AES Wireless Phono Oscillator Kit
Built On A Metal Chassis
Instead of using the wooden board provided by AES, for mounting the components of
their Wireless Phono Oscillator kit, I decided to build the kit on a metal chassis,
for improved safety and convenience. I also incorporated a number of improvements
to the basic AES kit, as shown in the photos below.
Among the added features are:
12J5GT audio amplifier stage to boost low output sources.
Modulation level control on the front panel.
Stereo input jacks to mix both L & R outputs from stereo cassette players.
Fuse on rear panel.
On-Off switch on rear panel.
Antenna and ground binding posts on rear panel.
Silver Mica capacitors in RF Oscillator circuit for improved frequency stability.
Improved power supply filtering
For some reason, when I drew the above schematic, I forgot to show the additional power
supply filtering I added along with the audio amplifier stage. I don't know if the
added filtering is needed, I just added it to be sure that there would be no hum
on the plate of the audio amplifier stage, which would feed directly to the modulating
grid of the 12SA7. The extra power supply filtering was added by splitting the 2.2k
series resistor of the original B+ filter into two 1k resistors, and adding a third
33 uF capacitor between the junction of the two 1k resistors and ground. I figured the
lower total resistance of 2k would help compensate for the added B+ current drain
of the audio amplifier stage.
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