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Robert Boltman
2005-03-30, 12:45
Hi,

Getting really frustrated now. Don't know what to do...

I've got two SB1s - one in the lounge hooked up to hifi etc. the
second in the bedroom connected to a pair of powered "computer"
speakers, acting as a bedside table radio-alarm clock.

The set-up in the bedroom is producing a really annoying hum -
especially as the speakers are 6 inches from my ear!!

I have tried:
- alternate speakers
- alternate squeezebox
- plugging in to headphone jack / phono sockets
- pluggng squeezebox in to separate mains spurs/rings (a downstairs
one and the cooker one in the kitchen)
- a ground loop isolator
- an alternate power supply (from a Ipaq, same rating, 5v 2A as the
supplied one)

None of the above made any discernable difference.

I finally tried a third power supply (this time from an Iomega
external zip drive) which was only rated 5v 1A. This worked! But only
for 3 months... this weekend the SB started rebooting a lot (esp when
selecting max brightness), then the display started flickering, then
it simply would boot at all. Swapped back for the other power supply -
works fine, but the hum is back.

Arghhhhhhhhhhhhhhhhhhhhhhhhhhh! :-(

I assume that the SB draws more than an amp and so has knackered the p/s.

What do I do now? I love the SB, and it makes a great bedside alarm
clock, but I just can't sleep with the hum.

The hum isn't affected by the volume on the speakers, gets a lot worse
if only one channel is connected (using the phonos)?!? and is really
quite audible - it can be heard the other side of the room, not just
when I'm lying next to it.

Hmmm. (no pun intended ;-)

What do I do now??

Thanks for any suggestions - sorry for the long windedness.

cheers
Rob

momerath
2005-03-30, 13:03
Do I understand correctly that you have your SB plugged into the phono
inputs on your amp/receiver? If so, do you have any other input on
the receiver? Aux or tape should work better. I dont know in what
way record players' outputs are technically different from newer
components, but they are.

~Michael


On Wed, 30 Mar 2005 20:45:32 +0100, Robert Boltman
<robert.boltman (AT) gmail (DOT) com> wrote:
> Hi,
>
> Getting really frustrated now. Don't know what to do...
>
> I've got two SB1s - one in the lounge hooked up to hifi etc. the
> second in the bedroom connected to a pair of powered "computer"
> speakers, acting as a bedside table radio-alarm clock.
>
> The set-up in the bedroom is producing a really annoying hum -
> especially as the speakers are 6 inches from my ear!!
>
> I have tried:
> - alternate speakers
> - alternate squeezebox
> - plugging in to headphone jack / phono sockets
> - pluggng squeezebox in to separate mains spurs/rings (a downstairs
> one and the cooker one in the kitchen)
> - a ground loop isolator
> - an alternate power supply (from a Ipaq, same rating, 5v 2A as the
> supplied one)
>
> None of the above made any discernable difference.
>
> I finally tried a third power supply (this time from an Iomega
> external zip drive) which was only rated 5v 1A. This worked! But only
> for 3 months... this weekend the SB started rebooting a lot (esp when
> selecting max brightness), then the display started flickering, then
> it simply would boot at all. Swapped back for the other power supply -
> works fine, but the hum is back.
>
> Arghhhhhhhhhhhhhhhhhhhhhhhhhhh! :-(
>
> I assume that the SB draws more than an amp and so has knackered the p/s.
>
> What do I do now? I love the SB, and it makes a great bedside alarm
> clock, but I just can't sleep with the hum.
>
> The hum isn't affected by the volume on the speakers, gets a lot worse
> if only one channel is connected (using the phonos)?!? and is really
> quite audible - it can be heard the other side of the room, not just
> when I'm lying next to it.
>
> Hmmm. (no pun intended ;-)
>
> What do I do now??
>
> Thanks for any suggestions - sorry for the long windedness.
>
> cheers
> Rob
>

Marc Sherman
2005-03-30, 13:16
momerath wrote:
> Do I understand correctly that you have your SB plugged into the phono
> inputs on your amp/receiver? If so, do you have any other input on
> the receiver? Aux or tape should work better. I dont know in what
> way record players' outputs are technically different from newer
> components, but they are.

http://en.wikipedia.org/wiki/RIAA_equalization

- Marc

ron thigpen
2005-03-30, 14:35
i've never seen a set of powered (amplifiers built in) computer speakers
that have a phonograph level input. i suspect he is using the term
more generically. RCA type jacks/plugs are often referred to as "phono
jacks". it's a holdover from olden times.

now, plugging the SB1 analog outs into the headphone outs on these
speakers, that's another thing entirely.

