Unitrunker Digital Audio out clipping, decoding errors

I've been using UT with both my old tapped Pro2006 (control) and RTL-SDR stick (voice) and it's generally worked okay. However while trying to tune the audio I noticed the audio output through VAC is very loud and clipped which is making it difficult for DSD+ to decode without errors. This is especially true with weaker signals. There doesn't seem to be any adjustment for UT to adjust the audio gain, and controlling through windows, while the volume can be adjusted, the audio is still being clipped and does nothing to help with decoding. Using DSDTune really made no difference. The audio from SDR# is a lot cleaner and seems to decode with fewer errors, although it doesn't help much when decoding the area's trunking system.

Is there some type of setting that can help with this issue? Thanks!

Hey what are your VAC settings?

Here are mine

Have you tried using VB-Audio Virtual Cable? It's a direct competitor for Virtual Audio Cable, much cheaper in price if you choose to buy it as it's donationware (it offers up to 3 virtual audio cables, however, while VAC offers up to I think 255 which is crazy) and just might work better overall. I used to use VAC myself but found it overly complex to do the simplest things like (tada) pass the audio signal from SDR# or whatever SDR app I happen to be using to a virtual audio cable so DSD+ can pick it up. I never had much success with VAC without a lot of config editing and even then it just never performed well.

First time I used VB-Audio Virtual Cable it took like 4 seconds to install it, a few more seconds to set it as the default recording device and set it for 16 bit 48 kHz, then I started SDR# and changed the audio output to the virtual audio cable, started it, fired up DSD+ and tuned in a DMR/TRBO system and voila, in under a minute I was listening in without another issue.

Can't get much easier than that.

But obviously if you require more than 2-3 virtual audio cables it won't be of much use I suppose, just thought I'd point it out as a potential option and for ease of installation and use.

I don't think it's my VAC settings since they're working just fine in SDR# w/ the DSD Interface. I did notice listening to a different system (all Moto, btw) that the audio wasn't as hot as the one in my county, but still was clipping. Adjusting audio levels in the Windows Mixer does work but the clipping is still there. If there was just a way to adjust levels within UT.

Btw @Amraks, shouldn't you be using 48kHz instead of 44.1? Might work with some systems but not all.

Hey ryan I think I had errors with them settings but I will try again.

My setup wasn't having a bar of it was get underflows.

Went back to my settings that where working.

I Take that back Ryan
Was setting my bits as 24 bit some programs didn't like it. as its is now set 16 bits with 48..

getting better sound quality and virtual cable 5 isn't lagging out when traffic gets busy.

My system had been running for 20 days with these settings lol
Its a new computer with 6 cores should handle a good load.
I guess when I bought the system 20 days ago I had some interesting things going on.

RyanThaDude said:

I've been using UT with both my old tapped Pro2006 (control) and RTL-SDR stick (voice) and it's generally worked okay. However while trying to tune the audio I noticed the audio output through VAC is very loud and clipped which is making it difficult for DSD+ to decode without errors. This is especially true with weaker signals. There doesn't seem to be any adjustment for UT to adjust the audio gain, and controlling through windows, while the volume can be adjusted, the audio is still being clipped and does nothing to help with decoding. Using DSDTune really made no difference. The audio from SDR# is a lot cleaner and seems to decode with fewer errors, although it doesn't help much when decoding the area's trunking system.

Is there some type of setting that can help with this issue? Thanks!

Click to expand...

I get the same clipping and decoding errors, forcing me to use SDR# to get clean audio. I requested a volume setting in UniTrunker right after the author added dongle support a long time ago, but I don't know if he intends to add such a setting.

A couple things I found out. If I have a great signal the errors are minimal to nearly non-existant and the decoded audio is great. However, if the signal is weak, this is where the clipping hurts the decoding on DSD+. Since there might be a some noise this raises the audio levels which in turn cause the audio to further clip which means it just completely errors out and the decoded audio is illegible. Now if I listen to the same frequency on SDR# through DSD the audio is not clipped therefore, while it does have some errors due to the weaker signal, it's still very legible.

While going through the configuration.xml(?) file I found a Volume setting in there, which was preset at 31 but changing it on my voice device didn't seem to make any difference.

Update: Somehow I finally got the volume mixer working correctly on my computer, and now it will lower the volume coming out of Unitrunker (it never had any effect before). Lowering the volume to 50% has cleaned up my DSD+ decode considerably, and is good enough for me to drop SDR# now.

I've been having the same issues but haven't been able to get the volume mixer working. Any tips?

nlurker said:

Update: Somehow I finally got the volume mixer working correctly on my computer, and now it will lower the volume coming out of Unitrunker (it never had any effect before). Lowering the volume to 50% has cleaned up my DSD+ decode considerably, and is good enough for me to drop SDR# now.

Click to expand...

Right-click on the speaker in the notification tray (next to the clock) and select "Open Volume Mixer". Once the Volume Mixer opens, look in the "Device" section and look for the down arrow just under the icon. It may say "Speakers" but some computers may vary. Select the associated Virtual Audio Cable line. This should change the Device from Speakers to Line 1. The slider will control your volume control. You may also need to enable "Volume control" on your virtual cable in the "Virtual Audio Cable Control Panel".

A few tips: Download a volume level meter app (I use This one) to aid in controlling your volume. Try adjusting while tuned to a weaker frequency since noise will drastically raise the audio level. Also note that while this does adjust the volume that feeds DSD+ it does not stop the clipping since there is no control of the volume within Unitrunker itself and still overloads internally but overall will still make a difference in the amount of errors on DSD+.

RyanThaDude said:

A few tips: Download a volume level meter app (I use This one) to aid in controlling your volume. Try adjusting while tuned to a weaker frequency since noise will drastically raise the audio level. Also note that while this does adjust the volume that feeds DSD+ it does not stop the clipping since there is no control of the volume within Unitrunker itself and still overloads internally but overall will still make a difference in the amount of errors on DSD+.

Click to expand...

Ryan, thanks for your tip. This level meter is quite useful. After lowering the volume to 25% I am getting legible results, though still not as good as with SDR#, which has its own internal volume control. Still hoping that Unitrunker gets its own volume control someday.