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High Voltage Power Supply Drive

  The BC-1 is a semiconductor type control amplifier using desecrate components with "high voltage power supply drive adopted". The BC-1 gives exciting sounds with instantaneous explosive power by means of high voltage poser supply of +/- 120V which is as eight times as that of conventional control amplifiers using operational amplifiers (linear IC), mainly.
Improvement of Low Level Lineality by
Post Attenuation Schem

   A traditional control amplifier has been employing the pre attenuation method that the input signals are made to decline with attenuaters at the first stage of an amplifier, after that the signals are amplified. This method, however, degrades the sound quality, as low level signals once attenuated are buried into the thermal noises and fluctuations. No matter how excellent amplifier after that the signal made to decline once, the original signal quality can't be restored again. For example, the contents on a paper which were made by size reduction copy once can't be 100% restored by means of a copying machine with a size expanding copy, as detailed information have been lost at the first size reduction and the reproduced copy is felt rough outlined and isn't vivid on the expanded copy. BC-1 uses "Post Attenuation Method" to avoid these degradation. The input signals are amplified at the input stage of BC-1 before attenuation, then made to decline at the later stage of the amplifier to the necessary level to the output. It becomes possible at the next generation high end control amplifier, BC-1, of the dynamic range as well hardly to make it deteriorate and keeping the high purity as to.  The high voltage power supply in BC-1 enables "Post Attenuation Method" without loosing dynamic range and low level linearity.
Pure Balanced Amplification
  The BC-1 employees six blocks of amplifiers in one channel, and a perfect balanced circuitry is built, and high S/N and high input/low output impedance are realized.  The amplifier for the 1st stage works as a buffer amplifier which comprises a combination of a DIAMOND CIRCUITRY and FET source followers. As for the 2nd stage, a differential amplifiers with Current Feedback manner is used.  The 3rd stage amplifiers employee the same construction as the 1st stage is used.  Since signal unbalance between plus and minus polarity in a balanced circuitry degrades the THD, every BC-1 is tuned carefully in the factory process by means of matched pair of feedback resisters, as perfectly rejects common mode noises and forces the THD minimized.
Attenuator by 8 Circuits/58 Positions

  The BC-1 uses a volume control by a highly reliable switch which consists of 8 circuits with 58 positions, instead of the conventional variable resisters, as a result, different state of the sound can be realized.  The circuitry of the 58 positioned switch shapes 8 circuits with the balance which is enabling only 2 resisters at each position and works as a voltage divider by the selected 2 resisters which are carefully tuned to keep the accuracy of 0.2 dB at every position out of 58 positions.  These resisters are custom order made to a long experienced manufacturer in the audio equipment industry.  Furthermore, copper plates are installed between each section of the switch for shielding and absorbing acoustic vibration which may cause the deterioration to the sound due to electrical contact vibration. The switch also arranges anti vibration material in conjunction with the copper plates to avoid mechanical resonance. The switch is mounted to the chassis of the amplifier with a shock absorber to be immune from the external vibrations, as well.
The L/R balance adjustment circuit by relay change is adopted

@The relay was used for the balance circuit which performs the level compensation with a delicate L/R channel. The resistance change type balun adjustment circuit was adopted. General into this portion, even if it is in ATTENNUTER using a quality resistance change type switch type If continuation variable volume is adopted, the tone quality grade will also fall victim. Although it is large-scale at BC-1, it is large-sized ATTENNUTER here. The balance adjustment mechanism which used the relay by the same circuit system was adopted. a center position -- the amount zero of attenuation -- each L/R channel -- from a one position eye -0.5dB - 1.0dB - 1.5dB - 3.0dB and -infinity -- <BR> selection of dB can be done In addition, the resistance which every position of this passes is 1 circuit neighborhood. Since it is two, signal degradation can be suppressed to the minimum.
Low Impedance of Power Supply by
3 Dimensional/Multiple PCB Construction

  In the traditional control amplifier, the power supply feeds necessary voltages to multiple points which need to be voltage supplied. Therefore it is impossible to arrange the sensing point for the feed back of the voltage regulator at each point.  A feed back type voltage regulator can reduce its internal impedance by reversed supplemental energy.  Even though those reversed energy is correctly generated at the sensing point, the reversed energy makes bad influences to the part of the PCB pattern which is apart from the sensing point due to copper trace's impedance which is not "zero" even though several millimeters. The BC-1 doesn't aim to decline the impedance by the reversed energy, but the  three-dimensional structure as a new idea is adapted, and it is working for the decrease of effective impedance by arranging the specially designed capacitors in the neighborhood of the actual electric current consumption point to be able to supply instantaneous power.  In other words, the separate PCB with BY-PASS capacitors confronts the amplifier PCB and to be closed to arrange it and to do the shortest distance feed in each section of the amplifier by three-dimensional wiring scheme.
Moreover, the circuit board which set up shield layer so that a feed pattern and an electrolytic capacitor might not influence the part of the amplifier is arranged, too. And, because it could be structured in compact size and a feed loop was minimized small to a limit of ultra-low-impedance to the necessary point became possible, the amplifier could realize "Superior Impulse Response" and "Stability at Wide Frequency Range
".
Mechanical Earth Construction