--rt

momerath wrote:
> Do I understand correctly that you have your SB plugged into the phono
> inputs on your amp/receiver? If so, do you have any other input on
> the receiver? Aux or tape should work better. I dont know in what
> way record players' outputs are technically different from newer
> components, but they are.

> <robert.boltman (AT) gmail (DOT) com> wrote:
>>I've got two SB1s - one in the lounge hooked up to hifi etc. the
>>second in the bedroom connected to a pair of powered "computer"
>>speakers, acting as a bedside table radio-alarm clock.

ron thigpen
2005-03-30, 14:41
Robert Boltman wrote:

> Thanks for any suggestions - sorry for the long windedness.

it sounds like you've already successfully debugged the problem. from
your description of the problem, it sounds like the SB P/S is generating
or passing some noise that is making it's way into the analog outs.
swapping P/S units resolved it, no?

if this is the case, you might try one of two solutions: find an
alternate P/S with the appropriate output that doesn't pass/generate the
noise, or, on the theory that it is passing noise, try doing some
filtering of your A/C.

--rt

Robert Boltman
2005-03-30, 14:50
Right - to clear up some confusion - when I said phono, I meant RCA
outputs - nothing to do with record players. Sorry.

I've got powered, amplified computer speakers, no separate amp etc.

Ron:
Although a particular different p/s helped, two others I tried didn't
and the one that was successful was under-rated. I guess I could try
and find some more. If it's passing it through what sort of filter
would you suggest - I've seen various products but I wondered if many
of them were just hi-fi snake-oil... perhaps not.

Another thought I had was to use the digital output and then an d-to-a
- perhaps a cheap amp with digital in and a tape loop. Would that
isolate it? (I could always just run speakers off the amp I suppose
but I only really need very small speakers for a bedside table.




On Wed, 30 Mar 2005 16:41:46 -0500, ron thigpen <ron (AT) fuzzsonic (DOT) com> wrote:
> Robert Boltman wrote:
>
> > Thanks for any suggestions - sorry for the long windedness.
>
> it sounds like you've already successfully debugged the problem. from
> your description of the problem, it sounds like the SB P/S is generating
> or passing some noise that is making it's way into the analog outs.
> swapping P/S units resolved it, no?
>
> if this is the case, you might try one of two solutions: find an
> alternate P/S with the appropriate output that doesn't pass/generate the
> noise, or, on the theory that it is passing noise, try doing some
> filtering of your A/C.
>
> --rt
>
>

ron thigpen
2005-03-30, 15:15
Robert Boltman wrote:

> Although a particular different p/s helped, two others I tried didn't
> and the one that was successful was under-rated. I guess I could try
> and find some more. If it's passing it through what sort of filter
> would you suggest - I've seen various products but I wondered if many
> of them were just hi-fi snake-oil... perhaps not.

Yeah, you just don't know what's gonna work till you try it. Might try
visiting RadioShack and seeing what they've got. It's an easy return
anyway. I've had good luck finding wallwarts at a local thrift shop
that carries a lot of electronics. They have a huge rack of P/Ss and
cords.

There are some reasonably priced and effective A/C line filters out
there. I've heard good things about the Isobar filtering powerstrips.
I use a Brickwall on my hifi, but that's overkill for this application.

> Another thought I had was to use the digital output and then an d-to-a
> - perhaps a cheap amp with digital in and a tape loop. Would that
> isolate it? (I could always just run speakers off the amp I suppose
> but I only really need very small speakers for a bedside table.

This might just work. Especially promising would be the use of the
optical digital out. Those cables aren't electrically conductive and
should provide isolation.

--rt

Jeff Moore
2005-03-30, 15:19
2005-03-30-16:50:31 Robert Boltman:
> Another thought I had was to use the digital output and then an d-to-a
> - perhaps a cheap amp with digital in and a tape loop. Would that
> isolate it?

