[net.audio] need interconnect cable recommendations...

philb@orca.UUCP (07/08/86)

	Hey!
	  I am in the process of building interconnect cables for the 
	home entertainment system. I'm currently using homebuilt cables
	made from Radio Shark RG-59 and cheap RCA pin plug connectors.
	These cables a re used to pass the usual line level high impedance
	audio (and maybe a little video) between components.  I have 
	determined that this is not a preferred method so I need to 
	correct this using much higher performance components especially 
	the cable. I understand that oxygen free wire is supposed to be 
	the hot ticket these days. Is it really? Are there other types 
	that perform equally/better? What brands and types are recommended 
	as well as where to get them?


	Phil Biehl
	Tektronix, Inc.
	Wilsonville, OR
	uucp: {allegra,decvax,ihnp4,ucbvax,zehntel}!tektronix!orca!philb

fish@ihu1g.UUCP (Bob Fishell) (07/11/86)

> 
> 	Hey!
> 	  I am in the process of building interconnect cables for the 
> 	home entertainment system. I'm currently using homebuilt cables
> 	made from Radio Shark RG-59 and cheap RCA pin plug connectors.
> 	These cables a re used to pass the usual line level high impedance
> 	audio (and maybe a little video) between components.

Being the heretical sort who believes that Ohm's, Kirchoff's, and Thevenin's
laws apply even in audio systems, I won't make a recommendation re "high
performance" interconnects.  I do have something to say on the subject of
RG-59 as an audio cable.

Much of this stuff has aluminum shielding and a copper-plated iron core 
(read: CHEAP!).  Some of the better stuff has copper shielding and a copper
core, but I think that Radio Hack carries the cheapo stuff.  Not only is
it a bitch to work with, even in video applications, but the aluminum-shielded
stuff is impossible to solder (read: BAD CONNECTION).  Finally, all RG-59
has a solid core, which, if you're concerned about skin effect, is decidedly
not the thing to use as an interconnect.

If you want to make do-it-yourself interconnects, try some shielded microphone
cable, instead.  It's designed for audio applications.  It usually has two
stranded conductors plus a wound copper (read: SOLDERABLE) shield.  You can
twist the ends of the conductors together for a low-impedance signal path,
and use the shield as the common, or use both conductors and ground the shield
to the chassis, if you so desire.

Myself, I use the interconnects that came with my equipment.
-- 
 __
/  \
\__/			Bob Fishell
			ihnp4!ihu1g!fish

shop@uwmcsd1.UUCP (Thomas Krueger) (07/11/86)

> > 
> > 	Hey!
> > 	  I am in the process of building interconnect cables for the 
> > 	home entertainment system. I'm currently using homebuilt cables
> > 	made from Radio Shark RG-59 and cheap RCA pin plug connectors.
> > 	These cables a re used to pass the usual line level high impedance
> > 	audio (and maybe a little video) between components.
> 
> Being the heretical sort who believes that Ohm's, Kirchoff's, and Thevenin's
> laws apply even in audio systems, I won't make a recommendation re "high
> performance" interconnects.  I do have something to say on the subject of
> RG-59 as an audio cable.
> 
> Much of this stuff has aluminum shielding and a copper-plated iron core 
> (read: CHEAP!).  Some of the better stuff has copper shielding and a copper
> core, but I think that Radio Hack carries the cheapo stuff.  Not only is
> it a bitch to work with, even in video applications, but the aluminum-shielded
> stuff is impossible to solder (read: BAD CONNECTION).  Finally, all RG-59
> has a solid core, which, if you're concerned about skin effect, is decidedly
> not the thing to use as an interconnect.

Belden makes an RG-59/U with copper 22 guage (7X30) center conductor and
95% coverage copper shielding for CCTV applications... the number is
9259, the attenuation (from the book) is 2.1 dB per foot at 50 MHz.
Nominal impedance is 75 ohms.

