Behringer iNuke NU3000 Measurements

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ICG

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Speaking of ticking bombs inside Behringer equipment - I found something interesting in the IRS4227 data sheet that I hadn't noticed before. It states that the die attach in the D2pak (RoHS version of course) is subject to wear out after 1000 thermal cycles. By wear out it means a 50% increase in Rth. Must be some sort of epoxy. It will take more than that to die, but it eventually will, just like the old aluminum TO-3. Found out about that from the 78xx regulator data sheets. The TO220 has no such warning but is "not recommended for surface mounting". Crack them open and they are definitely soldered. With a package with that small a thermal mass it's not that hard to rack up several thousand thermal cycles at subwoofer frequencies.

The thermal cycles are not equal to the frequency nor the times it is switched on and off. The thermal cycle in semiconductors is counted from a temperature of ambient temperature (or even the lowest operational temperature spec, which is -10, -20 or even -40°C) to the highest operational temperature, which is around ~150°C. As long as the amplifier got a working cooling system of any kind and no (artificial) heat spots, there are no thermal cycles. These cycles are usually only reached in extreme lab enviroments while testing cycles. So no, that are not 'time bombs'.
 
Some right and some wrong information here.

The IRFS4227 datasheet states that thermal resistance junction to case increases from .45 C/W to .65 C/W after 1000 thermal cycles. This is called at "end of life" because themal resistance stabilizes at the latter value until "end of life" of device, not because the device ceases to operate. These values are lower compared to thermal resistance from the device to the air, about a few C/W in this application, so a 10:1 ratio, negligible loss of thermal performance.

On the other hand the idle dissipation in these transistors is low, and they are fan cooled permanently. This results in the transistor dies being close to ambient temperature at idle power and being close to maximum temperature at full power at low impedance load and/or bass duty. There is very little thermal mass. So there are *full* thermal cycles, following music program intensity, taking place in these amplifiers at low load impedances and/or bass duty. Not at 8 ohms full range, of course. A "thermal-cycling life test fixture" could be the optimum sarcasm.

It's well known that wide thermal cycles reduce the life of SMD boards, causing intermittent solder joints requiring rework or in some cases replacement when many parts blow due to an open connection. Fortunately the output stage uses IRS20957 control circuit with built-in short-circuit protection, this will limit the degree of damage in case one FET becomes shorted due to open gate. This protection is not even found in many class D subwoofer power modules from Harman group discussed in some threads here, so the INUKEs are better than that.

In fewer words: There will be intermittent solder joint problems in these amplifiers when operated at lower impedances and/or low frequency duty, repairable in many cases.

The power supply has a similar pair of anti-feature and feature, the gates of the IGBTs are transformer-driven to act as a firewall, because such IGBTs can fail exploding and leaving a hole in PCB if one gate becomes open. Another solution in SMPS is to use power zeners and fusible resistors to contain damage in the unfortunate but common case the gate of a power transistor becomes shorted to the drain, done in the best circuits, often underlooked, just repaired by swapping the transistor and blown gate resistor.

The PCB approach used in more reliable equipment is to have separate SMD boards, of materials and thicknesses optimized for long life of SMD, containing all small signal circuits, and the use a main board of materials optimized for rigidness and power handling, with thru-hole power devices mounted to a heatsink.

Also, the cooling approach used in more reliable equipment is to allow the heatsinks to heat to relatively hot before starting proportionally driven fans, this reduces amplitude of thermal cycles, as the heatsink is allowed to keep hot from one high power passage to the next.

The attached picture shows a *reliable* prototype capable of 2x1000W/8r (BTL) short term (for a few milliseconds, as other products are sometimes rated), >1800W for a few seconds @ 230V, and >600W for indefinitely long period with 50mm fan, 3:1 crest factor. *Reliable* in the sense that it does not exhibit substantially faster aging when operated at maximum ratings, and self-diagnostic too, it gives different fault codes when operated outside ratings, to help locate the problem, even from remote location.

And this other picture shows INUKE:
1e49d520_inuke1000-amp-amplifier-fan-swap.jpeg
 

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Yes, IRGB20B60PD1

Relatively good, but there are newer like IKP20N65H5, one of my preferred ones. With help of 1~10 nF capacitor and gapped core for minimum magnetization current, IGBT can achieve very low loss in amplifier SMPS, also idle loss. INUKE power supply has no resonant switching, and it could have because it is not regulated, duty cycle is fixed at close to maximum, _SHDN pin is the only one driven in the SG3525A.

