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post #1 of 13 Old 08-06-2018, 12:41 PM - Thread Starter
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Question Reversible Stereo?

Hello, all -

Perhaps an odd request. How to set up a surround system so that it can also be used to play stereo, both in the normal way via the front speakers, but also to be reversible, that is to allow playing stereo audio through the (identical) rear speakers instead? That would of course also entail flipping left to right.

Why would I want to do this? My room will double as home theatre and music studio production/control room. I would like to be able to use a stereo pair of the home theatre speakers as an additional option for music playback from the studio computer while producing, mixing, and mastering music. However, the production area and desk face the back wall, opposite to the screen for the home theatre.

There seem to be at least 2 ways to do this:
#1 . Digitally, inside the processor
#2 . with some sort of analogue switch, at line-level, before the input to the rear stereo channels of the multi-channel amp. This switch would select between the proper rear channel outputs of the surround processor, and the (flipped) stereo outputs from the computer interface. This would also keep a cleaner signal path for audio from the computer, since it bypasses the processor completely.

Any advice appreciated, including recommendations on processors which might digitally accomplish such routing options (option #1 ), or analogue switches for option #2 .

So ideally this system would be flexible enough to allow:
- (front direction) surround video playback from any video source (including the computer, if possible)
- (front direction) surround audio playback from source to be determined (ideally computer)
- (front direction) stereo audio playback, from computer or any gear directly connected to processor (CD player, turntable, Sonos, etc.)
- (rear direction) stereo audio playback, from computer {this is the challenge faced herein)

Adding a sub into the equation, to hope for 2.1 playback in either direction, would be even better!

If it matters, some specs on the gear:
- 4 Linn Espek speakers (front and rear, left and right)
- 1 Linn Ekwal speaker (center)
- 3 Linn 5125 amps (for tri-amping; cards installed)
- 1 Linn AV5103 processor (in need of repair or replacement)

- studio computer: MacBook Pro
- studio audio interface: MOTU 896mk3 Hybrid (includes multiple balanced analogue outs, optical out, SPDIF out)

The room will be used 95% of the time as the music studio, and only occasionally for surround playback of audio or surround video home theatre use.

Thank you!

Best regards.
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post #2 of 13 Old 08-06-2018, 06:37 PM
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You need a digital matrix switch. Take a look at MiniDSP products.
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post #3 of 13 Old 08-12-2018, 10:24 AM - Thread Starter
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Originally Posted by ltusler View Post
You need a digital matrix switch. Take a look at MiniDSP products.
Thank you for the suggestion.

I'd rather keep the stereo reverse signal path all analogue, if possible, and avoid the processor with that path altogether. Is there an inexpensive analogue switcher that anyone might recommend?

I know there are pricey ones ($1k and up) but that seems overkill...just would like a simple clean analog switch; that ideally could be rack-mounted. Otherwise I could wire up something myself, but not sure where to get a rack-mount plate for it. Maybe RedCo or some similar company could make a mounting plate.

Well, on that note, I just want ahead and searched RedCo and found a 4-input stereo switcher. Does anyone have experience with this model? Or any similar to recommend? This one is about $300, not bad if well made:
https://www.redco.com/Redco-IS41-4x1...-Switcher.html

Cheers.
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post #4 of 13 Old 08-12-2018, 10:28 AM - Thread Starter
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P.S. The only concern with that model is that it's all balanced, whereas the Linn gear, like much hi-fi gear, is all unbalanced RCA. This is a conversion issue I have to address regardless, since the outputs from my pro audio interfaces which will provide one of the input options are indeed balanced.
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post #5 of 13 Old 08-13-2018, 10:15 PM
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The way I deal(t) with my main surround system and my stereo desktop system needing to be fed from the same AVR is I use the Zone 2 out function of my AVR for the Zone 2 stuff, even though it goes to the same room to the desk speakers, and my set of powered desktop speakers transform instantly into my rear surround speakers with the push of a button, namely an A/B switch very much like this:
https://www.amazon.com/AuviPal-Switc...SIN=B01MRPATRW

