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Author Topic: How to get encoded sound to PA amps?  (Read 14697 times)
redeemed763
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« on: April 17, 2014, 04:19:13 pm »

I am setting up a new BYT this summer, my first "real" one as my last versions were just taking my indoor equipment and setting it up outside ad hoc with long cables.

I am building some PA speakers for mains and subs, I will likely use a couple prebuilt cabs for surrounds. My problem lies in amplification, it seems that most folks are either just running mono or stereo with PA systems, or they are just playing DVD's which have no drm so there is no problem. Those who have smaller setups just use an AVR that can decode the hdcp signal. In my case, my AVR is not powerful enough to drive my speakers properly and a pre-pro or avr with pre-outs is out of my price range.

What is the best way to do this, surely this is a common predicament on here?
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Sparge
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« Reply #1 on: April 17, 2014, 06:00:53 pm »

Forgive me as I re-state your dilemma to make sure I understand...

You mention surrounds and a sub.  I'll take that to mean you want to run full 5.1 sound outside.  You have an AV receiver capable of 5.1 now, but you believe it doesn't have the power output needed for outdoors.

You mention your budget doesn't allow for a pre-processor (or a new AV receiver with pre-outs) to break out the 5.1.  Does your budget allow for the three separate stereo amplifiers you'll need to run six channels?  That's easily $600 or more right there just for amps.

I'll assume you're using a Blu-ray player as your source.  There aren't a lot to choose from but some Blu-ray players have decoded 5.1 (often 7.1) pre-outs on them already.  You might consider replacing your Blu-ray player with one that has analog pre-outs like this one...

  http://www.amazon.com/gp/product/B00752R4QO

That one's about $300.  Blu-ray players with analog outputs are going to be on the expensive side because you're paying for the built-in Dolby/DTS decoders.  Since the pre-outs on the player have a fixed output level you're probably also going to want to buy a little six-channel mixer to make audio adjustments easier.  However, you could simply adjust the input levels for each channel on the amplifiers instead.

There is another less expensive option.  It produces lower quality audio, but it's cheap!  That option is to use a "direct-injection" box with your existing AV receiver.  The DI box connects to the speaker-level outputs of your receiver and provides near line-level outputs that can be fed into other amplifiers.  The audio can pick up some coloration, distortion and/or frequency roll off due to being run through the first amplifier (AV rx), then through the circuitry of the DI box and finally through the second amplifier.  However, most non-audiophiles won't notice the difference!

Here's an 8-channel DI box for about $120 that will let you do 5.1 sound with two channels to spare:

  http://www.behringer.com/EN/Products/DI800.aspx

You won't need a mixer as you'd still use the master volume on your AV receiver to adjust overall sound levels.

-Sparge-
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waverz
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« Reply #2 on: April 17, 2014, 09:04:13 pm »

Well said sir.

Forgive me as I re-state your dilemma to make sure I understand...

You mention surrounds and a sub.  I'll take that to mean you want to run full 5.1 sound outside.  You have an AV receiver capable of 5.1 now, but you believe it doesn't have the power output needed for outdoors.

You mention your budget doesn't allow for a pre-processor (or a new AV receiver with pre-outs) to break out the 5.1.  Does your budget allow for the three separate stereo amplifiers you'll need to run six channels?  That's easily $600 or more right there just for amps.

I'll assume you're using a Blu-ray player as your source.  There aren't a lot to choose from but some Blu-ray players have decoded 5.1 (often 7.1) pre-outs on them already.  You might consider replacing your Blu-ray player with one that has analog pre-outs like this one...

  http://www.amazon.com/gp/product/B00752R4QO

That one's about $300.  Blu-ray players with analog outputs are going to be on the expensive side because you're paying for the built-in Dolby/DTS decoders.  Since the pre-outs on the player have a fixed output level you're probably also going to want to buy a little six-channel mixer to make audio adjustments easier.  However, you could simply adjust the input levels for each channel on the amplifiers instead.

