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Are they?

Posted by David Aiken (A) on February 14, 2009 at 13:38:12

In Reply to: Some solutions are out there... posted by dlarkin_dc on February 14, 2009 at 11:14:04:

You asked specifically about "just to get L/R and center (sub optional)" and the devices you linked to are 5.1 devices, not the 3.1 device you specifically asked about.

More importantly, you asked about a decoder. The second device you listed is a repeater—it simply repeats the digital input signal so that the digital signal can be sent over a longer cable run. The output is still digital. It does allow you to get a non-HDMI digital output from digital input but you're still left with digital output of the original input kind, ie if you input bitstream you will output bitstream and if you input LPCM you will output LPCM. No decoding occurs in this device. It's not what you're asking about.

While the Gefen device will decode some bitstream codecs but not all (it won't decode the new hi def codecs used with Blu-ray) and do the digital to analog conversion, it outputs a low level signal. You can't hook speakers up to it. It's still a source device. If you are going to use it for a 3 way system, you still need 3 channels of amplification and a way of balancing the speaker levels for those 3 channels plus the sub if you use one. Subs have gain controls that let you do balance a volume controlled line level output from a receiver/controller but that won't balance the volume of the line level output of the Gefen to your speaker levels so the sub output from the Gefen is useless to you if you want a sub. You're also going to need another amp to drive your centre speaker and it's going to have to have a volume control and you're going to have to adjust that control separately to the volume control of the amp driving your speakers because the Gefen has no volume control for its outputs.

You need to think your sub options. The .1 channel in surround formats is a dedicated LFE channel that needs it's own amp (usually contained in the sub) but with an output that needs to be level matched to the other speakers. The gain control of the sub will let you do that but it won't adjust the volume of the sub's output when you adjust the volume of the speakers. You need a volume controlled sup output which the Gefen doesn't provide. In addition, if you want the sub to work with material that does not have a dedicated LFE channel, you need some way of inserting a crossover in your 3 channels (L/R/centre) and passing the low frequency content from them to the sub. That's not possible in the Gefen box which does not perform crossover functions.

So, unless you've got some way of matching the levels of the 3 channels so that you get equal volume for equal input from all of them at your listening position, and of controlling the volume of all 3 channels together once their levels are matched, and of providing a crossover for the sub if you need that, the Gefen device is only half or less of what you need.

The 5.1 receiver will do what you want in one box and you won't find an equivalent one box product that will do all of the things you need for 3, or 3.1 channels. You can get by with the Gefen box, a stereo amp, and another amp if you're prepared to put up with level matching your channels afresh every time you want to do a volume change but I really don't think you want to do that.

I think Kal was spot on when he said "no such thing". No one makes a 3.1 decoder/controller device.

David Aiken

Edits: 02/14/09 02/14/09

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