Unit or circuit to properly convert stereo to mono for AM Tx is ?

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Fran3
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Unit or circuit to properly convert stereo to mono for AM Tx is ?

Post by Fran3 » Thu Jan 03, 2019 11:12 am

For our AM we have a board that only provides stereo out via XLR Left and XLR Right.
We need to convert it to mono to feed our audio processor and AM transmitter.
We can build a restive network but that will have maybe 3db loss.
A nicer solution would be an active circuit to properly 'mix' the Left and Right channels into a single mono out.
What unit do you guys suggest?
Thanks

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Bill DeFelice
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Re: Unit or circuit to properly convert stereo to mono for AM Tx is ?

Post by Bill DeFelice » Thu Jan 03, 2019 1:06 pm

I've often used the Lattice Combiner/Splitter
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Fran3
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Re: Unit or circuit to properly convert stereo to mono for AM Tx is ?

Post by Fran3 » Thu Jan 03, 2019 2:09 pm

OK, that raises the question of...

What small in-line line-amp can be used to recover the 6db loss and even add more gain if needed...

either screw terminal or XLR connectors

Thanks,

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Deep Thought
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Re: Unit or circuit to properly convert stereo to mono for AM Tx is ?

Post by Deep Thought » Thu Jan 03, 2019 2:14 pm

I wouldn't worry too much about the loss through a passive combiner...you should be able to easily make that up at the audio processor. The RDL 600 ohm passive combiner is only -3dB. Any active combiner will just be the same passive network plus an amplifier anyway.

If you still want to do it with an active device use one of these:
https://www.rdlnet.com/downloads/datasheets/st-mx2.pdf
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ncradioeng
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Re: Unit or circuit to properly convert stereo to mono for AM Tx is ?

Post by ncradioeng » Thu Jan 03, 2019 2:22 pm

RDL makes these -

STA-1 stereo amp
https://www.rdlnet.com/product.php?page=54

STA-1M mono amp
https://www.rdlnet.com/product.php?page=55

I would think there would be enough reserve input gain on your audio processor to make up for the combiner circuit loss. It may have an input pad that can be set for different input levels.

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kkiddkkidd
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Re: Unit or circuit to properly convert stereo to mono for AM Tx is ?

Post by kkiddkkidd » Thu Jan 03, 2019 4:37 pm

I have been using RDL STA1 & 2's to make mono feeds. Connect your stereo audio to the input, tie the outputs together in phase and adjust the levels for a good mix.

The MX2 or MX3 will do the same thing but I seldom have the mixers and almost always have several STA's in the truck...
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TPT
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Re: Unit or circuit to properly convert stereo to mono for AM Tx is ?

Post by TPT » Thu Jan 03, 2019 7:50 pm

Another device is the Henry Engineering USDA 2x4 Utility Summing & Distribution Amplifier. Couple on E-Bay for various prices. Stereo in, either two separate stereo outputs or mono outputs.

Not impressed by audio fidelity (I have a couple of these--use them to mix the outputs of our STORQ automation and Simian into one feed as a back-up to the consoles). But for $50 or so will provide adequate mix-down to provide a mono feed for the AM.

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Re: Unit or circuit to properly convert stereo to mono for AM Tx is ?

Post by NECRAT » Thu Jan 03, 2019 8:41 pm

TPT wrote:
Thu Jan 03, 2019 7:50 pm
Another device is the Henry Engineering USDA 2x4 Utility Summing & Distribution Amplifier. Couple on E-Bay for various prices. Stereo in, either two separate stereo outputs or mono outputs.

Not impressed by audio fidelity (I have a couple of these--use them to mix the outputs of our STORQ automation and Simian into one feed as a back-up to the consoles). But for $50 or so will provide adequate mix-down to provide a mono feed for the AM.
Be a little weary of the Henry boxes. I've had a few that blew caps after being on for a while. Simple fix, off the shelf (not odd balls), but still annoying to deal with.
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Re: Unit or circuit to properly convert stereo to mono for AM Tx is ?

Post by TPT » Fri Jan 04, 2019 10:12 pm

On the Ebay stuff I automatically replaced the caps.

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