Timewave DSP-9+, Operating Manual

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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 indicator LED on the front panel of the DSP-9+ rarely flashes and the Normal
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-9+. Use the Gain control on the DSP-9+ to control
the listening volume.
The factory default input impedance of the DSP-9+ is 22 ohms. This impedance is appropriate
for most radios when driven by the speaker output of the radio. Optionally, configure the DSP-
9+ for a high input impedance by removing the shorting jumper in position 1. Remove the back
bezel and the back panel of the DSP-9+ to access this jumper. Refer to the Back Panel Jumper
Function Table on page 12 for details on the jumper settings.
Audio Output
The DSP-9+ has three audio outputs:
1) On the lower left hand corner of the DSP-9+ front panel is a 3.5 mm headphone jack
connected for stereo headphones. Use of mono headphones requires a monaural-to-stereo
adapter (see the appendix on page 20 for details). Direct connection of mono headphones
will short the DSP-9+ audio power amplifier and may damage the DSP-9+. The DSP-9+
speaker output is muted when a headphone plug is inserted.
2) The Speaker Output RCA phono jack on the rear panel of the DSP-9+ provides adequate
output to drive a 4 or 8 Ohm speaker. The front panel audio 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-9+ provides adequate output
power to drive a 600 Ohm or greater load. The front panel audio 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-9+ when driving a 10 kOhm or greater load. When the DSP-9+ power is switched off, the
Line Output is attenuated 6 dB 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-9+ in the CW and data modes, and
mutes the DSP-9+ 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.
Use the PTTI bypass in the voice mode to prevent unwanted transmit audio from the transceiver
from causing audible interference. Many transceivers do not mute their audio outputs
completely during transmit. The extra gain from the DSP-9+ with AGC on (up to 36 dB) makes
the transmit audio audible and may even cause oscillation from feedback to the microphone.