Re: Switching audio via an Ocelot and SECU's

[nobody@xxxxxxxxxxxx (Dave Houston)]

The hum is probably from ground loops rather than from unshielded cables.
Baluns serve to isolate the different grounds. If you do use shielded cable,
only connect the shield at one end.

"Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:

>"John W" <Don't_Spam_Me@xxxxxxx> wrote in message
>news:66mdnUjmAdtIJUPeRVn-gg@xxxxxxxxxxxxxxx
>> Since you are using amplified speakers, the SECU16 relays will easily
>handle
>> the line level (i.e. unamplified) audio that you need to feed the
>speakers.
>> The 38W you refer to is the output of the amplifier in the speakers.
>Input
>> to the speakers is a relatively low voltage (line level) like that put out
>> by the sound card in your PC.
>
>Yes - but my concern is still that the low voltage line level inputs will be
>subjected to hum if run through unshielded wire.  I've seen people tackle
>this with baluns, mini coax and other forms of ground loop isolation and
>still have hum issues.  I'd hate to wire it up and find out that there's
>some sort of unresolvable hum issue.
>
>> I use PC-style amplified speakers for my whole house audio and have no
>> problems with buzz or hum even though some of them have 50 feet of cable
>> connecting them.  I use regular telephone cable (twisted pairs) for
>cabling
>> and buy it in boxes of 1000 feet for under $30.  I use the same cable for
>my
>> PIR's and other SECU inputs as well.
>
>It could be that you're just lucky not to have any hum issues.
>Unfortunately, I've already discovered I couldn't run one set of amplified
>speakers through 3 position RCA stereo switchbox without outrageous hum.  I
>was trying to switch inputs from a small TV, a PC and a portable MP3 player
>into a set of amplified speakers and as soon as the RCA cable from the PC
>was plugged in, there was an outrageous hum problem.
>
>I'm anticipating a number of devices feeding into the SECU audio switcher
>with the output going to at least 3 sets of amplified speakers.  My gut
>tells me at least one of those combinations is going to hum if wired through
>twisted pair.  But I can simulate it pretty easily with uninstalled CAT-5
>pieces I have lying around before I go through the trouble of pulling cable.
>I just think the electrons in Canada behavior themselves better in audio
>systems.  :-)
>
>> So far, I have not tried switching audio sources with SECU relays but I
>may
>> do that to switch from my SpeakEasy to my PC sound card so I can play
>MP3's > from my PC on the same speakers.
>
>That's where I think you might run into hum and crosstalk issues.  Of
>course, I live within a few hundred meters of a big cell tower, so that
>might explain why hum is a bigger problem for me.