#1606024 - 03/19/19 09:53 AM
RBUS cable lengths and noise
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ricco
Planeteer
Registered: 01/12/16
Posts: 140
Loc: Victoria BC, Canada
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I seem to recall reading somewhere in past posts about the correlation with noise and RBUS cable length. I have been experimenting with 2 RPC-1 inputs in my computer, and running 2 RBUS cables out from my VS 2480. The cables are both very long: 15ft!!
I can notice faint crackles and distortion on tracks I have sent over to REAPER and recorded, then listened back to through the VS 2480. I've played about with levels out recorded and back in listening. I've also tried reassigning tracks IN/OUT on REAPER...also whether I use RBUS1 or RBUS2 for the OUT to REAPER.
I recall Bear had a schematic showing us all how to make out own RBUS cables; I was thinking of making up a couple shorter sets and trying it out as well, seeing as the likelyhood for anyone wanting to trade a shorter cable for one of these jumbo buggers is unlikely...especially if they are no good for what I'm trying to use them for.
Just curious though: they MUST have had an operational use for the longer cables? Maybe just for their synths, or ADAT? And could that noise I'm hearing be due to the length of RBUS cable? Any thoughts/help appreciated. Rick (ricco)
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#1606029 - 03/19/19 12:44 PM
Re: RBUS cable lengths and noise
[Re: ricco]
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Starliner
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Registered: 05/19/09
Posts: 3173
Loc: Florida - Dunnellon
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This is also very interesting to me. I am considering running longer R-Bus cables from my studio desk with an SI-24 on one end, to my VS systems on another wall 90 degrees away. It might even be more than 15 feet, so it would need to be a custom-built cable.
I'm also curious to see what this noise might look like on an O-scope.
But, if I will run into a noise issue, I have to seriously rethink running long cables at all. I would have to put the SI-24 on a mobile cart at the very least, or not use it at all. And, I'm not fond of the idea of plugging / unplugging into an R-Bus connection repeatedly.
So whatever you discover, I am interested in a solution or workaround as well.
Starliner
PS: I have the R-Bus cable pin-out diagram if you need it.
Link to Bear's adapter post: Bear's Adapter
Edited by Starliner (03/19/19 01:38 PM) Edit Reason: Link added
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Half The Lies They Tell About Me Aren't True!
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#1606037 - 03/19/19 02:08 PM
Re: RBUS cable lengths and noise
[Re: Starliner]
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uptildawn
Planeteer
Registered: 12/15/01
Posts: 9067
Loc: on land
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Let me suggest that whenever I've had faint crackles on my pc-recorded tracks coming in from an outside digital source path, the problem has always had something to do with either clocking, or the physical connections needing to be reset. Ricco, you might try re-seating your cables and also to double check your setting in both machines for digital sync, word clock, sample rate, etc. Be sure that only one unit is set as master and if already set correctly, then consider switching the master setting to the other machine (if only two machines are involved - for more digital machines, the same applies, just with more options).
Starliner - consider making a longer run using two cables, connected with a gender changer adapter, if necessary. You can avoid having to make a special extra long cable that way. If the adapter connections are solid, it shouldn't create an issue.
You might also use this as a means to test whether or not the longer run will cause noise issues and this way you can confirm the use of, or reject the idea, without having lost a lot of time, effort and cash on a special cable.
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uptildawn
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#1606203 - 03/21/19 04:58 AM
Re: RBUS cable lengths and noise
[Re: uptildawn]
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ricco
Planeteer
Registered: 01/12/16
Posts: 140
Loc: Victoria BC, Canada
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Thankyou Starliner and uptildawn: I might have added that the crackles and hiss are fairly slight. I know what the crackles from mis-matched clocking sound like...and it's not anywhere that severe. Just when you push the levels to just before unity....around -4, -8.
I have double-checked the physical connections, and sync settings to no avail. But I will keep playing with it...and keep you posted should I discover a fix for it. Thanks again, Rick (ricco)
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#1606204 - 03/21/19 05:22 AM
Re: RBUS cable lengths and noise
[Re: ricco]
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uptildawn
Planeteer
Registered: 12/15/01
Posts: 9067
Loc: on land
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When I first switched most of my work to a pc and interface, with multiple 8-ch preamps some years ago, I would hear little crackles and pops - very slight - and not all the time. One day I happened to be zoomed in on a track and noticed that I could see a tiny tick in the wave form right where I heard a slight tick in the mix.... That's when I discovered that I had somehow developed a problem with the preamps staying in sync with the computer system. The ticks were random throughout the multitrack recording and would randomly happen on different tracks, too. sometimes it sounded like crackling.
I forget now what it turned out to be - maybe a dodgy adat or word clock cable, I think. But that's why I mentioned it.
Pushing the levels up to a certain point and then having that action produce crackling and hissing sounds more like a circuit board problem...... maybe power supply filter caps, or other electrolytic caps in the preamp/mixer sections?? Maybe some problem with the physical faders, or attenuators?... if those are even ordinary pots.... Have you ever tried thumping the sides or top or back of the unit while it's making these sounds? Used to be a clear indicator with older electronics, like preamps, receivers, etc. Maybe it would have some affect?
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uptildawn
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#1606257 - 03/21/19 04:47 PM
Re: RBUS cable lengths and noise
[Re: uptildawn]
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Starliner
Planeteer
Registered: 05/19/09
Posts: 3173
Loc: Florida - Dunnellon
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Uptildawn,
Thanks for the suggestions... good call on linking two cables together with an adapter to check it out. I may also make a "test point adapter", so I can access the cable to check the signals with my scope.
Thanks Rick for keeping us posted.
Starliner
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Half The Lies They Tell About Me Aren't True!
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#1606494 - 03/23/19 08:12 AM
Re: RBUS cable lengths and noise
[Re: uptildawn]
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ricco
Planeteer
Registered: 01/12/16
Posts: 140
Loc: Victoria BC, Canada
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That's a very good suggestion...directed banging the VS. I gave it a try...with no improvement. But I believe you are on to something "uptildawn" as the crackles are indeed intermittent...a vital piece of info I left out of my original explanation.
Anyways...I'll employ that Wave Display trick to see if I can isolate and snuff out any future noise. Thanks again!! I was about to get all involved with trying to sell the long RBUS cables and make shorter ones. I suppose that might still be worth trying...however I'll hang onto the longer cables for now, until I'm more certain they are the problem...or part of it. cheers Rick (ricco)
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#1606512 - 03/23/19 02:04 PM
Re: RBUS cable lengths and noise
[Re: ricco]
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Starliner
Planeteer
Registered: 05/19/09
Posts: 3173
Loc: Florida - Dunnellon
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Rick,
If you're inclined to open the VS and have a "technical" background, you also might get a can of component freeze spray, and see if you can change the symptoms with pinpoint blasts on different components.
This is a long-standing technique of technicians to try and find thermally-related problems of an intermittent nature. I've also used heat, such as bringing the tip of a hot soldering iron close to a component (but unplug the iron first and don't physically contact the conductive surfaces). But, you have to be more careful, as some components can be damaged by excessive heat.
You can also use a plastic rod or wooden dowel (think electrically insulated) to tap on specific areas if you suspect a loose connection or mechanical failure. And a close visual inspection of solder connections is always a good idea, especially dealing with intermittent problems.
Good luck and keep us posted!
Starliner
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