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R2R Shunt Volume with 3 selectable sources
December
2014
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INTRODUCTION
There are many methods to implement a volume control on audio system:
normal potentiometers with good quality like the
ALPS
It is very cheap but with some limits on
noise and precision so this is not
suggested in true hi-end systems.
PGA2310
high-performance, stereo audio volume control chip
Used in many audiophile components based on op-amp design, not suggested in
hi-end audio with no feedback and vaccum tubes
stepper attenuator like the DACT
As you know I love DACT because these
have really none negative effects on the sound but these are difficult to
control remotely, about the quality see the
testimonials.
integrated DAC volume
control
The integrated DAC volume control like in the ES9018 chip is very good if
compared to normal digital control implemented by the operating system (this
lost resolution) but a good stepper attenuator is much better (see
ESS article)
Shunt volume
It is the newest trend in volume control, it
reduce the components in the signal path so it promises better
performances, near or better than DACT if high quality resistors are used.
There are many good articles about this attenuator like
the Logarithmic resistor ladder and
Logarithmic Attenuator Calculator.
Two encoders near the display
allow to select the input and to change the volume level.
A good infrared
remote command is included and it add lcd backlight switch off, mute button
and standby function (necessary a second transformer).
It can easily
integrated the same chassie of your custom pre-ampl. or integrated
amplifier.
The firmware has been design with standby configuration, so
one little 6-7VAC 50W transformer always powered for the controller module
and another bigger transformer for your pre-ampl or integrated amplifier.
I can modify the firmware on your request to have no stadnby
configuration.
Quanghao
sell this complete module assembled including the aluminium
remote at 250$ + shipping.






REMOTE


RELAY POSITION
| display (-dB) | mute relay | 6 relays status |
| 0 | 1 | 111111 |
| 1 | 1 | 111110 |
| 2 | 1 | 111101 |
| 3 | 1 | 111100 |
| 4 | 1 | 111011 |
| 5 | 1 | 111010 |
| 6 | 1 | 111001 |
| 7 | 1 | 111000 |
| 8 | 1 | 110111 |
| 9 | 1 | 110110 |
| 10 | 1 | 110101 |
| 11 | 1 | 110100 |
| 12 | 1 | 110011 |
| 13 | 1 | 110010 |
| 14 | 1 | 110001 |
| 15 | 1 | 110000 |
| 16 | 1 | 101111 |
| 17 | 1 | 101110 |
| 18 | 1 | 101101 |
| 19 | 1 | 101100 |
| 20 | 1 | 101011 |
| 21 | 1 | 101010 |
| 22 | 1 | 101001 |
| 23 | 1 | 101000 |
| 24 | 1 | 100111 |
| 25 | 1 | 100110 |
| 26 | 1 | 100101 |
| 27 | 1 | 100100 |
| 28 | 1 | 100011 |
| 29 | 1 | 100010 |
| 30 | 1 | 100001 |
| 31 | 1 | 100000 |
| 32 | 1 | 011111 |
| 33 | 1 | 011110 |
| 34 | 1 | 011101 |
| 35 | 1 | 011100 |
| 36 | 1 | 011011 |
| 37 | 1 | 011010 |
| 38 | 1 | 011001 |
| 39 | 1 | 011000 |
| 40 | 1 | 010111 |
| 41 | 1 | 010110 |
| 42 | 1 | 010101 |
| 43 | 1 | 010100 |
| 44 | 1 | 010011 |
| 45 | 1 | 010010 |
| 46 | 1 | 010001 |
| 47 | 1 | 010000 |
| 48 | 1 | 001111 |
| 49 | 1 | 001110 |
| 50 | 1 | 001101 |
| 51 | 1 | 001100 |
| 52 | 1 | 001011 |
| 53 | 1 | 001010 |
| 54 | 1 | 001001 |
| 55 | 1 | 001000 |
| 56 | 1 | 000111 |
| 57 | 1 | 000110 |
| 58 | 1 | 000101 |
| 59 | 1 | 000100 |
| 60 | 1 | 000011 |
| 61 | 1 | 000010 |
| 62 | 1 | 000001 |
| 63 | 1 | 000000 |
| 64 | 0 | 000000 |