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Author Topic: Quad Amping using MC's digital XO questions  (Read 1544 times)

ths61

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Quad Amping using MC's digital XO questions
« on: November 04, 2019, 12:16:35 am »

Is there any reason why this configuration should now work for all 8 channels ? 

Should any other settings be made ?

I am not able to get sound out of channels 5 and 6 on an 8 channel USB DAC.

  • Left channel is copied to odd channels.
  • Right channel is copied to even channels.
  • Then high and low pass filters are applied.



I have tried using both "7.1 channels" and "2 channels (inside 7.1 channel container)" in the output format.

TIA
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mattkhan

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Re: Quad Amping using MC's digital XO questions
« Reply #1 on: November 04, 2019, 03:50:21 am »

You should use "2 channels (inside 7.1 channel container)" though 7.1 should work as long as you don't upmix

No obvious problem there, what does the analyser show if you put full bandwidth pink noise through it?
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mwillems

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Re: Quad Amping using MC's digital XO questions
« Reply #2 on: November 04, 2019, 08:10:08 am »

You should use "2 channels (inside 7.1 channel container)" though 7.1 should work as long as you don't upmix

No obvious problem there, what does the analyser show if you put full bandwidth pink noise through it?

I agree the config looks good and that 2 channels in a 7.1 container is the right output format.  The "missing channels" (5 SL and 6 SR) are sub 40Hz channels, where there isn't a lot of content in most commercial audio so depending on how you're testing for signal there may just not be any "there" there.  mattkhan is right, full bandwidth pink noise will answer the question one way or the other.

If you don't see activity in the analyzer with full bandwidth pink noise, you might want to post some more screen shots of your settings.  If the analyzer shows sound but you still hear nothing from the speakers, you might want to elaborate a little on your audio connection path downstream.
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mojave

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Re: Quad Amping using MC's digital XO questions
« Reply #3 on: November 04, 2019, 08:38:04 am »

You can put pink noise through the system using Tools > Advanced Tools > Audio Calibration.
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ths61

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Re: Quad Amping using MC's digital XO questions
« Reply #4 on: November 04, 2019, 10:51:33 am »

...what does the analyzer show if you put full bandwidth pink noise through it?

If you don't see activity in the analyzer with full bandwidth pink noise, you might want to post some more screen shots of your settings.  If the analyzer shows sound but you still hear nothing from the speakers, you might want to elaborate a little on your audio connection path downstream.

You can put pink noise through the system using Tools > Advanced Tools > Audio Calibration.

Thanks for the response.

I tested using REW's frequency sweep plots [14Hz-20KHz] for each of the 8 channels individually (to validate proper XO point and 48dB slope) as well as all outputs simultaneously to check the combined frequency response. 

I even swapped frequent ranges between the problematical channels and retested.  Same channels are silent.

Channels 5 and 6 are always silent in all of the tests.
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mwillems

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Re: Quad Amping using MC's digital XO questions
« Reply #5 on: November 04, 2019, 12:10:58 pm »

Thanks for the response.

I tested using REW's frequency sweep plots [14Hz-20KHz] for each of the 8 channels individually (to validate proper XO point and 48dB slope) as well as all outputs simultaneously to check the combined frequency response. 

I even swapped frequent ranges between the problematical channels and retested.  Same channels are silent.

Channels 5 and 6 are always silent in all of the tests.

What does MC's internal analyzer show for those channels?  Does it show no signal or do you see signal there?
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ths61

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Re: Quad Amping using MC's digital XO questions
« Reply #6 on: November 04, 2019, 01:30:16 pm »

What does MC's internal analyzer show for those channels?  Does it show no signal or do you see signal there?

Are you referring to Tools->Options->Audio-> Settings -> DSP & Output Settings -> Analyzer ?

Here is a screen capture of some pink noise.  It appears all 8 channels are firing away.  The overlaid traces are hard to make out, but if you watch it closely in realtime, they are there.

