8
Audio Input
The audio input of the DSP-59+ is an RCA phono connector on the rear panel of the DSP-59+.
Matching the output level of the radio to the input level of the DSP-59+ is necessary to take
maximum advantage of the wide dynamic range of the DSP-59+. The best way to make these
levels match is to use an adjustable audio output of the radio (typically the speaker output) as the
input to the DSP-59+. After connecting the DSP-59+ to the radio, follow this simple procedure
to match the audio levels. First, tune the radio to a strong signal after setting the radio output
level gain control to a convenient midrange position. Then, adjust the output level control on the
radio so the
Overload red
indicator LED on the front panel of the DSP-59+ rarely flashes and
the
Normal
yellow
indicator LED always flashes with the normal audio input levels. Proper
adjustment ensures optimum signal-to-noise ratio and minimum distortion. Adjust the radio
output level only to maintain the proper input level to the DSP-59+. Use only the
Gain
control
on the DSP-59+ to control the listening volume.
The factory default input impedance of the DSP-59+ is 22 ohms. This impedance is appropriate
for most radios when driven by the speaker output of the radio. The DSP-59+ can be configured
for a high input impedance by removing a shorting jumper (position 1). This jumper is accessed
by removing the back bezel and the back panel of the DSP-59+.
Audio Output
The DSP-59+ has three audio outputs:
1) On the lower left hand corner of the DSP-59+ front panel is a 3.5 mm headphone jack
connected for stereo headphones.
Use of mono headphones requires a monaural-to-stereo
adapter.
Direct connection of mono headphones will short the DSP-59+ audio power amplifier
and may damage the DSP-59+. The DSP-59+ speaker output is muted when a headphone plug
is inserted. Headphone sensitivity may vary substantially among different types. If your
headphones seem too sensitive, a useful accessory is an adjustable inline attenuator (Radio Shack
P/N 42-2459).
2) The Speaker Output RCA phono jack on the rear panel of the DSP-59+ provides adequate
output to drive a 4 or 8 ohm speaker. The front panel gain control adjusts the audio level from
this output. The maximum output power is approximately 2.5 watts into a 4 ohm speaker, or 1.6
watts into an 8 ohm speaker.
3) The Line Output RCA phono jack on the rear panel of the DSP-59+ provides adequate output
power to drive a 600 ohm or greater load.
The front panel gain control does not adjust the
audio level from this output.
The output level is 6 dB below the audio input level to the DSP-
59+ when driving a 10 kohm or greater load. When the DSP-59+ power is switched off, the
Line Output is attenuated 6 dB (this keeps the TNC level constant whether the DSP-59+ is on or
off.) in level if it is driven from a low impedance source such as a receiver speaker output.
PTTI Input
The Push-To-Talk Input electronically bypasses the DSP-59+ in the CW and data modes, and
mutes the DSP-59+ in the voice mode. Use the PTTI bypass in the CW mode to hear a fixed
frequency sidetone which may be different from the frequency of the selected CW bandpass
filter.
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