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Behringer inuke NU6000 vs KAM KXD7200 bench tested

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teslaman View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote teslaman Quote  Post ReplyReply Direct Link To This Post Posted: 24 July 2012 at 6:55pm
Originally posted by Timebomb Timebomb wrote:

Cheers for taking the time to test these, the Inuke 6000 looks good, shame about the current draw...looks like it would be trouble on generators...
Its interesting that the 6000 will sustain its output without dropping the voltage, the Inuke 3000 drops the level after a few seconds much like the Kam, it also has no breaker on the back.

As far as the current draw goes its not going to be any worse than any other amplifier that doesn't have PFC built in, and that includes virtually all of the heavyweight units and a lot of the switch mode supply ones too. With no PFC they all use rectification into a set of capacitors which will always pull peaky currents. Hence I wouldn't be worried, it's not a case that the Behringer is poor, more that the Kam is Good! For domestic appliances the rules are changing such that anything above a certain power needs PFC but for "professional applications" it's not mandatory, hence multi-kW amplifiers with no PFC.
I have amps from QSC, Void, Matrix and Ohm and none of them have PFC so will all draw peaky current from the mains.......

As for the sustained output, I may re-visit that and see if it does eventually limit the power or not but as I've shown, for music signals it should be just fine.

Originally posted by U.Viktor U.Viktor wrote:

i have seen the original manufacturer of those KAM internals somewhere in the china backstage of prolight&sound in frankfurt. It still pulls the hot air to its capacitors quickly dry them out and let you buy another one of this scrap.
About the iNUKE: the whole thing has built around the IRS20957S which barely hits the entry level, it has made for cheapest car radios and does not even have real output feedback. The sample frequency is not 348Khz (or only in low signal or steady-state) because it is free running variable freq. controller with the lack of sync. capability.
As I saw it would make a voltage doubler circuitry by a relay and center tapped primary caps for low line operation. good luck with that! And deal with 200A+ current spikes and heavy AC line distortion :-D

U.Viktor I've noticed that you have a very black or white view of things! I agree that pulling hot air across the capacitors is a bad idea and they are only 85 degree rated types too. The generally accepted rule of thumb is that if the rated life of the capacitor is, for example, 2000 hours at 85 degrees then the life will double for every 10 degree reduction in temperature. Ultimately it's going to depend on what temperature they run at but thanks to the efficiency of the amp and taking account of the nature of music signals I doubt they will run that hot. I'll take a guess (for the sake of calculating a number) at 65 degrees in which case life might be 8000 hours which is the equivalent of 333 days of continuous running or 1000 days at 8 hours a day. Lets remember this amp is targeted at musicians, DJ's etc. and not touring companies! I suspect their usage might be a few hours a week in which case I don't think they have much to worry about, do you?

With regard to the iNuke, the IRS20957S is hardly entry level, it is used in some reference designs which have extremely good audio performance, I know because I've tested them! Yes, the typical application circuit is a self-oscillating second order delta-sigma type modulator but it happens to work quite well. You can of course use it differently if you wish, it's up to the designer. It can also be synchronised to an external clock if needed but not over it's entire PWM modulation range.
If you wanted you could turn it into a UcD type circuit with feedback from after the output filter, maybe that would appeal more to you?

The voltage doubler arrangement for 115V supplies is, I agree, a bit (no, a LOT) of a tall order! I can only assume they don't use a 10A IEC socket for the US market, otherwise it's going to be very limited in power before that 12A breaker goes! Stick to 230V I think...

Originally posted by U.Viktor U.Viktor wrote:

Does the 2x 2000W@4R with 33% burst ratings mean 2x 700W@4R CONTINUOUS real power?

During those particular test yes it is but I'm not saying that's the best the amplifier can do, that's just the result of the 33% test signal I used to represent worse case audio abuse. As I stated I think the Behringer will probably do about 1~1.2kW per channel continuous sine wave, limited by its 12A circuit breaker. For music it will happily produce 2kW into 4 Ohms per channel.  The Kam can only do 650W into 4 Ohms continuous sine wave but its happy to deliver 1.6kW under music conditions. Should be absolutely fine for most people...

Originally posted by audiomik audiomik wrote:

David

looking at your results for the iNuke:
"At 4 Ohms both channels driven we get 1.80kW: Peak mains current is now at 80A!"

