BCD436HP/BCD536HP: 536 External Speaker and Volume Knob

[welshtorg]

I’ve installed my BCD-536HP inside the console of my Toyota Tundra. Being inside the console, I knew I needed an external speaker. Hooked up a modded Motorola non-amplified speaker, and sounded great. Being inside the console, the volume knob wasn’t easily accessible, so I decided to put an inline volume knob in the setup. The new setup was a mono 3.5 cord to a volume controller, back to the speaker. New setup up not as loud, and the volume control was not linear with the sound (basically the volume was only affected in the last 1/8 of the knobs travel). Replaced everything, new speaker (Uniden BC-20 this time), new volume controller (different model), and new 3.5 mm cord. No better. Even took the new setup into the house and tried it on the inside BCD-536HP. Same mediocre performance.

I’m not quite sure I want to invest in an amplified speaker, and I’ve read where certain amplified speakers can damage the unit.

Any suggestions or ideas?

 

[ofd8001]

I've had good results with the Uniden BC23A. Unfortunately your predicament is a little different with a desire for some type of volume control. You may try reaching out to Scannermaster to see what they may suggest.

 

[richardbritt]

I am using a 536 and a BC23a amplified speaker in my Dodge Dakota and the same thing in my car. Both blast me out of the vehicle if I turn them up too high. The speaker has a built in volume control. I put my scanner volume on around 7 and adjust the external speaker volume so I can hear it over road noise or the music radio.

 

[Ubbe]

(basically the volume was only affected in the last 1/8 of the knobs travel).

You'll get that when the volume control has a too high resistance and/or speaker too low impedance.
Can you state exactly what you where using as a volume controller so it might be possible to find out how it is designed and its resistance value?

It needs to use a logarithmic potentiometer but in reverse, value change quick at the lowest volume setting but change slowly at max volume.

/Ubbe

 

[n1chu]

“I’ve read where certain amplified speakers can damage the unit.”

Wondering how an amplified speaker can damage the scanner? The scanner’s external jack only supplies what it does, and an amplified speaker takes only what it’s given, not feeding anything back into the scanner… or does it?

 

[Dewey]

“I’ve read where certain amplified speakers can damage the unit.”

Wondering how an amplified speaker can damage the scanner?

And if the amplified speaker uses a common ground?

 

[kruser]

“I’ve read where certain amplified speakers can damage the unit.”

Wondering how an amplified speaker can damage the scanner? The scanner’s external jack only supplies what it does, and an amplified speaker takes only what it’s given, not feeding anything back into the scanner… or does it?

The 536 has a BTL output for the external speaker jack.
Neither the tip or the sleeve of that jack are grounded to the chassis.
An amplified speaker will often ground the sleeve connection thru the 12 VDC power feed.
Grounding either terminal of the external speaker jack will short out one half of the audio amplifier chips output. I've never heard of anyone blowing the audio chip by plugging in something the does ground either side of the output to the chassis but it's not advised to do such.

Even things like BT transmitters don't play well with the 536 when they are also being powered externally which will often create a path to ground. Run a BT transmitter on it's internal battery only works fine as there's no path to ground.

I think the SDS200 also has a BTL output.

 

[Dewey]

The 536 has a BTL output for the external speaker jack.
Neither the tip or the sleeve of that jack are grounded to the chassis.
An amplified speaker will often ground the sleeve connection thru the 12 VDC power feed.
Grounding either terminal of the external speaker jack will short out one half of the audio amplifier chips output. I've never heard of anyone blowing the audio chip by plugging in something the does ground either side of the output to the chassis but it's not advised to do such.

Even things like BT transmitters don't play well with the 536 when they are also being powered externally which will often create a path to ground. Run a BT transmitter on it's internal battery only works fine as there's no path to ground.

I think the SDS200 also has a BTL output.

Exactly!

