Garmin GPS - 2820 - audio quality via line out

Author

2820 - audio quality via line out - feeback/hum

asalvador@gmail.com

2006-10-24, 10:33 am

Anyone out there hear a discernable humming feedback sound from their
2820 when the line out is used? It's only noticeable when the port is
set to "Headphones" (which unfortunately produces the best sounding
output when MP3's - or XM - are used).

I happened to contact Garmin about it, and they said their test unit
did not produce the effect. They encouraged me to return it to the
supplier and get a new one. Having followed their advice, turns out
the replacement unit does the same annoying thing. I wouldn't mind so
much except I shelled out the extra $200 for the XM receiver and would
like to enjoy my music in the purest sense, at least with the same XM
quality as my replaced Roady2 receiver.

Option Two is having Garmin themselves ship out another unit, but only
after I pay up 2820 retail price - the credit will make it back to me
once they get my unit in return. Can you imagine, however? My credit
card will have three 2820 purchases in my crazy attempt to have clean
sound.

If you're feeling up to it, here's a quick way to replicate the
problem:

1) Provide some manner of power to the 2820 (vehicle or home adapter)
2) Plug some headphones into the line-out jack
3) Turn on the unit (stop any MP3 music or Audible content if it
starts up)
4) Check your Line Out audio setting - switch to Headphones if not on
already (now hear that?) - keep switching between the two, saving each
change to hear the hum come and go.

If you don't hear any distinction between the two settings, you might
be lucky enough to have a proper working unit. One thing I noticed is
that the loudness of the feedback directly corresponds to the
brightness of the screen, suggesting interference of some kind. In
other words, I can make the hum become quite noticeable with the screen
manually placed on the brightest setting. If you happen to be
listening to some music that has some highs as well as lows, or an
audio book, or an XM talk channel, that sound let's you know it's there
one way or another.

Thoughts anyone? I know I could operate in "Line Out" mode instead of
"Headphones" but once you hear the difference in audio quality, it's
hard not to hate the flatness of line out's sound output. In fact,
Garmin even recommended that I use "Headphones" mode to get a better
sound, so they know which is sonically better, too. Right now, I'm
putting up with the hum since road noise masks most, if not all of it
once underway, but anytime I have to stop, there it is again.

A unit this pricey, with so many features for audio, and an improvement
over existing StreetPilot's simply shouldn't have this audio defect.
Anyone else experiencing this too?

Thanks for listening.

Jack Erbes

2006-10-24, 12:33 pm

asalvador@gmail.com wrote:

<snip>
> One thing I noticed is
> that the loudness of the feedback directly corresponds to the
> brightness of the screen, suggesting interference of some kind. In
> other words, I can make the hum become quite noticeable with the screen
> manually placed on the brightest setting. <snip>

That does sound like interference from the video system, may even be
from the power source for the backlighting. Does the loudness of the
hum change if you move the headphone cable around on or closer to the
display? If it does it may be that your headphone leads are picking up
the interference.

If you have any of those removable toroidal core EMI suppressors around
it might eliminate the interference. Here is an example of one:

http://tinyurl.com/ym27q6

Those are often snapped onto or molded into the cords on some devices.
If you can find a detachable one, loop the headphone cord around it once
and close it, putting it close to the GPS receiver. It might suppress
the hum.

You may be able to find one of those at a electronics supply house or a
place like Radio Shack if you are in the U.S.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)

RIck1254

2006-10-24, 12:33 pm

> That does sound like interference from the video system, may even be
> from the power source for the backlighting. Does the loudness of the
> hum change if you move the headphone cable around on or closer to the
> display? If it does it may be that your headphone leads are picking up
> the interference.

I think Jack has a good point here. You may just have a broken or poor
ground cable in your headset. Have you tried more than one headset?.

It's really unlikely that you managed to pick up 2 defective units

asalvador@gmail.com

2006-10-24, 3:33 pm

Thanks to both you and Jack for writing back so quickly.

The humming feedback sound can be heard, not only via a cheapie set of
headphones but also when using the 2820 with my XM tape adapter, an
accessory that came with my Roady2 receiver and is in proper working
order.

I just think there's either a bad bunch of 2820's (at least two of
them) with some poor shielding in regard to the "Headphones" line out
setting, OR this is the way all unit behave. I certainly hope not the
latter.

Perhaps someone out there with a StreetPilot 2820 can oblige me and do
a little test...

Thanks again to all parties interested.

