# Rainbow Kraftwerk 2270



## FoxPro5 (Feb 14, 2006)

*Rainbow Kraftwerk 2270 amplifier*

I first became interested in these amps about 6 months ago when I noticed them pop up on Rainbow's website. So when I saw one for a very reasonable price, I jumped on it.

Specifications:
KW 2270	
2 Channel
Part number: 271026	
Peak output power: 2 x 270 Watt
Output power RMS at 4 Ohm: 2 x 135 / 1 x 450 Watt	
Output power RMS at 2 Ohm: 2 x 230 Watt	
Load impedance: 2 x 4/2 | 1 x 8/4 Ohm
Total distortion factor (THD+N): 0.02 % @ 100Hz/1W
Signal-to-noise ratio (S/N): > 85 dB A-weighting	
Frequency response at -3 dB: 10 - 50.000 Hz	
Damping factor at 4 Ohm: > 200
Input sensitivity line input: 1 / 5.5 V
Operating voltage: 11 - 18 V DC	
Input current / Peak input current: 51 A	
Dimensions (WxDxH): 376x273x59 mm	
Weight: 4.2 kg	
Certification: E11 10R-023307 / CE	

Pictures:









































About the amp:
The KW 2270 is a two channel that is made work in conjunction with Rainbow's 2 channel pre-amp unit, the KW 2V8. The pre amp provides all the active contols for the amp including the crossovers, gain, phase, and clip indicator LED's. So, by itself, the KW 2270 is just an amp. It does have a dip switch located on the board that allows you to switch the input insensitivity from 5.5v to 1v. Rainbow recommends the switch be changed to the 1v position. I tried this momentarly and the output was way too stong. In fact, at 5.5v this amp does plenty of power.

Build quality:
At first glance, this amp has a nice aluminum cover with an attractive logo and stainless steel looking terminals. I found myself saying, "Wow...zee Germans done good with this." But when I first picked it up I was surprised how light it was. Almost floated away in my hand. The end caps are made of hard plastic. Total weight is ~9 lbs. 

When I opened it (which requires you to remove 10 screws on one of the end caps and slide the cover off) it looked like there was something spilled on the board. I thought it might have gotten wet, but when I touched it it was kind of sticky. Maybe it was some sort of glue, I don't know.

The speakers terminals are very nice. The are made of Rhondium-plated something or other. I love the fact that there are angled down. It made installation a snap. 

The square board you see laying off the end is the backlight for the logo. When the amp is powered on the blue led's reflect off the aluminum foil and shine through the top. 

Performance:
I first tried the amp in bridged mode to the DIYMA Ref 12. After a little level matching on my HU, it had the sub pounding in no time. I was pretty impressed with the rated 450 watts. It did the job just fine and got slightly warm after about 30 minutes of play.

Since there is no gain on the amp, I had to level match via the HU. Compared to the rest of the channels, I found I needed to attenuate the non-fader channel by -12dB to keep it from overpowering the midbass. After a week or so I changed that from anywhere from -6 to -16dB depending on the type of music. I'm not a bass head and I aim NOT to hear my sub at all in my system. This amp did that job just fine.

After a week or so, I switched the amp to my midbass drivers (Lotus RW165). At 135 watts, I was expecting pretty mediocre performance since I had come from ~ 250 watts in the previous two amps I had on the mids. Boy was I wrong. This amp has plenty of cahounas. Again with the input sensitivity fixed at 5.5v, I still needed to attenuate the mids down about 3 dB to properly match the midbass output with the rest of the system. All level matching was done by ear only, btw.

Pros:
Seems to produce rated power quite effortlessly
Has connections for external thermostat and fan modules (see pictures on the RCA plugs side were it says VCC GND VEE)
Has a time delayed soft start function built in that prevents turn on pop (and it indeed works)
Lightweight gain block that does it's job very well
Fairly good form factor with 270 real world watts in a 15x11" case

Cons:
No onboard active filtering. However this is also a pro if you don't need it. 
Cost: At an estimated MSRP of $430 for the amp alone, you don't get much for $1.60/watt. Add in the pre amp at $199, and you are at $2.33/watt. 
Has somewhat of a cheap 'in your hands' feel.

Conclusion:
If you need a good 2 channel amp and you can find one of these for a reasonable price (I'd say $.75/watt or less) than the KW2270 deserves a look. If you are concerned with the ultimate in bullet proof build quality, than buy something from the good ole USA. If you need a powerful sub amp and are concerned with weight, put this amp on your list. If need on board crossovers and all kinds of bells and whistles, look elsewhere. If you just need an amplifier and nothing else, this would be a good one to try!


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## legend94 (Mar 15, 2006)

great review
audiojunkies sold off the last few at around cost but i was afraid to try them


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## 3.5max6spd (Jun 29, 2005)

Have had about a dozen or more of the Kraftwerk amps pass thru my hands since release and yet had one come back. They seem to be doing just fine, no complaints.
SRP is nothing you have to worry about with a rainbow dealer, they are sold most times at a competetive/lucrative price points.

Nice review.


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## FoxPro5 (Feb 14, 2006)

Thanks guys.

I'd be interested in finding out the efficiency of this amp. I know the mono is above 90%. Any idea 3.5Max??


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## DonutHands (Jan 27, 2006)

i hope this offends no one, but that amp looks like crap. the way you said it feels cheap in your hand, to me, it looks that way as well. i would much rather have my aura 'PE special' amp any day of the week.

it really looks like rainbow paid someone to crank out a cheap amp so they could put their logo on it and jack up the price.

just my 2 cents.


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## FoxPro5 (Feb 14, 2006)

Cheap looking perhaps, but not cheap performing. It don't know if it was Rainbow's design strategy to keep it light. It might have been. I've had amps MUCH heavier and they did a poorer job of dissapating heat. I've felt the amp a few times after it has beat the hell out of my midbass and it is barley warm. My Xetec on the other hand is very warm...and still driving a 4 ohm load.


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## 3.5max6spd (Jun 29, 2005)

The way i look at it... i see TWO toroids/tranformers in a small 2ch amp, in a fairly symmetrical layout w/enough mosfets that could fit running up and down each side of the board, quality caps.....I can probably find you guts of nearly 50+ amps that 'SRP' the same or claim same power, whose board dont appear as well laid out/built.

The casing apparently is good enough to deal with the heat byproduct. I personally would have loved to see the whole lineup use the casing they use on the Monoblock.


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## FoxPro5 (Feb 14, 2006)

Well here's the Aura RPM 2300 which has 2x40 amp fuses and does the same as the Kraftwerk 2270 (450x1 @ 4 bridged): http://ampguts.realmofexcursion.com/Aura_RPM_2300_Stage_2/inside1.jpg

And here's an Audison LRx2.250 which has very similar power ratings (2x120 @ 4 ohms 13.8v) and has a single 30 amp fuse: http://ampguts.realmofexcursion.com/Audison_LRx_2.250/inside1.jpg

I have no idea what makes one better than the other when it comes to the components and layout of the board. And I could really care less. As long at it does what it's supposed to, I'm happy.


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## Dracona (Jan 27, 2010)

Hi everyone.
I know that this is very old thread. Sorry about that but I want to ask ...
Is this Rainbow KRAFTWERK provides high SQ? Now I can buy this amp + pre amp very cheap. Is it worth for SQ. I'm also interested in KRAFTWERK 4 chanel amplifier.
Thanks


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