The yellow video port is ignored.
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post #6 of 13 Old 08-14-2018, 08:28 AM - Thread Starter
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Quote:
Originally Posted by m. zillch View Post
The way I deal(t) with my main surround system and my stereo desktop system needing to be fed from the same AVR is I use the Zone 2 out function of my AVR for the Zone 2 stuff, even though it goes to the same room to the desk speakers, and my set of powered desktop speakers transform instantly into my rear surround speakers with the push of a button, namely an A/B switch very much like this:
https://www.amazon.com/AuviPal-Switc...SIN=B01MRPATRW

The yellow video port is ignored.
Thank you for this. So it's the same source (the Receiver) in both scenarios, either driving the desktop speakers (rear speakers in left-right switched, relative to left-right orientation when using them as rears of the surround system) or driving the entire set of speakers as a surround system?

In my case, I want to be able to switch to a different source, namely the computer audio interface (MOTU 896) when using the first pair of speakers in that switched left-right orientation. Maybe that can also be achieved through processor zones (I was planning to buy only a preamp/processor, not a receiver, since I have separate amps for the speakers). Ideally, though, I would like to bypass the processor in the first scenario, to avoid it adding any additional undesirable distortion/coloration to the sound, especially if the processor always utilizes an additional A/D - D/A signal path. I'd rather have the first option follow:

computer -> audio interface -> analogue outputs, switching left and right cable -> analogue switch in A/V rack -> 2 channels of surround amps which drive the 2 rear speakers

The alternative would be to send a digitial signal to the processor from the computer interface (SPDIF or lightpipe), and use the processor's D/A conversion. That decision would depend on whether the interface or the processor has the better DACs. I wonder if any processor's zones allow internally flipping the stereo (left/right) as described, to avoid a hardware additional switch altogether in this case?:

computer -> audio interface -> digital outputs -> surround pre-/processor > zone 2 outputs (switched left/right) -> analogue switch in A/V rack -> 2 channels of surround amps which drive the 2 rear speakers

In either case, the other position of the switch would carry the regular (main zone, surround rear) signals from the processor, for full surround listening.
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post #7 of 13 Old 08-14-2018, 08:37 AM
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Quote:
Originally Posted by Reverberation View Post
There seem to be at least 2 ways to do this:
#1 . Digitally, inside the processor
#2 . with some sort of analogue switch, at line-level, before the input to the rear stereo channels of the multi-channel amp. This switch would select between the proper rear channel outputs of the surround processor, and the (flipped) stereo outputs from the computer interface. This would also keep a cleaner signal path for audio from the computer, since it bypasses the processor completely.
A third way is to use analog switches for the speakers themselves. Switches that work with speaker-level signals are frequently used in audio showrooms so people can easily audition several different speaker systems.

ETA: Calling them "analog" could be a bit misleading. No electronics of any kind are involved, just mechanical switching hardware.

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post #8 of 13 Old 08-14-2018, 10:00 AM - Thread Starter
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Quote:
Originally Posted by Selden Ball View Post
A third way is to use analog switches for the speakers themselves. Switches that work with speaker-level signals are frequently used in audio showrooms so people can easily audition several different speaker systems.

ETA: Calling them "analog" could be a bit misleading. No electronics of any kind are involved, just mechanical switching hardware.
Thank you for the suggestion. That third method would work if there were 2 different amps driving the different signal path options; in my case, it's the same amp driving the speakers for both options, so I have put the switch earlier in the signal path (before the amp).

By the term "analog" I was just distinguishing against any additional A/D-D/A conversion steps. I would rather have a single conversion, D/A, from either the computer interface or the processor.
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post #9 of 13 Old 08-14-2018, 11:27 AM
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Quote:
Originally Posted by Reverberation View Post
Thank you for this. So it's the same source (the Receiver) in both scenarios, either driving the desktop speakers (rear speakers in left-right switched, relative to left-right orientation when using them as rears of the surround system) or driving the entire set of speakers as a surround system?
Yes. They are self amplified speakers so the switch is for analog stereo RCA connections but had I wanted to use an A/B switch for a speaker level scenario I could have used this, mounted in a wall (or in a plastic box* to keep the wires tidy and concealed) :
https://www.amazon.com/OSD-Audio-AB1...70_&dpSrc=srch

Note: the A/B selection is used as "two INs (A and B), one OUT to the speakers" and one of those two INs could actually be from the exact same stereo amp however the L and R wires are flipped (stereo reversed) for this option, "B".

