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!philbfish@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!"