The readers will be happy to know that the headless v2.2 attenautor I wrote about in my last post on June 27th has now held a vacuum for two weeks without any measurable air infiltration!
While I wait for the last few parts for the v2.2 attenuators, I have been designing and collecting parts for the v3.0 attenuator. As I described in the May 9th post, the v3.0 attenuator is based on reed relays instead of telecom relays in a vacuum chamber. I am still in the design/testing phase for the v3.0 attenuator but here are a few pictures to show the progress.
v3.0 attenuator front.
v3.0 attenuator top.
In the top view there is a red “yoke” that holds two small magnets. The yoke is attached to a small stepper motor (grey motor just to the left of centre in the photo) that will rotate the magnets in front of a series of reed relays and associated attenuator resistors. The reed relays and resistors will be soldered to the edge of the PCBs in the silver “Half-cut/Castellated Holes”.
The larger stepper motor (black motor just to the right of centre in the photo) supports the input knob shaft. A larger motor is desired here to provide an improved tactile feel while the owner turns the knob manually. The improved feel is provided by magnetic damping caused by electrically shorting the stepper motor coils. If the input shaft stepper motor is too small, it doesn’t have enough torque to provide the proper feel.
v3.0 attenuator rear view.
The photo of the rear view shows two layers for attenuator resistors. Each layer will have 12 steps. A total of eight layers or 96 steps will be possible. I still need to design and build the rear cover that will include the RCA connectors and a cover for the attenuator sections.
v2.2 attenuator (left) and v3.0 attenuator (right) compared.
The photo above shows the size difference between the v2.2 attenuator (left) and v3.0 attenuator (right). The v3.0 is considerably smaller than the v2.2 attenuator. For comparison the front face of the v2.2 attenuator is 3 5/8” square whereas the front face of the v3.0 attenuator is 2 3/4” square or about 25% smaller. The overall length of the v2.2 attenuator is 7 1/8” whereas the v3.0 is expected to be 5 1/4” long are about 25% shorter.