Then checking the Behringer website info, and your images earlier in this thread, for this Amplifier it appears to be using a single IEC type 10A (rms) power connector.
Now your measurement is peak current, albeit with a reduced duty cycle, but the peak current rating of a 10A IEC connector is still only 14.14 amps.....
When I last looked up CE Compliance Regs, this would be a 'Fail'!
The KAM seems to be substantially better performing in this respect with only a 2:1 overload compared with over 5:1 for the NU6000.

OK, like me you have limited loads in terms of continuous power dissipation measurements, but how long will it take for the IEC connector to heat up to an unacceptable level and fail do you think?

Anyway, an interesting set of test results, but would like to see the sinewave output just into clipping and 33% voltage squarewave responses of both Amplifiers to be able to compare their performance with other Amplifier tests.

Don't know which type of Current probe you have, but the Amplifier output current waveform into a Resistive Load with no signal input can be interesting 
Then again, output current measurements into a Load with an Inductive component, just like the Le of a 'Speaker, give some 'spectacular' results with Class D....... 
A couple of MilliHenrys and 4 Ohms in series with 50% output Voltage at 1kHz? Wouldn't want to overload the output stages with too much back EMF now would we

Just seen UVictor's posts whilst writing this one - max continuous output without 'tripping' for 5 minutes would be interesting - and the test described above with the Inductive component added can show marked differences in performance where the various clocks aren't properly locked or synchronised respectively in different Class D/SMPSU Designs.

Keep up the good work
Mik

Hi Mik, I think the traces I put up for the limiter operation will give you some idea of the output under just clipping conditions since the limiter holds the output at the just clipping point. If you'd like to see some more detail i can use a phosphor scope and zoom in to see it properly Smile

The current probe I use is a Honeywell CSNR161,  DC-150kHz with 0.5% accuracy, it's nice little device Smile

I have a 0.65mH inductor here that will take 50A plus (an air cored beast from an old UPS) so I could use that but I don't have anything around 2mH. I don't suppose it would matter much, I could just change the test frequency to get the phase shift needed. I would expect the class-D to be very good with inductive loads (and capacitive ones) owing to its 4-quadrant operation. If I get the time i'll try something, what conditions would you suggest?


Edited by teslaman - 24 July 2012 at 6:56pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote teslaman Quote  Post ReplyReply Direct Link To This Post Posted: 24 July 2012 at 7:38pm
Originally posted by U.Viktor U.Viktor wrote:

The 80A peaky line current draw comes from the AC line current distortion due primary side peak rectification.
This is not a real problem for the IEC connector but could have serious consequences if many of these connected to the power network, It is a PROBLEM for the electrical service provider, circuit breakers and especially risky when diesel generator is the power source!
It has a high probability not only KILLS the amps itself but hurting other sensitive equipments connected to the same network (CD players, mixers, etc..)
It is not a big surprise that most of modern high-power amplifiers have power factor correction (PFC) to eliminate these potentially killer current peaks...

As already mentioned there are a lot of products out there just as bad, why would this one be any worse?
I doubt that a flatted-top sine wave caused by this kind of load would cause any harm to other equipment, why would it?

Originally posted by snafu snafu wrote:

so it doe's roughly what it says on the tin ?.
As expected.
Good on behringer, keep up the good work.


Yes, I think it does and for the "weekend warriors" like myself £270 gets you a powerful, efficient bass amp! Since it's not bad run full range either then it could get you out a tight spot if your mid-top amp went down too but I'd stick with class-AB for that myself I think.

Originally posted by U.Viktor U.Viktor wrote:

Anything bellow 1% THD is OK. 
THD is not the most important thing how well a professional amp would perform.
However the lack of real output feedback in the iNUKE is a serious problem and renders this amp USELESS anywhere above driving sub sections. The undamped/uncontolled output LC filter causes unpredictable signal level variations with different speaker loads probably creates huge spikes in the mids/high freq. range.
I have seen/heard first series PKN amps ~10years before with similar problems so Behringer should have learnt something :-)
That KAM has at least two blatant design mistakes 1. see those electrolyte caps in the HOT airflow(!) 2. see the "PFC inductor" has made from single layer insulated magnet wire (light yellowish). Also the winding technology of that inductor deserves a possible failure due insulation weakness+bad construction.

Those design mistakes will be paid by poor guys without understanding of electronics and believe that a sub ~200EUR amp could be reliably good for their applications. Of course NOT.


Whether 1% THD is OK or not depends very much on what the spectrum of it is. 1% of low-order (2nd, 3rd, 5th harmonic) is normally fine but if it was huge amounts of 9th, 11th, 13th, etc. then it would sound horrible, especially as a mid-top amp.