From the sociological point of view, amplifiers like INUKE are karma checkers, it will last reasonably if there is fair people at the party, parties of friends I mean, including techs in process of learning, and may blow otherwise. The next reliability level does not have that "feature" haha. Karma checks in a sustainable world should be performed only with biodegradable and renewable resources, like fights of throwing surplus tomatoes.

EDIT: I just noticed the symbol shows a MOSFET, but the part number is a fast IGBT with diode from IR.
 
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Some right and some wrong information here.

The IRFS4227 datasheet states that thermal resistance junction to case increases from .45 C/W to .65 C/W after 1000 thermal cycles. This is called at "end of life" because themal resistance stabilizes at the latter value until "end of life" of device, not because the device ceases to operate. These values are lower compared to thermal resistance from the device to the air, about a few C/W in this application, so a 10:1 ratio, negligible loss of thermal performance.

On the other hand the idle dissipation in these transistors is low, and they are fan cooled permanently. This results in the transistor dies being close to ambient temperature at idle power and being close to maximum temperature at full power at low impedance load and/or bass duty. There is very little thermal mass. So there are *full* thermal cycles, following music program intensity, taking place in these amplifiers at low load impedances and/or bass duty. Not at 8 ohms full range, of course. A "thermal-cycling life test fixture" could be the optimum sarcasm.

It's well known that wide thermal cycles reduce the life of SMD boards, causing intermittent solder joints requiring rework or in some cases replacement when many parts blow due to an open connection. Fortunately the output stage uses IRS20957 control circuit with built-in short-circuit protection, this will limit the degree of damage in case one FET becomes shorted due to open gate. This protection is not even found in many class D subwoofer power modules from Harman group discussed in some threads here, so the INUKEs are better than that.

In fewer words: There will be intermittent solder joint problems in these amplifiers when operated at lower impedances and/or low frequency duty, repairable in many cases.

The power supply has a similar pair of anti-feature and feature, the gates of the IGBTs are transformer-driven to act as a firewall, because such IGBTs can fail exploding and leaving a hole in PCB if one gate becomes open. Another solution in SMPS is to use power zeners and fusible resistors to contain damage in the unfortunate but common case the gate of a power transistor becomes shorted to the drain, done in the best circuits, often underlooked, just repaired by swapping the transistor and blown gate resistor.

The PCB approach used in more reliable equipment is to have separate SMD boards, of materials and thicknesses optimized for long life of SMD, containing all small signal circuits, and the use a main board of materials optimized for rigidness and power handling, with thru-hole power devices mounted to a heatsink.

Also, the cooling approach used in more reliable equipment is to allow the heatsinks to heat to relatively hot before starting proportionally driven fans, this reduces amplitude of thermal cycles, as the heatsink is allowed to keep hot from one high power passage to the next.

The attached picture shows a *reliable* prototype capable of 2x1000W/8r (BTL) short term (for a few milliseconds, as other products are sometimes rated), >1800W for a few seconds @ 230V, and >600W for indefinitely long period with 50mm fan, 3:1 crest factor. *Reliable* in the sense that it does not exhibit substantially faster aging when operated at maximum ratings, and self-diagnostic too, it gives different fault codes when operated outside ratings, to help locate the problem, even from remote location.

And this other picture shows INUKE:
1e49d520_inuke1000-amp-amplifier-fan-swap.jpeg

Your prototype mounting technique:

How is < 600W of power dissipated using x6 TO-220 packages mounted on the PCB underside, fixed using the PCB as a mount, surely this isn't safe ?
 
Your prototype mounting technique:

How is < 600W of power dissipated using x6 TO-220 packages mounted on the PCB underside, fixed using the PCB as a mount, surely this isn't safe ?

Lets assume 85% efficiency at 2000W. This is 300W loss, about 21W * 14 power devices. Thermal grease starts to be effective (low thermal resistance) at low contact pressure, as long as it does not drain/void, contact surfaces are flat, and part to part TO-220 height tolerance is satisfactory. The PCB shown is 2oz 4 layer, so it actually provides some pressure. Also there are 6 screws on each side.

