Whistler Wendy: Safe TRX2 speaker connections

Status
Not open for further replies.

Anderegg

Enter text in this field
Premium Subscriber
Joined
Mar 7, 2010
Messages
2,279
Location
San Diego
Wendy, can I safely connect the speaker output jack on a TRX2 to a PC sound card input jack? Can I connect the TRX2 speaker output to a small mono TRS mini mixer going to a PC? I don't want to kill my new scanners or blow the audio circuits like the Unidens.

Paul
 

WhistlerWendy

Member
Premium Subscriber
Joined
Sep 9, 2015
Messages
351
Location
Northwest Arkansas
Wendy, can I safely connect the speaker output jack on a TRX2 to a PC sound card input jack? Can I connect the TRX2 speaker output to a small mono TRS mini mixer going to a PC? I don't want to kill my new scanners or blow the audio circuits like the Unidens.

Paul
Sorry, you can only connect it to an external speaker.
 

Ubbe

Member
Joined
Sep 8, 2006
Messages
5,501
Location
Stockholm, Sweden
Always use a ground loop isolation transformer when connecting a scanners audio to a PC.



/Ubbe
 
Last edited:

Anderegg

Enter text in this field
Premium Subscriber
Joined
Mar 7, 2010
Messages
2,279
Location
San Diego
This explains why Whistler showed no interest when approached about a remote app for the scanners.

So ground loop isolator as shown would be what I need? What happens if I connect one to a PC, it blows the audio output circuit?

Paul
 

Anderegg

Enter text in this field
Premium Subscriber
Joined
Mar 7, 2010
Messages
2,279
Location
San Diego

Ubbe

Member
Joined
Sep 8, 2006
Messages
5,501
Location
Stockholm, Sweden
I have a 3.5mm stereo attenuation cable, but is that the same as a ground loop isolator?

Paul
Hard to tell, but most are that are supposed to be connected to a low impedance 8 ohm speaker out and the other end a 1 kohm low signal to a PC or stereo amplifier input.

Search on ebay or amazon for a "ground loop audio isolator 3.5mm".

I have 7 scanners running and they have a common antenna ground and at least one of the scanners are always connected to the PC with an audio cable or USB, so there will hopefully never be any voltage spikes that could wreck either the PCs audio input or a scanners audio amplifier. To be more sure of not damaging anything, while configuring and disconnecting cables, one could have a grounding wire connected to all scanners chassi and the PCs chassi.

/Ubbe
 

Anderegg

Enter text in this field
Premium Subscriber
Joined
Mar 7, 2010
Messages
2,279
Location
San Diego
So my eventual rig will have 4 TRX2's running into a little passive audio mixer which will be connected to my PC. Would I only need one ground loop isolator cable between the mixer and the PC? Also, my mixer has mono TRS jacks, is this a problem that will short the scanners audio jack?

Remember back before Phase II when you could plug audio jacks into audio ports and stuff, like just stick them in without a care...this is like scanner AIDS.

Paul
 

buddrousa

Member
Premium Subscriber
Joined
Jan 5, 2003
Messages
8,758
Location
NW Tenn
Paul I use 1 per scanner in my setup. In your case I would use 5 just to keep everything isolated.
 

Anderegg

Enter text in this field
Premium Subscriber
Joined
Mar 7, 2010
Messages
2,279
Location
San Diego
I just popped one on my mixer output...my stream feed is now cleaner, especially in the quite periods between talking, no more crackling. :-D

Paul
 

zzdiesel

Member
Premium Subscriber
Joined
Mar 17, 2006
Messages
2,000
Location
Kennett / Dunklin Co, Mo.
Always use a ground loop isolation transformer when connecting a scanners audio to a PC.



/Ubbe
Thanks for recommending this ground loop transformer. I wish I'd heard about these 10 years ago.I got mine in today from an eBay sale. It's the best scanner accessory I've ever acquired. I have to look at it often to verify it's still turned on.
 

Machria

Member
Premium Subscriber
Joined
Apr 24, 2014
Messages
508
Location
Long Island, NY
Always use a ground loop isolation transformer when connecting a scanners audio to a PC.



/Ubbe
Huh! So what in laymen's terms does this do? Isolate the scanner ground from the audio input's ground?

I used to plug my scanner headphone jack into a phono or other RCA audio input on my stereo amp in order to listen to the scanner over my stereo speaker system...

Are you guys saying we can't do that anymore? Thankfully I never tried it on the TRX, YET!! ;)
 

Anderegg

Enter text in this field
Premium Subscriber
Joined
Mar 7, 2010
Messages
2,279
Location
San Diego
Yup, seems like we can no longer connect scanners to anything else that is itself powered, or else the other devices DC current can flow back into the scanner and damage the audio circuit.

But look at the upside...the parts removed to cause this makes our scanners 10 cents cheaper to buy...yay!

Paul
 

wa8pyr

Technischer Guru
Lead Database Admin
Joined
Sep 22, 2002
Messages
5,399
Location
Ohio
Huh! So what in laymen's terms does this do? Isolate the scanner ground from the audio input's ground?

I used to plug my scanner headphone jack into a phono or other RCA audio input on my stereo amp in order to listen to the scanner over my stereo speaker system...

Are you guys saying we can't do that anymore? Thankfully I never tried it on the TRX, YET!! ;)
Ground loops have been a problem as long as I've been tinkering with this stuff, nearly 40 years.

The issue comes when you have a scanner powered off the household electric circuits connected to something else that is also powered off the household electric circuits. The multiple paths to ground from these various devices create a loop which can pick up electrical interference by induction. A handheld scanner powered by batteries is probably not going to be affected.

In addition, some devices (like a good quality stereo amp) will have impedance transformers on the inputs, which also serve as effective ground loop isolators. Most computers, however, do not have any kind of impedance transformer on the sound card input or output, and are fairly poorly shielded to begin with, so you end up with a ground loop.

The outboard ground loop isolator (a small transformer) simply isolates one device from the other, breaking the loop while still passing the audio.

And thanks to the folks who provided the links for the inexpensive isolators. I've been making my own with little surplus audio transformers for years and mounting them in 35mm film cans, but I'm out of transformers and these are much neater and cleaner.
 

Machria

Member
Premium Subscriber
Joined
Apr 24, 2014
Messages
508
Location
Long Island, NY
Thanks for the info Tom, appreciate it. I've never had a problem with this, 1 because I've only had handhelds, and 2 I'm always inputting into a Denon amp/stereo system which I suspect falls into the "high end" category being they cost $2k and up. ;)

Good to know though....
 
Status
Not open for further replies.
Top