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mwillems

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Re: Quad Amping using MC's digital XO questions
« Reply #7 on: November 04, 2019, 02:11:40 pm »

Ok, that result means that, as far as MC is concerned, it is sending signal to those channels.  That suggests the disconnect may be somewhere downstream of MC.  Have you verified that those channels play sound correctly with other software?  I.e. if you have REW send a signal test directly to those channels on the USB DAC (not through JRiver) do those USB outputs play sound correctly?  Can windows play sound from those channels (i.e. try using windows built in sound test functions for 7.1 systems)?

EDIT:

Forget what I said above, the waveform for the two quiet channels looks very odd.  Specifically it looks like there's a high pass and a low pass on the same channels at 250Hz?  Are you sure your PEQ is still set correctly, it looks like the SL and SR got both a high and low pass at 250Hz, but L, R, RL, and RR got no filter at all (or maybe just a high pass at 40Hz)?
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mattkhan

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Re: Quad Amping using MC's digital XO questions
« Reply #8 on: November 04, 2019, 02:41:31 pm »

the internal pink noise is not so useful for this task as it is designed for main speaker level setting hence is band limited pink noise (to 500-2000Hz) which is why I said full bandwidth pink noise, e.g. via REW

you did this though so it can't be that :)

I gave it a quick try (albeit using MC25) and get the expected result. Can you show the settings for a particular HPF or LPF?
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ths61

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Re: Quad Amping using MC's digital XO questions
« Reply #9 on: November 04, 2019, 03:26:12 pm »

Ok, that result means that, as far as MC is concerned, it is sending signal to those channels.  That suggests the disconnect may be somewhere downstream of MC.  Have you verified that those channels play sound correctly with other software?  I.e. if you have REW send a signal test directly to those channels on the USB DAC (not through JRiver) do those USB outputs play sound correctly?  Can windows play sound from those channels (i.e. try using windows built in sound test functions for 7.1 systems)?

EDIT:

Forget what I said above, the waveform for the two quiet channels looks very odd.  Specifically it looks like there's a high pass and a low pass on the same channels at 250Hz?  Are you sure your PEQ is still set correctly, it looks like the SL and SR got both a high and low pass at 250Hz, but L, R, RL, and RR got no filter at all (or maybe just a high pass at 40Hz)?

MWillems,

I swapped the XO points around so they are not on the same channels as the original post.  Channels 3 & 4 are now the sub channels.

I also made the XO points different on the duplicated channels just to see what it looked like in the Analyses.  Made one a at 40Hz and another at 70Hz.  Both traces separated by 30Hz as expected.

I think it maybe a hardware problem because the software changes appear to work as expected on 6 of the 8 channels.

As for the odd shape, the amplitude fluctuates with which specific sample PINK NOISE track I play.  It appears correct in the REW plots.
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ths61

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Re: Quad Amping using MC's digital XO questions
« Reply #10 on: November 04, 2019, 03:31:41 pm »

the internal pink noise is not so useful for this task as it is designed for main speaker level setting hence is band limited pink noise (to 500-2000Hz) which is why I said full bandwidth pink noise, e.g. via REW

you did this though so it can't be that :)

I gave it a quick try (albeit using MC25) and get the expected result. Can you show the settings for a particular HPF or LPF?

I posted the information above in the original post, but have moved the XO points to different channels since then to test.  Crossover points are at 40Hz and 250Hz with 48dB slopes.  No PEQ or convolution yet.

As for Pink Noise, I used various Pink Noise tracks from various test disks as well as used frequency sweep plots in REW.
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mojave

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Re: Quad Amping using MC's digital XO questions
« Reply #11 on: November 04, 2019, 03:56:24 pm »

the internal pink noise is not so useful for this task as it is designed for main speaker level setting hence is band limited pink noise (to 500-2000Hz) which is why I said full bandwidth pink noise, e.g. via REW

Full range pink noise is available in JRiver. I use it all the time.





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mattkhan

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Re: Quad Amping using MC's digital XO questions
« Reply #12 on: November 04, 2019, 03:57:50 pm »

Full range pink noise is available in JRiver. I use it all the time.
have literally never noticed that option   :)
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ths61

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Re: Quad Amping using MC's digital XO questions
« Reply #13 on: November 04, 2019, 04:57:52 pm »

Well, as an aside, I just re-upped for a V26 master license.  :) :) :)

Thanks guys for the information and confirmation.  I think I have a hardware issue with the 2 silent channels.
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