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Author Topic: Cleanest computing platform  (Read 2306 times)

Ken Webster

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Cleanest computing platform
« on: April 22, 2019, 10:26:33 am »

Hi, I tried asking this question before but didn't get a useful answer so I may as well ask again.

The situation is that we are using very old PCs to handle A/V at church.  The video projection PC is being upgraded, it handles lyric slides and videos. While we could combine music and lyrics into a presentation, this is not flexible to also cater for live worship where the lyric slides may well need amending.

I have for some time been looking into the requirements for our music PC.  This is about 75% of our worship, 25% being live.  CD's are ripped into .WAV files using EAC, we really try to avoid compressed, lossy, downloaded or streamed music if possible.  My question is, what computing platform, PC, All in one or laptop, is likely to cause the least adverse effects on what is essentially a small analogue PA system?  My concern is RF noise from the device and also supply earth stability.  Given that the device is plugged into the same supply and over copper connections whether analogue audio or digital, there may be some noise added to the system.  The aim is to eventually use an HDMI audio extractor/DAC.  While that gets the DAC outside the case, it's still connected to the PC via HDMI and supply earth.  The supply earth being the signal reference for the DAC.  Considering that the connectivity of supply earth to ground peg is likely poor in terms of signal reference potential (not fault condition), there seems a good chance that a device with unstable earth potential could have an adverse effect on single end audio.  I want to make a choice that gives me the best chance at the cleanest possible audio over the  analogue system.

Is there any information on this anywhere?

Regards,
Ken
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Erik Jerde

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Re: Cleanest computing platform
« Reply #1 on: April 22, 2019, 02:19:22 pm »

Hi, I tried asking this question before but didn't get a useful answer so I may as well ask again.

The situation is that we are using very old PCs to handle A/V at church.  The video projection PC is being upgraded, it handles lyric slides and videos. While we could combine music and lyrics into a presentation, this is not flexible to also cater for live worship where the lyric slides may well need amending.

I have for some time been looking into the requirements for our music PC.  This is about 75% of our worship, 25% being live.  CD's are ripped into .WAV files using EAC, we really try to avoid compressed, lossy, downloaded or streamed music if possible.  My question is, what computing platform, PC, All in one or laptop, is likely to cause the least adverse effects on what is essentially a small analogue PA system?  My concern is RF noise from the device and also supply earth stability.  Given that the device is plugged into the same supply and over copper connections whether analogue audio or digital, there may be some noise added to the system.  The aim is to eventually use an HDMI audio extractor/DAC.  While that gets the DAC outside the case, it's still connected to the PC via HDMI and supply earth.  The supply earth being the signal reference for the DAC.  Considering that the connectivity of supply earth to ground peg is likely poor in terms of signal reference potential (not fault condition), there seems a good chance that a device with unstable earth potential could have an adverse effect on single end audio.  I want to make a choice that gives me the best chance at the cleanest possible audio over the  analogue system.

Is there any information on this anywhere?

Regards,
Ken

Toss a simple USB audio output device like the radial one on pretty much any functional computer and you’ll be fine.  If you’ve got ground loop problems then consult an electrician or move the computer to the same circuit as your mixer.

Honestly it sounds like you’ve been paying too much attention to the home stereo audiophools.  You’re probably getting more “damage” to your signal through your PA setup than you’ll ever get through a functional computer system.
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Ken Webster

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Re: Cleanest computing platform
« Reply #2 on: April 22, 2019, 11:07:45 pm »

Toss a simple USB audio output device like the radial one on pretty much any functional computer and you’ll be fine.  If you’ve got ground loop problems then consult an electrician or move the computer to the same circuit as your mixer.

Honestly it sounds like you’ve been paying too much attention to the home stereo audiophools.  You’re probably getting more “damage” to your signal through your PA setup than you’ll ever get through a functional computer system.

