APOX-2

24 Tap Constant Impedance Volume Controller

Here is version 2 of the APOX Remote Controlled Volume Control Board. This is a 24 tap series resistor style volume controller. (It can also be used with multi-tap transformers if desired)
The APOX-2 Board

The APOX-2 will have the following features:

The Volume control board is now separate from the Input select board. It has the same features as before.


24 Setting Relay Controlled Volume Setting.
A series type attentuation is used with 24 taps, therefore 48 resistors are used for balanced volume control. The advantage of this scheme is that the pre-amplifier will always see a constant impedance.

The board accommodates axial or radial resistors. Also a multi-tap transformer may be used in place of the resistors

A pre-amplifier can be easily installed between the inputs select and the volume control. Left and Right Differential output and input connectors for your own pre-amplifier exist. (Short these together if pre-amp is not used)

Audio Mute or a DIM(Set volume to lowest level) can easily be incorporated into the firmware

A Microcontroller, controlled via I2C will be placed on this board. This allows the remote control board to stay the same for future products. And give DIY people the chance to make there own I2C controlled boards if needed.
Schematics now available! NOTE: These schematics may be subject to change!
The volume control board has been broken up into two boards. That way, people using only RCA style connectors need only 1 volume control board. Fully Differential L and R users will need to get two of the volume control boards.
Click here to Download the APOX2 REV. 1 volume board schematics in Adobe Acrobat pdf format
Pics
Test Results Click here for test results
Resistor Tables
APOX-2 RESISTOR TABLE
Switch Pos. 5K dB 10K dB 20K dB 50K dB
1 N/A MUTED N/A MUTED N/A MUTED N/A MUTED
2 5.1 -59.8282 10 -60.021 15 -62.5014 30.1 -64.4089
3 7.5 -51.9722 15 -52.0622 27.4 -53.4759 61.9 -54.7045
4 12.4 -46.0208 24.9 -46.059 49.9 -46.7192 121 -47.4127
5 13.7 -42.2254 27.4 -42.2574 49.9 -42.9652 133 -43.1987
6 15 -39.3801 30.1 -39.4009 56.2 -40.0724 150 -40.0706
7 20 -36.6302 40.2 -36.6393 80.6 -37.1111 200 -37.1281
8 28 -33.8332 56.2 -33.8369 121 -33.982 301 -34.0064
9 24.9 -31.9309 49.9 -31.9346 100 -32.0438 249 -32.0699
10 30.9 -30.034 61.9 -30.0383 133 -29.9951 316 -30.1066
11 40.2 -28.0594 80.6 -28.0627 150 -28.148 402 -28.1174
12 49.9 -26.1046 100 -26.1079 200 -26.1721 511 -26.1088
13 66.5 -24.0382 133 -24.0452 249 -24.211 634 -24.1279
14 75 -22.1783 150 -22.188 332 -22.1385 806 -22.1256
15 100 -20.1916 200 -20.2036 402 -20.1515 1150 -19.8887
16 124 -18.2289 249 -18.2356 511 -18.1447 1270 -17.9453
17 165 -16.1589 332 -16.1574 634 -16.1652 1690 -15.8914
18 210 -14.0836 422 -14.078 825 -14.1221 2000 -13.9586
19 261 -12.0476 523 -12.0441 1050 -12.0682 2610 -11.9488
20 316 -10.0887 634 -10.0846 1270 -10.0973 3240 -9.96599
21 412 -8.059 825 -8.05788 1690 -8.02023 4020 -8.00539
22 523 -6.02043 1050 -6.01696 2000 -6.07024 5110 -6.01973
23 1000 -3.09796 2000 -3.10143 4020 -3.12176 10000 -3.09767
24 1500 0 3010 0 6040 0 15000 0
TOTAL R 5000.1   10024.2   20006   50005  
RESISTORS IN YELLOW MAY NOT BE AVAILABLE IN 0.1%
There is also an excel spreadhseet here
assembly instructions APOX-2 Assembly Instructions here in WORD format!
P.S. Please feel free to update this document with any mistakes you may find. email it to support@apoxcontrols.com and we will post your changes.

[ Apox Audio ]