UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - My first valve radio project

GeoffK · 28th Dec 2016, 8:12 pm

Can't quite understand why you are going to all this trouble, when the gram plug is inserted it opens S16 and puts R11 across the pickup as a load, suitable for a crystal cartridge as S17 closes taking the other side of R11 to chassis, at the same time muting the radio input via R12 by shorting the final IF. The aerial input could also be looped to chassis to stop any RF input. A shame it will never be used as a radio. A preferable way might have been to get a purpose made audio amplifier, and have use of this as a radio.
Usually to couple a stereo signal to a mono input is to feed through a couple of resistors of around 1K to 10K depending on the input level, joining the resistors at the mono end.

28th Dec 2016, 8:12 pm	#174
GeoffK Heptode Join Date: Mar 2016 Location: Essex, UK. Posts: 602	Re: My first valve radio project - Philips 462A Can't quite understand why you are going to all this trouble, when the gram plug is inserted it opens S16 and puts R11 across the pickup as a load, suitable for a crystal cartridge as S17 closes taking the other side of R11 to chassis, at the same time muting the radio input via R12 by shorting the final IF. The aerial input could also be looped to chassis to stop any RF input. A shame it will never be used as a radio. A preferable way might have been to get a purpose made audio amplifier, and have use of this as a radio. Usually to couple a stereo signal to a mono input is to feed through a couple of resistors of around 1K to 10K depending on the input level, joining the resistors at the mono end.