You are here

Starquad cable

All about the tools and techniques involved in capturing sound, in the studio or on location.

Starquad cable

Postby Jay Menon » Mon Aug 17, 2009 8:53 pm

I just read up about starquad cable...two internal cores that cancel each other's interference - like a humbucker?

Anyway, question from a novice here - would you guys use starquad cable in preference to ordinary balanced cable? I'm thinking in terms of microphone cables of 10 metres length...and its for use at home...

Regards
Jay
Jay Menon
Frequent Poster
Posts: 807
Joined: Sat Sep 29, 2007 11:00 pm
Location: Wales
 

Re: Starquad cable

Postby christianmurphy » Mon Aug 17, 2009 9:00 pm

I'm no cable pro, but i guess it depends what you want it for... If you just need a decent quality microphone cable, then just buy that.

I can reccomend sommer and klotz, from previous experience.

Starquad is used if theres a bigger risk of interference. I think it would make barely any difference in a home environment...

Christian.
User avatar
christianmurphy
Regular
Posts: 258
Joined: Fri Jan 25, 2008 12:00 am

 


Re: Starquad cable

Postby Aural Reject » Mon Aug 17, 2009 9:27 pm

Personally, no.

I only use starquad cable if I know I'm going to be exposed to an environment where the possibility of interference is high....and that wouldn't normally be at 'home'....

Starquad also exhibits HF loss over distance.
User avatar
Aural Reject
Frequent Poster
Posts: 825
Joined: Thu May 01, 2003 11:00 pm
Location: Lancashire
 

Re: Starquad cable

Postby Jay Menon » Mon Aug 17, 2009 9:40 pm

Thanks Guys... your replies were very informative and useful...!

Regards
Jay
Jay Menon
Frequent Poster
Posts: 807
Joined: Sat Sep 29, 2007 11:00 pm
Location: Wales
 

Re: Starquad cable

Postby Hugh Robjohns » Mon Aug 17, 2009 11:16 pm

Jay Menon wrote:I just read up about starquad cable...two internal cores that cancel each other's interference - like a humbucker?

I think we know what you mean... but for the uninitiated there are four cores in starquad cable -- the clue in in the 'quad' part of the name ;) -- plus an overall screen.

The four cores are very tightly twisted with each other and rotate over a relatively short length. If you image the four cores arranged at the ends of the two arms that form a plus sign, then the two cores on the vertical arm are wired together in parallel to form one side of a balanced line, and the two cores on the ends of the horizontal arm are wired together in parallel to form the other side of the balanced line.

Obviously, with four wires in the cable, the core-core and core-screen capacitance will be much higher than a more conventional two-core cable, and that's the down side. it means there will be greater HF loss in long cable runs. Not a problem with 10 metres, or even 50, but a hundred metres or more will start to exhibit audible HF loss.

The upside is better rejection of very close source electromagnetically induced interference -- the kind of interference that might come from laying a mic cable alongside something that radiates strong and nasty interference -- like some kinds of mains dimmer cables, for instance.

If you consider a standard two-core mic cable lying for a short length alonsgide a nasty interference source, then some of that interference will break into both cores. To be rejected by the balanced input of whatever it is connected to, it MUST break into both cores equally.

However, the inverse square law dictates that there will be more energy transferred into the closer core and less into the further core -- and since the two cores twist around each other in a lazy spiral down the mic cable -- there's a good chance that one core will pick up slightly more interference from that close source than the other core. The result is audible interference because the imbalance means it won't all get rejected.

Starquad overcomes this problem because the cores are wired in opposite pairs. So replacing the standard mic cable above with starquad, one pair of wires will be effectively either end of that vertical bar of the plus sign, and will therefore pick up equal amounts of interference because they are the same distance from the nasty cable lying alongside. The other pair areon the horizontal arms, which means one core is slightly closer to the interfering cable than the vertical pair, but the other is slightly further away -- by equal and oppiste amounts. So the net average interference in the two cores will be exactly the same as that of the two vertical cores. Hey presto -- much better balance of interference and therefore better rejection. The much tighter cable twist helps too.

Starquad was invented for use in telephone cables back in the 1930s, and was adopted in the TV world in the 60s an 70s -- I think. It is widely used, particularly where there is a liklihood of having to lay mic cables alongside strong sources of interference.

would you guys use starquad cable in preference to ordinary balanced cable? I'm thinking in terms of microphone cables of 10 metres length...and its for use at home...

No, not particularly. With that short a cable run, and in a domestic situation, interference isn't likely to be an issue at all. No reason not to buy starquad if you can get a good deal -- but I wouldn't seek it out specially. You're very unlikely to gain an significant benefit.

