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solotibia 
Caracal
Joined: February/27/2014
Location: Brisbane, Aus
Points: 32
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 Topic: 'PIn 1'
Posted: March/10/2014 at 10:07pm |
Hi,
What is the Aurora 16 'Pin 1' expecting to 'see'. Is it a shield to shield connection as per the AES48 standard? Or something else?
Cheers,
Ian McLean
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PaulTech
Admin Group
Joined: August/13/2004
Location: United States
Points: 5495
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Posted: March/12/2014 at 1:30pm |
Do you mean Pin 1 of the AES D-Sub? If so it is In 1 Hot.
Here are the pin outs: http://www.lynxstudio.com/support_docs_result.asp?c=43
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solotibia
Caracal
Joined: February/27/2014
Location: Brisbane, Aus
Points: 32
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Posted: March/12/2014 at 4:20pm |
Thanks but no. I'm enquiring about the analogue out.
AES48-2005 specifies chassis shield to chassis shield, and definitely not chassis shield to audio ground. I have my cables 'telescoped' or 'shotgunned' so that Pin 1 is not connected at the receiving end (the amplifiers) as the amplifiers do not adhere to AES48-2005. This is because Pin1 connection on these is connected directly into the audio PCB, instead of the chassis.
I notice that Lynx describes the Auroras analogue outputs as "electronically balanced" http://www.lynxstudio.com/nav/getFile.asp?i=86&t=productfile. What does that mean? How is this achieved? Does the Aurora circuit expect to 'see', or does it relay on a Pin 1 audio ground connection at the amplifier end for its electronically balanced outputs to function correctly?
Thanks for the pinouts, but they don't help as they just refer to the Pin 1 connection as "GND".
I would attach the AES48-2005 standard, but there is no facility to do so.
Cheers,
Ian
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solotibia
Caracal
Joined: February/27/2014
Location: Brisbane, Aus
Points: 32
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Posted: March/14/2014 at 4:27pm |
http://www.kirkeo.org/sites/default/files/pdfs/node15/aes48-2005-f.pdf
I look forward to some answers.
Cheers,
Ian
Edited by solotibia - March/14/2014 at 4:28pm
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Bobcat
Admin Group
Joined: August/19/2004
Location: Costa Mesa
Points: 76
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Posted: March/20/2014 at 10:03am |
Hello,
Pin 1 is a shield connection and could be unconnected at one end without affecting the signal.
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Regards,
Bob Bauman
Lynx Studio Technology
Co-founder, Chief Hardware Engineer
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solotibia
Caracal
Joined: February/27/2014
Location: Brisbane, Aus
Points: 32
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Posted: March/20/2014 at 4:38pm |
Thanks Bob. That puts my mind at rest. So why is it called "GND"?
Cheers,
Ian
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solotibia
Caracal
Joined: February/27/2014
Location: Brisbane, Aus
Points: 32
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Posted: May/05/2014 at 6:43pm |
It has been suggested to me that rather than leaving the Pin 1 connections 'telescoped' that adding a 103k ceramic cap at the amplifier end of Pin 1 for each channel would be a superior solution. That this would better (in terms of any RFI protential) than telescoping. Would doing this impair the performance of an Aurora's analogue outputs in any way?
Cheers,
Ian
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Bobcat
Admin Group
Joined: August/19/2004
Location: Costa Mesa
Points: 76
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Posted: May/06/2014 at 10:06am |
Hi Ian,
I assume you are talking about connecting a capacitor to the unconnected shield at the unbalanced amplifier input. This will provide an AC path to ground for RFI and should avoid any ground loops for AC line currents. It's not a bad idea and it will not affect the analog out performance.
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Regards,
Bob Bauman
Lynx Studio Technology
Co-founder, Chief Hardware Engineer
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solotibia
Caracal
Joined: February/27/2014
Location: Brisbane, Aus
Points: 32
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Posted: May/21/2014 at 5:55pm |
Hi Bob,
I installed the caps on Pin 1 at the amplifier end of the cables. However, if I float the AC ground to the 32 amplifiers, I get hum when attempting to use only the Pin 1 ground connection as ground. Whereas usually with Pin 1 connected without the caps in place, and if I float the AC ground, there is no hum. If I then only connect one channel with Pin 1 connected (and all others with the cap in place on Pin 1), the hum (with AC ground lifted) disappears completely on ALL channels. Any clues? Could 32 caps be upsetting the Aurora circuitry?
If I use the system with both Pin 1 with cap connected and AC ground connected, there is zero hum. Indeed, the system is so quiet, that it could be described as being 'black'. However, sonically it has some upper midrange brightness when compared to using the system with Pin 1 not connected, and with AC ground connected. I am wondering whether the interaction of the caps and the Aurora's output circuitry could be the possible cause of this brightness?
Cheers,
Ian
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Bobcat
Admin Group
Joined: August/19/2004
Location: Costa Mesa
Points: 76
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Posted: May/23/2014 at 10:13am |
Ian,
1. Floating the AC ground of your amplifiers is not safe. I would recommend avoiding this. 2. AC hum which is cause by system ground loops is very finicky with signal paths are very subtle. In general, if you have a safe connection scheme that produces no hum, go with it. 3. Verify that pin 2 is connected to the signal input of your amplifiers and pin 3 is connected to the signal ground of your amplifiers. 4. Connecting a capacitor from pin 1 to the amplifier ground should have no affect on the frequency response of the Aurora output circuitry as long as the connections in 2 are made.
If you are still stuck, send me a simple diagram of your connection scheme that I can use to verify your setup.
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Regards,
Bob Bauman
Lynx Studio Technology
Co-founder, Chief Hardware Engineer
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solotibia
Caracal
Joined: February/27/2014
Location: Brisbane, Aus
Points: 32
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Posted: May/23/2014 at 6:36pm |
Thanks Bob,
1. I certainly would not operate the system with the AC ground floated. This was just for a quick test, triggered by that upper midrange glare. 2. Agreed. It seems that I have three options. Telescoped Pin1 (no hum). Pin 1 connected (no hum). Pin 1 with cap connected (no hum). I have to choose the best sound from these options. 3. Verified. 4. Pin 1 with the cap should be the best connection (no chance of RFI). But, thinking through issues in this discourse with you makes me think that the reason that it could be having issues, is that Pin 1 is not connected to the chassis before the audio ground in either the Aurora, or the amplifiers. I think that if the connection was indeed chassis to chassis we wouldn't need to have this discussion. Can you confirm just what Pin 1 is connected to in the Aurora? Is it chassis first, and then the audio? Or via the audio ground? Or...............? If the Aurora's Pin 1 is indeed connected to the chassis first, then that would only leave me to consider Pin1 at the amplifier end as being suspect. 5. How are the two separate Aurora 16 chassis connected together when two Auroras are being used in once system? 6. All 32 amplifier connections are balanced and use Canare cable. Currently Pin 1 on 31 channels are connected with the cap in place at the amplifier end, Pin 1 on one channel has no cap. The DB25 outputs of the Auroras feed two RME BoB16 25pin to XLR break out boxes via Mogami cable.
Cheers,
Ian
Edited by solotibia - May/25/2014 at 9:09pm
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'PIn 1'