More Thingking about Audio Processing

For over 80 years, receiver (and now transceiver) manufacturers have made increased improvements in improving receive-signal intelligibility.  Additionally, countless manufacturers have developed external audio processing units for improving intelligibility of just about any receive-unit with a
speaker or headphone output.

My current operating setup includes a pair of MFJ-752's and an MFJ-784 DSP (for left-channel audio), along with a pair of 1990's cascaded JPS DSP units (the NIR-10 and NIR-12) for the right-channel. Each channel is front-ended with an Autek QF-1A analog filter which enables the Stereo-Cw method I have written so much about.

The only real downside to cascading all of these units is the potential introduction of [so-called] "ground loops" into the audio line(s) for each channel.  Also in cascade mode, individual filter characteristics may create unexpected interactions.  With a properly wired switching arrangement, filter cascade can be switched in a given channel (left or right).  Additionally, having the ability to switch units from left-to-right (of the audio system) as well as Left-ear and Right-ear, creates the ability to "adapt" a given filter order to each receive mode (Cw, Ssb & RTTY) as well as to the listener's individual-ear differences.

Some filters are better at "Peaking" (the Autek QF-1A) while others are better at bandpass-notching (JPS NIR-10), Dynamic Peaking (JPS NIR-12) simple additional signal notching (MFJ-752); and of course, DNR - Digital Noise Reduction (NIR-10 & NIR-12), not to mention the 15-level DNR circuit built into the currently utilized Yaesu FT-2000 transceiver.

As mentioned earlier, intermixing a number of different audio units (with shared and/or separate
power sources) risks creating unintended ground loops throughout the audio lines.  These loops
can be mitigated somewhat with grounding straps and properly placed bypass capacitors.  While
use of a stereo equalizer at the end of the audio line can tune out any remaining artifact, ideally,
it should not be necessary at all.

 

A disadvantage to using the JPS NIR units to process the same signal heard in the opposite ear is the ~130-ms delay incurred by the DSP chip overhead resulting in a sort of delay-echo between the left and right.  While we can't speed up the DSP chips, we CAN introduce an audio delay to the unprocessed ear essentially counter-balancing the audio between the two ears.

Altho there are many ways to accomplish this, I took the easy way and inserted a little adjustable device known as a "Lip Sync Corrector" to create a timing match between the Left/Right audio lines.  ([CLICK HERE] to see how I DiD that.)

With above in place, I can reap the benefits of using combined analog and digital processing along
a single stereo-audio stream - Life is GooD!

Do YOU process radio receive audio?

What Discoveries have YOU made?