This control amplifier is designed to be partnered with the ROTEL stereo power amplifier which I have listed separately. Of course this control amplifier can be used with other power amplifiers but it is best to keep "mates" together!
This control amplifier (like its BIG brother the RB-990BX) is designed for the high-end/audiophile user. I talk a bit more about this further down in this description, please read as it gives some insights into the design philosophy of Rotel and how they put this equipment together.
ROTEL Control Amplifier
Made In Japan
Model: RC-990BX
Released to market in the early 1990's
RR-909 (Original) remote is NOT INCLUDED!
Six source inputs:
Phono (MM or MC selectable)
Aux
Tuner
CD
Tape 1
Tape 2
4 audio outputs
Tape 1
Tape 2
Main Output 1
Main Output 2
All inputs and outputs are gold plated RCA sockets
Screw down earth connector near the Phono input for signal ground
2x Switched AC outputs (240V AC) maximum 800W
MANUFACTURERS STATED SPECIFICATIONS:
Total Harmonic Distortion (CD/Tuner Input) no more than 0.004%
Intermodulation Distortion (CD/Tuner Input) no more than 0.004%
Input Sensitivity/Impedance:
Phono (MC) 250uV / 100 Ohm
Phono (MM) 2.5mV / 47K Ohm
CD 150mV / 18K Ohm
Tuner 150mV / 18K Ohm
Aux 150mV / 18K Ohm
Tape 1 or 2 150mV / 18K Ohm
Output Level typically 1V / 100 Ohm
Frequency Response:
Phono 20Hz ~ 20KHz (RIAA +/- .2dB)
CD, Tuner, Aux, Tape 1 & Tape 2 4Hz ~ 100KHz (+/- .5dB !!!)
Signal To Noise:
Phono (MC) 70dB (MM) 75db
All other inputs 100dB
These are the manufacturer claimed figures, and very impressive they are indeed but I am unable to confirm these figures because my test equipment has all found new owners.
How Rotel achieved these design measurements is detailed below...
COSMETIC CONDITION:
Very good case, front panel, rear panel, underneath and top side. This means NO dents, NO scratches (at all) or discolouration - dare I say it, like new!
NO knobs or buttons missing!
NO wear to any of the labelling
The RR-909 remote (which also can control the AM/FM Tuner I have) is missing in action (along with the remote for the CD Player! The remotes were all placed in a bag yonks ago, but the whereabouts of that bag is now a mystery to me.
GENERAL DISCUSSION/HISTORY/TESTING:
This Rotel control amplifier (along with the other Rotel components I have/am advertising) cost our business a fortune way back in the late 1990's but it was necessary for our "hi-end" clients.
It never missed a beat, just sat there ready to bring the big RB-990BX's to life!
My professional background is technical, yes I like to look and observe "how things were put together and designed"
First thing you notice is the weight, might be "just" the control amplifier but it is surprisingly heavy. All steel case, tough as nails and considering the low power requirements of this low signal level amplifier/control system, a MASSIVE toroidal transformer - I would suggest well and truly over engineered! A bit like a V8 cruising at 60Kph, this transformer would hardly know its working.
Inside (like all Rotel equipment) it is SO SYMMETRICAL!! The layout was designed by a person or team with a very logical, organised methodology, not like some other consumer equipment that is quite frankly a tangled mess inside.
Not only is it well laid out physically, there are completely separate power supplies for each channel along with easily identifiable separate audio paths for Left and Right channels.
You may notice that when looking at the "inside" photograph there is discolouration around the electrolytics - THAT IS NOT LEAKAGE! Rotel was in the habit of applying copious amounts of a glue/resin around their electro's to keep everything "secure".
The components used are high specification, no "elcheapo's" used here! Gold electro's, fully sealed pot's (probably ALPS) and the channel switches are operated via a flexible band actuator so that there are no wires carrying audio to and from the front panel.
Special attention has been paid to the design of the phono input section, this is based on TL071/NE5534 Op amps with discrete transistors at the front end. These Op amps are commonly used in broadcast industry audio equipment. Filters etc are looked after with styro caps and even the resistors are 1% metal oxides, not the "normal" 5% cracked carbon you will usually find in other phono sections. These passive component types are important, not necessarily because of an "improved" sound but it's all about stability over time - these components are far less likely to move out of spec over time.
Special mention should be made about the general outputs of this control amplifier, there are TWO sets of outputs - both are identical and these allow for the user to run their "ultimate system" with two RB-990BX power amplifiers, a bi-amp arrangement where you might like to split the audio across two seperate amplifiers.
Everyone used to ask about the obvious missing link on this control amplifier "where on earth is the tone controls?"
There isn't any at all!
The Rotel philosophy is to keep the audio signal path "clean" and uncoloured. Tone controls alter the colouring of the audio signal and are also a potential source of that dreaded beast "noise".
If you really want or need to have some tonal adjustments, you will need to do it with a seperate unit as this control amplifier cannot help you - it's whole purpose in life is to keep the frequency response as flat as possible in an attempt to achieve faithful reproduction of the signal source.
This is not always desirable to some people, including ourselves, we used to insert a component EQ system between a particular source and the control amplifier input because sometimes we wished to lift the bass or in the case of our Ribbon speakers, some adjustment to the tone response was needed anyway. The use of an EQ system is totally optional, some people detest them but others like to "tune" their system sound to suit the listening room characteristics - its a matter of personal choice really.
FINALLY ... so what does it sound like?
Superb in one word.
I cannot say that I am a true, diehard audiophile freak but I know good audio when I hear it and this control amplifier does it's job extremely well.
But don't accept my word for it, take a look around online at the discussion forums (search with Google) and you will see that "real life" users of this equipment (and the RB-990BX) love their Rotel gear.
