My listening is done with either a pair of Jamo CS5 amplified speakers or a pair of
Sennheiser HD-580 headphones connected to a Timewave DSP-599ZX box. Either way, they only
need to be driven with a line level signal source. Without exception, every amateur rig
I've ever listened to had inferior audio output amplification between the product detector
and audio output. I've found it easy to tap the audio from various rigs at or soon after the
product detector, resulting in incredible improvements in fidelity of received ssb audio.
These improvements include more extended passband response, smoother and more listenable audio
and also much quieter audio. If the tapped signal is very low level, I use my Behringer
MX-802A mixer to amplify it to line level using its "AUX SEND" bus.
Another alternative to external amplification is to replace the rig's af ouput stages with
something better. For the enterprising homebrewer, check out audiphile opamp info or some
sample circuits at Headwize.
Triton IV
It is VERY easy to add a line level audio output to the Triton IV. If you look at the IF-AGC
board (80279) schematic, the terminal pin labelled "Audio" on the schematic (off C21) is what
we want. What I did was run a shielded cable from that pin to an RCA jack on the rear panel.
I decided to use the "sidetone" jack, but you can use anyone you want. Just remove the wire
currently connected to it, and tape/label the wire so you can reconnect, if desired, in the
future.
With the 544 bottom cover removed, and with 544 resting on its top with front panel toward you:
if-agc board is to the left of the pto, with 2 if cans on it.
There is a row of 7 stake pins at the rear of the board (in back of blue S meter pot)
You will attach a shielded cable as follows: center conductor to third pin from the right,
shield to last pin on right.
Route the cable to the RCA jack you decided to use. Solder the center conductor of the cable
to the center pin of the RCA jack and the shield to the shield lug.
This mod takes the audio off before the AF Gain control. I control the volume with the level
control of my speakers. It would be easy to take the audio off after the gain control, by
consulting the schematic.
Future additions to this mod will include replacing some of the coupling capacitors that are
still in the audio path with more audio-friendly capacitors and perhaps higher values to
enable slightly more bass extension.
It may also be necessary to adjust C3 and tweak T1 on the SSB generator board (page 3-26 of
the manual) to properly center the ssb passband and pull in some bass extension. If you
adjust C3, you should also check that the CW offset hasn't been affected. You may need to
adjust C2 to bring the CW offset back to 750hz. Note - these adjustments should only be
undertaken by those experienced with such alignment.
A final note is that Ten-Tec may have used different xtal filters during the span of the
Triton IV/544 so your rig may be equipped with either a 2.5Khz or 2.7Khz xtal filter. It
probably would be fairly easy to wire in an Inrad 2.8Khz xtal filter for ultimate fidelity.
If you replace the filter, be prepared to align the SSB generator board, but this is not
very difficult for those with a little experience, a dummy load, an oscilloscope and a
general coverage receiver or frequency counter.
Corsair
Please click here to go to the new page of information on N1EU audio mods to the Ten-Tec Corsair
Omni VI
The stock Omni VI(+) suffers from a very constricted passband in ssb. ARRL measured about 1600hz in
their review. After experimenting a bit, I found a way to completely open the passband up to the full
width of the xtal filters. For those seeking hi-fi ssb rx audio from the Omni VI, and who are willing
to amplify the audio externally, a night and day improvement can be had from tapping the product
detector audio off U3-6 on the if/af board through a 1uF capacitor tack soldered to the pin, and a shielded
cable brought out for amplification. It is a requirement that you then adjust C10/C12 on the TX Audio board
to optimize the receive passband.
The Inrad 2.8Khz filters are really a necessity to complete the "mod" for the Omni VI. It goes without saying
that the notch filter, dsp, sidetone, fm, etc. are bypassed with this audio output.
Good Luck and happy listening!
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