  The four corners of the chassis are constructed with the Aluminum Alloy expruded shabes to secure mechanical robustness. It also works as the dispersion of the resonant frequency by the different kind of metals (Aluminum/Steel) is being carried out. The four foot are directly attached to the structures of the four corners and therefore  an unnecessary external vibration is never propagated to the internal equipment.We plan to keep this construction and the form factor for the future new products which could be piled up on the previous products, as will be able to secure mechanical/acoustic stability and "Mechanical Grounding" even though several sets are stacked. Furthermore, anti-vibration weights by CORIAN® resin (high tech-plastic material which hardened by the powder of oxidised aluminum with acrylic plastic invented by CORIAN® is arranged on the four corners of the set, and resonance such as the side wall, the top board and the bottom board is controlled cleverly, as the result, the regional resonance at each component could be suppressed at the minimum.
Noise Reduction for AC Line and
R
ectifying

 In accordance with the recent popularity of the home electronics equipment which have micro computer and personal computers, the power line noise degrades the wave form in the AC mains and deteriorates to a high quality audio sound.  The BC-1 has a "Line Filter" which is a "Closed Type" and allocated at the neighborhood of the AC inlet connector to cut the external noises and the orthopedics of the wave form is given The transformer of BC-1 has the most advanced shielding scheme while a conventional transformer with a troidal core is difficult to have "Static Shield" because of its construction. However, it has become possible by adopting "the insulation copper foil" of the new development to implement the shielding between the primary, secondary windings and the chassis as well as the whole shielding of the transformer to eliminate the electromagnetic couplings. Rectification noise is reduced by a BYPASS capacitor which is selected carefully from the quality of sound side.  The rectifying diode is a high speed type whose noise is rare in rectification to the level which it isn't almost anxious about, too. A bulk capacitor after the rectification influences the quality of sound of the amplifier greatly.  Thus, custom made capacitors of the new development were employed here. And, radiation noises generated by leakage flux due to charging current flow to the capacitor is prevented by means of three divided shielding blocks made of Aluminum casing with mechanical floating support by special dumper to shut-off the vibrations from the transformer, as the result, - 20dB mechanical suppression was obtained.
Signal Switching by Relay

 For the switching of the audio signals, relays are used to optimize the internal construction and improve operational feeling. These relays are custom made and have gold plated contacts with the mirror surface finish to prevent the sound degradation due to unstable contacts. It is not a variable resister in the L/R balance adjustment circuit as well again, but eleven step resistance changeover type balance adjustment circuit by the relay is adopted.  Thus, signal deterioration by a balance circuit is the level which can be ignored by this scheme.
Stand-by Function

  A stand-by switch is carried so that it could provide the best quality of sound when it is wanted to hear, too. An electrolytic capacitor is surely necessary in the amplifier. An electrolytic capacitor takes time to become good in quality sound before it is stabilized and an electrolytic liquid does it in the ionization of the pole after the voltage is applied. The stand-by that it is equivalent so called "pre-heating" is carried in the BC-1 to dispel this.  It comes to apply always a fixed voltage to the electrolytic capacitors when the main switch of the rear panel is put.  Still, the transistors of the amplifier final step is made cut off, and it gives careful consideration by the minimum power consumption while the front switch is off under the stand-by condition. Then, it becomes possible that the best quality of sound is shown from the moment when the front switch is put.
Remote Controlled Power On/Off

 The remote controlled power on/off scheme is commonly employed in our all products.  The BC-1 has a connector on the rear panel to be connected with external equipment, such as power amplifier, for the remote controlled power on/off. This system is completely isolated from the audio signals, there is no deterioration to the quality of sound at all without electrical coupling through the grounding loop.
Powerkon Connector

 The consideration to the AC input terminal is very important, too, because the source of the power of the amplifier is given by AC mains line persistently. The BC-1 uses PowerKon made by Neitric Corporation in Germany for the inlet of AC mains to secure superior reliability and product safety.   The conventional power receptacles easily comes off and the contact resistance is high, as a result, voltage drop is big while implication of the generality and ease of purchase. The PowerKon has one third of the contact resistance compared with the conventional connectors and the bigger maximum current rating of 20A as well as the lock mechanism is equipped to prevent unexpected pull out of the AC cord.
Bundled Pin for Ridged Installation

  The foot of the bundled with the BC-1 are coated by Teflon with the under cushion material at the time of shipping for prevention of a wound such as an installation base. However the ridged installation can be implemented if the attached pins are used. It is suggested the ridged installation for the customer to hope for the un-fluctuated sound.
Use of Custom Components
   In order to achieve ultimate sound regeneration, components must be selected carefully based on desired sound quality. BP-1 uses many custom components, including resistors used in the signal section, copper foil capacitors used for input/output and phase compensation, relays, and electrolytic capacitors used for the amplifierfs power supply system. This enables us to deliver refined and differentiated sounds that could not be achieved with off-the-shelf components.
Some special order electrolysis capacitors which carried out trial production examination
New electrolytic capacitors
Mirror finished [super polished] gold (clad) contact relays
Custom Carbon Resister
New copper foil styrol capacitors

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