There are also those compressible thermal pads of different thickness, compressibility and thermal conductance, mostly used in computers, but don't think they are better than alumina pads and thermal paste in terms of thermal resistance.
 
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Lets assume 85% efficiency at 2000W. This is 300W loss, about 21W * 14 power devices. Thermal grease starts to be effective (low thermal resistance) at low contact pressure, as long as it does not drain/void, contact surfaces are flat, and part to part TO-220 height tolerance is satisfactory. The PCB shown is 2oz 4 layer, so it actually provides some pressure. Also there are 6 screws on each side.

There are also those compressible thermal pads of different thickness, compressibility and thermal conductance, mostly used in computers, but don't think they are better than alumina pads and thermal paste in terms of thermal resistance.

Thanks for the insight. It does appear in your picture that the FR4 board is slightly stressed(curved) and may be fatigued, but then again this is a prototype. What you say is true, a computer CPU shows obvious effects when thermal compound dries, I remember my Intel 3.0GHz CPU alert utility all of a sudden started reaching its default thermal threshold.
 
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The board is intended to be bent, SMD is properly oriented and pads have thermals. Only SMD parts close to inflection points at the center are decoupling caps (1206/1210), snubbers (1206), diodes (SMA/SMB), and sensing NTCs (0603). Bend is across ~75mm length. Have you tried bending a 2oz 4 layer PCB like that? Requires >1 kilogram per pair of TO-220 devices. Material is good fiberglass, 2 copper planes at both sides and 2 in the middle. And you are right that it is a prototype, I'm evaluating it: loosening the screws after a year of operation results in PCB becoming nearly straight again.
 
Some right and some wrong information here.

The IRFS4227 datasheet states that thermal resistance junction to case increases from .45 C/W to .65 C/W after 1000 thermal cycles. This is called at "end of life" because themal resistance stabilizes at the latter value until "end of life" of device, not because the device ceases to operate. These values are lower compared to thermal resistance from the device to the air, about a few C/W in this application, so a 10:1 ratio, negligible loss of thermal performance.

On the other hand the idle dissipation in these transistors is low, and they are fan cooled permanently. This results in the transistor dies being close to ambient temperature at idle power and being close to maximum temperature at full power at low impedance load and/or bass duty. There is very little thermal mass. So there are *full* thermal cycles, following music program intensity, taking place in these amplifiers at low load impedances and/or bass duty. Not at 8 ohms full range, of course. A "thermal-cycling life test fixture" could be the optimum sarcasm.

It's well known that wide thermal cycles reduce the life of SMD boards, causing intermittent solder joints requiring rework or in some cases replacement when many parts blow due to an open connection. Fortunately the output stage uses IRS20957 control circuit with built-in short-circuit protection, this will limit the degree of damage in case one FET becomes shorted due to open gate. This protection is not even found in many class D subwoofer power modules from Harman group discussed in some threads here, so the INUKEs are better than that.

In fewer words: There will be intermittent solder joint problems in these amplifiers when operated at lower impedances and/or low frequency duty, repairable in many cases.

The power supply has a similar pair of anti-feature and feature, the gates of the IGBTs are transformer-driven to act as a firewall, because such IGBTs can fail exploding and leaving a hole in PCB if one gate becomes open. Another solution in SMPS is to use power zeners and fusible resistors to contain damage in the unfortunate but common case the gate of a power transistor becomes shorted to the drain, done in the best circuits, often underlooked, just repaired by swapping the transistor and blown gate resistor.

The PCB approach used in more reliable equipment is to have separate SMD boards, of materials and thicknesses optimized for long life of SMD, containing all small signal circuits, and the use a main board of materials optimized for rigidness and power handling, with thru-hole power devices mounted to a heatsink.

Also, the cooling approach used in more reliable equipment is to allow the heatsinks to heat to relatively hot before starting proportionally driven fans, this reduces amplitude of thermal cycles, as the heatsink is allowed to keep hot from one high power passage to the next.

The attached picture shows a *reliable* prototype capable of 2x1000W/8r (BTL) short term (for a few milliseconds, as other products are sometimes rated), >1800W for a few seconds @ 230V, and >600W for indefinitely long period with 50mm fan, 3:1 crest factor. *Reliable* in the sense that it does not exhibit substantially faster aging when operated at maximum ratings, and self-diagnostic too, it gives different fault codes when operated outside ratings, to help locate the problem, even from remote location.

