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Guess I have to void the 3 year warranty. I hoped being the small one, sitting inside a closet, and the variable speed would be enough. Not so. I'll let it run a few days first.
 

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did a noctua nf r 8 fan swap on the 3000dsp without any of the included resistors and as it got hot, the fan speed seemed to ramp up and it was still way to loud! I am assuming it was hitting the Noctua top speed at 1800rpm? the kit came with two resistors, one that limits at 1300rpm and one at 900 i think, I soldered in the 1300rpm and a huge difference, and much better. Is there a consensus on which one to use? has anyone tried the 900rpm limit? i would worry about not enough air movement..
 

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The Ultimate Behringer iNuke NU3000DSP Fan Mod (CLICK HERE FOR PICTURES):




After purchasing an iNuke, I found the stock fan far too loud for home theater use. I liked seeing what people were experimenting with here (slower fans, inline resistors to slow down the stock fan, natural convection), but I didn't like the compromise that in almost all cases the capabilities of the fan were reduced or eliminated. Aside from the lowered cooling ability, I was concerned that any fan bearing, no matter how silent, would not address the issue of the noise form the air rushing out of the louvers in the front bezel. This mod not only reduces the fan noise to imperceptible levels, but also substantially increases the heatsink area and CFM of air flow.

I chose a fluid dynamic ball bearing because it is the quietest and longest lasting type of case bearing available. I went with the Cougar 140mm fan because it has a true Matsushita designed fluid dynamic bearing. Here is an excellent write up and a list of fans with the best fluid dynamic bearings: fan bearings. Another benefit of the Cougar, aside from its impressive build quality, is the inclusion of an inline resistor that will drop the fan from a maximum of 1200rpm (19.2dB) to 700rpm (16.4dB). I did not use the resistor since the system is absolutely imperceptible at a couple meters, but even with the resistor installed, this fan will still push as much air as the stock fan. Without the resistor, this fan flows 70.5CFM (19.2dB) compared to the stock fans 55.5CFM (40.9dB). Make sure to get the 3-pin design and not the 4-pin PWM fan. This fan has some awesome rubberized insulation that I didn't want to screw up, so I just used a cheap 3-pin to 2-pin adapter listed below. The one down side of the Cougar is it doesn't include a fan grill. I picked up a 2-pack from newegg.com for $5. I'm not into a flashy home theater, so I went with the black fan, but it is also available in a bright orange blade fan that will match the iNuke.

As for the heatsinks, I used black anodized aluminum 28x28x13mm IC heatsinks. I would have used straight fin heatsinks below the fan for improved cooling performance, but I ultimately chose the cross cut style because I could not predict how air would flow across the heatsinks on the power supply side and I didn't want to buy two different types. I first cleaned all of the tabs with a little alcohol to remove any oils. By bending the output stage MOSFET heat tabs up to about a 60 degree angle a heatsink can be mounted on the top and bottom. I left the power supply heat tabs flat and placed a single heatsink on top of each. Make sure none of the adjacent heatsinks are able to touch each other, and also make sure the power supply heatsink fins are inline so they don't block flow from each other or cause unnecessary turbulence.

I masked off the lid and took measurements of the internal components to be able to layout the cutout for the fan. Make sure to measure repeatedly and keep track of the front, back, left, and right. After determining a center point, I took a nail a punched in an impression to guide the pilot bit of the hole saw. I fortunately already owned a 5 1/4" hole saw, but if you don't, then you will have to figure in an additional $35 for a hole saw from amazon.com. Once the hole was cut out, I used a pocket square and the fan grill as a guide to punch and drill the fan mount holes with a 13/64" drill bit. I then cleaned up the cut aluminum with a rat-tail and flat basterd file (I had to misspell this since this site doesn't like the proper name of a tool).

I installed the fan utilizing the included rubber mounting tabs and then snipped off the ends. I didn't want to have a gaping hole in the back (lol), so I purchased a few 8-32 machine screws and reinstalled the stock fan grill. I was considering cutting a piece of the stock fan shroud and limiting the amount of air that could flow directly out of the back, but after running it, I believe there is plenty of cold air flowing out of the front of the amp even with the back completely open. In the end I have an amp that is effectively silent, yet is cooled far better than the stock Behringer design. I am very pleased with it, and I do not baby it in anyway. The obvious limitation is that nothing can be set on top of the top-mounted fan, and if it is rack-mounted, it will have to have an open slot above it. My total cost was $42.04. If you have to buy the hole saw and a role of masking tape, figure the price at about $80. This puts a silent "3000w" home theater amp with on board DSP at about $360.

