Making Progress

I made good progress this week assembling and testing the Panel Power, Panel Source and Control boards for the left and right channels of the v2.2 stepped attenuator. Here are a few of the results:


Panel Power, the PCB for the front panel power switch:

  • The light sensor is a big improvement. The light sensor is used to control the brightness of the power and source LEDs according o the room light level;

Panel Source, the PCB for the front panel source selector switches:

  • LED brightness control tested and shown to function well - a big imrovement;

  • The simplified schematic using standard logic gates instead of a programmable device (CPLD) has improved the speed of construction because the programming of this board is no longer required;

Control, the PCB with the Bluetooth radio module (with micro-controller) and stepper motor driver:

  • Change ladder step selection logic to reduce connections to the ladder from 18 to 12 - this has not been tested yet;

  • Modify the board to use the improved vacuum chamber cable feed through - again not tested yet;

  • The Trinamic IC StealthChop mode provides almost silent operation of the stepper motor - it is wonderful to see (and not hear) the volume control knobs glide silently up and down the dial;

  • Add light sensor so the brightness of the power LED is tailored to the room light level. This is only used for the “Headless” version as shown in the DÆ Passive Preamp v2.1 - I will build a pair of the headless version after I complete the version I am working on now.


I have started constructing the other boards and have already finished one of the Front Connector Plates (see description of Front Connector Plate in my March 18th Blog post). Next week I will finish all the boards for at least one ladder section. I had to make a few last minute changes to the Rear RCA Connector board and re-order these boards. The boards are now being manufactured. I hope to get these updated Rear RCA Connector boards in the third week of April so I am not delayed too long.

v2.2 Stepped attenuator under construction and testing.

v2.2 Stepped attenuator under construction and testing.