[HaBi 1]    YIPL: NOTES

YIPL: NOTES This mixer-amplifier uses 24 diodes to produce 12 separate tone pairs without mixing them at their source. Each diode is silicon, low current, and the pair should be matched if possible. A single pure tone needs no diodes, of course. A telephone earpiece is a perfect, low cost speaker for this unit, and has the added advantage of coupling tightly with a telephone mouthpiece if you.want to play this instrument to your friends, over the phone. A 50K ohm trimmer tunes each oscillator. All parts in this project are 10% or better tolerance, but the capacitors should be drift-free types (mylar, epoxy, or mica), or else the oscillators will detune easily. Two batteries are recommended for ease of construction and stability of tone. This simple mixer and amplifier can be used in the electronic organ described last issue. 1) Power to the speaker will be lost at low frequecies if a suitable enclosure is not used. A small metal or plastic box is fine. The box can, of course, contain the rest of the parts. Tones can be found for suitable notes in any sound engineering manual. 2) If played into the phone for any reason, the speaker should be lined with a circle of foam to form a good seal that is held tightly to the mouthpiece.

[HaBi 1]    YIPL: NOTES