Hi again Phil!
Thanks yet again for a detailed explanation. Unfortunately I'm still a
little puzzled, and the reason for my puzzlement comes from the below text.
So, unbalanced signals are transmitted along a pair of wires, but are
susceptible to interference. The answer? Go balanced! In a nutshell, a
balanced signal is the same as an unbalanced signal, but with the
addition transmission of a anti-phase signal (think mirror image). That
is, a balanced signal is transmitted along three wires (aka 3-pole) -
the signal (known as +ve or in-phase), the signal ground, and an
anti-phase (-ve) signal. Typical examples are microphones, outputs of
mixing desks, DMX transmission lines, etc.
Now the science bit...
Let's think of how electrical interference affects an unbalanced signal:
put simply, it adds electrical noise to the signal which can be usually
heard as a buzzing noise. Now, a balanced signal is affected by the same
interference, but (and it's a big 'but'), because the balanced signal
has a 'phase' and 'anti-phase' version of the signal, the interference
affects both signals equally. The clever bit is done by the balanced
input stage of your equipment, where the phase and anti-phase signals
are processed by a differential amplifier circuit that is able to reject
the electrical interference (known in the trade as common mode noise
rejection).
Me again;
This seems to imply that ANY three wire cable will automatically, via
the anti-phase component, cancel any electrical noise. Is it that the
'common mode noise rejection' is not incorporated in all equipment, or
is there another explanation?
Regards
Max
Philip Tyler wrote:
> The construction of starquad cable is such that any electrical interferen=
ce that it may pick up gets cancelled out in a balanced system. So although=
there are four conductors, usually two blue and two white you actually use=
both of the blue together for say the live connection of the XLR and the t=
wo white for the return with the shield going to earth. Then the particular=
'twist' that is employed in the starquad helps reduce or even cancel out t=
he effect of any interference.
>
> OK for the majority of the time when recording outside you may not always=
require this particular attribute of starquad but it is very useful to hav=
e. So if there was anything which might interfere with your recording you w=
ill be far less likely to be bothered by it. I think it is always better to=
be prepared rather than to find you arrive somewhere and having set up to =
record find that something is inducing a buzz on your mic cables.
>
> Phil
>
>
> ----- Original Message ----
> From: Max Catterwell <>
> To:
> Sent: Monday, 8 September, 2008 13:59:46
> Subject: Re: [Nature Recordists] Microphone cabling
>
>
> Very many thanks for that Phil but I'm confused; why would I buy four
> strand when only three are needed?
> Max
>
> Philip Tyler wrote:
>
>> Depends what type of cables you are making, if you are making up 'unbala=
nced' cables then the cable you linked to would be fine.
>>
>> If on the other hand you are making up XLR cables for use with microphon=
es with 'balanced' connections then I would recommend using star-quad cable=
.
>>
>> Have a look at the Canford Audio site for star-quad cable, they do some =
very nice cable that conforms to the BBC spec for star-quad and it is very =
supple and comes in different colours. It's what I made my two longer XLR c=
ables from and the cable is very nice.
>>
>> Look here:
>>
>> http://www.canford. co.uk/Products/ 30-436.aspx
>>
>> Phil
>>
>>
>>
>> ----- Original Message ----
>> From: Max Catterwell <maxcatterwell@ o2.co.uk>
>> To: naturerecordists@ yahoogroups. com
>> Sent: Monday, 8 September, 2008 8:55:39
>> Subject: [Nature Recordists] Microphone cabling
>>
>>
>> Hi all!
>> I have decided to start making my own mic cables. I have no problems
>> with the practical skills involved, but am having far more trouble with=
>> the actual cable. Is there a preferred type (not make) recommended for
>> our interest? After much web fruitless web searching, I finally found a=
>> UK site that appears to sell decent cabling, and particularly this one:
>> http://www.connectr onics.uk. com/Musiflex. htm
>> Is this design OK?
>> Any suggestions of sites to look at re making up cables, and other UK
>> suppliers would be gratefully received.
>> Max
>>
>>
>>
>>
>>
>>
>>
>>
>> ------------ --------- --------- ------
>>
>> "While a picture is worth a thousand words, a
>> sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause
>> Yahoo! Groups Links
>>
>>
>>
>>
>>
>>
>
>
>
>
>
>
>
> ------------------------------------
>
> "While a picture is worth a thousand words, a
> sound is worth a thousand pictures." R. Murray Schafer via Bernie Krause
> Yahoo! Groups Links
>
>
>
>
>
|