The iNuke does have "real" feedback, its whole topology depends upon it to function, but I guess you mean it's taken before the output L-C filter. I don't agree that's always a big problem, the DCR of the inductor is likely 20-30 mOhms and the output impedance of the closed-loop power stage will be very low, especially at low frequencies. The output impedance of the amp is therefore going to be very low until the highest audio frequencies and so it doesn't matter what the load impedance swings are like they will not significantly affect the response of the amp. To calculate a number let assume the output impedance of the amp is bad, say 100 mOhms. If the load impedance went from 2 Ohm to 1000 Ohms then the output level would vary by just 0.21dB, I wouldn't say that's a disaster! The resistance of the speaker cable is likely to be far more significant so the amp is pretty blame-free all of a sudden....

On the Kam PFC inductor I would entirely agree it looks a bit weedy and badly constructed, I would at least expect it to be dipped in varnish to stop the windings vibrating.

Originally posted by spongebob spongebob wrote:

Teslaman - I can't confess to understanding all of the technical details that you have provided in these posts, but I would like to thank you for such an in-depth contribution to this forum. Do you think you will be reviewing other amplifiers in a manner similar to the above?

If there are any "interesting" amps out there that people want testing then I will consider it. The only problem is time as I don't have much and it takes quite a while to do all this stuff. The reason I was keen with the iNuke and Kam is because they are cheap and yet promise great power, if they lived up to their names then they are game changers for the weekend warrior types like myself. As it is I think they are good for bass, especially at 8 Ohms per channel, and not too bad for full-range or mid-top use though I would still prefer a class-AB in this role.

Originally posted by infrasound infrasound wrote:

Thanks as well.

Great writeup, but the current comparison in the PFC section isn't so clear (although I can tell, doesn't make clear which is Berry, and which is Kam)

Feel free to give your opinion on sound quality (perhaps compared to the QX?), complete with disclaimer Smile

Yes sorry for that, I'll re-read and make it clearer.
My listening tests were a bit flawed due to the venue but I may still give an opinion, maybe Tongue

Originally posted by Muckerbarnes1 Muckerbarnes1 wrote:

Good work David.
 
With such high current variation I would not like such a device in any rack with any brand name. Also miffed at the linearity of the amps. Very poor.
 
The Behringer's storage is somwhat less at operating voltage. 10.6F x 84V = 890.3 Coulombs x 2 (rails) = 1780.8 Coulombs = 74.8 Joules. This is 17.9 calories... They are deffo LOW CALORIE  LOL

Already covered the current thing but can you elaborate on your disappointment with the linearity. I guess you mean the THD? I didn't think it was too bad but certainly no decent class-AB!

The energy figures I used included the primary side capacitor storage as that is very relevant for switch-mode supplies, that energy is just as accessible from the secondary side as from the secondary caps directly. Yes there are some small losses in the transformer and switching devices but that energy is still available to the amp.
How it compares to a 4kW class-AB is a relevant point but I dont really have one I can take figures from. If it were to have say 40,000uF per rail and a rail voltage of 150V then the class-AB would have an energy storage of 900J. From that perspective the Class-D's are a bit lightweight and hence cannot generate the same power at 31Hz as they can at 1kHz. They're not disastrous by any means though.

Originally posted by kedwardsleisure kedwardsleisure wrote:

im confused about the storage figures,surely ripple is a better measure than capacitance?

Ultimately for the period of time between refreshes (100Hz for our 50Hz mains) its the energy stored that will be used to fill the gaps. A smaller stored energy will lead to a faster lowering of voltage, or more ripple, hence the two are related. Its just easier for people to comprehend I thought, ripple is of no concern to the end user, just the available undistorted output power.

EDIT for spelling


Edited by teslaman - 25 July 2012 at 9:23am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote audiomik Quote  Post ReplyReply Direct Link To This Post Posted: 24 July 2012 at 9:50pm
David
thanks for your replies

Re: "he current probe I use is a Honeywell CSNR161, DC-150kHz with 0.5% accuracy, it's nice little device

Firstly your current probe may struggle with it's bandwidth limit to really see what's happening to the current output with an Inductive component in the load.

Do you have a differential input Analog 'scope with a 'third' input such as simultaneous trig view or better still 4 Channel?
If so, then use the differential input to look at the current by using a low value non-inductive power resistor (a number of 2 Watt metal film type in parallel for approx 0.1R) and the third/fourth inputs to look at the Amplifier Output Voltage and act as a sync source.