And this other picture shows INUKE:
1e49d520_inuke1000-amp-amplifier-fan-swap.jpeg

:nod:really good explanation,thank you.
 
Wow, these INUKE amplifiers are designed in a hurry and with very low budget. Anti-features:
- Pre-filter feedback class-D, IRS20957 used in IRS2092 mode.
- Maximum dead time setting in IRS20957.
- No current limiting in speaker outputs, just over-current shutdown.
- Thermal fan speed control, but no thermal limiting, just thermal shutdown.
- Clip limiter is driven from level at input of amplifier, not from true output clipping, -9dB maximum attenuation.
- Power supply is not regulated, control circuit is inspired by old QSC or the like.
- Power supply has no current limiting, just over-current shutdown/hiccup mode.

Thanks for posting the schematics.


Hello all, hello eva (we have a fighting background here in the forum).


This posting is to celebrate the 6th anniversary of my first post within this thread (30th of may 2012). I changed my mind about inuke since I got myself an inuke 6000DSP for use from 100 Hz and up.
Pre filter Feedback: not the highest end circuitry, but OK for me. You can always adjust the EQ, pull or push some db at 18kHz to match the connected speaker using the internal DSP. Also, you can save different setups for different Speakers.
As for thermal Change in the Response of high freq Content because of Feedback be4 the filter: the change is both slow and low in amplitude compared to the situation at a concert in the 2nd row and some guy in front of you is rising hand - effectively blocking the direct path from compression tweeter to your ears. 30, 35db.... level change at 18kHz - instantly! And who cares? Nobody.


PSU copied from old QSC design? It works.
Components undergoing thermal cycles? Just Limit use case to 8 Ohms (still 2 x 1050 Watts RMS at 8 Ohms - inuke 6000DSP - for cheap) - this will greatly increase reliability. And if the amp finally blows after years, there is always a dustbin big enough to eat the amp. BTW - for EUR 400, I get a new one. Who cares? Nobody. At least for "non critical missions". I am doing some light DJing at local parties - that is inuke use case - not "Touring".
In contrast: If my XTI6002 blows, that would be more of a blow financially (I use it for subwoofers <100Hz). I love both my amps, but the inuke 6000DSP is almost as good as the XTI6002 - at 16% of the cost!
PSU has no current limiting just hiccup mode? Great issue maybe at 2 Ohms, but again - if you use it at 8 Ohms...Who cares?. THE KEY TO ALL OF THESE ISSUES IS DE-RATING - use it at lower continuous power, at higher ohmic loads, or both.
Noisy fan? Not an issue in professional use!
In other (home use) cases : -> swap both fans by Arctic F8 and limit the use case to 2 x 450W at 8 Ohms (with the bonus of short 2 x 1000W power bursts still possible - what a 2 x 450W amp cannot do). This will suffice for most "domestic" use-cases.
 
OK, it can be considered reliable driving two 8 ohm loads at 1000W, >80Hz , for 400 euro. That's 5W/euro.

What if you want to drive eight 8 ohm loads at 1500W? 1500*8/5=2400 euro!
Are you actually making any savings? No.

Can this gear be repaired or recycled easily? No.
Is good for any land to pay the Chinese for doing more testosterone work, to do less testosterone work in the land?

EDIT: I have one proposal for you. Do you have a capacitance meter? Could you measure the electrolytics in the inuke 6000 you say is lasting 6 years? Could you make a rough estimation of total working hours at full volume during those 6 years? Could you post quality pictures of the PCB to determine signs of aging after 6 years?
 
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@Eva, sorry I meant to say my first post within this thread was exactly 6 years ago - the iNuke that I have was purchased later - and opened / cleaned when I did the fan mod. No idea how long it will last but if it fails and turns into a smoking cloud in a few years, the financial pain of getting a new one for me will be negligible compared to the pain I feel for not selling my Bitcoin 5 months ago.
 
