Conference napalm::commusic_v1

Well, my computer probably generates more RFI than audible interference.
But, no, I haven't cranked up the amps that my DX-7 drives to ear-bleeding
levels yet.  If I ever do, watch out; they'll be over in a flash.

And, by the way, speaking of 'LOUD', has anyone else read the discussion on
'ROCK MUSIC and LOW IQs' in the MUSIC notes file?  Well, the gist of it is that
the fellow who started the note wanted to know if anyone had any evidence that
rock music tended to lower listeners' IQs.  I really don't think he was truely
serious, but the response was probably one of the liveliest in that notes
file's otherwise dull history.  There was a section of the responses that
talked about how loud rock music should be played.  It started me thinking
about an old debate we used to have in music school: "Loudness for loudness'
sake vs. Loudness as a 'degree of freedom' or separate axis for compositional
manipulation".  Well this reminded me of a piece we did on a new music concert
by one of the Sonic Arts Union fellows (Robert Ashley, I think, but maybe Tom
knows for sure) that was called something like "Wolfman" which involved an
actor in a wheelchair, a microphone, and as much VOLUME as you could muster. 
Does anyone remember this piece's actual title and composer? Tom? 

Since 1970 I have had no neighbors (I guess nobody wanted to live near me) 
but the housing situation is becoming so serious that two of the three lots 
adjacent to mine are now being built.  I don't anticipate any complaints 
from them (after all, I'm First Settler).
    John Sauter

Jim -

	Yup, it's Wolfman by Robert Ashley. Actually, that's just a
vocal solo - the 'background' music is usually '4th of July' (also
by Ashley).

	...and, as I mentioned earlier, the recording I have of it
says 'to be played at the loudest possible volume'.

							- Karl

	Are we talking about RFI noise problems associated
	with computers???

	john walton

Actually, I've had no complaints from neighbors in my apartment about
either RFI or volume levels, but I have run into a rather interesting
RFI problem from my Yamaha DX9 -- I have a CHEAP cordless phone and
if the base unit is within about 20 ft. of the DX9 when I turn on the
DX9, the phone goes nuts!  I've given up on the cordless phone.

						Daniel Glasser

	I'm glad someone answered that question.
	Because I work in EMI engineering. We measure RFI,
	and try to limit these emissions.
	From what I've seen of DX9-7, Oberhiem, Linn, Roland
	Korg and others I'm suprised there hasn't been more 
	problems. 
	Sooner or later the FCC will catch up with these.
	Home computers have been regulated, but has anyone
	got an FCC class B sticker on any of there keyboards
	and stuff??

	John

I have a Korg digital delay (that uses a 12-bit micro BTW) that 
I have sitting on a shelf under my TV, and believe me, you can
forget about good TV reception when you've got the delay on.
Yes, it sure does have a warning about FCC reg #xxx part 15
subpart J on the back.  Luckily my neighbors don't know enough
about it to be dangerous to me.  

On the subject of Audio noise, I have a pair of Sennheiser 
monitor headphones that I use for everything.  They're not
efficient at all; it takes 10 watts or so to get them sounding
good, but they give very true reproduction.  Cheap too.
I got 'em at Natural Sound on Rt. 9 in Framingham.

My cheap little BOSS DD2 digital delay does have a class B sticker on it,
and I guess I'm a little amazed as I understand this kind of testing is
expensive. But what does class B really try to prevent? How hard is it if a
$150 digital delay can meet the spec? Don't all consumer digital based devices
have to meet class B? Also if the above mentioned Yamaha equipment does produce
significant EMI/RFI wouldn't it cause problems with radio mike systems on stage
(or is the fact that they are FM prevent it?)?

-seymour-

Yes the testing is expensive, but you only do it on a prototype.
It's not that hard; if the logic circuits used don't have too fast an edge
(they're not schottky TTL as the 11/780 is) and their currents are low
(lots of CMOS) and the PCB has a ground-plane, and clocks are buffered to
make them slower-edged (not lower frequencye) and the clocks are not on
long PC runs, and maybe the box is a well-made metal enclosure, and the
power is isolated well (both ways), and the ins and outs are filtered so
that EMI doesn't go in or out, it should work OK.  Yes, being FM helps.
Thomas

Thanks for the info. What are the possibilities of using DEC's testing labs
to check out suspect equipment?

A little off the point, but I was got some interesting sounds from my Casio
MT-40 played 3-6 inches from a 5 watt FM ham transceiver. The radio would
broadcast what the Casio was playing at the same time that RFI from the
radio contorted the bongo bass line from the Casio. Varying antenna orientation
changed the sound somewhat. The feedback was unearthly. The possiblities
for those noise-is-good explorers is enormous. Anyone else out there actually
LIKE noise besides me?

-seymour-

I suppose what really made my digital delay easy to pass was the fact that it's
in a little potting metal foot enclosure and uses an ac power converted that
should isolate pretty well. Why would someone's fairly recent device mess up
radios or tv's in the area other than poor design? Just how good is class B?
I know the standard caveats stuck onto a lot of consumer computer peripherals
saying something to the effect that you should reorient the antenna of the
receiver affected if you have problems. In the case quoted, simple unshielded
ribbon cables were used, so I can understand the path of interference.

What spec MUST a musical/computing device meet? Do you think that the problem
indicates a defect in either piece of equipment, i.e. a manufacturing defect,
such as a bad ground, unsealed metal enclosure, etc.

I almost missed out on home computing because my first "home" computer was a
KIM-1 that was just a pc board and left herringbones on several channels of
a tv across the room. I did some EMI testing in the Coast Guard and realize the
problem potential for people in apartments for innocuous looking devices. The 
frustrated me so much that I sold the computer rather than try to shield it,
as it was the type that had a keypad for programming on the pc board.

I've noticed no problems with any of the equipment I have including my Pertec
disk drives with the aforementioned ribbon cables, but then my test equipment
consists of a Monkey Wards 1976 vintage tv with rabbit ears.

-seymour-

A home computing device is covered by more stringent standards than mini
computers, because there are more of them in homes to interfere with the
Lucy Show.

The first synth I built interfered like crazy with my Dad's antenna on the
roof until I shielded it with Al foil connected to the power common.  It 
run off a 9V battery.  It was nmos logic based.

Thomas