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How do I easily convert a stereo power output to mono?

BenThePCGuy

Jan 25, 2016
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I have an amplifier board with a stereo output that goes directly into passive speakers. Is there an easy way to convert the stereo to a mono signal? I'd like to house the device with an existing single old Celestion 8" full range speaker.

The board just takes a barrel DC input - 8-24 Volts and the output is 25 Watts per channel.

TDA7492P 50W+50W Wireless Bluetooth 4.0 Audio Receiver Digital Amplifier Board

D13802.jpg
 

Martaine2005

May 12, 2015
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Hi Ben,
Simply, just use one channel.
The electronic amps don't care about having all channels working.
So choose left or right! your choice..

Martin
 

BenThePCGuy

Jan 25, 2016
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Sorry. I didn't make it clear, I'd like to combine the two stereo channels into one so that the one speaker can play both channels. If I were to just use one channel then I'd get Ringo's drums isolated from the rest of the music because tracks were often recorded with wild stereo separation.

I know I could use one channel to do this but I'd have to have the bluetooth source switched to mono. This works fine with the player on my Android phone because I have a mono switch in the software (HTC ONE M9 & Poweramp).

What I'm looking for is a way to combine the two stereo outputs into one mono feed.
 

Martaine2005

May 12, 2015
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Oh ok.. Ringo was never very good! Buddy is much better!!
You can use a stereo to mono adapter which effectively just joins both positives and negatives together.
Or just connect both together without the adapter. No harm will be done.

Martin
 

AnalogKid

Jun 10, 2015
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The line-level L and R signals are not available to be summed at the input to the amp. It sounds like the only option is to combine the signals at the amp output, and at 50 W output there could be considerable harm done. This board basically is two switching power supplies with full four-quadrant operation. One channel might not like having to sink a lot of current from the other channel. For protection, you might have to add series resistors to the outputs to combine them into the speaker. This will attenuate the signal and mess with the transient response a little, but the larger the resistors the less the potential for damage.

My respect for Ringo has slowly increased over the years. He was left-handed and playing a right-handed kit (something Phil Collins didn't try), was an above-average time-keeper, and single-handedly popularized the drum riser. Musically not the flashiest guy, but neither were the rest of them; he was the perfect backup for a vocal group.

ak
 
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Martaine2005

May 12, 2015
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ak is correct.
A resistor on both left and right positives would form a simple mixer and avoid potential damage.
However, I have never had any problems doing this. Sometimes a speaker blows or amp blows and I have no choice while playing live..
If you keep it well below distortion levels, the voice coils wont be fighting each other.

I forgot Phil Colins was known as Buddy.. I was talking about Buddy Rich..One of the original best drummers.. I followed his footsteps and loved playing "let there be drums"..
Then in my band at 12 years old was playing "wipe out" like the original..I really miss those days..

Martin
 

AnalogKid

Jun 10, 2015
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If you keep it well below distortion levels, the voice coils wont be fighting each other.

Maybe you mean the output stages won't fight...

I referred to Phil only in the context that Ringo (universally regarded as "worse" than Phil) was playing with a handicap and better than most people think. I'm not what you would call a big fan of his, but I recognize that the guy was perfect for his place and time.

OTOH, huge BR fan, saw him six times. When PBS aired Rich At The Top in 1973, U-Matic was less than 2 years old and very expensive, and Beta and VHS were 3 and 5 years away. Still, I had a bootleg copy of the program - on 2" Quad tape. I could play it only at work after signoff, but that was a perk of working nights/weekends in a tape room.

ak
 

Martaine2005

May 12, 2015
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Maybe you mean the output stages won't fight...
Yes, I am technically disfunctional.:p
That's really interesting about BR.. My uncle who sadly passed and we buried last week actually did a duo with him..I still have my uncles kit. I had a copy of Keith Moons double bass drum pearl white 13 piece kit.. Never had dual bass pedals like todays kids!!
Thanks Ak.. that brought back some nice memories..

Martin
 

CDRIVE

Hauling 10' pipe on a Trek Shift3
May 8, 2012
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When we're talking about low power High Z outputs like earphones this is an easy thing to do. When you get down to 4Ω to 8Ω @ 50 Watts it's a new ballgame. You're going to have to sleuth that board to couple the two channels together at a point where power levels are considerably lower.

BTW, they make another version of your board with a low level Input/Output jack.
http://www.ebay.com/itm/TDA7492P-50...188824?hash=item27ff6efed8:g:f4EAAOSw5VFWKMl3

Somewhere near where that jack ties into the circuit is where the coupling of the two channels needs to happen.

Chris
 
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