AWE32 PnP - "Humm" problems
DJ Mastermind
TR-565 Reciever. When I turn the receiver to that channel. I get a very
audible humm sound. Sometimes it fluxuates and is louder than other
times.
I hear this whether the computer is on or not. The card is at the bottom
of the case (away from power supply- MID Tower), the MIC input level is
all the way down. It's plugged into the line-out, not the speaker out.
And I'm using a fairly expensive cable (MONSTER series 400, $30).
I've also plugged the computer into a separate outlet on the other side
of the room, and made sure that the stereo is properly wired and
grounded.
Here's my list of theories:
1. The Power supply on my computer (230w) is not grounded to the case.
What I mean is the power supply came with 5 wires to plug into the
on/ off switch. 4 of them get hooked to the switch, the other one is to
ground to the case. On mine, however, I see that the ground wire was cut
off (with wire cutters).
2. The outlet on the other side of the room is on the same circuit as the
one the stereo's plugged into. However, I live in an apartment and I'm
afraid that every plug in the house is on the same circuit, so running an
extension cord to another room might not help either.
I'm willing to change the power supply if needed, but I'd rather not
spend the money unless I have to. Any suggestions are appreciated
Thanks in advance
Tony
Patrick R. Mullen
Tony:
Actually, you WANT the computer AND the stereo amp hooked to the same
outlet, sharing a common ground: otherwise you could find a surprisingly
large ground-voltage differential between the two systems (and end-up
generating a current between the soundcard and the Amp that could
blow-out the AWE). We keep our PC's and amps in our soundcard lab
hooked-up to 1200 Watt UPS voltage regulation systems for that reason.
ALL of your PC peripherals should be connected to the chasis ground,
especially the AWE, video system, hard drives, and floppy drives. Make
sure the chasis ground isn't just floating, and is tied to the internal
power supply housing ground.
The "Humm" you're experiencing probably comes from more than one source.
Our own AWE32 use to humm like a bug, 'till we did the following:
(1) Disable the OPL3 FM synth: it generates 80% of the noise you'll get
from your AWE (the OPL3 output gets run into the EMU8000 mixer; even
when the FM synth isn't playing anything, it generates low-amplitude
digital junk). To disable the chip under DOS, just don't load the
driver. Under Windows, you can do this by removing any OP3 FM drivers
in the device menu.
(2) The analog amp stage on the AWE is not very good (plus the card
itself is only two-layer, unlike the higher-quality Audiotrix-Pro and
CrystaLAke Multimedia 140, which are 4-layer). You need to (a) use only
the line-out for analog audio, (b) turn the volume down to 50% of max on
BOTH the mixer settings for Master Volume and Line-Out Volume, (c) set
the MIC and Line-In volume to zero, (d) set the CD-ROM audio input
volume to zero, (e) set AGC (Automatic Gain Control) to OFF, and (f) set
the volume gain to x1.
(3) There is an electrical device on some AWE's that can actually
pick-up sounds near the soundcard and pass them into the system (acting
as an electret mik). This means that AUDIO fan-noise can get picked-up
and make its way into the mixer circuitry. You may want to invest in a
quiter power supply fan. (I know this last bit sounds crazy, and WE
didn't believe it ourselves when we first heard of it, but we later
found that we could record our voices - while shouting at the AWE with
the mik disconnected!)
(4) The AWE has no 5-volt/12-volt ISA Bus power line filtering (which
the Audiotrix-Pro and CrystaLake Multimedia 140 have). If your computer
power supply is putting out dirty DC power into the bus, your AWE will
pick this up. You can use an oscilloscope to check out your ISA bus
lines for noise (we dumped our generic 220 Watt supply, and switched to
an industrial-strength 400 Watt clean-line unit we got from a company in
New Jersey that specializes in making replacement power supplies for
PC's that meet rigurous DC output requirements).
(5) Even if you use a heavily shielded analog cable, the AWE connector
bracket will act as an intenna, and pick up EMI from every device you
have in the room. We can even here our mouse move on ours: the AWE
bracket picks-up EMI emmisions from the serial cable and RS232
connector. The solution involves building a shielding cage around the
AWE and the card bracket, and then properly grounding it.
(6) The PC monitor needs to be a minimum of 2 feet away from the AWE,
and the monitor should be EMI shielded. The stereo amp should be kept a
similar distance away, and the speakers even further.
(7) I don't know how this one works, but I have actually seen a
computer system that -- when the line-out cable is improperly inserted
into the AWE connector -- acts like a bloody radio! No matter where we
moved the machine, just touching the case with the speaker/stereo cables
would produce clearly audible AM music & voice. We looked for a nearby
transmitter, but couldn't find one. In the end, the best we could do
was to solder the stereo cable directly to the AWE line-out pads on the
card surface (no matter how good the chasis ground was, we still got the
local radio broadcast from a particular station). Fortunately, we
haven't seen this problem in our soundcard lab...
After all this, we STILL couldn't get better than 75 dB S/N on the AWE
line-out: we gave-up and switched to using the S/P-DIF connector and a
Sony Digital Amplifier (but we ran into digital noise problems from THAT
setup, and had to solve THOSE problems one at a time as well).
