Pick one…

I haven’t been able to finish much over the last weeks, but I do have some progress to show on various projects. One of them is these balanced selector switches:

Selector switches

Closer view

Each board selects between two inputs or two outputs via relays, so the four PCBs together form a two-in/two out balanced switch. The plan is to build a software(Arduino)-controlled switchbox for easy comparison of different sources and amps. The design is extremely simple, with basically just a small-signal relay per input controlled by a single transistor. The onboard LED is duo-color so it lights red when one input is selected and green when the other is selected. The input/output connectors are Neutrik D-series XLR which I managed to buy a pile of very cheaply some years ago in a surplus shop – I much prefer this metal version over the PCB-mounted plastic version that is normally used.

Now, to be able to make accurate comparisons between amps or sources, it is important that the output levels of the two components being compared are equal. Because I have built the boards to each select between two inputs for the same channel, the gain control must be implemented in software instead of hardware, but that should be manageable – even for me 😉

The most likely contender for the job of gaincontrol is the PGA4311 IC from TI which is a four-channel, digitally controlled analog volume control. I haven’t really finished the design of the gaincontrol PCB yet, but much of the inspiration comes from here. For the output buffers I will probably use a variation of the OPA1632 circuit shown here (but with a THS413x opamp instead).


3 Responses to Pick one…

  1. Pingback: One amp to rule them all? | theslowdiyer

  2. Pingback: Surrounded – again! | theslowdiyer

  3. Pingback: Switched on? | theslowdiyer

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