Uniden Mod for Headset audio

[Chrome69]

I am looking for the mod for Uniden units to boost the Audio out of the headphone jack? Anyone can tell me where i can find it? Looking to do this to a BC92XLT, BC246 and if possible a BC350C

Any help would be greatly appreciated

Brian

 

[MarkEagleUSA]

I don't know about the 350, but the 92, 246, and possibly the 396 use this audio output circuit. It discusses a workaround to boost output from the jack.

 

[Chrome69]

thanks for the tip, it would seem a simple stereo plug will boost it safely with out doing anything to the circut. i will try that first and see if i get any better results.

Brian

 

[MarkEagleUSA]

it would seem a simple stereo plug will boost it safely with out doing anything to the circut

It does! Seems to work best with 4 ohm speakers, though small wattage 8 ohm's work too.

Keep in mind this isn't the same as using a stereo-to-mono adapter. You need to physically wire the stereo plug to the end of the speaker wire, using the TIP and GROUND.

 

[Al42]

Keep in mind this isn't the same as using a stereo-to-mono adapter. You need to physically wire the stereo plug to the end of the speaker wire, using the TIP and GROUND.

It looks more, to me, like ring and ground, but you still have an 18 ohm resistor in series with the external speaker. That cuts the power output to less than 500 mw, with only about 150 mw at an 8 ohm speaker. An 8 ohm speaker directly across the output, which is how the internal speaker is wired, gets just over 1 watt. (Assuming 1% THD and a 5 volt supply in both cases.)

 

[MarkEagleUSA]

It looks more, to me, like ring and ground

Look again:

If the earphone plug is replaced with a stereo type it is possible to increase the power delivered to the earphone. By leaving the second contact on the plug (the ring contact just behind the tip) open, the 10 Ohm resistor is disconnected. Then the earphone power is increased to 38 mW.

you still have an 18 ohm resistor in series with the external speaker

Unfortunately, you can't do anything about that externally.

 

[MacombMonitor]

Not sure if this applies to the most recent models, but in the past, taking a small piece of wire, and wrapping it around the outer ground of the antenna connector, then over to the outer ground of the earphone connector, did the trick. This bypasses the resistor that limits the audio level to the earphone jack.

 

[MarkWestin]

Hello,

All (most?) of the new units are using a balanced output system, so the "ground the antenna to the earphone" trick no longer works as expected. On these units, this does short the resistor to ground, but only on one side of the circuit and will probably only cause the amplifier chip to overheat, and will cause the batteries to wear down faster.

Not recomended for the newer units.

This link from a previous post in this thread shows the problem:

http://home.hvc.rr.com/bpetrow/audio.htm

Mark

 

[Al42]

It looks more, to me, like ring and ground

Look again:
Quote:
If the earphone plug is replaced with a stereo type it is possible to increase the power delivered to the earphone. By leaving the second contact on the plug (the ring contact just behind the tip) open, the 10 Ohm resistor is disconnected. Then the earphone power is increased to 38 mW.

You're correct - I was looking at the schematic backwards.