In the end, we decided that a PC with a soundcard is NO SUBSTITUTE for a
professional rack-mounted audio studio equipment rig. Maybe when
everything in the PC world goes optical, and EMI is no longer a
consideration, will we see PC's becoming competitve (in terms of audio
quality) with more professional studio gear.
Cheers!
Pat Mullen
MSS Lab Group
P.S. -- We'd like to thank Lance Massey of Massey Studios of New York
City for his help in tracking down some of the audio bugs we ran into,
and for suggesting some of the more imaginative cures!
Also, Mathias C. Hjelt (http://spider.compart.fi/~mhjelt/awe/) provided
us with a detailed analysis of the AWE, and additional information on
how to squeeze a few more S/N dB out of the line-out port (plus he
showed us how to use the S/P-DIF port on the AWE).
Mike Carrothers
writes:
Tony-
If you still get the humm with the computer off, nothing in the PC is
at falut. Makes since right? No power to the cards in the PC, or to the
PC, it shouldn't make noise.
Do you still get the humm if you unplug the cable? Are you sure the
cable is right?
Just some suggestions.
Mike
breivik
>(7) I don't know how this one works, but I have actually seen a
>computer system that -- when the line-out cable is improperly inserted
>into the AWE connector -- acts like a bloody radio! No matter where we
>moved the machine, just touching the case with the speaker/stereo cables
>would produce clearly audible AM music & voice. We looked for a nearby
>transmitter, but couldn't find one. In the end, the best we could do
>was to solder the stereo cable directly to the AWE line-out pads on the
>card surface (no matter how good the chasis ground was, we still got the
>local radio broadcast from a particular station). Fortunately, we
>haven't seen this problem in our soundcard lab...
>
>After all this, we STILL couldn't get better than 75 dB S/N on the AWE
>line-out.
This is similar to my problem with soundblaster16 and the furnished
speakers and microphone. I am not connecting any radio/TV or stereo
equipment or cards. Radiostation is heard in the bacground if using DC
converter. The biggest problem is however that as soon as I plug in
the microphone for recording of voice, I get recorded a local
radiostation as well. Loud and clear ! Recording with mic plug
unplugged however only produces the silent (low) background noise
which I guess should be expected. Recording from a portable cassette
deck through inline connector produces no radiosignals.
I have tried Creative support, but they know nothing and just vaguely
hints on my Dell Dimension XPS P100c or disturbances in the area. My
neighbour next door has no problems wit his SB16 card when recording.
Can I try to disable FM Music Synthesizer ? What does that mean and
how do I do that in Win95?
Any other suggestions ?
--
Tilbyr Internett kurs og tjenester.
PGP public key and fingerprint available at
http://www.uit.no/pgp/servkom.html
Patrick R. Mullen
>
> "Patrick R. Mullen" <prmu...@MCIMail.com> wrote:
>
> >computer system that -- when the line-out cable is improperly inserted
> >into the AWE connector -- acts like a bloody radio! No matter where we
> >moved the machine, just touching the case with the speaker/stereo cables
> >would produce clearly audible AM music & voice. We looked for a nearby
> >transmitter, but couldn't find one. In the end, the best we could do
> >was to solder the stereo cable directly to the AWE line-out pads on the
> >card surface (no matter how good the chasis ground was, we still got the
> >local radio broadcast from a particular station). Fortunately, we
> >haven't seen this problem in our soundcard lab...
> >
> >After all this, we STILL couldn't get better than 75 dB S/N on the AWE
>
> This is similar to my problem with soundblaster16 and the furnished
> speakers and microphone. I am not connecting any radio/TV or stereo
> equipment or cards. Radiostation is heard in the bacground if using DC
> converter. The biggest problem is however that as soon as I plug in
> the microphone for recording of voice, I get recorded a local
> radiostation as well. Loud and clear ! Recording with mic plug
> unplugged however only produces the silent (low) background noise
> which I guess should be expected. Recording from a portable cassette
> deck through inline connector produces no radiosignals.
> I have tried Creative support, but they know nothing and just vaguely
> hints on my Dell Dimension XPS P100c or disturbances in the area. My
> neighbour next door has no problems wit his SB16 card when recording.
> Can I try to disable FM Music Synthesizer ? What does that mean and
> how do I do that in Win95?
>
> Any other suggestions ?
> --
> Tilbyr Internett kurs og tjenester.
> PGP public key and fingerprint available at
> http://www.uit.no/pgp/servkom.html
Breivik:
The problem with AM radio transmission pick-up may be related to how the
house-wiring is grounded. A friend of mine suggested that we try
running a new ground wire from the computer chassis and power-supply
ground directly to a water pipe. In addition, the microphone jack must
make good grounding contact with the soundcard (which is why we soldered
the mik line to the soundcard I/O pads in the first place. You'll just
have to experiment and fool around with a little bit of everything till
something works! Also, the speaker system you use, if directly tied to
the line-out of the soundcard, can act as an intenna. You may want to
hook the soundcard output to a good-quality stereo amp.
Cheers!
Pat Mullen
MSS Lab Group
prmu...@MCIMail.com