AC3 Decoding cheaply

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I got my Sonic Voom unit yesterday, the unit is small and compact - It has 2 inputs an optical and coaxial (corresponding cables are included) and the unit has 3 outputs a 5.1ch output (looks like a DIN plug slot) and 2 for the headphones (this looks like a hole with a slot next to it ( 0--- ).
The unit included a LI-ion battery, power cable, optical & coaxial cables & surround sound headphones.

The unit is very easy to set up, (1) put in the battery (the unit will work as a portable unit on batt power), (2) plug the unit in, (3) connect a cable to the headphone output (I used a homemade cable with a mini-stereo plug (headphone size plug) on one end and red & white rca plugs at the other (note this does not come with the unit) (4) connect the optical cable (note - you will have to take off the protective caps to get the cable into the hole, this took me awhile to figure out and the manual says nothing (that I can see) about it). (5) turn on the power (on not batt) and set the volume & output (in my case it was optical). (6) Enjoy.

I am using it on the Fortec classic NA and it works great, although the Fortec seems to act a little clunky sometimes when you turn on the optical output but I chalk that up to the limited memory of the fortec classic NA.

The fortec did freeze one time when switching from standard audio to AC3 on one of the Equity channels and I had to power the unit down from the main (back of the unit) power switch.

The only other anomaly I found is that on some (or all of the PBS) stations the Fortec volume does not work (you can turn it all the way down and the level does not change) this is no big deal because you can just use the tv volume. Volume works fine on all other channels.

Pros:
- cost (the thing was cheap as chips at $10 + shipping)
- Does what it says, it decodes ac3
- The headphones that come with it sound great
- the unit is easy to set up (once you figure out that you need to remove the protective cover from the fiber optic cable - this only took me 10min of head scratching).

Cons:
- Fortec classic NA seems a bit slow sometimes with optical turned on (this is not a problem with the voom product just a heads up to Fortec users)
- there can be an audio lag in switching channels (although this my be another fortec problem or I could be switching channels too fast)
- Manual is pretty useless (it is a rudimentary manual) just the basics and thats it
 
So far I have had no problem with the decoder, it is hooked up to my Ultra with the RCA coax and then the audio to the TV with a mini-phone plug to RCA "Y" cable.
Bob
 
The only other anomaly I found is that on some (or all of the PBS) stations the Fortec volume does not work (you can turn it all the way down and the level does not change) this is no big deal because you can just use the tv volume. Volume works fine on all other channels.

That's the way it should behave when doing AC3 passthrough. AC3 is actually a bitstream of compressed data and when it passes it onto an external decoder it must do so untouched. Otherwise it would destroy the data and the external decoder wouldn't be able to decode it. In order to have volume controlled by the receiver on ac3 audio, the receiver would have to do the ac3 decoding internally. Then it could alter the volume by manipulating the resulting PCM data. The reason it works on other channels is they have normal Mpeg audio and it decodes that internally into PCM data, which it can then manipulate to adjust volume, before it sends it out the Spdif.
 
- the unit is easy to set up (once you figure out that you need to remove the protective cover from the fiber optic cable - this only took me 10min of head scratching).


Tell me about it.
It drove me crazy trying to figure out why the cable wouldn't fit in the unit.
 
Expecting the shipment later today.

Does it also reproduce the PCM audio output from the SPDIF interface when the receiver is viewing non-AC-3 channels?

Kudos, Rdel, for the find! It's an awesome deal... These can be used on PCs, portable DVD players, notebook computers, and many other devices as well as FTA receivers! I need to find out if I can feed these things an AES digital stream from pro gear as well...
 
That's the way it should behave when doing AC3 passthrough. AC3 is actually a bitstream of compressed data and when it passes it onto an external decoder it must do so untouched. Otherwise it would destroy the data and the external decoder wouldn't be able to decode it. In order to have volume controlled by the receiver on ac3 audio, the receiver would have to do the ac3 decoding internally. Then it could alter the volume by manipulating the resulting PCM data. The reason it works on other channels is they have normal Mpeg audio and it decodes that internally into PCM data, which it can then manipulate to adjust volume, before it sends it out the Spdif.

There ya go...I learn something new every day, Thanks. That actually makes allot of sense, I guess it confused me becouse it would control the volume on the non ac3 channels (although it doesnt take much to confuse me, Eh :D ).
 
Does it also reproduce the PCM audio output from the SPDIF interface when the receiver is viewing non-AC-3 channels?

It works fine on all the channels (non ac3). I can use it for all the channels on g10r and the pbs.
Let us know what you come up with on the pro gear Tron, If anyone has an problems with their unit please post(for the other people who have the same units can look for something different)
Thanks rdel
 
They came in today (well, yesterday, since its past midnight :) )... haven't had a chance to open them yet, but it seems as though they come in boxes of five from Cyberhome (very convenient since I ordered five).

Its great that they can do uncompressed digital audio as well. AES is a bit different from consumer SPDIF, but they are very close cousins, and many instruments can interface to both. I'll (hopefully) be able to do the test tomorrow...
 
It came today (even if shipping was overkill for such slow service!) and it works just fine. It's nice to be able to watch those PBS channels without using the TV-Out on my computer. Those 6 or so PBS channels are worth it.

I also look forward to messing around with those headphones on the computer DVD player.
 
I don't know how many of the devices CompGeeks had in stock, but we've bought them out and they're now on backorder. I waited too late and will have to wait for them to replenish their stock.

DANG IT!!!
 
Just got my AC3 decoder from WalMart yesterday. About $29 delivered. Works as advertised. Now to find a reasonably priced headphone stereo plug to stereo RCA connector so I can plumb the audio into my ILO.
 
i want to thank
rdel for comIng up with this GREAT fix
got me a set of these for 15 bucks US
work great

BIG THANKS


Your welcome:)

If anyone finds BBC on the PBS channels, please let me know. I was hoping that the lineup on one of the amc channels would be the same as KUSM PBS ( which has the bbc world news on at 11 pm) but I can't find anything.
thanks guys
rdel
 
10pm Mountain Daylight Time weeknights
on Montana PBS (AMC-3 Ku band).
30 minute BBC World newscast.

If you have C-band, try 127 West and look for the 24/7 BBC World feed.
 
Probably wouldnt be a bad Idea to try and come up with some sort of a schedule, I also watched Monty python last night also one of the PBS's had DW news on at about 10 or 10:30 pm est (I did not note the channel or time but will in the future). I also want to that whoever found this unit I was really wanting to get these PBS stations.

Also Scott have your heard the Cyberhome surround headphones that come with this unit? I thought they sounded really good (although I am far from a connoisseur - and am very new to AC3).
 
10pm Mountain Daylight Time weeknights
on Montana PBS (AMC-3 Ku band).
30 minute BBC World newscast.

If you have C-band, try 127 West and look for the 24/7 BBC World feed.

Thanks Mike:)
 
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