4 Pair Multipair Cable

[Rob_Beech]

Chris is unbelievably helpful and hats off to him but it just seems that nobody else there realises that they're at work anymore. I've as good as stopped using them as a supplier because I can no longer guarantee an order to go through without cancelling randomly, being delivered to an address 100 miles away, being incorrect, having parts missing, broken. I will add though that the last thing I ordered from there a couple of weeks before Christmas (special offers, not cutting my nose off to spite my face etc) did arrive next day, all present and correct but I purchased £15000 of stuff in 2007 near enough and about £600 in 2008 because of it.

[Andrew C]

Very odd Rob.

 

The only time I have real trouble is if I do a "Pre-noon" delivery order. I don't know which carrier they use for the expedited orders, but their standard delivery nearly always beats them. This is probably down to the carrier rather than CPC.

 

Occasionally a missed item, occasionally a rogue unexpected item but certainly not like your experience.

[dan slv-tech]

Id echo what rob said bout orders being randomly cancelled- ive had this happen on two occasions, both for no real good reason.

worst is you dont get any notification that its cancelled so like a lemon your sat there waiting for a delivery that will never arrive.

Again last year I speant about £600, not much I know, but principle remains.

Now I use other suppliers for bits n pieces or cpc if I really have too.

 

As its an automated system, surely an email saying " sorry theres a problem with your order" wouldnt go a miss.

 

dan

[Chris Beesley]

Anybody got a tin hat I can borrow :)

 

With regards to the issues above - can I ask you to send me your CPC account numbers and I will chase this up... poor service is not acceptible and I need to ensure the problems are rectified here.

 

To answer Andrew's post - all shipments are via UPS with the exception of small items sent in Jiffy bags by Royal Mail or large bulky items (flight cases etc) sent by another courier. The standard and pre-noon are both with UPS, our contract for standard deliveries is 24-48 hour delivery - however UPS usually deliver all items next day.

[Matt Riley]

Surely it is just easier to buy a 6 way 15 m system from thomann for £31. Even if you lose a couple of channels along the way, and maybe have to fix it, it will take less time to rebuild than to build. Also, it's not a touring application, and won't be abused. We've got one for use in the studio, and it hasn't lost any channels yet.

 

M

linky to the product here

[revbobuk]

Of course if you are sending balanced audio, then you could do all 4 at once down a single run of Cat5. Make up a couple of boxes with XLR connectors and an RJ-45 socket, and there you go.

[Charlie Jeal]

That's not a very good idea at all Revbob as the OP will need 12 conductors to do 4 balanced lines.

[revbobuk]

Nope - just 8. Which is what you get in Cat5 cable - the rejection of external interference comes from the twist, not from a screen conductor. I've built one of these myself, and it works really well. You can see the finished result here

[Charlie Jeal]

Nope - just 8. Which is what you get in Cat5 cable - the rejection of external interference comes from the twist, not from a screen conductor. I've built one of these myself, and it works really well. You can see the finished result here

 

 

Bob just you can make it still doesn't mean its a very good idea to make a shielded balanced line connection take 3 conductors : hot, cold, and shield or just maybe all the professional companies are doing it wrong?

 

Bottom line is your link is a very bad although cheap idea and I wish people would stop promulgating this type of nonsense as professional advice.

 

Charlie

[revbobuk]

I'd suggest you have a read of this thread where the subject was discussed at length, before you dismiss the idea as nonsense.

[Charlie Jeal]

Bob there are professional people I respect on there saying the same thing as me. Just because a thing can be done does not make it a good idea, IF your suggestion was a good idea tell me why it isnt normal practice and vdc trading aren't out of business. Bob FWIW I've been earning a good living in the sound business for 26 years now and I've never seen anyone who wants to be taken seriously even think about your idea. The professional situations where audio is carried over CAT5 cable use a protocol such as ethersound for transmitting the signal digitally or the cable is used from a digital control surface to and on-stage dsp mixrack.

 

I'll say it again CAT5 cable should not be used for running mic level signals ever and the use at line level is questionable

 

Charlie

[Shez]

I'll say it again CAT5 cable should not be used for running mic level signals ever and the use at line level is questionable

 

Would you care to elaborate on why it's questionable?

I can see practical reasons why CAT5 isn't always useful - it doesn't coil and generally handle like mic cable needs (and obviously has issues if phantom is required) to but for line level installation purposes, it's not a problem. The last couple of large commercial radio stations I worked at had no problem with using huge quantities of twisted pair that had no outer jacket at all. When you're wiring up hundreds of connections on a krone, stripping off outer jackets every time you terminate just isn't practical. We got through boxes of the stuff - it's quite normal in that environment.

Balanced audio simply needs a twisted pair in order to work properly. No screen necessary. If the receiving equipment has a poor CMRR, the presence of a screen can help to alleviate potential problems, but they're caused by shortcomings in the equipment, not the cable.

[bruce]

I'll say it again CAT5 cable should not be used for running mic level signals

 

That I would agree with.

and the use at line level is questionable

 

Perhaps someone should tell the BBC this... it's common practice to use unshielded twisted cables in the broadcast environment.

 

edit: beaten to it..

[Dmills]

Yep, nothing wrong with a simple twisted pair as long as the common mode impedance at the receiver is reasonably high.

Screening can only help with electric fields (in the audio band anyway), you deal with the far more problematic magnetic fields by twisting the pairs.

 

It is worth noting that a screened cable will (in properly designed kit) have the screen terminated directly to the case right at the connector, apart from reducing common mode voltages, it does not form part of the signal wiring.

 

When I built a very similar box for sending 4 signals down a cat 5 cable, I used transformers at one end but that was because I was concerned about use between buildings or across equipotential zones (or with kit with poor input stages), not because it is generally required.

 

See any number of papers by Whitlock, Muncy, Waldron and company for the gory details.

 

Using the cat 5 infrastructure for audio has been a popular game with broadcasters for a while now, and using multicore twisted pairs between bay frames has been standard for a LONG while now.

 

Regards, Dan.

[Gareth Connor]

To qualify the point about using twisted multipair cable for audio in broadcast installations, the cable used looks like typical "telephone cable", but does have an overall screen. The best known type was supplied by Canford under the identifying name of PSNxx, where the xx signified the number of cores (not pairs) - a bit daft, but that's the standard.

PSN has now been replaced by the KSM range.

http://www.canford.co.uk/ProductResources/ig/2273.pdf

 

Gareth.