Audio Conditioner/Mixer Control Panel
This was a conceptual idea based on a standard audio mixer. I decided to include inputs for the external demodulators in my SWL system. Basically, it is an
audio mixer that controls the Line Level audio from four receivers, plus the output from four separate demodulators. It also features audio response shaping by
virtue of "tilt" and "contour" controls, and the traditional "bass" and "treble" functions. There are also "Line In" and "Line Out" (Mix Bus, Pre and Post audio)
selection, and a headphone amplifier, jack and level control.

The circuitry has been designed and finalized, as of August 2009, and I finished it for beta testing in 4 weeks.

Having spectral and functional control over the recovered audio of a good receiver makes all the difference one can imagine. The tone functions are a
combination of what might be found in a premium home audio system, along with circuitry borrowed form recording studio consoles and broadcast studio
spectral enhancement. The Equalization selector has four modes: Flat, Bass & Treble, Contour and Tilt. The Contour control gangs the bass and treble to
produce either a happy=face audio response or a mid-range peaked response. The M/R response position is very similar to "Signal A" format used for Telco
transmissions. It's a familiar response known to Hams as "DX response." The happy-face function boosts the bass and treble simultaneously to adjust for
loudspeaker shortcomings or room acoustics. The Tilt control is similar to the contour control, but reciprocal; when bass is boosted the treble is attenuated,
and vise versa.

There are three "AUX AUDIO" inputs/outputs which are connected to the Mix Bus, and the Pre and Post contouring circuits. This is a standard practice for
mixing boards when there are necessary or desired feeds for Telco lines, audio recorders, remote power amps and feeds to accessory/ancillary systems.

There are three speaker selectors to facilitate local, remote and aux loudspeaker systems ... 8 Watts, 4 to 32 Ohms.

Finally, there's a Line Gain and Power Gain control, for each respective audio section and an associated meter for those functions (VU and Watts).
The APC-1 which
controls the audio in the
SWL rack, sitting above
the RFP-1
er which controls all the
antenna and RF feeds
Here are the pair
connected to a
W-J 8718MFP
APC-1 Audio Controller

RFP-1 Antenna Signal

W-J 8718MFP

W-J 8718A

W-J DMS-105A
Here is the basic system, minus the SDM-1 Demodulator that I built some
months after assembling this system.

I also added a Power Line conditioner (
bottom of this page) and an ultra
12 Volt power supply.