						- Tom

-- 
Thomas Krueger				...ihnp4!uwmcsd1!shop	or
University of Wisconsin Milwaukee	uwmcsd1!shop@rsch.wisc.EDU
Computing Services Electronics Shop
3200 N. Cramer St.			(414) 963-5172
Milwaukee Wi 53211

ron@argus.UUCP (Ron DeBlock) (07/12/86)

In article <1225@uwmcsd1.UUCP>, shop@uwmcsd1.UUCP (Thomas Krueger) writes:
> > Much of this stuff has aluminum shielding and a copper-plated iron core 
> > (read: CHEAP!).  Some of the better stuff has copper shielding and a copper
> > core, but I think that Radio Hack carries the cheapo stuff.  Not only is
> > it a bitch to work with, even in video applications, but the aluminum-shielded
> > stuff is impossible to solder (read: BAD CONNECTION).  Finally, all RG-59
> > has a solid core, which, if you're concerned about skin effect, is decidedly
> > not the thing to use as an interconnect.
> 
> Belden makes an RG-59/U with copper 22 guage (7X30) center conductor and
> 95% coverage copper shielding for CCTV applications... the number is
> 9259, the attenuation (from the book) is 2.1 dB per foot at 50 MHz.
                                           ^^^^^^^^^^^^^^^^^^^^^^^^^
> Nominal impedance is 75 ohms.
> 

Hmmm, I usually see specs for dB attenuation per 100 feet.  2.1 dB/foot
at 50 MHz is VERY bad.  A mistake, maybe? :-)

I have a couple of questions I would like to know the answer to:

1) Just how important is the skin effect at audio frequencies?  Audio is
pretty low on the spectrum, I wouldn't think it would be that big of
a problem.

2) What about impedence mismatch?  With a 75 ohm transmission line connected
to a 4 or 8 ohm load, I would expect quite a bit of reflected power.  Or
doesn't that matter at audio frequencies?

Please try to back up your answers with calculations or actual measurements,
there's enough guessing/speculation/quoting of manufacturer's (somewhat
dubious) specs on the net.

-- 
Ron DeBlock	KA2IKT

	uucp: ...!{allegra, ihnp4}!bellcore!argus!ron
	      ...!{siesmo, allegra!princeton}!caip!andromeda!argus!ron
	arpa: argus!ron@bellcore.arpa
	bitnet: ron%njitcccc(soon orion).bitnet

"Beware of programmers carrying screwdrivers."

michaelk@copper.UUCP (07/14/86)

>> stuff is impossible to solder (read: BAD CONNECTION).  Finally, all RG-59
>> has a solid core, which, if you're concerned about skin effect, is decidedly
>> not the thing to use as an interconnect.
>

1) You might want to run the skin-effect program that I posted earlier. I
   wrote it for speakers but...use the impedance level in your interconnect
   instead of speaker impedence.  Skin effect will actually be even less
   than calculated because: only one lead is 22 Ga. in coax, the "return"
   lead is a good bit better.  I don't think you will find anything
   significant unless the (parallel) input  capacitance of your next
   stage is incredibly large.

2) Conductors being solid-core does not "hurt" skin effect wise. 
   At VHF frequencies (above 50 Mhz say) you can use a hollow tube
   and have the same impedance as a solid rod of the same diameter.
   Having copper in the middle doesn't hurt.  At low frequencies
   it helps.  

   Skin  effect is why RG-59 can be made with a copper-
   plated iron conductor.  RG-59 is primarily sold as TV cable (at RS)
   where the lowest frequency (channel 2) in the cable is over 50 Mhz
   (and channel 83 is MUCH higher).  
   

3) If you would like a lower-capacitance interconnect you might try
   RG-62 that has a mostly-air dielectric.  Depending where you get
   it, it costs little more than  RG-59 which is about the same size .


-- 

Mike Kersenbrock
Tektronix Software Development Products
Aloha, Oregon

michaelk@copper.UUCP (Michael Kersenbrock) (07/14/86)

In article <328@argus.UUCP> ron@argus.UUCP (Ron DeBlock) writes:
~
>1) Just how important is the skin effect at audio frequencies?  Audio is
>pretty low on the spectrum, I wouldn't think it would be that big of
>a problem.

Not much.  My 12-gauge speaker wires (with 4-ohm speakers) has a small
bit of impedance increase starting at about 40,000 Hz.  That still is
"wiped out" by the DC-resistance of my wire.

>
>2) What about impedence mismatch?  With a 75 ohm transmission line connected
>to a 4 or 8 ohm load, I would expect quite a bit of reflected power.  Or
>doesn't that matter at audio frequencies?
>

The "characteristic impedance" of a transmission line assumes that your
interconnect is long enough to be a transmission line.  The turnover
point (where transmission-line effects start to "work") was something
like lambda/20  depending upon how much effect you decide
is effect (and depending upon how good my memory is).  This is
not significant anyway.  If we assume the point is lambda/50, (where
lambda is the wavelength) then (assuming a 0.66 velocity factor),
lambda at 30,000 Hz is about 21,000 feet.  So even using generous
numbers you still need your cable to be at least 400 feet long for
a miniscule effect at 30Khz.