Ta, yes, a USB based DAC would be an easy way to just do sound but I want the 2 computers set up identically so they can be used as fail-over for each other or even is a dual role if need be.  The only way to control the projector is via remote which is very marginal at the distance.  The remote has a video mute which can be used to blank the screen while the video or slide presentation is being cued or during communion focus or preaching. However, it may not un-mute when needed.  So there is a need to control the A/V feed and blank screen from the desk.  To solve this, we are aiming to do HDMI over cat 6 through an HDMI switcher.  This will allow us to simply switch between video sources (computers, disc player etc) or blank the screen.  We have already started installing the HDMI cabling and testing reveals a far superior image clarity on the projection screen even though the resolution hasn't changed.  This has been tested with an HDMI audio extractor and the audio quality is very good.  All this is good for the A/V side of things but what about audio only?  You can get HDMI switches that allow the audio and video to be sourced separately from different device.  Doing it this way solves a lot of issues with the professionalism of the presentations and uses the same DAC for everything maintaining consistent sound quality.  It may well be cheaper to go for a simpler switcher and a simple USB DAC to handle the music & A/V separately.

Yeh, I figured this would give the impression I listen to home HiFi advice too much.  Like many of us I do like to have nice music at home though I definitely wouldn't call myself an audiophile.  However I am well aware of the principal that the audio chain is made of many links that each degrade the sound quality.  Therefore the way to setup a superior system is to start with the best available source, then minimise both the number of links as well as the noise and distortion at each ink.  This is the reason I have made an effort to obtain the best quality music files that I can.  I chose EAC ripping because it's free and well regarded for accuracy, though it can be a pain to learn to use.  Yes, I know older audiophiles have used it.  It beats downloads or WMP ripping for accuracy  hands down.  There are other accurate rip options but this is free.  I have been all over this PA system from end to end and the clarity is now good.  There are other issues with the room though but at least the system is pretty much as good as I can get it now.  In fact my audiophile friend tells me it's the best, true sound reinforcement system he has heard.  So what a I am trying to do here is simply complete the last links in this setup/upgrade strategy.   I am well aware that historically PCs were considered very poor for S/N.  PC PSU filtering was historically pretty rubbish in terms of affect on S/N.  Same can be said of RF shielding.  I am aware these things and sound cards have improved quite a bit in recent years, I just don't know how much.  I am not too concerned about sound cards if we go to an external DAC.  I am not too concerns about earth loop hum as that is under control now but I am concerned about choosing the cleanest option with new equipment and avoiding band-aids after purchase.  The is a lot to consider, often laptops don't support audio well.  I have one that will not take an analogue mic input though by it's spec it should.  OP and hardware don't always wok well together.  I am a bit dubious about lite computing devices for this reason.  However a lite option may generate less noise, maybe not, I don't know.  So, I am just putting a feeler out there for advice on it.  Which is cleanest?

If the earth is not taking noise to ground well, an electrician will not be helpful with that, at least not the ones around here.  They only care that it's safe in regard to supply spec and have no idea about mV earth reference stability.  That isn't an audiofool thing BTW, it's just part of the well known standard performance optimisation strategy, combining many minor improvements at every link to achieve a much larger sum total improvement overall.  I have been doing this a long time and know from decades of experience this approach works.

Ken
« Last Edit: April 22, 2019, 11:49:00 pm by Ken Webster »
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Erik Jerde

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Re: Cleanest computing platform
« Reply #3 on: April 22, 2019, 11:25:23 pm »

Ta, yes, a USB based DAC would be an easy way to just do sound but I want the 2 computers set up identically so they can be used as fail-over for each other or even is a dual role if need be.  The only way to control the projector is via remote which is very marginal at the distance.  The remote has a video mute which can be used to blank the screen while the video or slide presentation is being cued or during communion focus or preaching. However, it may not un-mute when needed.  To solve this, we are aiming to do HDMI over cat 6 through an HDMI switcher.  This will allow us to simply switch between video sources (computers, disc player etc) or blank the screen.  We have already started installing the HDMI cabling and testing reveals a far superior clarity on the projection screen even though the resolution hasn't changed.  This has been tested with an HDMI audio extractor and the audio quality is very good.  All this is good for the A/V side of things.  You can get HDMI switches that allow the audio and video to be sourced separately from different device.  Doing it this way solves a lot of issues with the professionalism of the presentations and consistently uses the same DAC for everything maintaining consistent sound quality.  It may well be cheaper to go for a cheaper switcher and a simple USB DAC to handle the A & V separately.