@Eva, I just checked your site, SPKPWR.
Seems, at least per the datasheet, the SP2-12000 would be up to the task of 4 x 8 Ohms / 1500W per channel on 230V AC. Not sure if that is true for continuous subwoofer use, but if true - this would be a tremendous value, having that power in 2 units of rack height. There must be something to these amps if guys like Danley Sound Labs use it. I don t think this beast is available here in europe - at least it is not widespread. If it was - due to tax and duty - the cost would be north of EUR 3000 I am pretty sure. Anyway - very interesting for me!
about the iNuke / back to topic: I am not a paid Behringer guy, so I ll tell you the disadvantages also: The 2 sensitivity knobs on my unit have coarse grating and bad matching (what I 've experienced to a lesser degree also on XTI6002), plus on the iNuke, one of them seems stiff / hard-steering. Very cheap design.
Initially, I had a Camco D Power 2 for the top speakers (Class H), that had no any issues (I d see the clip lights very rarely). When one channel started to randomly fail in summer of 2015, I got into warranty discussion for weeks with the company in Wenden/Sauerland. They did not find the issue on the amp, but after weeks agreed to send me a replacement issue. During that weeks, I couldn't play music and I remembered that I had an unopened iNuke6000DSP from Thomann in my storage room, that I 'd bought in Dec of 2014 for the most incredible price of the century: EUR 329 shipped (!!), just to sell it later for ~EUR 380, what I had forgotten to do. So I hooked it up, and have since never gone back to Camco, nor have I ever again seen any clip light. The Camco is still under 6 year warranty, but I can't sell it used, even at half price, although I am pretty sure the sound quality of that class H amp is WAY higher than iNuke's - the loss seems to be about EUR 600.
Bottom line: With an amp that cost EUR 329 shipped initially, there is NO WAY EVER to reach a painful loss of EUR 600 or more.
 
FWIW, Behringer lists these specs in the iNuke 3000 DSP brochure.

Not Found Page | Music Tribe - Behringer

NU3000:
RMS
Stereo
-------
8 Ohm per channel, stereo 315 W
4 Ohm per channel, stereo 620 W
2 Ohm per channel, stereo 1040 W

Bridged mono
---------------
8 Ohm 1250 W
4 Ohm 2075 W

Seems to be as measured above.

is this what its tested in a real bench and not berhinger dream watts is it tested like this guy did

YouTube

its nice to se real watts and ok behringers amps plays good.

this evning i playing with one behringer nu3000 for the tops and a nu6000 for the base and its insain for the low price
 
I can’t find the input level specs for my NU3000DSP anywhere, so I’ve just done my own tests. The results, given the comments above, were surprising:

I set the amp up with a variable amplitude 600 Hz sinewave input, and a resistive 8 ohm 50 watt load on the output of one channel. The amp was in stereo configuration, not bridge. I ran the test with output voltage across the load of about 12 volts peak (24v p-p), corresponding to an output power of about 8 watts RMS. Nice and low to avoid damaging anything.

With the gain control set at 12 o’clock, more or less middle of the range, the input to achieve *8 watts* output was about *1 volt peak* (2 volts p-p).

With the gain flat out, the input to achieve 8 watts was about 200mV peak.

This is dramatically different to what’s reported above (300W @ 0.75v input at 50% gain). I decided to post here in case others are seeing a similar anomaly, in other respects my amp works fine, and both channels have the same behavior, but this is Australia, and the export model may be ‘different’. BTW, my test results are guaranteed correct, done with professional test gear.

With an amp of the sensitivity that I have, there are considerations when driving it with typical professional sound gear, which often has clipping limits of only a couple of volts +/-. With the gain at 50%, an input of 2 volts peak will give an output of only about 30 watts, not 300. If you want more, you need to increase the gain. If you want to retain a fair degree of upside adjustment on the amp itself, you’ll need to drive it with a source with reasonable voltage swing capability.

None of this is a problem for me because I drive the NU with a source with plenty of output swing capability. Given that the input sensitivity is not included in the specifications in my manual, it was just a matter of DIY, however it is odd to not have such a key parameter specified.
 
No, it’s a normal single ended source (voltage to ground). I added the p-p value because I figured that some readers might misinterpret peak.

To clarify the test conditions:

Input (50% gain) 1 volt peak, approx. 0.7 volt RMS.
Output (both tests) Approx 12 volts peak, 8 volts RMS (more or less). Equates to 8 watts RMS output power across 8 ohms.

Hope that clarifies, sorry for the confusion.

One more point, there is a reference in prior posts to config settings for input and output gain. I can’t find anything like that on my unit.

HTH
 
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