If you use the Toslink (optical) digital output from the SB, that'd
definitely isolate it from the next component -- no electrical
connection at all, thus no ground loops or whatever other nasties.

I'm still curious about what's causing the problem, though -- if that
particular SB1 sample is prone to noise leakage, or if there's a ground
loop (is the SB using wired ether, connected to other equipment powered
from a different hunk of your mains?) or some kind of RF pickup...
Here's where my ignorance shows, do ethernet connections routinely have
any sort of optical or transformer isolation?

If you choose the digital-out method, the question becomes what to have
next in the stream. A standalone DAC would seem the natural thing to
have your powered speakers plugged into, but standalone DACs, as things
largely bought by highfalutin' audiophiles, might mostly be unexpectedly
expensive. A/V receivers (plenty of sales volume at the low end of the
market) have gotten shockingly cheap these days -- but that could be a
bulky rig for your bedside table, and one would usually expect to plug
passive speakers into one. I guess you were talking about using a line
out from one such, basically just to get the use of the DAC. Better
confirm that that works properly with the particular model you
consider.

Robert Boltman
2005-03-30, 15:28
Yeah, stand-alone DACs seem steep for this setup...

Cheap a/v amp off eBay might do the trick. I can always bung it on the
floor under the bed - it's not as if I need to touch/see it ever. Just
as long as that doesn't humm as well!!!

I'd be happy to plug passive speakers in to it if I could find
half-decent small ones, but we're talking sub-sub bookshelf here to
fit on the bedside table. The powered ones I've got sound really good
for their size so I'm happy with them though.


On Wed, 30 Mar 2005 17:19:48 -0500, Jeff Moore <jbmml-sdd (AT) jbm (DOT) org> wrote:
> 2005-03-30-16:50:31 Robert Boltman:
> > Another thought I had was to use the digital output and then an d-to-a
> > - perhaps a cheap amp with digital in and a tape loop. Would that
> > isolate it?
>
> If you use the Toslink (optical) digital output from the SB, that'd
> definitely isolate it from the next component -- no electrical
> connection at all, thus no ground loops or whatever other nasties.
>
> I'm still curious about what's causing the problem, though -- if that
> particular SB1 sample is prone to noise leakage, or if there's a ground
> loop (is the SB using wired ether, connected to other equipment powered
> from a different hunk of your mains?) or some kind of RF pickup...
> Here's where my ignorance shows, do ethernet connections routinely have
> any sort of optical or transformer isolation?
>
> If you choose the digital-out method, the question becomes what to have
> next in the stream. A standalone DAC would seem the natural thing to
> have your powered speakers plugged into, but standalone DACs, as things
> largely bought by highfalutin' audiophiles, might mostly be unexpectedly
> expensive. A/V receivers (plenty of sales volume at the low end of the
> market) have gotten shockingly cheap these days -- but that could be a
> bulky rig for your bedside table, and one would usually expect to plug
> passive speakers into one. I guess you were talking about using a line
> out from one such, basically just to get the use of the DAC. Better
> confirm that that works properly with the particular model you
> consider.
>
>

Jon Myatt
2005-03-30, 15:29
When I had this, it was a duff cable. Have you tried changing the cable,
or is it permanently attached to the speakers?

Jon.

Robert Boltman wrote:

> Hi,
>
> Getting really frustrated now. Don't know what to do...
>
> I've got two SB1s - one in the lounge hooked up to hifi etc. the
> second in the bedroom connected to a pair of powered "computer"
> speakers, acting as a bedside table radio-alarm clock.
>
> The set-up in the bedroom is producing a really annoying hum -
> especially as the speakers are 6 inches from my ear!!
>
> I have tried:
> - alternate speakers
> - alternate squeezebox
> - plugging in to headphone jack / phono sockets
> - pluggng squeezebox in to separate mains spurs/rings (a downstairs
> one and the cooker one in the kitchen)
> - a ground loop isolator
> - an alternate power supply (from a Ipaq, same rating, 5v 2A as the
> supplied one)
>
> None of the above made any discernable difference.
>
> I finally tried a third power supply (this time from an Iomega
> external zip drive) which was only rated 5v 1A. This worked! But only
> for 3 months... this weekend the SB started rebooting a lot (esp when
> selecting max brightness), then the display started flickering, then
> it simply would boot at all. Swapped back for the other power supply -
> works fine, but the hum is back.
>
> Arghhhhhhhhhhhhhhhhhhhhhhhhhhh! :-(
>
> I assume that the SB draws more than an amp and so has knackered the p/s.
>
> What do I do now? I love the SB, and it makes a great bedside alarm
> clock, but I just can't sleep with the hum.
>
> The hum isn't affected by the volume on the speakers, gets a lot worse
> if only one channel is connected (using the phonos)?!? and is really
> quite audible - it can be heard the other side of the room, not just
> when I'm lying next to it.
>
> Hmmm. (no pun intended ;-)
>
> What do I do now??
>
> Thanks for any suggestions - sorry for the long windedness.
>
> cheers
> Rob
>

