Equipment - 1970s vintage Astor audio mixer (type 4170-411-01)

[photo of the mixer]


Included with edit suite hire, if needed.  For those jobs that need extra mixing channels than provided by just the eight-channel Yamaha mixer wired into the edit suite, 24dB of headroom, or a vintage 1970s sound.  Not available for off-site use (needs a lot of TLC, and very awkward transportation requirements would be entailed).

Mains powered (well, you could power it alternatively, if you had a very meaty 50 Volt DC supply), barely portable (it's designed for a fixed installation, is big, heavy, and the chassis is not very rigid), all discrete transistor circuitry, vintage audio mixer.

In this case, “Astor” was the Australian “Radio Corporation Pty Ltd” in South Melbourne.  This mixer is ex-ABC radio equipment, from Adelaide (Studio 511, going by hand-written servicing comments on some of the parts).

Equipment features
Number Details
12 Input channels with:
  • Low impedence XLR microphone connectors, or higher impedence 6.35 mm TRS line-level input connectors (both are floating transformer balanced audio inputs, neither with phantom power)
  • Pre-amp attentuator and input switching, with +8dBu or -20dBu line input, or -40dBm, -60dBm or -75dBm microphone input levels
  • Line input or group bus input (one or more input channels can be switched over to being the group one or two bus level controls to the master or reverb buses)
  • Variable pre-fader -30dB pad
  • Pre-fader channel output and insert (balanced Bantam TRS connectors on front patch-panel)
  • 180 degree phase switch
  • Bypassable passive L/C/R treble boost/cut, adjustable-frequency mid-range boost, & bass boost/cut calibrated equaliser controls
  • Bypassable switchable low-pass filter with 45, 70, and 160 Hertz rolloff frequencies.
  • Two indepependent reverb sends with pre/post switching and level controls
  • Non-latching pre-fade-listen monitor switch
  • Channel output Penny & Giles fader, mute switch, group bus send switches, master bus send switch, and stereo pan controls
  • Two post-fader group outputs
  • Individual 50 Volt “line open” tally signals, and one master “microphone(s) alive” tally signal
2 Reverb return inputs with:
  • Balanced 6.35 mm TRS connectors
  • Independent level controls
  • Independent output switching to PFL, group, and master buses
2 Master output channels with:
  • Independent Penny & Giles master faders
  • Pre-fader channel output and insert (balanced Bantam TRS connectors on front patch-panel)
  • 180 degree phase switch
  • Mute switches
  • Non-latching pre-fade-listen monitor switches
2 Independent master faders for the two reverb send channels
1 Bantam/TT TRS connector patch panel for all input and master channel sources, inputs, outputs, inserts, monitor inputs, master outputs, tone generator output, and spare rear-panel sockets
1 Monitor switcher for the main VU meters, studio-floor and control-booth monitor bus outputs (selects from main, reverb and uncalibrated-PFL output buses, plus five tape monitor inputs)
1 Meter bridge with:
  • Two large VU meters fed from the monitor switcher, with attentuator switches to set 0VU at +8dBm, +16dBm, or +20dBm reference levels
  • Two smaller VU meters for the reverb channels, with 0VU fixed at +8dBm
2 +8dBm floating transformer balanced main (left and right) outputs (with parallel-wired XLR and 6.35 mm TRS connectors)
2 +8dBm floating transformer balanced reverb send outputs (6.35 mm TRS connectors)
2 +8dBm balanced studio-floor monitor send outputs (6.35 mm TRS connectors), with independent level controls, and auto-muting when an input-channel microphone is alive
2 Balanced control-both monitor send outputs (6.35 mm TRS connectors), with a combined level control, and auto-muting when the built-in control-booth intercom microphone is alive
1 Unbalanced, adjustable-level, headphone monitor socket for the monitor bus (6.35 mm stereo TRS connector, on the rear panel)
1 Front panel microphone for slate recording, and intercom to the two studio monitor busses and an independent third talkback output (+8dBm balanced 6.35 mm TRS connector).
2 Dual-redundancy 50 Volt DC linear power supplies

If anybody can tell me what the NOL, ROL, & POL abbreviations stand for on the switches that pad the main VU meters, I'd like to know.  The Astor mixer (type 4170-411-01) manual says nothing about it, and I could only guess at their meanings.  (Normal, reserve, & peak output levels, perhaps?)  I do know what they do technically, though:  0VU at the NOL position is +8dBm (normal metering), at ROL position it's +16dBm (8dB attenuation), and at POL it's +20dBm (12dB attenuation).

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