Bonasus

RCM Audio BONASUS integrated amp ($11,950) has a dual mono construction. Its amplifier has two independent circuits power supply, pre-amplifier, and power amplifier. Channels are connected through ground loop. Steel body. 40 kg.

The sound of Bonasus amp is life like. Turn the volume as high as you want. Do not worry. No hiss. No hum. Only life like music. Here are some considerations in the design and manufacturing of RCM Audio Bonasus sound machines!

• Integrated amplifier – Optimal in home use. Compact build is for many users principal condition of choice. Necessity to buy additional cables indispensable in separate systems, principally raise expense of whole system what have big influence for final decision.
• Dual mono construction – Bonasus amplifier is made of two independent circuits power supply, pre-amplifier and power amplifier. Channels are only connected through ground loop. There are advantages to this design. Integration of all circuits inside of one housing minimize interference especially, that of the power supply. Electrical separation of channels increase resolution of signal.
• Output power – parameter which is for less experience users some kind of magic rule (more watts – better equipment), but in normal home conditions deliver a lot of trouble. Real power use at home audio system is from 0.1 to 6 Watt. RCM Audio folks are convinced that most of users have problem with „syndrome of 11 hour”. It means that when they put volume control over „11 hour” system stops play music (i.e. becomes noise). RCM Audio eliminates this problem put up amplifier which have “only” 16 watts power. It forced us to build tube amp, because only tube is able to work on low volume with full range of sound. Semi-conductor constructions have a lot of imperfections, which principally complicate circuits in low power audio amplifiers. Properly circuit configuration in our amplifier secure very good linearity in whole power range. It means that independent of position of volume knob, user receive smoothness of operation in frequency range characteristics. Important is also configuration of output stage, which works in ultralinear A/B class push-pull. We have often questions why only 16 Watt, when that set is able to deliver 25 watts or more? Answer is very simple – output stage work in optimal points, which we choose after many listening tests, and result, is output power on this level. Of course that output power require loudspeakers with efficiency 88dB or more.
• No feedback loop – feedback loop is remedium for imperfection circuits with high power is not necessary in our amplifier. To say nothing about well know bad influence of it for sound quality we take care for another factor with have big influence on our amplifier. Feedback loop decrease amplification what force designers to increase output power and production of “empty watts” and have bad influence for pick power of amplifier. There is possible to solve this problem by increase power supply part but its complicate construction and results are often no so good, we try to eliminate this.
• Power supply – traditional circuit with tube rectifier and filtering use capacitors and choke, the first stage work polipropylene capacitor after is choke and then electrolytic capacitors, total capacity 1680 uF each channel. Past choke filtering is divide to two circuits, one is to input stage and the second to output stage. In input stage additionally working polypropylene capacitors which decouple disturbance appear in this stage. All other circuits of amplifier (logic, input selector, displays) are supply from separate transformer.
• Operation and work check – we equip our amplifier in “soft start” function which provide proper warm-up of tubes before switching on anode plate voltage. This improve tube lifetime. Bonasus have also circuit to test condition of power tubes what give user possibility to check if is necessary change them.
• Chassis – this element, which have very big influence for good sound is take in our construction seriously. Very rigid steel chassis, have big mass itself which is able to absorb inside parts vibrations. All transformers and chokes are in shielding cans and spill special semi-elastic damping mass. Reason is one – to eliminate vibrations appear in time of working.
• Parts and circuit – key to good sound of amplifier is right selection of parts. After many tests and experiments we reach result satisfy our expectation use selected components from Kiwame, Riken, Bourns, Mills, Audyn or Solen. Parts in signal section are mounted without PCB but „point to point”. We use tubes like: rectifier 5AR4, duo-triode 12BH7 and tetrode 6CA7.

RCM Audio Bonasus is a high quality built integrated amplifier, easy to operate, ensuring years of enjoyment. Over and beyond the discussed features, in shape sound of amplifier very important is direct coupling input stage with phase inverter or AC heating what give longer life time of tubes. Positive influence of AC heating for the sound is well known, but using it in most of constructions increase hum in speakers.

RCM Audio recipe is very simple: the highest possible quality main transformer and proper placing wireing give non-problem use advantage of AC heating. Bonasus is an example of device in which use of traditional verify solutions is join with modern technology. Result is the amplifier which is perfect choice for demanding customers.

Technical Specification:

SENSOR Prelude IC

Selected as Product of The Year 2007 by Polish Hi Fidelity on-line journal, RCM Audio SENSOR Prelude IC MC/MM phono stage ($2,950) is the best value we have seen in a phono stage. great dynamics. On the back panel of SONOR phono stage, you will find all the necessary switches to easily set the optimum impedance, gain and mode of input stage (balanced or single-ended).

HiFi Journal of The Netherlands says (text translated):

“The RCM Sensor Prelude IC clearly isn’t a ‘me-too’ product but the result of thorough investigation and long listening sessions. Sonically, it has a rather unique mix of clarity and grooviness. Many a ‘clear’ sounding component tends to sound somewhat lean or even stuck-up. The RCM is fully fleshed out in it’s presentation which, in combination with a strong PRaT factor results in a moving reproduction of swing (obviously, that had to be present at the time of recording; a below-par rhythm section will be reproduced as such by the RCM). The most special thing about this Phono stage is that it doesn’t position itself at one side of the ‘pleasure verses perfection’ dilemma. Detail? Yes. Transparency? Absolutely, but combined with a very good sense of musical communication. The Sensor Prelude IC raises the delicate signal of a Moving Coil cartridge with care, dedication and enthusiasm. Very,very, highly recommended.”

RIAA correction is achieved via a passive split network with two separate RC filters, low noise resistors and 1% tolerance polypropylene capacitors.
To ensure high precision in the RIAA correction each component of the filter is hand picked and measured to guarantee a tolerance of less then 0.3 dB in the frequency range 20Hz – 20 kHz. This is done for every unit built so that the customer receives a unit sounding as good as the reference unit in our laboratory.

All other components in the preamplifier are selected to ensure perfect channel balance. RCM Audio SENSOR Prelude power supply is housed in a separate metal case to eliminate interference with the sensitive circuits in the phono preamplifier. It is fully balanced and has oversize filtering capacity and low output impedance.

Because of the extremely high gain capability of up to 76dB combined with a very low noise floor the Sensor Prelude IC can amplify very low output MC cartridges with ease. Music emerges from a black background and images are finely crafted and spread out before you in a sound stage that is both wide and deep. Detail retrieval is exceptional and the ability to communicate Pace, Rhythm and Timing (PRAT) is very satisfying. Sensor Prelude IC performs at such a high level that it can be used in the most expensive audiophile systems, however its very reasonable pricing allows music lovers at all levels to enjoy the superb sound it makes.

RCM Audio SENSOR Prelude phono stage technical specifications are shown below:

In summary, I love RCM Audio SENSOR phono stage so much, and find it so much better than ZYX ARTisan that despite having three ARTisan phono stages (as of Nov. 2009), we decided to post our opinion on this website. We had to do this in fairness to our customers. We also reduced the price of ZYX ARTisan and established a program to ship both ZYX ARTisan and RCM Audio SONOR to our customers and let them choose whichever they prefer.

Roger Adamek of RCM Audio

Now, what can I tell you about the man behind these great products (Bonasus amplifier and SENSOR Prelude IC phono stage)? It is best for you to read into his personality through some of his other arts: photos. Read the man through the lens of his own camera.

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I left Warsaw knowing that I would be back. Great people, great food, great audio products by RCM Audio.