Re: [TenTec] audio on Omni-VI+

["Dr. Gerald N. Johnson" <geraldj@weather.net>]

Looking at schematics I don't see anything but the notch filter 
inherently limiting bandwidth on the IF/AF board. Maybe its that notch 
filter not getting out of the way when not in use. Maybe its the DSP. 
And I'm looking at the Omni VI, not the plus.
A test you might try is to disconnect the two cables between the IF/AF 
board and the DSP and hook them together. Take the DSP out of the 
circuit and see how it sounds. If it sounds much better that would point 
at the DSP board having the bandwidth limitation.
The DSP chip interface to the analog world is through a TLC32041 which 
has low pass filters in and out. They are clocked by the DSP chip so are 
really hard to change.
The manuals I have on computer show the same part numbers for the audio 
and the logic boards, so the differences have to be all in the software 
and hard to change from here.
I suspect that jumping around the DSP is as effective as tapping for an 
external audio amp. It wouldn't be any harder to bring out an audio tap 
for an external amp as to add a tiny toggle switch to select DSP or not 
DSP. Needs to be a SPDT, common to the audio output section, like the 
constant level output jack, one contact to the input of the DSP and the 
other to the output of the DSP with the cable from DSP out to audio 
disconnected.
73, Jerry, K0CQ

On 2/6/2011 2:28 PM, yash@aol.com wrote:
> Gerald
> your right on the limits of communications audio ,but the VI+ does not even 
> pass audio in that range, in normal operation. I run a B-line, a flex 5000 and 
> a Kenwood ts-480 ,all produce beautiful,clear audio. Iam not talking ssb HI-FI 
> or any of that nonsense. My old s-line had much better audio than the ten tec 
> has in its normal unchanged state. The VI+ always sounds like it has a BAD head 
> cold. I have been able to upgrade the audio quality with the Inrad mod, better 
> but not good. Will give N1EU's direct takeoff suggestion for the audio a try. 
> The quality of the VI+ audio was mostly a result of tweaking for CW and never 
> listening to ssb on the rig. No other manufacturer seems to have a audio 
> problem like the VI+'s. It was also in the Omni V's and a few other earlier 
> rigs. Just my opinion
> thanks
> dale wt4t
>
>
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> -----Original Message-----
> From: Dr. Gerald N. Johnson<geraldj@weather.net>
> To: tentec@contesting.com
> Sent: Sun, Feb 6, 2011 11:29 am
> Subject: Re: [TenTec] audio on Omni-VI+
>
>
> Communications audio isn't full and robust. It has a limited bandwidth
>
> by the IF filters and proper audio to limit you hearing atmospheric and
>
> circuit noise, hum, and rumble. Adding bandwidth to any of these reduces
>
> the S/N of the desired signal and allows you to filter more atmospheric
>
> and circuit noise and QRM with your ears.
>
>
>
> I often use a passive low pass filter on the speaker to reduce filter
>
> leakthrough and audio state high frequency noise outside the IF filter
>
> pass band. One I use is described at:
>
> http://www.geraldj.networkiowa.com/papers/speakerfilter.pdf
>
> Its really handy for cleaning out DSP artifacts.
>
>
>
> 73, Jerry, K0CQ
>
>
>
> On 2/6/2011 8:31 AM, yash@aol.com wrote:
>
> >
> >    Have been using my ,new to me ,Omni VI+ for a few weeks,like the rig,hard to
> fault for a 10+ year old rig. I have one problem that I would like to change.
>
> The audio quality. In stock form the rig sounds "nasally" to me ,constricted and
>
> choppy. I installed the Inrad audio kit ,2 caps and 1 resister,it made a nice
>
> change in the quality of the audio. I noticed that INrad also mentions changing
>
> the OEM 6 MHz filter with a #755 of their design. Has anyone done this filter
>
> change? Is there another route to getting the audio sounding full and clean with
>
> this rig? Other than the audio the VI+ is great.
>
> > thanks
> > dale wt4t
> >
> >
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