RIck1254 wrote:
>
> I think Jack has a good point here. You may just have a broken or poor
> ground cable in your headset. Have you tried more than one headset?.
>
> It's really unlikely that you managed to pick up 2 defective units

Seagull

2006-10-24, 10:33 pm

asalvador@gmail.com wrote:
>
> The humming feedback sound can be heard, not only via a cheapie set of
> headphones but also when using the 2820 with my XM tape adapter, an
> accessory that came with my Roady2 receiver and is in proper working
> order.

Does it cause this problem in another car? How about when running on
AC power in your house? You need to isolate the exact combinatin
(or combinations) that lead to the hum.

This really sounds like a ground loop. It could be crappy power wiring
in your car or it could be a defective unit or cable.

Cheers,
John

--
\ carpe cavy!
seagull @ aracnet.com \
http://www.aracnet.com/~seagull/ \ (seize the guinea pig!)

asalvador@gmail.com

2006-10-24, 10:33 pm

I can always try another car but the same 12 volt receptacle which
powered the aforementioned XM Roady2 radio did so without the hum
(using the same cassette tape adapter which I now use for the 2820).
So I think I can rule out the car and the necessary accessories as the
source of the problem in that scenario.

The second scenario - in the house: when I use the 2820's included
power supply and simple ear-bud headphones attached to the line out
jack, the same hum can be noticed as previously detailed.

So two different places, two different power sources, two different
audio connections to the line out jack - same results. And just to
punctuate things, the second 2820 behaves exactly the same way. To me,
the brightness of the screen is the key. Somewhere in the 2820's
internals, when the line out is set to "Headphones" the audio out
through the jack is processed differently - indeed, the Garmin tech
told me that the "Line Out" setting is "unfiltered" - so perhaps the
'filtered' Headphones setting is processed in a manner that gets
interference from the screen's relative brightness.

Guess having a 2820 would go a long way in testing this thing out...

Thanks everyone, cheers!

Seagull wrote:
> asalvador@gmail.com wrote:
>
> Does it cause this problem in another car? How about when running on
> AC power in your house? You need to isolate the exact combinatin
> (or combinations) that lead to the hum.
>
> This really sounds like a ground loop. It could be crappy power wiring
> in your car or it could be a defective unit or cable.
>
>
> Cheers,
> John
>
> --
> \ carpe cavy!
> seagull @ aracnet.com \
> http://www.aracnet.com/~seagull/ \ (seize the guinea pig!)

Jack Erbes

2006-10-25, 4:33 am

asalvador@gmail.com wrote:

> I can always try another car but the same 12 volt receptacle which
> powered the aforementioned XM Roady2 radio did so without the hum
> (using the same cassette tape adapter which I now use for the 2820).
> So I think I can rule out the car and the necessary accessories as the
> source of the problem in that scenario.
>
> The second scenario - in the house: when I use the 2820's included
> power supply and simple ear-bud headphones attached to the line out
> jack, the same hum can be noticed as previously detailed.
>
> So two different places, two different power sources, two different
> audio connections to the line out jack - same results. And just to
> punctuate things, the second 2820 behaves exactly the same way. To me,
> the brightness of the screen is the key. Somewhere in the 2820's
> internals, when the line out is set to "Headphones" the audio out
> through the jack is processed differently - indeed, the Garmin tech
> told me that the "Line Out" setting is "unfiltered" - so perhaps the
> 'filtered' Headphones setting is processed in a manner that gets
> interference from the screen's relative brightness.

In home stereos the "line out" output is a low voltage/high impedance
output intended to be used as an input to another equipment. A
headphone output would be at a higher voltage and lower impedance (like
8 to 32 Ohms) in order to drive the small speakers in the headphones.

Here is a wiki link that explains some of the details on that:

[url]http://en.wikipedia.org/wiki/Line_[/ url](electrical_engi
neering)

So the "headphones" and "line out" settings on the 2820 appear to cause
the 2820 to select one of two very different kinds of audio outputs.

And the reason it sounds better when set to and using headphones is
because the impedance is matched and there is enough power to drive the
headphones better.

The humming problem and its relationship to screen brightness sure
sounds to me like there are some kind of internal shielding issues in
the 2820. But that is a guess. And if two of them have the same
problem then they most likely all will.

I'd probably test the humming thing with a number of different
headphones if I had them around, especially if you can find some better
quality ones, and it they always hum and I couldn't live with that I
guess I would give up on owning a 2820.

