Rotel RKB-850 Amplifier, 8 x 50W

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General:

Perfect for an active amplification system, multi-room, or a home theater.

Rotel has been designing and manufacturing award-winning power amplifiers for over 50 years. That considerable expertise has now been applied to a new generation of rackmount custom installation amplifiers that set new standards for performance, reliability, and ease of installation.

The RKB-850 is rated at 8 x 50 Watts RMS into 8 ohms all channels driven, and can double that output into 4 ohms as a result of its sophisticated, efficient Class D design. The amplifier is rugged and extremely reliable, but Rotel has gone one step further to maximize long service life by utilizing dual thermostatically controlled fans to exhaust heat away from the output modules and power supply.

One of the many custom-friendly features the RKB-850 offers is input linking. A second input can source from any ‘upstream’ input - so B can source from A, C can source from B and D can source from C. You can create four individual stereo zones, two dual zones or three common zones plus an individual zone. In other words, two Sonos Connects (for instance) might be divided between kitchen and patio (A+B zones) and Master Bedroom and Bath (C+D).

Other features include input signal sensing, buffered link output, a sum-to-mono feature, a rear panel RS232 connection allowing connection to automation systems to provide full control and feedback, and four front panel trim pots to allow easy level adjustment to balance zones.

This unit was rack mounted so it has no feet in place. Let us know if you'd like us to install a set prior to shipping by adding a note to your order.

Brand Background:

Rotel is a family-owned Japanese manufacturer of hi-fi audio and video equipment: home theater, amplifiers, compact disc players, etc. Rotel was started by Tomoki Tachikawa in Tokyo Japan in 1957 as a hi-fi electronics manufacturer. It is currently run by the nephew, Peter Kao.

Ownership:

Single Owner 

Connections:

8 sets of 5-way binding posts for bananas or spades. 4 sets of RCA inputs for line level.  Detachable IEC power cord. 

General Sound:

Neutral sound with little to no coloration 

Cosmetic Condition:

8 - Very Slight Signs of Use

https://skyfiaudio.com/pages/our-rating-scale

Working Condition:

Working perfectly and tested in our lab.

Included:

Just the unit and power cord

Packing:

Will be packed using our highly developed in-house process and custom packing materials.

Original MSRP:

$2,000.00

Dimensions:

17" × 3.9" × 16.7" (W x H x D)

Weight:

25 lbs.

Age:

2018

Link to Manual:

https://www.rotel.com/sites/default/files/product/manuals/RKB-850-8100V02-OM.pdf

Recommended Cables:

Kimber Kable - RCA Interconnects - Better

Kimber Kable - RCA Interconnects - Best

Kimber Kable - Speaker Cables - Better

Kimber Kable - Power Cords - Better

Testing Process:

We start with a visual inspection of all internal components to make sure that there are no signs of heat stress or damage. Capacitors are checked for telltale signs of predictive failure including bulging, shrunken wrappers, or physical leakage. We also inspect the PCBs for discoloration from resistors or transistors that may have been running hot. On vintage units we often spot check select capacitors for value and ESR.

If the amplifier passes visual inspection, we move on to a controlled power on sequence using a Sencore safety analyzer to monitor current draw in real time. Once the amplifier is determined to be safe to operate, we connect it to full AC mains for function and power testing. We connect the speaker outputs of the amplifier to a Sencore PA81 Power Analyzer which acts as a dummy load, DC offset monitor, and oscilloscope interface. We start with a low level 1KHz test signal at the amplifier’s input and slowly increase its amplitude while monitoring the output on an oscilloscope for signs of noise, clipping, distortion, or improper channel balance. We continue increasing the signal level until the amplifier reaches clipping. At this point we take an output power measurement and compare it to the spec sheet of the amplifier to verify proper performance. If the device under test has both balanced and single ended inputs they are both tested at this time. We finish off the bench evaluation with a 1KHz square wave check and a 20Hz to 20KHz sine sweep to assess the amplifier’s frequency response characteristics. This battery of tests will usually reveal if the amplifier has any issues that need further attention.

Before the device leaves the bench, we perform a listening test with actual music using a variety of preferred test tracks. Our benches are outfitted with familiar monitor speakers which help us identify inconsistencies that will not always show up on our test gear. The main things that we are listening for are hum or noise with no signal present, proper center image, clicks, pops, or any other obvious undesirable audio characteristics.

If the unit passes all of these tests it is moved to our long term testing rig where we simulate real word operating conditions for 6-8 hours. This allows us to monitor the unit for signs of thermal runaway or intermittent issues that only crop up when the unit has fully come up to temperature.

Specs:

CONTINUOUS POWER OUTPUT
50W/Ch (All channels driven, 8Ω)

TOTAL HARMONIC DISTORTION (THD)
(20Hz–20kHz) <0.08%

FREQUENCY RESPONSE
10Hz - 100kHz +0dB, -1.4dB

S/N RATIO (IHF "A" Weighted)
108dB

GAIN
30dB

INTERMODULATION DISTORTION (60Hz:7kHz, 4:1)
<0.08%

DAMPING FACTOR
>150

SPEAKER IMPEDANCE
4Ω minimum

INPUT SENSITIVITY
0.6V

INPUT IMPEDANCE
100kΩ

CROSSTALK / SEPARATION
>60dB