This was an interesting little project which came through the shop, a 1934 RCA Victor T4-8A cathedral radio. This radio had been fully restored, down to the bare metal of the chassis and completely re-wired by a boutique restorer, then it was on to Rain City Audio for some specialized finish work for its new owner.
The restorer did an immaculate job, removing and polishing every component and re-painting the transformers, running all new wire and all new components.
First up was the addition of a passive mixing network and some coupling capacitors. This radio uses an interesting, reflexed arrangement for its IF/Detector/1st Audio stage, but tapping into it is straightforward.
On the backside, the radio got a switched outlet for powering the Bluetooth receiver, and some small adhesive pads to hold it all in place. I shortened the length of the power cable between the USB power supply and the receiver for good measure.
Configured this way, the radio receives AM and has its volume controlled through the front panel; the Bluetooth audio’s volume is controlled by the source. And with this, the 1934 radio gets a new life playing anything its owner chooses.