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PCI Max and Background Noise
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Hugo
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Joined: 11 Aug 2002
Posts: 5
Location: Silicon Systems

Post Reply with quote
Although PCS are helping out on this problem I though I'd ask others if they'd experienced it.
The output of the PCI Max in our Intel-845 based P4 PC's has a background noise level, totally independent of audio input. I have no measurements, but "very annoying" describes it! Worse obviously on classical music content than rock.
Any experiences of this?

Thanks for any informartion/suggestions.
Hugo
Silicon Systems

Sun Aug 11, 2002 5:54 pm View user's profile Send private message Visit poster's website
fred
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Joined: 04 Aug 2002
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Post Reply with quote
I posted on the same topic in the "Improvements and Suggestions" forum and have not received any replies. I'm including my post below. It's been suggested that I move the internal cables around inside the PC, but this hasn't helped. If I'd had any idea that this was such a severe problem with PCI Max, I wouldn't have bought it. It makes the stated S/N ratio of >60 dB meaningless!

---MY ORIGINAL POST---
I have the PCI Max w/Comet antenna and am delighted with all aspects of the product with one exception: there's a tremendous amount of noise induced in the audio from the PC.

If I transmit an unmodulated carrier, the background noise varies from a low hum to what sounds like an old vacuum cleaner running, depending on how busy the CPU is. If I move the mouse (which sends lots of rapid fire interrupts to the CPU), the buzzing increases to about 50% modulation. Same thing if another app is running and using lots of CPU cycles and/or making lots of calls to the hard drive.

This is particularly annoying during music with quiet passages or when playing spoken word recording.

Is this a common problem with the PCI Max, or am I doing something wrong?

I'm running the card in a machine with a 400 MHz PIII, 100 MHz bus. Frequency response, stereo separation, and transmit range are all superb. But this noise problem makes the audio sound lousy!

Suggestions?

[ This Message was edited by: fred on 2002-08-27 11:44 ]
Tue Aug 27, 2002 4:43 pm View user's profile Send private message
Hugo
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Joined: 11 Aug 2002
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Location: Silicon Systems

Post Reply with quote
Thanks for the reply.
Yes this is the same problem, and your PC has a quite differemt spec. to mine.

Marko had the following the comments:
1. Current card have some improvements (no good for us)
2. A new version card card will be released in the future. (possible for us as I'm trying to evaluate the cards for sale in our Silicon brand PC's)
3. Do a series of component mods (bypassing some SM cap's from memory, so a little fiddly).
Marko's the one to email re details of the mods, which I will attempt to do soon, so I can let you know the outcome.

Regards
Hugo
Tue Sep 03, 2002 7:32 pm View user's profile Send private message Visit poster's website
Hugo
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Joined: 11 Aug 2002
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Location: Silicon Systems

Post Reply with quote
Thanks for the reply.
Yes this is the same problem, and your PC has a quite differemt spec. to mine.

Marko had the following the comments:
1. Current card have some improvements (no good for us)
2. A new version card card will be released in the future. (possible for us as I'm trying to evaluate the cards for sale in our Silicon brand PC's)
3. Do a series of component mods (bypassing some SM cap's from memory, so a little fiddly).
Marko's the one to email re details of the mods, which I will attempt to do soon, so I can let you know the outcome.

Regards
Hugo
Tue Sep 03, 2002 7:32 pm View user's profile Send private message Visit poster's website
dj m
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Joined: 20 Jun 2002
Posts: 11

Post Reply with quote
Marko, I have the same noice problem too on one of my PCI Maxes. It works in other PC's, but not in my P4 2GHz (400Mhz/100Mhz) on a MSI motherboard. Do you have a solution?
Thu Sep 12, 2002 11:05 am View user's profile Send private message
dcmicroradio
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Joined: 25 Sep 2002
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Location: The Criminal Enterprise Known as Dade City, Florida USA