Richard Elen
2005-03-30, 16:21
I think what's going on here is that the supply getting to the analog
audio circuitry in the SB is not sufficiently well smoothed for audio
applications. I assume that the hum is 60Hz or 120Hz and is a smooth hum
rather than a buzz or harsh sound. If not, these notes may not help.

You need to note a couple of things.
First is the power rating of the SB. Somewhere in the docs or even on
the box you should find the correct voltage and power consumption and of
course the connector polarity. Any third-party PSU you try should have
5V out, the correct connector and polarization, and AT LEAST the
current-providing capability that the SB demands, and preferably 150% of
it - presumably 2A is good.

If you were originally having problems with the supplied SB PSU, this
suggests one of two things:
a) the smoothing in the PSU had partially failed. You can check this by
trying the PSU from the SB downstairs which presumably works fine. You
do not say you've tried that. If that makes no difference, then we can
assume:
b) some aspect of any smoothing of the analog supplies inside the SB had
failed. You can check this by swapping the two SBs which you have
apparently done and didn't fix it, which again points at (a).
In fact, I do not know whether or not (b) is actually valid, as I don't
know what goes on in the SB for supply smoothing to the analog stages.
The fact that a different PSU fixes the problem suggests that this is
NOT due to hum loops or interactions between the SB and the speakers.

Providing a fully-smoothed audio-quality PSU of the right current and
voltage will probably solve /either/ problem, even if it is the result
of a smoothing failure in the SB. You want to locate a third-party
supply that is designed for audio devices such as boomboxes, portable CD
players, etc. The best supplies for this purpose are generally, but
today not always, linear (heavy transformer inside and fixed AC input
voltage) types rather than switch-mode (small, light and universal input
voltage); however it can be quite hard to find linear power units with
current delivery in excess of 1A, so by all means try a switch-mode if
the supplier tells you it is designed to drive audio devices.

Certainly you should not get the hum if you use the digital outs, but
you may well get signal degradation of other kinds if there is excess
ripple on the clocking and digital output circuit supplies, so this is
worth fixing at source.

Hope this helps,
--Richard E

> Robert Boltman wrote:
>> The set-up in the bedroom is producing a really annoying hum -
>> especially as the speakers are 6 inches from my ear!!
>>
>> I have tried:
>> - alternate speakers
>> - alternate squeezebox
>> - plugging in to headphone jack / phono sockets
>> - pluggng squeezebox in to separate mains spurs/rings (a downstairs
>> one and the cooker one in the kitchen)
>> - a ground loop isolator
>> - an alternate power supply (from a Ipaq, same rating, 5v 2A as the
>> supplied one)
>>
>> None of the above made any discernable difference.
>>
>> I finally tried a third power supply (this time from an Iomega
>> external zip drive) which was only rated 5v 1A. This worked! But only
>> for 3 months... this weekend the SB started rebooting a lot (esp when
>> selecting max brightness), then the display started flickering, then
>> it simply would boot at all. Swapped back for the other power supply -
>> works fine, but the hum is back.
>>
>> Arghhhhhhhhhhhhhhhhhhhhhhhhhhh! :-(
>>
>> I assume that the SB draws more than an amp and so has knackered the p/s.
>>
>> What do I do now? I love the SB, and it makes a great bedside alarm
>> clock, but I just can't sleep with the hum.
>>
>> The hum isn't affected by the volume on the speakers, gets a lot worse
>> if only one channel is connected (using the phonos)?!? and is really
>> quite audible - it can be heard the other side of the room, not just
>> when I'm lying next to it.