-- 

Mike Kersenbrock
Tektronix Software Development Products
Aloha, Oregon

dms@fluke.UUCP (07/14/86)

The thing that matters a whole lot more than so-called "oxygen-free"
copper when it comes to shielded audio cables is the coverage factor
of the shielding.  The main problem with cheap shielded cable is that
the braid is pretty sparse and may only cover half of the area.  The
more dense the braid is, the better it keeps out interference.  The
frequency of the interference is also important, but with audio cables
you're usually trying to keep out everything from power line frequency
to hundreds of megahertz, so you need dense coverage.  No braid can give
complete 100% coverage.  Foil-covered wire gives the best shielding, but
is not as flexible.  If low capacitance is critical to you, scope probe
wire would be excellent (probably overkill on all regards, but I notice
the request for info came from Tektronix).  
	I don't know how oxygen-free "oxygen-free" interconnect cables
are but I'd be curious to know the oxygen content in ppm for standard
anealed copper versus that of the fancy stuff.  It's true that grungy
connections have been known to form copper-oxide rectifiers unintentionally 
and rectify large rf signals (e.g. you live under an a.m.  transmitting 
tower) giving you continous radio music no matter what you're listening 
to.  If you're afraid of copper-oxide discontinuities in your wire you 
could use silver wire (silver-plated wire is readily available for r.f.
work) which is lower resistance than copper, with the added benefit that 
silver does not oxidize as easily as copper, but when it does, its oxide 
is electrically conductive.  
	Regarding the alleged high oxygen content of normal wire:  When
copper ore (sulfides and carbonates generally) is refined, the first
step is "roasting" which is heating the ore in an oxidizing atmosphere
(air) this burns the sulfer out of the sulfides, converting them copper
oxide, and creating the sulfer dioxide emissions smelters are famous
for.  This step also burns out most arsenic, selenium, tellurium and
some of the lead which are generally present in copper ores.  Then 
the oxidized ore is heated with flux in a reducing atmosphere
where the oxygen combines with carbon in the fuel leaving metalic
copper, and the nonmetalic residue dissolves in the flux becoming the
slag.  This step is the reason why smelters and refineries, especially
in the old days, frequently have the words "reduction company" in their
name.  An ancient but still used part of the last operation is to insert
a large wooden pole (tree-trunk) into the melt towards the end of the
operation.  Much of the remaining oxygen combines rather spectacularly
with the carbon of the log, purifying the copper a little more.  Then
the molten copper is poured into molds, and as it cools, oxygen comes
out of solution since solid copper cannot hold as much oxygen as liquid
copper.  The oxygen erupts from the surface giving these raw ingots the
name "blister copper".  If you made you're wire from this (which 100
years ago you probably would have) you might have problems.   All
copper used for electrical conductors is electrolytically refined now
days.  In this operation the blister copper is used as one electrode in
an electrolytic cell.  The electrolyte is mostly sulfuric acid and
copper sulfate.  The copper is electolytically transferred from the raw
blister copper to a thin sheet of pure copper which it builds up on.
Gasses and insoluble solids are not transfered to the pure copper, and
the electrolyte is designed so than non-copper metals fall to the bottom
of the tank as a sludge or remain dissolved in the electrolyte.  The
silver and gold which are usually present in copper ores are reclaimed
from the sludge.  Somebody could probably advertise audio cables made
from "100% pure electrolytically refined copper", add a paragraph or two
of techno-mumbo and sell them as well as oygen-free copper.
	Now MY interconnects, on the other hand, were personally blessed
by the Pope in Saint Peter's Square on the Feast of the Ascension.  
Ave Maria! The clarity of the highs, the richness of the bass!  The
superb definition of every sweet note in between!  I hear subtleties in
music that I never knew were there!  I finally have come home my Mother
Church after so many years astray.  Oh, you should have seen what the 
Baptists did to my power amp, and with the power on, no less.  It is 
too horrible to imagine.

			---David

	David Sherman		decvax\
	John Fluke Mfg Co.	ihnp4  >!uw-beaver\
	PO Box C9090    MS 275G		   allegra >!fluke!dms
	Everett, WA 98206 USA	ucbvax >!lbl-csam /
	(206) 356-6373		hplabs/

=====An audiophile is what I use to sharpen the needle on my record player.=====

chris@umcp-cs.UUCP (Chris Torek) (07/15/86)

In article <476@copper.UUCP> michaelk@copper.UUCP (Michael Kersenbrock) writes:
>   Skin  effect is why RG-59 can be made with a copper-
>   plated iron conductor.  RG-59 is primarily sold as TV cable (at RS)
>   where the lowest frequency (channel 2) in the cable is over 50 Mhz
>   (and channel 83 is MUCH higher).  