Yeh, I figured this would give the impression I listen to home HiFi too much.  Like many of us I do like to have nice music at home though I definitely wouldn't call myself an audiophile.  However I am well aware of the principal that the audio chain is made of many links that each degrade the sound quality.  Therefore the way to setup a superior system is to minimise both the number of links as well as the noise and distortion at each ink.  This is the reason I have made an effort to obtain the best quality music files that I can.  I chose EAC because it's free and well regarded for accuracy, though it can be a pain to learn to use.  Yes, I know older audiophiles have used it.  It beats downloads or WMP ripping for accuracy  hands down.  There are other accurate options but this is free.  I have been all over this system from end to end and the clarity is good.  There are other issues with the room though but at least the system system is pretty much as good as I can get it now.  In fact my audiophile friend tells me it's the best, true sound reinforcement church system he has heard.  So what a I am trying to he here is simply complete the last links in this setup strategy.   I am well aware that historically PCs were considered very poor for S/N.  PC PSU filtering was historically pretty rubbish in terms of affect on S/N.  Same can be said of RF shielding.  I am aware these things and sound cards have improved quite a bit in recent years, I just don't know how much.  I am not too concerned about sound cards if we go to an external DAC.  I am not too concerns about earth loop hum as that is under control now but I am concerned about taking the cleanest option when choosing new equipment.  The is a lot to consider, often laptops don't support audio well.  I have one that will not take an analogue mic input though by it's spec it should.  OP and hardware don't always wok well together.  I am a bit dubious about lite computing devices for this reason.  So, I am just putting a feeler out there for advice.

If the earth is not taking noise to ground well, an electrician will not be helpful with that, at least not the ones around here.  They only care that it's safe in regard to supply spec and have no idea about earth reference stability.  That isn't an audiofool thing BTW, it's just part of combining many minor improvements at every link to achieve a much larger sum total improvement overall.  I have been doing this a long time and know from decades of experience this approach works.

Ken

You're going to be best served by keeping your audio path separate from your video path - at least at the level it sounds like you're working at.  Even when I'm routing audio through a video router (Ross Ultrix, ~$50K) I still land each audio source separately to the audio console.  That way level differences are easily handled if you're switching sources.  As far as cleanest source, you're still not going to get any better than a simple USB DAC.  One like the radial I mentioned earlier that is bus powered and doesn't require drivers on any (modern) system.  It's also significantly simpler than getting a video switch and audio extractors involved.  There's a lot less to go wrong and it's a lot easier to troubleshoot.

You are smart to get a video switch in place to feed your projector.  The ability to dump to a graphic or to black is really nice, especially if the worship leader or pastor wants to stop by pre-service and check their slides without them going up on the screens.  You can also check video audio levels in your cans pre-service without having to throw them up on the screens.  If you're intending to be able to cut sources live make sure you have a switch that is either two bus or is really fast.  They've gotten a lot better in even just the past five years but there can still be some really noticeable cut delay on some cheaper units.  You also want to make sure that you get one that will do scaling.  The ones that don't do scaling will often make the projector re-sync it's signal every time you change sources.

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Ken Webster

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Re: Cleanest computing platform
« Reply #4 on: April 24, 2019, 07:28:59 pm »

You're going to be best served by keeping your audio path separate from your video path - at least at the level it sounds like you're working at.  Even when I'm routing audio through a video router (Ross Ultrix, ~$50K) I still land each audio source separately to the audio console.  That way level differences are easily handled if you're switching sources.  As far as cleanest source, you're still not going to get any better than a simple USB DAC.  One like the radial I mentioned earlier that is bus powered and doesn't require drivers on any (modern) system.  It's also significantly simpler than getting a video switch and audio extractors involved.  There's a lot less to go wrong and it's a lot easier to troubleshoot.

You are smart to get a video switch in place to feed your projector.  The ability to dump to a graphic or to black is really nice, especially if the worship leader or pastor wants to stop by pre-service and check their slides without them going up on the screens.  You can also check video audio levels in your cans pre-service without having to throw them up on the screens.  If you're intending to be able to cut sources live make sure you have a switch that is either two bus or is really fast.  They've gotten a lot better in even just the past five years but there can still be some really noticeable cut delay on some cheaper units.  You also want to make sure that you get one that will do scaling.  The ones that don't do scaling will often make the projector re-sync it's signal every time you change sources.

