firewire galvanic cable isolation?

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frits

Active member
Joined
Oct 20, 2005
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38
Location
netherlands
Ok guys, lets start with the problem....

Since I finally have a real mixing studio :green: I keep on hearing noises from my computer setup..... this is a commen problem and most of the time we can solve it by lifting some grounds or replacing them.

Though now I have a new desk with a D.C. coupled signal path ( ehh yes there is one cap at the input ) and what ever I do I can hear the rubish from my computer!

now I was wondering if it is posible ( or maybe even in the market ) to isolate the firewire plug from the computer. with some optocouplers or maybe lift the schield on one side :roll:

any one tried something like this.......
 
[quote author="frits"]did it help?...

P.S i'm using a bare bone[/quote]

Yes, it did help. Using a power transformer I did not need to connect the notebook's ground to the safety ground, may be it is the main issue.
 
-computer slix barebone
-interface presonus
-polygram 88 channel analog mixing desk

the problem is already there when i hit the presonus with the shield if the fire wire.... can i do without?

P.S. thanx for thinking with me guys
 
Get the noise condition happening, and disconnect the Presonus audio I/O one connection at a time. I would bet that the noise does not go away until the last connection is broken.

Most likely this can be eliminated by lifting audio shields on the Presonus audio I/O cabling at the Presonus. That would be preferred to lifting power ground connections or the FW shield.

Of course I am assuming that you know that the monitors and anything else connected to the console are quiet and "de-buzzed".
Mike
 
[quote author="sodderboy"]
Most likely this can be eliminated by lifting audio shields on the Presonus audio I/O cabling at the Presonus. That would be preferred to lifting power ground connections or the FW shield.
[/quote]

Try this - most likely your PC/Soundcard will be making the earth filthy and possibly causing an earth loop too.
 
olaf-
is this with both interfaces connected to the same source? I have never had this problem with the 002 connected to 120 VAC- "balanced power" or not.
Have you found a "long term solution"? You should.
My experience is the same with PC's and laptops- there was always a solution without cutting into a molded data cable.
Will this be the next battle in the War Against Noise? I have an installation planned for a shared interface studio; installed Dual Core Mac and guest laptop access.
Whats the buzz regarding the buzz, frits?
Mike
 
I was getting noise from my interface cable once... It ended up wrapped in tin foil.

Yes, it worked.
 
ok guys i think i'm gonne make my firewire opto box since that is according to me :?: the only solution......

thanx for thinking ya all, keep on posting!!
 
[quote author="frits"]ok guys i think i'm gonne make my firewire opto box since that is according to me :?: the only solution......[/quote]
Good luck finding optocouplers running at >500MHz, and then building a bidirectional opto bridge which is transparent to the FW protocol stack.

If you really have money to burn and don't care about the latency that is introduced, you could possibly use something like this.

The cheaper/faster solution would be to build a linear supply, or run the computer off (rechargeable) batteries during mix sessions, or...

JDB.
 
doesn't RME sell a firewire extender. It's usually offered as a solution for these type of problems for RME soundcards. RME uses it's own firewire protocol so i don't know if this box wil work with your presonus.
 
Hi ,

Very old thread :)
I have a question about galvanic cable isolation too please

In my studio i cut all pin 1 ( on receiver end 99% of time )  on balanced cable to remove all ground loop, it work like a charm / black background now
All chassis of gears have own wire return to the star ground ( rear of mixing desk )

A firewire cable have 9 pin AND a braided shield  to connect chassis connection  i think...


The ONLY " ground loop , i can hear and see " it s the firewire cable now .. ( .or usb3 / thunderbold cable interface )

I see a lot of topic about modify cable , but they talk about the power ground connection inside the cable  ( and need that connection )

but the BRAIDED  shield ?
In past Radio/TV etc , it was not uncommon to cut the shield at receiver end  too on a lot of cables

So that why i ask question here , i m not 100% sure and don t want to burn a chipset or something

Thanks
Seb


 

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Cutting pin one is not good practice or there would not be a pin one included inside XLR cables.

Study "pin one problem" a lot has been written about this.

Good luck.

JR 
 
JohnRoberts said:
Cutting pin one is not good practice or there would not be a pin one included inside XLR cables.

Study "pin one problem" a lot has been written about this.

Good luck.

JR

You are wrong in my opinion
But when i read completly the manual of my console ( Soundcraft serie 600 ) , they mention the grounding sheme for a professional studio
pin one is remove sometime at receiver end , sometime at transmitter end ( that why there is terminal ) , depend of what design electronicaly used ( that why there is terminal on XLR , to have choice / other people can add 100ohms resistor and 10 to 100nF capacitor en // instead off cut it " in the air "

take a look if you want >>>page 37 to 40 of the PDF attached ...write maybe by genious designer of soundcraft circuit :) ?
yes , i already study the pin 1 problem 5 years ago , isn 't the problem, because my studio is dead silence , volume max > just the amplification hiss of old 80's circuit , no hum ./ no buzz with no computer
So the ground sheme is valuable

The only "problem"  is the groundloop created between my computer (  with TB to firewire adapter )  and audio interface because they are both to earth , and the screen of firewire cable is the only cuript in this case

this " un-knownledge about grounding a studio is a good things for compagny sell $$$ for just a meter of  wire
when i discover this grounding sheme i understand that the most important things is the technical part,
a good braided screened with foil and 2 twisted conductor cable is just perfect in most case
The way you wire it count a lot for the ultimate " black " background




 

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I have always kept the ground at the receiver, cut at the transmitter if needed.

This is also the prescription in the CBS network Engineering Standards. CBS ran very large networks of studios; and at the time this was published had probably run into every possible situation.

But not computers. Laptops are usually very very badly "grounded".
 
PRR said:
I have always kept the ground at the receiver, cut at the transmitter if needed.

This is also the prescription in the CBS network Engineering Standards. CBS ran very large networks of studios; and at the time this was published had probably run into every possible situation.

But not computers. Laptops are usually very very badly "grounded".

Happy to confirm to cut the shield is a common practice , need that info for Firewire cable now ..
It s crazy that anyone in planet have already try to cut it :)

PS ;
Very good link CBS !
 
Seabstudio said:
Happy to confirm to cut the shield is a common practice , need that info for Firewire cable now ..
It s crazy that anyone in planet have already try to cut it :)

In more than 15 years using a firewire cable to connect a computer to a soundcard, I never had that problem due to the firewire connections themselves. And I'm talking about a lot of different setups, different gear involved over time and different locations.

I also never had anyone with that problem.

There can be ground loop problems in a studio situation, also mains interference or bad power supplies, but those are solved at the source and not at the firewire cable itself.
Your problems lies elsewhere and not in the firewire cable connections

Just my 2 cents
 

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