that more efficient class-D amps are more likely to need PFC because their average power draw is less than linear amps.
And the regulations do say that rules for the ">1kW professional" exemption are under consideration, so you can guess what that means...
Of course for high-power amps it makes a lot of sense to have PFC -- more power can be drawn without tripping breakers, and the amp becomes almost immune to mains voltage drops because the PFC acts as a pre-regulator.
Ian
I found a review of the Camco Vortex 6 which mentions EN61000-3-2
http://www.ashly.com/brochure/camco/vortex_prod-partnertest.pdf
and it says that this "does not stipulate a limitation of the harmonics contained in the mains current for consumers for professional uses with more than 1kW of power consumption under nominal conditions i.e. for power amps loaded with bandwidth-limited pink noise and an averaged output power of 1/8 of their sine power."
It also says that this does not apply to the Vortex 6 because "under the given conditions it already draws more than 1kW nominal power from the mains" (it's a class-H amplifier with SMPS without PFC).
Now the PL380 is a class-D amp with claimed overall efficiency of 85%, so at 1/8 power it's probably *just* over the 1kW limit with 2 ohm loads -- but not at 4 ohms.
I suspect all the high-power amp manufacturers are steering very close to the wind here -- what makes the situation worse is that more efficient class-D amps are more likely to need PFC because their average power draw is less than linear amps.
And the regulations do say that rules for the ">1kW professional" exemption are under consideration, so you can guess what that means...
Of course for high-power amps it makes a lot of sense to have PFC -- more power can be drawn without tripping breakers, and the amp becomes almost immune to mains voltage drops because the PFC acts as a pre-regulator.
Ian
Workhorse said:Hi Toino,
The resonance is achieved through leakage inductance which in this case is around 5.5uH. The caps are 2 X 0.47uF 400V Vishay.
The Ferrite core is EPCOS 3F3 EE55. Operation is halfbridge.
Hey,I donot reverse engineer, what I do is analysis, so i am analyst in nature, therefore no arrests.
Dear Workhorse,
Has this xformer any air gap?
Do you think, such a 3F3 EE55 could be OK with just 9 primary turns at 80kHz switching frequency?
Thanks very mutch,
Tamas Tako
appologies for appearing 'out of the view' but i have a quick comment to make about the reasons for rules and limits about mains harmonics and the rational for exempting some equipment.
the 'damage' done to the integrity of the mains is really caused by millions of small poor power factor loads such as the legions of tvs and computers etc. these are the products that collectively 'flat top' the mains and cause currents to flow in the power utilities neutral conductors, not so much the use of a relatively small number of high power products.
it is also accepted by the regulators that it becomes much more difficult and expensive (note that i did not say impossible) to add PFC as the power demanded by a product increases.
this is why the seemingly illogical exemptions exist, it's simply that forcing the rules on to products like this will not improve the mains harmonic situation which is the only intention of the EN6100-3-2 standard.
of course as no doubt eva is already poised to write, there may well be reasons other than regulatory why one might put an active PFC in a product !
the 'damage' done to the integrity of the mains is really caused by millions of small poor power factor loads such as the legions of tvs and computers etc. these are the products that collectively 'flat top' the mains and cause currents to flow in the power utilities neutral conductors, not so much the use of a relatively small number of high power products.
it is also accepted by the regulators that it becomes much more difficult and expensive (note that i did not say impossible) to add PFC as the power demanded by a product increases.
this is why the seemingly illogical exemptions exist, it's simply that forcing the rules on to products like this will not improve the mains harmonic situation which is the only intention of the EN6100-3-2 standard.
of course as no doubt eva is already poised to write, there may well be reasons other than regulatory why one might put an active PFC in a product !
ttako said:
The transformer has no air gap.
the size of the core is small, but again its not meant for CONTINUOUS DUTY CYCLE LOADS, its for average music load.
The switching frequency is 116KHZ..........|||
Also this amp has heavy limiting of powerbandwidth in LF region........it simply suxxx.
look my board
I have made a 8KW class d amp,ideas come from QSC pl380,the lastest version can provide 8kw@4ohm load in 1 minute,please look it for my blog ,http://damp.blog.dianyuan.com
I have made a 8KW class d amp,ideas come from QSC pl380,the lastest version can provide 8kw@4ohm load in 1 minute,please look it for my blog ,http://damp.blog.dianyuan.com
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