Read more here: http://www.avsforum.com/forum/155-diy-speakers-subs/1876417-ultimate-behringer-inuke-1000-3000-fan-mod.html#post31387689

The Stock Fan

For anyone wondering, the fan in a recently shipped iNuke300DSP is a "Bi-Sonic BP802512HL-03-W". It is a 12V 80x80x25mm 2-pin fan with a maximum of 55.53CFM at 4000rpm and a stated 40.9dB-A

Here is the datasheet: http://datasheet.octopart.com/BP802512HL-03-W-Bi-Sonic-datasheet-525890.pdf

These are a couple interesting links I found when looking for the best heatsink design:


Why you should consider straight fin heatsinks, if possible, when you know the direction of airflow:
https://www.aavid.com/sites/default/files/technical/papers/elliptical-pin-fin-heatsink.pdf

Why you should choose anodized heatsinks for natural convection systems:
http://www.aavid.com/product-group/extrusions-na/anodize

PARTS:

COUGAR CF-V14HB Vortex Hydro-Dynamic-Bearing (Fluid) 300,000 Hours 14CM Silent Cooling Fan (Black) - $17.99
http://www.newegg.com/Product/Product.aspx?Item=N82E16835553007

APEVIA G-140MM 140mm Fan Grill 2 in 1 pack - $4.99
http://www.newegg.com/Product/Product.aspx?Item=N82E16811998078&cm_re=140mm_fan_grill-_-11-998-078-_-Product

FREE Shipping 10pcs 28x28x15mm Cheap CPU Black Aluminum Heatsink With Blue Thermal Conductive Double Sided Adhesive Tapes - $15.00
http://www.aliexpress.com/snapshot/6451300353.html?orderId=65459518779892

30cm Fan Adapter Cable Case Ventilation 3-Pin Plug 2-Pin Jacket Coupling - $2.50
http://www.ebay.com/itm/30cm-Fan-Adapter-Cable-Case-Ventilation-3-Pin-Plug-2-Pin-Jacket-Coupling-/331312882600?

4x 8-32 Machine Screws with Washers and Nuts - $1.56
 

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LOl I went and hacked my NU-1000DSP before I thought to look for what others have done.

I built a circuit that reduces the minimum voltage to the fan. From the factory the Behringer applies 7.6V minimum to the fan, which is pretty noisy, ramping up to 16V(!) with temperature. The (noisy) fan that comes with the unit starts up at 3.9V and shuts at 3.6V. The circuit I built applies 3.6V to the fan at ~8.5V input. This voltage ramps up to around 14V when 16V is applied.

Like many others, I glued some small heatsinks to the 4 MOSFETs to reduce the fan requirements.

The result is that when the unit is stone cold the fan does not run. When playing, the fan sometimes cycles on and off at a very low, inaudible speed. I'm quite pleased.

The circuit will cause the transistor to get a bit hot under some conditions, so I placed it in the breeze, by using one of the slits in the plastic shroud and pulling the wires through. I knotted the wires so the circuit is hanging in the breeze. I entombed the exposed conductors of the "hairball" circuit in high temp hot melt, but left the transistor's tab exposed.

The zener needs to be a low-current 1/2W BZX type.
The capacitor quiets some squealing (oscillation? power supply ripple?)
 

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I built a circuit that reduces the minimum voltage to the fan. From the factory the Behringer applies 7.6V minimum to the fan, which is pretty noisy, ramping up to 16V(!) with temperature. The (noisy) fan that comes with the unit starts up at 3.9V and shuts at 3.6V. The circuit I built applies 3.6V to the fan at ~8.5V input. This voltage ramps up to around 14V when 16V is applied.
If your willing to severely limit the airflow of the fan, a simple 80mm fan replacement makes much more sense. Or, a simple inline resistor would slow the stock fan.
 

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LOl I went and hacked my NU-1000DSP before I thought to look for what others have done.

I built a circuit that reduces the minimum voltage to the fan. From the factory the Behringer applies 7.6V minimum to the fan, which is pretty noisy, ramping up to 16V(!) with temperature. The (noisy) fan that comes with the unit starts up at 3.9V and shuts at 3.6V. The circuit I built applies 3.6V to the fan at ~8.5V input. This voltage ramps up to around 14V when 16V is applied.