I'd look for a decent two-core cable from a reputable supplier. I particularly like double-screened cables (reussen screen) which are also widely used in broadcasting.

Hugh
User avatar
Hugh Robjohns
Moderator
Posts: 20348
Joined: Thu Jul 24, 2003 11:00 pm
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: Starquad cable

Postby Steve Hill » Tue Aug 18, 2009 7:26 am

It's probably only really useful if you are also using your home for purposes which might create a lot of electrical interference...

Image
User avatar
Steve Hill
Frequent Poster
Posts: 3266
Joined: Tue Jan 07, 2003 12:00 am

Re: Starquad cable

Postby Aural Reject » Tue Aug 18, 2009 7:28 am

Ah, maybe I should use it here then Steve.... :tongue:
User avatar
Aural Reject
Frequent Poster
Posts: 825
Joined: Thu May 01, 2003 11:00 pm
Location: Lancashire
 

Re: Starquad cable

Postby Setter » Tue Aug 18, 2009 9:05 am

Re the picture of the upcoming Studio SOS

I can see the diffusers / acoustic treatment but where are the chocolate hob-nobs?

Still, much better picture of Paul and Hugh than usual.

J

Sorry
Setter
Regular
Posts: 220
Joined: Wed Nov 06, 2002 12:00 am

Re: Starquad cable

Postby Hugh Robjohns » Tue Aug 18, 2009 10:02 am

Oi!

:D

hugh
User avatar
Hugh Robjohns
Moderator
Posts: 20348
Joined: Thu Jul 24, 2003 11:00 pm
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: Starquad cable

Postby plodsmeade » Tue Aug 18, 2009 9:20 pm

I particularly like double-screened cables


Is that typically labelled as 'digital' in so far as it gets used for AES patching or DMX etc..

Was wondering if that was any better than your standard single-screen mic cable for analogue audio use.
plodsmeade
Poster
Posts: 36
Joined: Tue Jan 03, 2006 12:00 am

Re: Starquad cable

Postby Hugh Robjohns » Tue Aug 18, 2009 9:36 pm

No. The properties of a 'digital cable' include very low capacitance and a specific nominal impedance (110 ohm for AES3 and 75 ohm for S/PDIF or AES3-id. Often they have conductive plastic screening too, but not double (reussen) screening.

Hugh
User avatar
Hugh Robjohns
Moderator
Posts: 20348
Joined: Thu Jul 24, 2003 11:00 pm
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: Starquad cable

Postby mjfe2 » Tue Feb 13, 2018 2:57 pm

Hugh, I never thanked you and the others for these great replies. V comprehensive.

What sort of distances are we talking where starquad HF loss becomes an issue?
User avatar
mjfe2
Frequent Poster
Posts: 591
Joined: Sat Oct 10, 2009 11:00 pm
Location: London, UK

Re: Starquad cable

Postby Hugh Robjohns » Tue Feb 13, 2018 3:48 pm

It will depend on the input impedance of the preamp, and how much top-end content there is in the source signal! As I said, earlier it's not I'd start worrying about at all until you're into very long cables -- 100m or more maybe.

H
User avatar
Hugh Robjohns
Moderator
Posts: 20348
Joined: Thu Jul 24, 2003 11:00 pm
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: Starquad cable

Postby mjfe2 » Tue Feb 13, 2018 5:01 pm

Hugh Robjohns wrote:It will depend on the input impedance of the preamp, and how much top-end content there is in the source signal! As I said, earlier it's not I'd start worrying about at all until you're into very long cables -- 100m or more maybe.

H

Thanks Hugh. And what does EMI sound like? I'm guessing RFI is anything from local radio stations to that infamous mobile phone stuttering sound?
User avatar
mjfe2
Frequent Poster
Posts: 591
Joined: Sat Oct 10, 2009 11:00 pm
Location: London, UK

Re: Starquad cable

Postby Hugh Robjohns » Tue Feb 13, 2018 5:39 pm

mjfe2 wrote:And what does EMI sound like? I'm guessing RFI is anything from local radio stations to that infamous mobile phone stuttering sound?

EMI = electromagnetic interference -- usually hums from the mains being induced into the cable electromagnetically.

The cable screen is there as an electrostatic screen and protects against RFI (radio frequency interference). The twisting arrangement of a standard cable's signal wires protects against electro-magnetic interference, and the quad arrangement against the same for really close sources. The two signal wires and differential receiver protect against anything unwanted that makes it through! :D

H
User avatar
Hugh Robjohns
Moderator
Posts: 20348
Joined: Thu Jul 24, 2003 11:00 pm
Location: Worcestershire, UK
Technical Editor, Sound On Sound


Who is online

Users browsing this forum: No registered users