High-quality Chinese replica of the famous Japanese volume control ALPS rk27, 100K with elements of loudness.
Since the original has not been produced for about 10 years, this solution is the best option for building high-quality amplifier, because the build quality and elements of this WG are at a fairly high level.
The loudness scheme was developed directly for this 100K attenuator, and the elements were selected exclusively of high quality: WIMA polypropylene film capacitors and vishay dale 1% RN metal film resistors (military acceptance).
The need for loudness:
The sensitivity of human hearing is different to sounds of different frequencies, which have the same sound pressure. In other words, sounds of the same sound pressure, but of different frequency, are subjectively perceived by a person as sounds of different volumes. The greatest hearing sensitivity is manifested at a sound frequency of about 3 kHz. The decrease in hearing sensitivity at frequencies less than and more than 3 kHz is greater, the lower the sound pressure.
Recording of musical sound signals is usually carried out at a sound pressure level of 90–92 dB, at which the necessary tonal balance is set. In the future, when listening to other conditions of this sound signal with lower sound pressure, due to a change in the sensitivity of a person’s hearing, a lack of high and low frequencies will be subjectively felt. To compensate for this effect, loudness is applied by changing the frequency characteristics of the sound. Loudness is usually carried out in accordance with the curves of equal volume Fletcher-Manson.
Principle of operation:
The WG has 22 provisions. The TC operates in the first 11 positions, in 1 position the output signal level is minimal, and the blockage in the region of 1 kHz is 15 dB and the slope is about 2 dB / octave. With increasing volume, the depth of the TC decreases. Starting with 12 shopping malls it is not involved. To disconnect the TC, the module is equipped with a high-quality A-12W-K relay from FUJITSU, to which 12V power is supplied observing the polarity.
Thus, when using this WG, there is no need to introduce a volume control without loudness to be able to listen to phonograms in analytical quality without correction.
The board provides the ability to connect loudness by default, that is, the TC can be either turned on or off by default (without power supply).