Like many others, I glued some small heatsinks to the 4 MOSFETs to reduce the fan requirements.

The result is that when the unit is stone cold the fan does not run. When playing, the fan sometimes cycles on and off at a very low, inaudible speed. I'm quite pleased.

The circuit will cause the transistor to get a bit hot under some conditions, so I placed it in the breeze, by using one of the slits in the plastic shroud and pulling the wires through. I knotted the wires so the circuit is hanging in the breeze. I entombed the exposed conductors of the "hairball" circuit in high temp hot melt, but left the transistor's tab exposed.

The zener needs to be a low-current 1/2W BZX type.
The capacitor quiets some squealing (oscillation? power supply ripple?)


that is impressive.... i wonder if this would be safe on a inuke 3000!
 

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BTW the SMPS in the NU-1000 is a very simple "open loop" (unregulated) half-bridge topology. Its output voltage changes with AC input voltage and load. Because (as all offline power supplies are), it is fed with a bridge and capacitors, which shows 120 Hz ripple under load, the power supply output rails show 120 Hz ripple under load and significant drooping. This will increase THD+N in the amp outputs, especially one with (presumably) low gain (and thus low "PSRR" (power supply rejection ratio)). I took a quick look at the output with a scope, while driving an 8 ohm resistor, didn't see anything untoward with the scope's FFT function. I was tempted to look at it with our Audio Precision 2 at work, but yesterday's hackfest had to come to an end.

I imagined building a regulated LLC (resonant) power supply for it (my area of expertise in my day job), that would not only not droop under load, providing greater peak power, but would also have greatly reduced 120 Hz ripple to reduce power supply induced THD+N. I built a prototype once for an audio customer and demonstrated said reduction.

However, when I cranked it up, I disabused myself of that notion because I probably won't hear the difference. It would also defeat the idea of buying a $200 PnP "1 kW" amp with DSP.

P.S. Does is there an other-than-fan hacking thread for these amps for me to copy the above? :)
 

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I was thinking of doing what funkingitup did with his 3000 to my 1000 non DSP once it came in. Just get rid of shroud and put a big fan on top blowing out.
 

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has anyone placed sound deadener( dynamat type stuff ) on the fan shroud....seems to me that this will add mass to the flimsy thin plastic fan shroud and combat the resonance ( and sound ) ....just a thought...but the fans do sound like a plane taking off when they are on full speedc
 

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Just popped the top on my new 3000 and the fan was installed to blow in and this seemed a bit odd to me what with the shroud set-up. If doing a fan swap and removing the shroud, along with heat-sinks, would it not be better to have the fan exhaust the heat rather than just move the heat around???
 

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Just received an NU3000DSP yesterday. Plugged it in and turned it on. Sounded like a vacuum cleaner LOL. I just got done swapping the stock fan out with a Noctua NF-A8 FLX. Wow, what a difference. Highly recommenced. I also added the aluminum heat sinks as shown in prior posts. Took me all of 30 mins to do the entire mod. :TT
 

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I have racked up a little over a year of daily use with zero problems from the 140mm top-mount mod. Has anyone hit 2 or 3 years with their Noctua mods? It's great to hear how they hold up.
 

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Another successful fan swap on a NU3000DSP. I've had my iNuke for 2 years and finally got around to this mod. I couldn't be happier. A Noctua NF-R8 redux-1800 is what I used and for all intents and purposes it's silent. The connector on the NF-R8 was loose when I attached it to the board so I removed it and used the stock connector. Well worth the $10 and 1 hour of labor.
 

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iNuke Fan Swap and DIY 12v trigger

I replaced my upgraded fan the other day, it was an Arctic Cooling F8. The bearings were starting to wear out and a droning noise was getting louder. Not bad but I knew what the cause was. I used to leave my nu3000 on 24/7, before my 12v trigger mod, the fan life was pretty good considering it was about three years of being on 24/7 continuous. For a replacement I used a Noctua NF-R8 Redux. I think Noctua makes the nicest 12v fans around.

Here's a pic of my 12v trigger relay to turn the inuke on and off with the AVR, before taping it up to cover the connections and support the wires. My old Onkyo 818 didn't have 12v trigger but my new Denon X3300W does. The 20amp 12V relay was I think all of $8 on Amazon and the rest of it was spare cords and parts I had laying around. Works like a charm and my living room no longer has an orange night light from the inuke :D
 

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