REMOTE SPEAKER SETUP

Even if your hi-fi amplifier does not have output terminals for remote speakers, it is easy enough to add them without complex switching equipment. With few exceptions, modern solid-state amplifiers have no output transformers and automatically match any speaker impedance between 4 and 16 ohms. The only important consideration is that the total impedance connected to the left and/or right speaker output is never less than 4 ohms, or the amplifier will attempt to deliver so much power output, the output transistors will self-destruct. If your main speakers have an impedance of 8 or 16 ohms, simply add remote speakers as shown :

Switch S1 turns the remote speaker on and off. Since transistor amplifiers usually put out more power at 4 ohms than at 8 or 16 ohms, adding the extra speakers does not substantially reduce the volume at the main speakers because the amplifier sees a lower impedance load and attempts to drive more power output into the combined speaker load. If your speakers are 4 ohms, and you plan to use 4 ohm remote speakers use the circuit modification shown. Switching in the remote speaker will result in the main and remote speakers being series connected for a total load of 8 ohms.

HOW TO MAKE - MIKE DESENSITIZER

Many cassette recorders do not have a high level (aux) input; they are meant only for use with microphones. If you try to dub directly from another recorder’s “line” output, or from across the speaker, the relatively high signal level overloads the microphone input, causing severe distortion. Good dubs can be obtained by attenuating the high level signal almost 50 dB, so the attenuated signal is essentially equal to microphone level. This recorder bridging cord provides about 50 dB attenuation in a single, easy-to-handle assembly. Connect resistor R1 in series with the shielded cable hot lead. Connect the free end of R1 to recorder plug PL2 and one end of resistor R2. Fold R2 back adjacent to R1 and solder the free end to the cable shield. Loop a wire from the shield to the PL2 outside (sleeve) terminal. PL1 should match the output jack of the recorder you dub from.

Part List For Mike Desensitizer

PL1, PL2 – Plugs to match existing tape equipment Shielded cable

R1 – 100,000 ohm, 1/4 – watt resistor

R2 - 10,000 ohm, 1/4 – resistor

STEREO SHUTOFF

It happens to just about everyone. One minute you’re listening to the hi-fi, the next you’re called away to answer the doorbell or a phone call. You forget all about the music, the record plays through, the automatic turntable shuts off — but the amplifier stays on until you happen to pass by and notice the glow from the pilot lamps. Yet, this simple circuit, which you can throw together in less than an hour, will automatically turn off the amplifier when the turntable shuts off. The relay coil voltage is taken from across the phonomotor; when the turntable motor is on, relay K1 closes and applies power to AC socket SO1; When the turntable shuts off, removing voltage from the motor, K1 opens, disconnecting power from outlet. Because the turntable automatic shutoff switch might not be able to carry the amplifier load, the AC power for SO1 is taken off before the automatic shutoff switch. Switch S1 bypasses the relay contacts and applies power to the socket even when the turntable is off.

Parts List For Stereo Shutoff

K1 – 117V AC relay with contacts rated at least 5 amperes at 117V AC (Radio Shack 275-207)

S1 – Switch, SPST (Shutoff bypass)

SO1 – AC Socket