Ch. 2 ranges between 54 and 60 MHz; 83, between 884 and 890 MHz,
according to the _Handbook of Electronic Tables and Formulas_ (for
some reason I have a copy of this book).  Incidentally, each TV
channel is 6 MHz wide; 2 starts at 54 MHz, and there are jumps at
channels 5 (76-82 MHz), 7 (174-180 MHz), and 14 (470-476 Mhz).
(This is what comes of not providing for expansion!)

>3) If you would like a lower-capacitance interconnect you might try
>   RG-62 that has a mostly-air dielectric.  Depending where you get
>   it, it costs little more than  RG-59 which is about the same size .

The _Handbook_ also lists the properties of a number of RG-*/U cables:

		 Cap			Attn dB per 100 ft
  Type	  Imp	 (pF	 Dia	   1	10    100   400	 1000
 RG.../U (ohms) per ft)(inches)	  MHz	MHz   MHz   MHz	  MHz	Remarks
 -------  ----   ----   ------   ----  ----  ----  ----  ----   --------
   59      73	 21	 .242     .30   1.1   3.8   8.5  14.0   TV lead-in
   62      93	 13.5	 .242	  .25    .83  2.7   5.6   9.0   Low capacity,
								small

RG-63U is higher impedance, and thicker, but has less loss at higher
frequencies, and a lower capacitance:

   63     125	 10	 .405	  .19    .61  2.0   4.0   6.3   Low capacity

There are others with even lower high-frequency losses listed,
RG-117U being the lowest, though more capacitive than any of the
ones above.  Oh well, enough esoterica: the _Handbook_ has plenty.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 1516)
UUCP:	seismo!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@mimsy.umd.edu

jdi@ingres.Berkeley.EDU (John D. Irwin) (07/15/86)

All nonbelievers please type 'n'...

I spent several hours auditioning cables this last weekend and was really
amazed.  I was listening on the dealer`s system which is quite familiar,
having the same speakers (EHS Sopranos).  I also used the power-amp I
have at home, but wasn't able to tolerate its affect on the sound for the
full time.  Anyway, the biggest 'find' I found was MIT-330 interconnect.

Boy, is this stuff expensive!  $115 for a 1 meter pair.  But it's really
great -- I made more change in my system by putting in two of these babies
then I did getting a new piece of equipment! (new CD player)

I'm not going to say much more about the 'sound' of the cable -- please
try it yourself -- do a little A/B with some cheap cables, say Monster
Interconnects on a system you feel comfortable with.  You'll love 'em!
(PS:  They're REAL transparent, but very capacitive -- they use double
sets of cables.  Multiple cables are the trademark of Bruce Brisson).

Another of Bruce's creations is MIT-750 speaker cable.  Using 5 parallel
conductors for each polarity makes this sucker big -- most people call
it 'garden hose'  (it's not green).  I liked it a lot but it was TOO
transparent in the highs for me -- speaker cable is a lot a function
of the speakers and amplifier used -- some cheap cable works great on
certain combinations, and vice versa.


I also got a chance to A/B the PS Audio CD-1 with my li'l Denon 1000.
The PS Audio is the one AHC (I think) practically raved about in a past
Sterophile.  Anyway -- it's really nice.  The sound is much less 
irritating in the highs than the Denon, and it has a MUCH bigger and deeper
soundstage.  It didn't have quite as much detail in the highs as the Denon
though.  The bass was deeper and better defined and placed on the stage on
the PS player.  Overall the frequency balance was better too.
I would buy this player except for two reasons -- shipping time
is apparently very long -- my dealer calls every day but can't get any.
Also, CD players won't reach their zenith for a while yet, so I keep passing
up good for better.  Kind of ironic when a new player would probably make
the most difference in my system.  Oh well.

Anyway, I'd be interested in hearing about other great and notsogreat
new or old components people have listened to recently.  Let's hear
from ya!

--
John Irwin (jdi@ucbvax)

seifert@hammer.UUCP (Snoopy) (07/15/86)

[ net.video added to newsgroups line ]

In article <1225@uwmcsd1.UUCP> shop@uwmcsd1.UUCP (Thomas Krueger) writes:
>>   Not only is
>> it a bitch to work with, even in video applications, but the aluminum-shielded
>> stuff is impossible to solder (read: BAD CONNECTION).  Finally, all RG-59
>> has a solid core, which, if you're concerned about skin effect, is decidedly
>> not the thing to use as an interconnect.

