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Audio Equipment (Flex 5000)

A Marshall MXL 990 runs into a Behringer MIC2200, into a Behringer DEX2496, into a Behringer EX3200, into a Behringer DSP1000P, into the Flex5k, using XLR cable/connectors (modified the Flex 5000a with a XLR/TRS combo connector).

Also note that no mixer is needed since the Flex interfaces audio to/from the PC using the Firewire cable and virtual audio ports (either the built in MME sound mapper or VB Cable virtual IN/OUT).



Audio Equipment (Heathkit)

Since the DDS/IF Filter Mod's, the HW-5400 now adds 4.0khz, and 6.0khz Tx/Rx bandwidth's to the standard 2.4khz selectable audio filters. (all 6 pole crystal Filter's). This radio is fully standard SSB as well as eSSB capable on the fly.

(See DDS and IF project pages for details on Mods)

The primary Microphone is a Marshall MXL990 studio mic,

The mic runs balanced into a Behringer MiniMic Modeling preamp, to a Behringer 2496 Ultra-Curve, to a Behringer DSP 1000P digital effects processor, to a Behringer MX602A mixer, to the radio line level input.

A line level audio input circuit (-10dBv) was added in parallel to the standard mic input circuit (see below). The line level audio is brought into the radio via unused pins on the 8-pin mic connector. The line level input was rewired to allow VOX keying circuit as well as the switching circuits that shut off the audio preamp circuits during TX operation and goes directly to the balanced modulator. It is required to manually turn off the mic gain control on the radio (front panel) when using the line level audio input.

The Heathkit mic input section has been modified by clipping out the original audio amplifier circuit feeding the balanced modulator and adding a homemade Analog Devices SSM2019 mic amp circuit. This homemade amp is placed close to the balanced modulator. This mic input maintains original radio functionality, including VOX.

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