Ta for that, some good points.  I like some of the features with the radial USB direct box.  Seems a good option to at least separate A/V stream from pure digital audio.  I may still go with  a switcher and extractor for all A/V sources though as I'm currently a bit short on mixer inputs beyond the stage lines.  The fact is that we mostly only play video from the one source which looks like becoming a laptop. The extractor outputs to RCA which bypasses gain on the board so, in the event of switching video sources (unlikely), it's a simply matter of fade out, switch HDMI source then fade in.  As for the music Computer, I'm leaning toward a PC again simply because they are a more easily serviceable item that tends to outlast the compact options.  Still don't have an answer to my original question on electrical noise, especially earth noise.  I guess that using an external DAC with XLR (lift earth) is going to minimise that to whatever is eddies around the supply earth.  Still would be interested in decent PC PSU filters.
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Matthias McCready

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Re: Cleanest computing platform
« Reply #5 on: April 25, 2019, 12:56:15 am »

The Radial USB Pro is a great product, on and off the stage. I have never under any circumstance heard "electrical" noise coming from it, I use these interfaces almost every day, in various venues and with lots of different computers.

I would keep video and music playback separate. For the space I love rack mounted mac mini's, many of my FOH locations have 2-3 mac mini's (just for audio). Although really any computer, even old curmudgeonly laptops, tend to be just fine for high-quality audio (without any electrical noise). Playing back music does not take a lot of processing power and is not heavy lifting by any means. If you have a decent DAC and a large hard enough hard drive; a windows 98 machine would even fit the bill and not have any weird sounds.  ;D Bring the back the beige!

As far as "audiophile" standards go any computer reading WAV/FLAC is a good source, (lower error rates compared to read rates, even of expensive players). If you have a decent external DAC your results will be good. As to what quality of DAC, should you get  I highly doubt a Radial would be the weak link in the chain. Even using it with D&B, JBL, L Acoustics, Meyer, or Nexo I never thought "I could really use a better DAC." More serious sound issues are usually related to speaker quality, deployment, room acoustics, and operator ability. Even MP3's over 3.5mm will sound good on a well-deployed quality rig, anything else is icing on the cake.

I am not sure what this "extractor" business you are talking about is, but it sounds like something to be avoided. If video world wants a switcher great, any quality switcher will offer XLR outputs. Good video equipment costs serious cash, it is a much more expensive game to be in compared to audio, as is such avoid cheap products when possible, in my experience you get what you pay for.

If you do not have enough I/O on your current console but are determined to keep it perhaps get a small 4-6 channel external mixer. This will allow for control over your different computer audio sources. At minimum (if I understand your situation correctly) you will want a stereo music input and a stereo video playback, 4 channels.

---




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Erik Jerde

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Re: Cleanest computing platform
« Reply #6 on: April 25, 2019, 08:35:50 am »

any quality switcher will offer XLR outputs.

Actually anything approaching high end doesn’t do anything with audio.  I have only seen audio capabilities on gear that’s rather low end all-in-one type boxes.  Some implementations, even on $4K switcher/scalers have been decidedly poor, noisy, and lots of crosstalk.
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Stephen Swaffer

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Re: Cleanest computing platform
« Reply #7 on: April 25, 2019, 07:22:55 pm »

Ta for that, some good points.  I like some of the features with the radial USB direct box.  Seems a good option to at least separate A/V stream from pure digital audio.  I may still go with  a switcher and extractor for all A/V sources though as I'm currently a bit short on mixer inputs beyond the stage lines.  The fact is that we mostly only play video from the one source which looks like becoming a laptop. The extractor outputs to RCA which bypasses gain on the board so, in the event of switching video sources (unlikely), it's a simply matter of fade out, switch HDMI source then fade in.  As for the music Computer, I'm leaning toward a PC again simply because they are a more easily serviceable item that tends to outlast the compact options.  Still don't have an answer to my original question on electrical noise, especially earth noise.  I guess that using an external DAC with XLR (lift earth) is going to minimise that to whatever is eddies around the supply earth.  Still would be interested in decent PC PSU filters.