Agreed that aluminum is major grief to solder, even with the special
aluminum solder.  Crimp-on type connectors seem to work ok.

> Belden makes an RG-59/U with copper 22 guage (7X30) center conductor and
> 95% coverage copper shielding for CCTV applications... the number is
> 9259, the attenuation (from the book) is 2.1 dB per foot at 50 MHz.
> Nominal impedance is 75 ohms.

TRUE audio/video-philes will settle for nothing less than 100% shielding.

Those with money burning holes in their pockets are reminded that
silver is the best conductor.

Snoopy
tektronix!doghouse.GWD!snoopy

wine@homxb.UUCP (07/16/86)

<placebo for line eater>

placebo placebo placebo placebo placebo placebo placebo placebo placebo placebo 
placebo placebo placebo placebo placebo placebo placebo placebo placebo placebo 
placebo placebo placebo placebo placebo placebo placebo placebo placebo placebo 
placebo placebo placebo placebo placebo placebo placebo placebo placebo placebo 
placebo placebo placebo placebo placebo placebo placebo placebo placebo placebo 
placebo placebo placebo placebo placebo placebo placebo placebo placebo placebo 
placebo placebo placebo placebo placebo placebo placebo placebo placebo placebo 
placebo placebo placebo placebo placebo placebo placebo placebo placebo placebo 
placebo placebo placebo placebo placebo placebo placebo placebo placebo placebo 
placebo placebo placebo placebo placebo placebo placebo placebo placebo placebo 
placebo placebo placebo placebo placebo placebo placebo placebo placebo placebo 

Enough said???

	Jim Gordon

wsr@lmi-angel.UUCP (07/18/86)

In article <> jdi@ingres.Berkeley.EDU (John D. Irwin) writes:
>I spent several hours auditioning cables this last weekend and was really
>amazed. [...]  But it's really
>great -- I made more change in my system by putting in two of these babies
>then I did getting a new piece of equipment! (new CD player)

I wonder how much of this effect is capacitive loading on the output
of the amplifier and how much is due to lower impedence of the cable.

It would be interesting to see how it sounds when you connect up the
system using the normal cables, and just connect the  monster cables
to the amplifier end (thereby still increasing the capacitance that
the amp must drive, but keeping the cables impedence the same).

Most amps tend to ring a bit when driving a slight (~0.1 uf)
capacitive load and break into a full fledged oscillation when the
capacitance is increased (around 1 uf). Ringing certainly adds a bit
of high-end sizzle!

I use 12-guage multi-strand tin-plated wire for my 4-ohm speakers. The
cable impedence is vanishingly small compared to internal impedence of
most speakers. Most importantly, the cable is *cheap*.

I did weave some of this into a 2x4 wire 10-ft braid (lots of wire)
into an attempt to reduce impedence. The net result was
mega-capacitance. My poor amp output was phase-shifted back so far
that its feedback loop was quite a bit less stable.

-- 
Wolfgang Rupprecht	{harvard|decvax!cca|mit-eddie}!lmi-angel!wsr

hsu@eneevax.UUCP (07/19/86)

In article <2419@umcp-cs.UUCP> chris@maryland.UUCP (Chris Torek) writes:
> ... Incidentally, each TV
>channel is 6 MHz wide; 2 starts at 54 MHz, and there are jumps at
>channels 5 (76-82 MHz), 7 (174-180 MHz), and 14 (470-476 Mhz).
>(This is what comes of not providing for expansion!)
>
Actually, the UHF TV Band is the provision for expansion. There are secondary
services that have spectrum allocations in that band.
The gaps in the VHF TV allocations is so that useful spectrum isn't
completely allocated to the broadcasters.
There are gaps between channels 4 and 5, and channels 6 and 7.
The first gap spans 72-76 MHz, and the second, 88-174 MHz. Your posting
seems quite unclear to me on that point.
You may note that the first gap is allocated to Radio Control and some
Land-mobile services. The second gap is allocated to FM Broadcast, AM
Aircraft, and FM Mobile services.
The FCC tries always to ensure an equitable distribution of available
spectrum.

-- 
David Hsu  (301) 454-1433 || -8798	"It was Dave, not me..honest!" -eneevax
Communication & Signal Processing Lab / Engineering Computer Facility
The University of Maryland   -~-   College Park, MD 20742
ARPA:hsu@eneevax.umd.edu  UUCP:[seismo,allegra,rlgvax]!umcp-cs!eneevax!hsu

"Who cometh to the bridge of death must answer me these questions three,
 'ere the other side he see....aiggggh!"