Your 0.65mH should be fine, try 2kHz input signal to start with when you have 4 Ohms resistive in series.... it still gets nearer than purely resistive to simulate a 'real driver'. You won't need high output levels to see what's happening and an FFT/Spectral analysis of the Current waveform at different Amplifier Output Voltages if you can do that will be interesting

keep up the good work!

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Post Options Post Options   Thanks (0) Thanks(0)   Quote simonh Quote  Post ReplyReply Direct Link To This Post Posted: 24 July 2012 at 10:25pm
Have to agree with spongebob Dave and thank you for taking the time out to carry out such a detailed analysis.  Now I must confess it's way over my head but it's clear to see that's it useful and beneficial to the guy's in the know.  Cheers S.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Nick Sasquash Quote  Post ReplyReply Direct Link To This Post Posted: 24 July 2012 at 10:33pm
Telslaman.... quality work, keep the amp tests coming Clap
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Post Options Post Options   Thanks (0) Thanks(0)   Quote vibez Quote  Post ReplyReply Direct Link To This Post Posted: 25 July 2012 at 7:34am
Having read this thread yesterday i decided to try my inuke (that usually run monitors ) on sub just for the fun ofit. I must confess that i was quite suprised by the result. i hung two 1850 loaded scoops off each channel and this little budget amp spanked them pretty well. I must admit that i wouldn't feel absolutely comfortable using this on sub long term but for emergency situations i wouldn't hesitate to use this to get me out of trouble. The only thing i did notice was that when it hit clip level the limiting was very audible but once limiter on dcx was set to prevent this it sounded pretty good and certainly delivered more bang per buck than i have ever heard from an amp in this price range. Haven't tried the dsp yet but will have a play at the weekend when i have more time.

Top review and suprisingly good budget amp
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MessyM2k8 Quote  Post ReplyReply Direct Link To This Post Posted: 25 July 2012 at 10:18pm
Nice report.
Out of interest, what test gear are you using?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote VentureSound Quote  Post ReplyReply Direct Link To This Post Posted: 26 July 2012 at 12:23am
Teslaman, thanks for all your tests, it was a very interesting read indeed.  I would be keen to see some similar results on a Peavey IPR series, as I guess they are somewhat comparable being class D, 'new generation' and cheap.
I've heard an IPR on subs and was suprised as well, sounded pretty good to me! Cannot remember the model, but it was one of the lower ones like 1-2KW.


Edited by VentureSound - 26 July 2012 at 12:24am
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Post Options Post Options   Thanks (0) Thanks(0)   Quote mini-mad Quote  Post ReplyReply Direct Link To This Post Posted: 26 July 2012 at 1:22am
i think what you have done is superb.
as suggested a few more "compare-the-power-amp.com"s would be very welcome by one and all.
you are a true soldier to the cause and i wish to thank you for all your hard work and the right up has been a damn good read.... gotta love those thermal pics too!!

keep up the good work and we all thank you for your time.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote bitSmasher Quote  Post ReplyReply Direct Link To This Post Posted: 26 July 2012 at 4:06am
Originally posted by VentureSound VentureSound wrote:

I've heard an IPR on subs and was suprised as well, sounded pretty good to me! Cannot remember the model, but it was one of the lower ones like 1-2KW.
Interestingly I'd read on another forum, a comparison between an iNuke and IPR - all subjective of course - with the user claiming the IPR sounded better on subs than the iNuke... with the IPR DSP about to arrive in Australia I'm keen to see some solid opinions and tests before I decide to buy one (or many)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Timebomb Quote  Post ReplyReply Direct Link To This Post Posted: 26 July 2012 at 2:01pm
Id be interested to read that if you've got a link BitSmasher?

I would be very keen to see measurements of the Peavey IPR and the Crest Prolite,  it seems only the smaller 2 models are available though, the larger ones have been forthcoming for several years now, and in the UK we haven't even got the IPR3000 yet i dont think.  They are defiantly on the short list for budget lightweights though.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote MessyM2k8 Quote  Post ReplyReply Direct Link To This Post Posted: 26 July 2012 at 5:16pm
Originally posted by VentureSound VentureSound wrote:

Teslaman, thanks for all your tests, it was a very interesting read indeed.  I would be keen to see some similar results on a Peavey IPR series, as I guess they are somewhat comparable being class D, 'new generation' and cheap.
I've heard an IPR on subs and was suprised as well, sounded pretty good to me! Cannot remember the model, but it was one of the lower ones like 1-2KW.


Peavey IPR 1600 Tested here


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