There is another less expensive option.  It produces lower quality audio, but it's cheap!  That option is to use a "direct-injection" box with your existing AV receiver.  The DI box connects to the speaker-level outputs of your receiver and provides near line-level outputs that can be fed into other amplifiers.  The audio can pick up some coloration, distortion and/or frequency roll off due to being run through the first amplifier (AV rx), then through the circuitry of the DI box and finally through the second amplifier.  However, most non-audiophiles won't notice the difference!

Here's an 8-channel DI box for about $120 that will let you do 5.1 sound with two channels to spare:

  http://www.behringer.com/EN/Products/DI800.aspx

You won't need a mixer as you'd still use the master volume on your AV receiver to adjust overall sound levels.

-Sparge-
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redeemed763
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« Reply #3 on: April 18, 2014, 09:47:22 am »

Purchasing the amps isn't an issue since we have been planning on buying them for the system all along, the sound system is being built primarily to do live music for my brothers band but they won't be using it very often. We already have a mixer so we may just use that as control and to get the pre amp signal boosted for the PA amps (if possible), I know these have a different input voltage than home audio line level signals.

I could buy a stand alone BR player but it would be preferable to use a laptop or macbook. I already have an external blu ray drive and I will need a laptop anyway to play some of the video content as it just just way easier to play a sound clip than author a dvd for everything.

Some of the issues I have with the BD players that already have pre outs is that, yes they are pricey, $300 is a lot when you can easily do the same job for under $100 and I feel like I am tying myself into something that has no path for upgrades. BR players are no longer being made with analog out (I forgot why) and as new BR formats and technologies develop, the old machines won't be able to do the job, we have seen this happen as old machines get "orhaned".
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« Reply #4 on: August 18, 2014, 03:46:52 am »

I use the Denon DN-A7100. It accepts optical or HDMI input and has 7.1 balanced outputs that can run directly to your PA amps. It's an older model and out of production, but there's one on eBay now for about $370.  The new model (still in production) is DN-500av and runs $1000.

Pyronious
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Seattle Starlight Cinema
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« Reply #5 on: August 18, 2014, 08:52:57 am »

Given that you have amps & mixer already, here is a cheap solution that works for me:  an old HK ADP303 Dolby Digital Processor.  I removed the plastic trim pieces on the side and screwed it to a 19" shelf bolted in my rack using longer screws through the plastic feet mounting screw  holes.  Be careful that the screws are the correct diameter and not too long or you will create a short to chassis to the electronics inside (yes, this is from experience...).

This processor accepts SPDIF input via either fiber optic or coaxial and outputs 5.1 channels with various options for LF routing.   A volume control is provided that adjusts all channels simultaneously as are trim pots to individually set each channel level behind a cover on the front panel (you will need a very small Alan wrench to remove the cover). 

I run fiber optic from my PC to this processor, and output the 6 channels of decoded output to my mixer if we have live music for pre-show.  Alternately, for movie only I have found there is sufficient output to connect the 6 channel outputs directly to the inputs of my EV Q66 (and Q44) amps via a simple RCA to XLR adapters I made so the mixer isn't necessary.  All are bolted in the same rack and I don't get hum from this despite essentially giving up the benefit of a balanced input.  It sounds good and uses Burr Brown DACs. 

Limitations:  Dolby Digital only; no DTS, No lossless.  It does decode stereo lossless for pre-show.  Some day I will find a lossless solution but for now this works well...

Did I mention cheap?  Here is one on eBay for under $35

http://www.ebay.com/itm/Harman-Kardon-DOLBY-DIGITAL-ADP-303-Decoder-/400754621189?pt=Receivers_Tuners&hash=item5d4ed63b05


* ADP303.jpg (1248.81 KB, 2538x1193 - viewed 415 times.)
« Last Edit: August 18, 2014, 02:00:03 pm by OutdoorGeek » Logged
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