1059A (MKII)

World renouned for over 40 years.The 1059A is a multiple input/output low noise amplifier that provides a near-perfect match to just about any microphone or recorder.  The 1059A includes a tone generator for testing amplifier performance and unknown lines, switchable excitation voltage for external accessories and a low pass/high pass filter selector.

The input jacks, J1 through J4, have input impedances ranging from 2 Megohms to 1,000 ohms.  Maximum amplification is available through J2 and J3 and medium amplification through J4.  J1 and its associated J1 GAIN control has adjustable amplification. With the J1 GAIN control advanced fully clockwise the output level of a signal fed into J1 will be roughly one-half that of the same signal fed into J2.

J1 can sustain approximately 1,000 volts DC.  Use this jackZZAAAP!! when it is unknown how much voltage or type of signal is on a line pair.  To operate the 1059A, insert the special 2,000 ohm headset supplied into output jack J6. The headset is worn with the gray tube under the chin with the sound output holes facing slightly (30 degrees) forward.  The 1059A is NOT designed to drive low impedance headphones.  Add a RadioShack 277-1008 Mini Audio Amp to drive lower impedance headsets.  Turn J1 GAIN fully counterclockwise (minimum) and advance the VOLUME control clockwise (turning on the amplifier) roughly one-third turn.  Advance the J1 GAIN control slowly clockwise until either a signal is recovered or the control reaches full clockwise.  If, while advancing J1 GAIN, a loud hum is heard, it probably indicates the line is carrying high voltage AC.  USE CAUTION!!!  Do not apply high level AC signals to any other input.

J2 (500K) is a high impedance input that provides the maximum amplification of the 1059A.  Utilize this jack when the DC and AC level and relative signal strength on a line pair is known.  J2 may also be used with external accessories such as the 1059XM Contact Microphone and 1040-4 Hot-Pack.

J3 is used when the line impedance or accessory is approximately 5K-50K ohms.  Utilize this jack with accessories such as the 2030 Carrier-Current Probe or when analyzing telephone systems.

J4 provides lower amplification and impedance (1,000 ohms) than J2 or J3.  Use this jack when the input signal level is too high for the other inputs.  This jack also can supply an excitation voltage (9 volts through 4,700 ohms) for external accessories such as the 1059AF audio filter or carbon/electret microphones.  Voltage is applied to the jack when the J4 VOLTS switch is in the UP position. If an additional stage of amplification is desired when using J4 to supply external voltage, the orange wire plugged into the small jack on J4 may be moved to the small jack on J3.  The J4 switch then becomes the J3 switch.

The TONE-ON switch powers an internal tone generator.  The output of the generator is fed through the last three stages of the amplifier and applied to output jacks J5 (50K impedance) and J6 (2K impedance).

The FILTER-IN switch selects the amplifier roll-off characteristics. Use this switch when excessive hum is encountered or a more "crisp" signal is desired.

A convenient check of the battery can be made by inserting the mini plug-clip lead cable (supplied) into J4, turning ON the 1059A power and placing the J4 VOLTS switch in the UP position.  Connect the clips to a voltmeter set on the 9 or 12 volt range.  Replace the battery when the reading is below 7.5 volts.  To change the battery, loosen the two cover screws one or two turns, slip off the cover and remove the old battery.  Install a fresh Alkaline battery, replace the cover being careful not to pinch the battery leads and tighten screws (don't over-tighten!).

As with any piece of electronic equipment, remove the battery during periods of prolonged storage.


1059 IR   - - - Infrared probe.
1059 KM - - - Contact microphone.
1059 AF  - - - Filter for detecting audio on AC power lines.

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