I'll stick my neck out a bit here.  There is nothing magical about being connected to earth and dealing with earth eddy currents.  If you built your entire system on a large copper plate that was isolated from earth, but had good connections and ran it off batteries that would work just fine-no earth connection needed.

I am not a Mac advocate (We have a good natured Mac/PC rivalry-Pastor loves them, I tolerate them in general as I am required to use PCs at my day job-after all PC or Mac its a tool with pros and cons.)  However, I very much like the Mac/QU combination we use.  The QU is OS compliant and the MAC sees it as an audio device-so digital from the Mac in to the QU without a DAC until the output of the QU.  I'm not sure how much less "noisy" an interface you could possibly get?

I understand the advantages of a switcher-but running Propresenter on the Mac covers all of our video needs and the Mac-QU connection cleanly handles our audio.  Perhaps we will get "better" someday-but when you are doing live media presentations that often change on the fly there is a LOT to be said for a simple hardware setup.
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Steve Swaffer

Matthias McCready

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Re: Cleanest computing platform
« Reply #8 on: April 25, 2019, 10:35:27 pm »

Actually anything approaching high end doesn’t do anything with audio.  I have only seen audio capabilities on gear that’s rather low end all-in-one type boxes.  Some implementations, even on $4K switcher/scalers have been decidedly poor, noisy, and lots of crosstalk.

I stand corrected... I am not a video guy and have never touched anything nicer than a Roland switcher  ;D

Thanks for the correction Erik
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Ken Webster

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Re: Cleanest computing platform
« Reply #9 on: April 25, 2019, 11:32:20 pm »


I am not sure what this "extractor" business you are talking about is, but it sounds like something to be avoided. If video world wants a switcher great, any quality switcher will offer XLR outputs. Good video equipment costs serious cash, it is a much more expensive game to be in compared to audio, as is such avoid cheap products when possible, in my experience you get what you pay for.

If you do not have enough I/O on your current console but are determined to keep it perhaps get a small 4-6 channel external mixer. This will allow for control over your different computer audio sources. At minimum (if I understand your situation correctly) you will want a stereo music input and a stereo video playback, 4 channels.

---

On the audio extractor:  HDMI is a mixed A/V bit-stream.  The extractor, extracts the audio bit-stream from that mixed stream and feeds the audio bit-stream to an integrated DAC which outputs analogue audio to a desk input.

I use something like this at home I have a vintage analogue HiFi and use an Essence HDACC to extract and convert digital audio to feed the HiFi.  To satisfy the family's desire/need for remote control, I put the HDACC in the analogue amps tape dubbing loop to provide remote volume control for the analogue sources.  This way, I don't have to put up with the TVs inadequate speakers because of the families need for a remote volume control.  In truth, I think my 80s AMC CD8a player provides slightly nicer analogue audio than the HDACC but they are pretty close to equal with a 1411 bit stream.  But that's another story.

Back to the church PA though:
I don't need to use stereo on the church mixer though I have been doing that because of split tracks.  However, the worship coordinator has decided to drop all spit tracks so I can go to mono channels now which will help with the shortage of inputs.  I have 12 stage inputs and 4 non stage.  I have been using inputs 11 & 12 (dual TRS/XLR) for the music PC or for stage Hi-Z because a service requires one or the other, not both.  For non stage sources we have:
Music PC (2ch)  currently 2 RCA in, Probably go to 1 XLR mono in.
Video PC (2ch) currently 2 RCA in, probably go to 1 RCA mono from HDMI switch.
Disc Player (2ch) currently 1 RCA in, probably go to 1 RCA mono from HDMI switch.
Radio Mic (2ch) currently 2 XLR in and will remain so.
portable device input (2ch) currently 1 RCA mono.

The extractor has RCA audio, I didn't get a say on this.
I like the fact the radial box is XLR and has ground lift. (isolates ground from signal path)

We may not strictly need all that but I think that given some things are RCA while others are XLR, if I go to merged mono, I will have enough inputs without taking up stage lines.

Ken
« Last Edit: April 25, 2019, 11:56:17 pm by Ken Webster »
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ProSoundWeb Community

Re: Cleanest computing platform
« Reply #9 on: April 25, 2019, 11:32:20 pm »


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