Post Reply with quote
I have a hiss in the background that sounds like multiplex noise, but it's not. When I disabled the WAVE control in Windows Control Panel, the noise abruptly stopped. If I unplug the audio from the card the noise goes away as well. I've emailed Marko for a more detailed solution.
Wed Sep 25, 2002 1:15 pm View user's profile Send private message Visit poster's website
dcmicroradio
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Joined: 25 Sep 2002
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Location: The Criminal Enterprise Known as Dade City, Florida USA

Post Reply with quote
Marko, how about a schematic so I can try some noise mitigation techniques
Wed Sep 25, 2002 11:00 pm View user's profile Send private message Visit poster's website
Hugo
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Location: Silicon Systems

Post Reply with quote
dcmicroradio, I read your post & its sln with great interest, but remembered our background noise is present with no audio input whatsoever (ie. unplugged).
I've been really busy lately so haven't even got around to emailing Marko re the board mods, someone else may wish to explore this.
Sat Sep 28, 2002 5:11 pm View user's profile Send private message Visit poster's website
pcs
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Joined: 18 Jan 2002
Posts: 3063
Location: Radio Land

Post Reply with quote
Hi!

As far as noise is concerned:

Many have reported great improvement as
soon as they moved antenna far from the PC
(make sure you feed it with coaxial cable).
I'm not sure how important SWR is in that
respect.

Another thing is the sound card. There are
sometimes high-level (speaker drivers) and
low-level outputs. Make sure you use low-
level output.

I suspect ground loops may be forming in
some cases and isolation audio transformer
would solve the problem for those cases.
Or driving audio from an external source.

There is also a difference between CD-ROM
and HD drives, some generate more noise than
others. Especially CD-ROM's generate lots of
interference on the supply line.


_________________
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Thu Oct 03, 2002 2:59 pm View user's profile Send private message Visit poster's website
dcmicroradio
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Joined: 25 Sep 2002
Posts: 15
Location: The Criminal Enterprise Known as Dade City, Florida USA

Post Still Have Lots of Noise. Reply with quote
As per Marko, I changed the audio card, hiss is gone. Now I have the same noise everyone else is hearing. In fact with no audio driving the card, the FM deviation is 12KHZ which is unusable. The noise is on the buss as it changes with processor activity. I've disconnected and removed everything not essential. No help. The concept is great. The performance is dissapointing. Also, the audio input connector leaves a lot to be desired. The plug often pops out as the seating is sloppy. If I can get this thing to work, I was planning to use as an in-band translator. As it stands now, It's uninstalled, and in my box of spare stuff. Questions I have are:

what is the input impedance for the audio? The card loads -10 to almost zero. Using an 8 ohm output, the sound card is reduced to about 10 percent to keep from overdeviating. 75 KHZ here in the States. I try to limit to about 60KHZ

What is the pre-emphasis? 50? 75? None?

Whats different about the new card? Any help for us who bought and cannot use?

Have a Great Day!!
Tue Oct 29, 2002 12:53 am View user's profile Send private message Visit poster's website
pcs
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Joined: 18 Jan 2002
Posts: 3063
Location: Radio Land

Post Nope, not everyone Reply with quote
Most users are more than happy with the way PCI MAX performs,
but with some PC configurations I guess it can be a problem.

There's a huge difference between different power supplies and
even CD-ROM's (making lots of noise usually).

We are about to release PCI MAX Ultra, which should deal with
the problems you guys are seing in every possible configuration.

We have also found a way to modify PCI MAX to eliminate 90%
of the noise. It requires an external power supply. If you think you're
skilled enough to try this out with a soldering iron, contact us via
email for a picture. We'll post it in the support section later as well.

_________________
Best regards,
Marko - PCS Electronics
--------------------------------------------------------
Turn your PC into a FM radio station!
http://www.pcs-electronics.com
fax +386 4 2316 128
Thu Nov 07, 2002 11:00 pm View user's profile Send private message Visit poster's website
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