BCD536HP: BCD536HP Volume is now 1/2 of what it used to be.

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jb_tas

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Hi All
has anybody fried the audio from NOT running a ground loop isolator from the ext speaker out to line in on the PC and the usb cable at the same time?
my volume has halved
I now need to turn it up to max to hear anything that's a bit quieter than usual.
I noticed that when I had the speaker out only, it worked fine but then when I added the usb cable it completed a ground loop and shorted out the audio thus (i don't know 4 sure im no expert) frying 1 of the audio out amps.
Hence I now only have 1/2 volume.
and can this be repaired or do I just toss this scanner and buy another 1.
Im in Australia and am not prepared to spend over $100 to send it back to the US and return.
Thanks to anyone who can help.
 

jonwienke

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Hi All
has anybody fried the audio from NOT running a ground loop isolator from the ext speaker out to line in on the PC and the usb cable at the same time?
Yes. If you don't isolate the ground, you can fry the audio amp.

It is cheaper to repair than buy new. But Uniden will probably have to do it.

But if you do decide to trash it, I will pay you shipping to give it a good home. PM me :)
 

jb_tas

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really my question is has anybody else done this and did it result in the volume being halved?
Im just trying to confirm that its what has happened to mine, I don't want to send it off if that's NOT the fault, it might be just me.
Thanks
 

dcisive

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Just for fun in case you happen to program your unit via the Sentinel program, go in and set your "Volume Offset" to +2 or even +3 and save it. Then go to the "Scanner" tab and upload the altered file with BOTH the boxes checked so it overwrites all. Give it a whirl you have nothing to loose. It may boost the output back to a nice level. I played with this setting and as an example found that while i typically listen at level 6 on my scanners volume of the 536, I would turn it down to 4 to not have it too loud. I ended up going back to "0" of course, but in your case it may do the trick. Give it a try.
 

jonwienke

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That's probably not a good idea. You can only boost an audio signal so far before it clips and distorts. Google "gain staging".

Also, Volume Offset is a per-channel setting, not a global setting, so you'd have to change it in every channel programmed in every Favorite List--a huge PITA.
 

dcisive

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While I agree with your statement Jon as a general one, having worked in and with several recording studio's over the years, the application I referred to of raising the level (yes on a Global level) is not only practical under some circumstances but super easy. I just take the very first saved freuency, alter it to say +2, then copy and paste it from top to bottom of my lists. It's instant and easy frankly for a TON of saved frequencies as I have. In this persons case I do think it would be a great test to see if it might help. It won't hurt. If it doesn't work oh well........can't say you didn't try. I'll stand on my idea and would love to hear if he has any success with it. Who knows
 

mancow

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I think this happened to me as well. I have a 536 on a remote proscan setup and I'm having to crank it up almost full tilt now. I didn't realize it had to be isolated.

Freaking wonderful...
 

ProScan

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I think this happened to me as well. I have a 536 on a remote proscan setup and I'm having to crank it up almost full tilt now. I didn't realize it had to be isolated.

Freaking wonderful...
If you can, use the Wi-Fi for the audio. It's the best sounding because no copper involved that can pick up noise and will not overdrive the sound card front end and is independent of the scanner volume control and is already isolated.
 

ChrisABQ

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I know I had issues when changing modulation from NFM to FM, it naturally is quieter than NFM. Also, have you tried the audio level of the REC Out port on the back (green)? It's a constant audio level not connected with volume, I'd be interested to know if that is working.
 

mancow

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If you can, use the Wi-Fi for the audio. It's the best sounding because no copper involved that can pick up noise and will not overdrive the sound card front end and is independent of the scanner volume control and is already isolated.
The location has Wi-Fi turned off (not my tower site). I agree that would be best. Maybe I can try connecting direct to the PC Wi-Fi even with no router in the mix and leave the rest connected via Ethernet?
 

jb_tas

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Just for fun in case you happen to program your unit via the Sentinel program, go in and set your "Volume Offset" to +2 or even +3 and save it. Then go to the "Scanner" tab and upload the altered file with BOTH the boxes checked so it overwrites all. Give it a whirl you have nothing to loose. It may boost the output back to a nice level. I played with this setting and as an example found that while i typically listen at level 6 on my scanners volume of the 536, I would turn it down to 4 to not have it too loud. I ended up going back to "0" of course, but in your case it may do the trick. Give it a try.
I've adjusted the volume offsets already and still not much sound under 8 on the volume.
if you can hear anything with volume at 4 your not affected I cant hear a thing with it on 4 and at 6 if I get real close and listen hard I can hear something un legible though, its just to quiet.

Mancow sounds like you've done what I have, so I'm not alone

After I've had it repaired I'm going to add a line out jack that bypasses the audio finals all together and add a disc tap at the same time, why Uniden didn't fit a line out is beyond me. or put in BOLD print in the manual that they have changed how the audio out is configured and the need of modified cables or a ground loop isolator.
As I stated in my first post it happened when I connected the USB cable, that's what grounded the radio to the PC.

sorry 15X scanners are NOT IN ANYWAY like the 536's I've a 996 here and yes they do have a specific rec out where the 4/536's do not.
 

jonwienke

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In this persons case I do think it would be a great test to see if it might help. It won't hurt. If it doesn't work oh well........can't say you didn't try. I'll stand on my idea and would love to hear if he has any success with it. Who knows
If you blow the audio finals, you can't fix that by boosting the input signal. Just like if you blow an audio amp, you can't fix that by boosting the output from the mixer board. You gotta fix the amp.
 

HogDriver

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For us non-radio techs, can you explain what this ground loop is and what we can do to fix it?!


Sent from my iPhone using Tapatalk Pro
 

jonwienke

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On some devices, the outer contact of the headphone/speaker jack is connected to ground. On Uniden devices, it is not, it is connected to a separate audio output that has the opposite polarity of the center contact. This allows the output voltage going to the speaker to be doubled without increasing the voltage going to the audio amps. But it requires that everything plugged into the headphone/speaker jack NOT be connected to ground, or the inverted audio output connected to the outer contact of the jack will be shorted out, and you will blow the audio amplifier.

Ground loops are also a problem when connected devices are running off separate power supplies, like a scanner and a computer. There can be a voltage between one device's ground and the other device's ground, and that causes a hum or buzz in the audio connection. If the voltage difference is great enough, it can damage the input or output of the devices being connected.

A ground loop isolator solves both problems by electrically isolating the input and output from each other, so that nothing can be shorted to ground, and ground potential differences cannot cause damage, hum, or interference in the audio signal.
 

jonwienke

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One other thing: if both amplifier outputs are on the same chip, the heat buildup caused by shorting one output can damage both outputs of the amplifier.
 

Tim-B

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So if I have the earphone jack of a scanner connected to the mic input of my laptop to record new unidentified talkgroups shoud I put one of these isolators between them to be safe?
 

jonwienke

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Yes.

And use line in, not mic in or you will have problems with clipping and distortion.
 

Tim-B

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Okay, thanks. I have recorded many times without one. I guess I was lucky then. The laptop I use only has one input. It has a little microphone icon next to it.
 
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