7.1 Analog Inputs and Output Question

[mccarty350]

Feb 6, 2022 23:40:37 GMT -5 grbh said:

I did quickly scan over the posts but as you say they were quite lengthy. Appreciate you following up my reply with your findings in point form.
Am looking forward to hearing from Emotiva as to how a 7.1 analog output has been modified on a supposed pure analog pass through.

At first glance, this does not seem to make any sense based on the description of the 7.1 analog inputs, and the supposed lack of any type of processing/channel management.

Right back at you thanks for trying to understand and help regardless. So far sounds like there's no processing except for level matching on the .1? The level matching is still a challenge but maybe one that's surmountable. i wish I had more than 2 presents to deal with this with but hell, maybe I could find a filter and apply it that raises/lowers the db across the whole frequency band? Not sure yet.

[mccarty350]

BTW Keith, I'm in Mount Juliet, I need to make a pilgrimage to your headquarters. Jeff Peace instructed me that I should make an appointment with you whenever I planned to visit just to meet you as a person for one and second to field any of my questions to you. The XMC-1 was his recommendation and is the standard platform that the Georgia Audio society leverages. I'm doing research on some of these use cases and sending it off to them in back end brain dumps as the next initiative we are looking at tackling is using multichannel dacs and software convolvers to do all signal processing from the source just because there are almost no PEQ or processing limits to a beefy PC versus buying dedicated hardware that has finite resources such as MiniDSP, etc.

Thanks!

John

[KeithL]

That's correct... and the level control works on ALL of the outputs... not just the .1 channel.

I think grbh is looking at things from the wrong direction...

The Volume control and level trims in the XMC-1 are ALWAYS done in the analog domain... by an eight-channel digitally controlled analog ladder network (with more channels used for the Zone 2 output).

(An 8-channel analog resistor ladder network, in integrated circuits, that is controlled by a control processor.)

If you're using a digital surround sound input of some sort then obviously the signal must be decoded.

Likewise, even if it's a digital two-channel signal, it must go through the DACs.

If you have a two-channel ANALOG source, the signal can be converted into digital using the XMC-1's two-channel A/D (analog-to-digital) converter, and then have processing available...

OR, in Reference Stereo mode, it can be routed straight to the Volume control and the output.

The XMC-1 does NOT have an 8-channel A/D converter...

Therefore the 7.1 Channel Analog Input is a sort of "analog bypass"... and can ONLY be routed to the analog level controls and output circuitry.

There is no way for an analog 7.1 channel input to be converted to a digital audio signal for further processing.

Feb 7, 2022 11:32:14 GMT -5 mccarty350 said:

Feb 6, 2022 23:40:37 GMT -5 grbh said:

I did quickly scan over the posts but as you say they were quite lengthy. Appreciate you following up my reply with your findings in point form.
Am looking forward to hearing from Emotiva as to how a 7.1 analog output has been modified on a supposed pure analog pass through.

At first glance, this does not seem to make any sense based on the description of the 7.1 analog inputs, and the supposed lack of any type of processing/channel management.

Right back at you thanks for trying to understand and help regardless. So far sounds like there's no processing except for level matching on the .1? The level matching is still a challenge but maybe one that's surmountable. i wish I had more than 2 presents to deal with this with but hell, maybe I could find a filter and apply it that raises/lowers the db across the whole frequency band? Not sure yet.

[mccarty350]

What about the options for levelling the subwoofer volume control to that of the other drivers?

Also the question regarding the digital spdif out and volume control...can volume not be done digitally on the digital output on the XMC-1?

Specifically I'm hoping to accomplish this at this stage:

PC -> HDMI-1 -> XMC-1 -> spdif optical output 1 -> Minidsp with all volume control done by the XMC-1. This is not possible unless I output the XMC-1 to analog is that correct i.e. no volume control via that output purely in the digital domain?

You probably answered this question in your response but I have failed to grasp it.

You probably answered this in

[mccarty350]

All, I have to apologize for dissemination of some false information based on a ridiculous circumstance. I often find a numerated or bulleted list to the be crispest way to convey information so here it goes:
1. The purchase of the XMC-1 was such a game changer that it resulted in the elimination of my preamp and dac. I had self fabricated RCA cables that were labelled and to length behind my system so in the course of this integration I added and removed a lot of cabling.
2. Apparently the cables on the left channel of my primary two channel amplifier were disconnected by my pulling one or many cables or power cords. This was not visible to me as I have a large lateral home-built flexy-rack that I leverage and it takes an effort to see the back side of my equipment as it is up against a wall.
3. To compound things, the speakers I was doing testing with happened to be Polk SDA's. For those that have never owned them one thing to know is that the left and right speakers are linked together with a proprietary interconnect cable that sends and juice information from the 'SDA effect' midrange for lack of a better term between both speakers.
4. As a result of my left channel being disconnected the left SDA speaker CONTINUED TO OPERATE to a degree in that the bass and midrange unit were still putting out sound due to power drawn from the right speaker over the proprietary interconnect.
5. Since it was just mid and bass all that I got was low frequencies and on top of that low frequencies at less volume than the right channel.
6. This led me to believe that bass management was limiting my frequencies in the left channel - which happened to be the channel fed by the .1 sub input. I also head the lower volume and was able to change it by changing the sub input/output level which led me to believe that was also from bass management.


So basically a comedy of obscure issues caused me to believe that the .1 of the 7.1 interface was due to bass management. My apologies for the madness and I hope this didn't lead folks down the wrong path on what the XMC-1's capabilities are. Thank you for assisting me Keith. I'm more than a little embarrassed by this and the time that it consumed of great other forum members that tried to help me out.

Thanks,

John

[ttocs]

A. It was still an exercise of ideas.
2. Head scratcher that it was, you persevered and continued on until you found the answer.
That third thing. You let us know what the outcome was.

Glad you found out what was going on and shared with us. Speaking for myself, I've had my share of oops-es with no end in sight. Welcome to the club!

[marcl]

Feb 8, 2022 13:16:41 GMT -5 ttocs said:

A. It was still an exercise of ideas.
2. Head scratcher that it was, you persevered and continued on until you found the answer.
That third thing. You let us know what the outcome was.

Glad you found out what was going on and shared with us. Speaking for myself, I've had my share of oops-es with no end in sight. Welcome to the club!

Agreed!  I like it when I do something wrong and figure it out.  It's kind of a double blind test of my brain.  Having one expectation, noticing something doesn't fit the expectation and then figuring out the expectation was inaccurate and the resolution correlates with what was observed.

[mccarty350]

It is, I just felt bad for dragging you all down the rabbithole. What an obscure situation right? It's usually cut and dry if the channel is plugged in or not right, you get no sound but not so with the SDA's. At one point I unplugged the left speaker from the back and heard sound still coming out and then I had the epiphany "Christ, it's getting juice and signal from the right channel as part of the SDA effect midrange being fed via the SDA interconnect" and it all became clear to me. If I had been testing with some of my other mains at random this wouldn't have happened, it was the perfect confluence of randomness and stupid

Thanks for giving me a pass on my idiocy. I intend on circling back and testing again now that this has been rectified but frankly I am demotivated to shuffle my cables again for now.

I agree that it did have value as an exercise and in the clarification of our questions by Keith however. I just hope that someone doesn't do a search on google having an issue and read my statements at the beginning of the thread and take them for fact that bass management is engaged without reading through a very lengthy thread.