Sometimes when running my 536 & 200, I need to preserve the quiet of the room so I'll use a ground loop isolator (this: https://www.amazon.com/dp/B0CJ9H6PZT) so I can run one scanner into the left ear of headphones and the other scanner into the right ear of the same headphones. Even then, they still mess with each other... If I use the speaker out jacks, one of the scanners will eventually "pop" (audio pop) after a few minutes and lose it's audio until I turn it off for a minute or two to allow the audio amp to recover. So I use both scanner's headphone jacks and even then, when one scanner is receiving the audio is calm, but as soon as the second scanner starts receiving, the audio for both scanners will rise to a louder audio level like the older Unidens when you could short the earphone ground to the antenna ground to get a louder audio output. The common ground is that both scanners are plugged into the same antenna splitter. (They're also plugged into the same surge protector, but I don't know if that causes a connection to the chassis ground)

 

[Ubbe]

I'll use a ground loop isolator (this: https://www.amazon.com/dp/B0CJ9H6PZT)

Like this or the exact model? It has a 3,5mm jack to connect a stereo audio plug to it that then has a common ground for left and right channel. It will probably mean that the RCA connectors have their left and right channel grounds connected together. You'll probably need a "true" galvanic isolator if using one half for one scanner and the other half for another scanner.

/Ubbe

 

[Dewey]

Like this or the exact model? It has a 3,5mm jack to connect a stereo audio plug to it that then has a common ground for left and right channel. It will probably mean that the RCA connectors have their left and right channel grounds connected together. You'll probably need a "true" galvanic isolator if using one half for one scanner and the other half for another scanner.

/Ubbe

Thanks Ubbe. I don't want to hijack the OP's thread, but to answer your question... yes, that is the exact model I use. For input from the scanners, I use the RCA jacks with mono 3.5 mm to RCA adapters on the scanner ends of the RCA cables. I know the scanner ear/head phone jacks are stereo, but they're supposed to tolerate mono plugs (I can't see where using one side of 3.5 mm stereo breakout adapters for the ear/head phone jacks would really make a difference for my application). I plug the 3.5 mm stereo headphones into the ground loop isolator output with the switch set to the "Lift" position. While it does have its problems, it works way better than just using a wye 3.5 mm stereo breakout adapter from the stereo headphones straight to the two different ear/head phone jacks.

 

[Ubbe]

it works way better than just using a wye 3.5 mm stereo breakout adapter from the stereo headphones straight to the two different ear/head phone jacks.

Your headphones use the same ground for left and right channel, if you look at the plug it uses. Your scanners use the same ground for left and right channels due to the antenna ground.

You could probably take a look inside the headphone cabling and try to separate the cabling to get one + and - lead for left and another totally separate + and - for the right channel.

You could also try and use the isolator backwards, using its outputs and inputs and see if that changes anything. But best would of course be to use an isolator that are totally galvanic. Both 536 and 200 use BTL amplifiers so you should use a stereo plug connecting them and then only use left and right channels as the + and - to feed the isolator and not use the ground of the stereo plug.

/Ubbe

 

[Bob1955]

I’ve installed my BCD-536HP inside the console of my Toyota Tundra. Being inside the console, I knew I needed an external speaker. Hooked up a modded Motorola non-amplified speaker, and sounded great. Being inside the console, the volume knob wasn’t easily accessible, so I decided to put an inline volume knob in the setup. The new setup was a mono 3.5 cord to a volume controller, back to the speaker. New setup up not as loud, and the volume control was not linear with the sound (basically the volume was only affected in the last 1/8 of the knobs travel). Replaced everything, new speaker (Uniden BC-20 this time), new volume controller (different model), and new 3.5 mm cord. No better. Even took the new setup into the house and tried it on the inside BCD-536HP. Same mediocre performance.

I’m not quite sure I want to invest in an amplified speaker, and I’ve read where certain amplified speakers can damage the unit.

Any suggestions or ideas?

I have a Uniden Bearcat BCT15X and for an external speaker that "ROCKS", purchase a Uniden Bearcat BC7 for $16.99 as the built in speakers are underneath all of the base scanners.