You said in an earlier post that:

>The humming feedback sound can be heard, not only via a cheapie set of
>headphones but also when using the 2820 with my XM tape adapter, an
>accessory that came with my Roady2 receiver and is in proper working
>order.

It that humming heard (via the cassette adapter) when the 2820 is set to
both headphones and line out? Or just on headphones?

If the humming comes and goes (on the headphones and the cassette
adapter) only when you set the audio output to headphones it might be
the conclusive proof that the problem is in the 2820's headphone audio
processing. And if that is the case, it looks like Garmin probably
decided to ignore the issue and go ahead with the sales plan. No way
could they have missed something like that in development and testing.

Jack

--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)

asalvador@gmail.com

2006-10-25, 10:33 am

It's the Headphones audio setting on the 2820 which produces the hum.
Line out audio setting does not.

Garmin Tech Support says Line Out setting is "unfiltered" so I bet the
'filtered' Headphone setting circuitry is getting interference from
whatever is driving the screen's relative brightness. That's what my
tests have shown.

The feeback sound, though noticeable, does get masked when vehicle
noise and audio content sound levels grow. Maybe folks just tune it
out. Perhaps many users haven't been taking advantage of the line out
jack and only use the 12-volt adapter's built-in speaker - no hum comes
out of it - but of course, it doesn't connect via the line out jack but
through the 2820's main connection point. Or simply, people who do use
the line out jack, use the Line Out audio setting, which does not
produce the hum yet sounds VERY flat sonically. No amount of treble
and bass on my car's head unit seems to make this sound as good as the
Headphone setting's output. So there's my dilemna.

Thanks for sticking with me, Jack.

Jack Erbes wrote:
> asalvador@gmail.com wrote:
>
>
> In home stereos the "line out" output is a low voltage/high impedance
> output intended to be used as an input to another equipment. A
> headphone output would be at a higher voltage and lower impedance (like
> 8 to 32 Ohms) in order to drive the small speakers in the headphones.
>
> Here is a wiki link that explains some of the details on that:
>
> [url]http://en.wikipedia.org/wiki/Line_[/ url](electrical_engi
neering)
>
> So the "headphones" and "line out" settings on the 2820 appear to cause
> the 2820 to select one of two very different kinds of audio outputs.
>
> And the reason it sounds better when set to and using headphones is
> because the impedance is matched and there is enough power to drive the
> headphones better.
>
> The humming problem and its relationship to screen brightness sure
> sounds to me like there are some kind of internal shielding issues in
> the 2820. But that is a guess. And if two of them have the same
> problem then they most likely all will.
>
> I'd probably test the humming thing with a number of different
> headphones if I had them around, especially if you can find some better
> quality ones, and it they always hum and I couldn't live with that I
> guess I would give up on owning a 2820.
>
> You said in an earlier post that:
>
>
> It that humming heard (via the cassette adapter) when the 2820 is set to
> both headphones and line out? Or just on headphones?
>
> If the humming comes and goes (on the headphones and the cassette
> adapter) only when you set the audio output to headphones it might be
> the conclusive proof that the problem is in the 2820's headphone audio
> processing. And if that is the case, it looks like Garmin probably
> decided to ignore the issue and go ahead with the sales plan. No way
> could they have missed something like that in development and testing.
>
> Jack
>
> --
> Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
> (also receiving email at jacker at midmaine.com)

Jack Erbes

2006-10-25, 3:33 pm

asalvador@gmail.com wrote:
> It's the Headphones audio setting on the 2820 which produces the hum.
> Line out audio setting does not.
<snip>
> No amount of treble
> and bass on my car's head unit seems to make this sound as good as the
> Headphone setting's output. So there's my dilemna.
>
> Thanks for sticking with me, Jack.

That's too bad that's not going to work for you. How about this, I'll
give you my 76Cx for it in a straight across swap. That does not play
MP3 files so you won't have the problem. :> )

I'm not much interested in the XM radio, MP3 player, and some of the
other bells and whistles on the newer 2820. But I do like the multiple
destination routing and track recording capabilities that have
disappeared from most of the other new Garmins. I've been kind of
looking at the older 2610's for a while. If I ever stumble across a
good buy on one of those I'll probably buy it to get something in the
car with a little bigger display.

Jack

--
Jack Erbes in Ellsworth, Maine, USA (jackerbes at adelphia dot net)
(also receiving email at jacker at midmaine dot com)

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