TimeTrax Complete Background Hum Noise ?

[Fred Lorenzen]

Hello Folks,

Perchance does anyone have the TimeTrax Complete package, which consist
of the TimeTrax adapter, XMDirect Universal Turner Box, and TimeTrax
time shifting software? The TimeTrax Complete is similar to the now
discontinued XMPCR with provides XM Satellite programming on a computer.

http://www.timetraxtech.com/tt_wizard_timetraxcomplete.asp

The reason I am inquiring is that I am experiencing some problem with
background hum noise when listening to all XM programming channels. The
background hum noise exists even when the TimeTrax or Xtreme PCR
software is not running.

On the TimeTrax Software Support Forum
http://www.satelliteguys.us/forumdisplay.php?f=84 located at
SatelliteGuys.Us there is some discussion on this topic. It appears that
many people who have the TimeTrax adapter are having the background hum
noise problem. The general conscious is that if you install a group loop
isolator
http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&product%5Fid=270-054
the background hum noise problem goes away.

I really don't understand exactly what a ground loop isolator is and how
it works. In seeing that numerous TimeTrax Complete customers are
experiencing the background hum noise problem I believe that there is
some kind of design flaw in the TimeTrax adapter and this ground loop
isolator is just hiding a design flaw in the equipment.

Would someone familiar with ground loop isolators comment on this and
provide some insight on what the underlying problem might be.

Regards,
Fred

[John A. Weeks III]

In article <j6dmd.100612$R05.77394@attbi_s53>, Fred Lorenzen
<fearless-freddie-SpaMeNot@mchsi.com> wrote:

> I really don't understand exactly what a ground loop isolator is and how
> it works. In seeing that numerous TimeTrax Complete customers are
> experiencing the background hum noise problem I believe that there is
> some kind of design flaw in the TimeTrax adapter and this ground loop
> isolator is just hiding a design flaw in the equipment.

Ground loops happen when the metal shield of the audio connectors,
which are supposed to be at zero volts, are actually at some
voltage level other than zero. This results in currents flowing
along the ground paths, and improper ground paths being taken.

The isolator puts a transformer in each audio path. This lets the
audio flow from device to device, but it does not have a direct
current path from the grounds on either side, thus, the ground
loop current does not flow.

> Would someone familiar with ground loop isolators comment on this and
> provide some insight on what the underlying problem might be.

Yes, it does sound like one of the devices is broken, and ground
on the shield is not really ground at all.

-john-

--
====================================================================
John A. Weeks III 952-432-2708 john@johnweeks.com
Newave Communications http://www.johnweeks.com
====================================================================

[Fred Lorenzen]

@ John,

Thank you for responding to my posting.

From your explanation I now understand the function of a ground loop
isolator.

I corrected my TimeTrax adapter background hum noise problem by making
my own 12VDC power cable.

I decided not to use the TimeTrax provided 120VAC/12VDC transformer and
made my own 12VDC power cable. I used an IDE Y adapter connected to my
computer power supply to provide the 12VDC power the TimeTrax adapter.
The background hum noise disappeared plus I now only have the TimeTrax
adapter and XMDirect Universal Turner Box powered when my computer is
energized.

I fully believe there is some flaw in the design of the TimeTrax
adapter. I have offered my suggestion to the TimeTrax tech department on
using the 12VDC from the computer power supply to corrected the problem
but their response is that it is not a power supply source problem. They
stand behind using a ground loop isolator to correct the problem. In my
book using a ground loop isolator is only hiding the problem and not
correcting the problem.

Regards,
Fred

"John A. Weeks III" <john@johnweeks.com> wrote in message
news:151120042056546511%john@johnweeks.com...
: In article <j6dmd.100612$R05.77394@attbi_s53>, Fred Lorenzen
: <fearless-freddie-SpaMeNot@mchsi.com> wrote:
:
: > I really don't understand exactly what a ground loop isolator is and
how
: > it works. In seeing that numerous TimeTrax Complete customers are
: > experiencing the background hum noise problem I believe that there
is
: > some kind of design flaw in the TimeTrax adapter and this ground
loop
: > isolator is just hiding a design flaw in the equipment.
:
: Ground loops happen when the metal shield of the audio connectors,
: which are supposed to be at zero volts, are actually at some
: voltage level other than zero. This results in currents flowing
: along the ground paths, and improper ground paths being taken.
:
: The isolator puts a transformer in each audio path. This lets the
: audio flow from device to device, but it does not have a direct
: current path from the grounds on either side, thus, the ground
: loop current does not flow.
:
: > Would someone familiar with ground loop isolators comment on this
and
: > provide some insight on what the underlying problem might be.
:
: Yes, it does sound like one of the devices is broken, and ground
: on the shield is not really ground at all.
:
: -john-
:
: --
: ====================================================================
: John A. Weeks III 952-432-2708 john@johnweeks.com
: Newave Communications http://www.johnweeks.com
: ====================================================================

[Bob Haberkost]

"John A. Weeks III" <john@johnweeks.com> wrote in message
news:151120042056546511%john@johnweeks.com...
> In article <j6dmd.100612$R05.77394@attbi_s53>, Fred Lorenzen
> <fearless-freddie-SpaMeNot@mchsi.com> wrote:
>
>> I really don't understand exactly what a ground loop isolator is and how
>> it works. In seeing that numerous TimeTrax Complete customers are
>> experiencing the background hum noise problem I believe that there is
>> some kind of design flaw in the TimeTrax adapter and this ground loop
>> isolator is just hiding a design flaw in the equipment.
>
> Ground loops happen when the metal shield of the audio connectors,
> which are supposed to be at zero volts, are actually at some
> voltage level other than zero. This results in currents flowing
> along the ground paths, and improper ground paths being taken.

Ground loops are, as the name implies, loops -through- ground, e.g., the drain wires,
connected as they are between the source and the load, *as well as* ground, allows
for a looped current around that path, in the process inducing noise into the signal
wires, rather than protecting them from it. The easiest way to prevent a ground loop
is to *break* the loop. This is most easily acheived by having a plan in how
equipment is interconnected. Any central distribution is a natural for grounding,
and all equipment is thus grounded to this central frame. The cabling that connects
to peripheral equipment is NOT grounded (the ground wire is not connected to terminal
strip, XLR shell, or otherwise) but the equipment is, however. Thus, any induced hum
is shunted away from the audio cabling, and your studio is -quiet-.
--
-----------------------------------------------------------------------------
If there's nothing that offends you in your community, then you know you're not
living in a free society.
Kim Campbell - ex-Prime Minister of Canada - 2004
-----------------------------------------------------------------------------
For direct replies, take out the contents between the hyphens. -Really!-

[powerondude]

As others have mentioned, the hum is caused by a ground loop between the
ground on USB and the ground on the audio out connection. Ground loop
isolators work by coupling the audio signal with a transformer. Don't
buy a cheap one - you will loose audio quality.

I had this problem with the DirectPCR www.powerondude.com when I first
designed it. I designed it out by making a change in the circuit. The
DirectPCR does not have the hum problem and it fully compatable with
TimeTrax and all other XM PCR programs.

-Mike


--
powerondude
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