23-11-2012, 07:22 PM
Thanks, Rob. The 4200 is a 2-unit valved radio with a push-pull o/p stage. Power is 7w into 4 ohms, which, for it's day was 'high power'. On the subject of the 'mixing'' resistors, I have seen values of anywhere between 100 ohms and 47k used. In this case with 2 x 100 ohm resistors a sinewave of 1kHz @ ca. 80mv from my audio generator produces about 5w o/p at full volume, which is a similar level to that produced by a strong local MW Station. I have yet to actually try the I-pod but I wonder if too high value of resistors will reduce the o/p. I was also wondering if damage to the I-pod's o/p would result from working into a Hi-Z load.
An unrelated problem is that there is some radio breakthrough when the I-pod's connecting lead is plugged in, via a switched jack which disconnects the detector o/p from the amplifier's i/p.
An unrelated problem is that there is some radio breakthrough when the I-pod's connecting lead is plugged in, via a switched jack which disconnects the detector o/p from the amplifier's i/p.
