[Orion] Orion's audio outputs explained

[Sinisa Hristov]

There are three DACs (called Left DAC, Right DAC and Speaker DAC)
generating three audio voltages which are then fed to headphone
and speaker amplifiers and LINE OUT, LEFT AUX and RIGHT AUX outputs.

Left DAC feeds the line-level LEFT AUX OUT (on the rear panel AUX I/O DIN connector)
and the left headphone channel.

Right DAC feeds the line-level RIGHT AUX OUT (on the rear panel AUX I/O DIN connector)
and the right headphone channel.

Speaker DAC feeds the line-level LINE OUT (rear panel CINCH connector) and the speaker.

The source for each DAC is independently selectable (from the AUDIO menu)
as Main RX, Sub RX or Both. When BinRX is active, source selection is automatic,
overriding user settings.

Strangely enough, when headphones are NOT engaged, Left or Right DAC will NOT use
a source that is not simultaneously used for Speaker DAC, EVEN if the source IS
selected for the Left/Right DAC. This prevents independent source selection
for the speaker and AUX outputs. TenTec must have had some reason for playing
such tricks, but I consider it dirty.

Advancing MAIN AF control will increase the Main RX source level, AND simultaneously
decrease the Sub RX source level. Decreasing MAIN AF control to minimum or muting it
will reduce Main RX source level to zero, AND increase Sub RX source level to maximum,
unless SUB AF is also decreased to minimum or muted. All of this applies to SUB AF
control too, mutatis mutandis.

Please note that we are talking about SOURCE levels here, before any of them
is actually applied to a DAC. In other words - the mutual influence is there
at all times, i.e. it does NOT depend on DAC source selections at all.

Therefore, Main RX and Sub RX levels available from a DAC will ALWAYS
reflect the RELATIVE ratio of MAIN AF position to SUB AF position.

Line-level outputs have full scale voltages of 1 V rms.
Driving impedance is low as they are driven directly by TL082 op amps.

The speaker and headphone amplifiers get the same signal mix
as corresponding line-level outputs (as described above),
with additional ABSOLUTE volume control applied.

Unfortunately, Orion doesn't have plain and simple line-level outputs
with levels completely independent of front panel volume settings,
as most prior rigs had. This was sacrified in order to save a few dollars
for an additional stereo DAC.


73,

Sinisa  YT1NT, VA3TTN