* example of plastic box (~$1 ea. at hardware/home improvement stores): https://www.amazon.com/Thomas-Betts-...tic+box+1-gang
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post #10 of 13 Old 08-14-2018, 11:36 AM
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Quote:
Originally Posted by Reverberation View Post
Ideally, though, I would like to bypass the processor in the first scenario, to avoid it adding any additional undesirable distortion/coloration to the sound, especially if the processor always utilizes an additional A/D - D/A signal path.
Although there can be exceptions, I find when using better gear (and preamp processors usually qualify) the added distortion/coloration is at exceedingly low levels and most importantly completly inaudible to the human ear unless you purposefully go looking for it by pegging your volume knob to max and putting your ear up close to the tweeters while playing a silent source. That is, in real world use it's of no concern because it is an inaudible distortion/coloration.
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post #11 of 13 Old 08-14-2018, 11:49 AM - Thread Starter
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Originally Posted by m. zillch View Post
Although there can be exceptions, I find when using better gear (and preamp processors usually qualify) the added distortion/coloration is at exceedingly low levels and most importantly completly inaudible to the human ear unless you purposefully go looking for it by pegging your volume knob to max and putting your ear up close to the tweeters while playing a silent source. That is, in real world use it's of no concern because it is an inaudible distortion/coloration.
Good thoughts. The pre/processor I would use (at least initially) is a Linn AV5103 which I just re-conditioned. Presumably it's quite a fine signal path (assuming age has not done too much harm).

So I will try this approach first, seeing if there is an easy way to set up a configuration switch inside the unit between the 2 playback configurations:
1. flipped stereo (can be done by swapping the L/R input cables) from computer interface, to rear channels.
2. normal 5.1 surround, using the rear channels (I know, these are actually properly called "surround" channels, but I've placed them somewhat to the rear) as part of the surround normally.

This saves buying or building an additional switcher box at this point.
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post #12 of 13 Old 08-19-2018, 02:43 PM
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The easiest way would be a processor that has a Zone2.

If you need more advanced routing, then you'd be better off with a Motu 16A using TRS to RCA or XLR adapters.
It has 2 8-ch ADATA and 2-ch spidf inputs, and 2 8-ch ADATA and 2-ch spidf outputs, it also has AVB and Thunderbolt and USB2.

The 896mk3 should be able to connect to it via optical for mic-pre's to the mac over AVB or TB or USB2.

If you need more inputs and outputs, you could connect another 16A or a 24AO or 24AI or any other Motu AVB product (they have a lot.)

HDMI from computer goes to sound processor HDMI in, HDMI outs go to TV's / Projectors, for video or audio on that cable.
If it has pre-outs those could come in on the 16A analog inputs, may required digital boost if the internal boost isn't enough to go from say RCA to XLR dbV, that would allow analog re-mixing of DD/DTS to PCM or a DAW or Dolby creators studio, or other sources like radio or VHS or whatever you have connected to the processor.

The advantage of using Motu AVB/TB/USB is that it is lossless from the mac to the amps with only 1 DAC step, any onboard processing is done in the digital domain (if any is even applied, otherwise it is bit-perfect.)

The 16A has like 128x128 routing and a number of EQ and basic XO features and level adjustments, accessible from any computer on the LAN or wifi.

There are multiple ways of doing this, depending on what you need out of the system both now and in the future...

Last edited by BassThatHz; 08-19-2018 at 02:48 PM.
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post #13 of 13 Old 08-19-2018, 04:15 PM
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This (or similar)?

https://www.amazon.com/Russound-AB32...ustomerReviews

It's a VIRTUAL channel unless stated otherwise.
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