smb@ulysses.UUCP (Steven Bellovin) (10/23/84)
At the risk of reopening an old topic, I thought I'd pass along a new datum. The new Carver Receiver (130 watts/channel) has a notice on the back saying that "class 1 wiring, as per local codes" should be used if speaker wires are run inside of a wall. Now, if someone could just tell me what "class 1" wiring is....
mat@hou4b.UUCP (10/24/84)
What this means is that the amp can produce voltages high enough
that the wires that you run must meet the same material and quality
standards that your 120 volt house wiring must.
Class 2 wiring is wiring that carries potentials of < 50 (or is it
52 ... ) volts. Phone wiring, bell wiring, and most remote control wiring
fall into class 2. So does audio wiring when it is driven by a low voltage
source. That Carver receiver can put 60 or 70 volts on the line -- like
most medium to high power audio gear, it packs a wallop.
from Mole End Mark Terribile
(scrape .. dig ) hou4b!mat
,.. .,, ,,, ..,***_*.
--
from Mole End Mark Terribile
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,.. .,, ,,, ..,***_*.seifert@ihuxl.UUCP (D.A. Seifert) (10/24/84)
> Class 2 wiring is wiring that carries potentials of < 50 (or is it > 52 ... ) volts. Phone wiring, bell wiring, and most remote control wiring > fall into class 2. sorry, phone wires have more than 50 volts on them when the phone rings. -- _____ Last one in the system buffer pool /_____\ is a rotten data block! /_______\ |___| Snoopy ____|___|_____ ihnp4!ihuxl!seifert
jdd@decwrl.UUCP (John DeTreville) (10/24/84)
sorry, phone wires have more than 50 volts on them when the phone
rings.
In fact, "ringing" is 90V at 20Hz. This is a good reason \never/ to put a
telephone in your mouth, as someone may phone you at just the wrong moment.
Cheers,
John ("Telephone Trivia") DeTreville
DEC SRC, Palo Altoreid@Glacier.ARPA (10/25/84)
> "class 1 wiring, as per local codes" should be used if speaker wires are > run inside of a wall. Now, if someone could just tell me what "class 1" > wiring is.... I think the short answer to your question is that Carver is bragging, very subtly, about what an enormous monster power amplifier he has built. It's quite ludicrous to have an audio cable classified Class 1, but in this circumstance it probably is. Every wire in a house, even intercoms to the front door, must obey an electrical code. The National Fire Protection Association (NFPA) publishes a National Electrical Code (NEC); many localities choose to overrule parts of it. "Class 1" wiring is an NFPA category for remote-control, signaling, or power-limited circuits. They categorize this kind of wiring in Class 1, 2, or 3 according to the power handled by the wires and the nature of the power source. Class 1 is for things that border on being dangerous, or whose failure could have serious side-effects. There are therefore more restrictions on what you can do with Class-1 wires. Class 2 is for low-power low-voltage things like thermostat and intercom wires, and almost all stereos. Class 3 is for low-power high-voltage things such as electric-fence conductors that are run indoors. You can't use Class 2 if the power source driving the circuit is capable of delivering more than 250 watts or so, and you can't even use Class 1 unless that circuit is inherently limited to 1000 watts and 30 volts. Many other conditions apply. Consult your local library if you care. Class-1 circuits must be insulated for 600 volts, and must normally use wire of size 14 or larger. You would probably do this anyhow. The code requirements that probably matter to you are that Class 1 circuits are required to be grounded just like ordinary AC line circuits, and that in general you are not allowed to pull Class 1 wires in the same conduit, or run them through the same electrical box, as AC line circuits. You would probably never even consider running a speaker wire through an AC junction box, but the code says you are not allowed to. There is actually in the NEC a list of particular kinds of wire that are the only ones permitted for Class-1 wiring. The list is long and tedious. No electrical inspector would have it memorized; most don't even know it exists. The only thing you really need to know about it is that stranded wire has vastly more stringent limitations than solid wire, and that if you plan on running stranded wire you should go to your library and get a copy of the NEC and read what it says about stranded wire and Class 1. Monster cable and zip cord do not meet the requirements; hand-made True Litz wire would also not be permitted. Romex 14+1 will do just fine. My house is speaker-wired with Romex 10+1. Brian Reid Stanford (currently EE/CS professor; formerly electrician)
mat@hou4b.UUCP (10/26/84)
Snoopy points out that the ringing voltage on a phone line exceeds 50 volts,
and therefore telephone wiring ought to be class 1.
I checked with a local expert on such matters and he informs me that telephone
wiring is indeed class 2, probably because of the strict current limiting
(20 ma) that is applied to the ringing current.
--
from Mole End Mark Terribile
(scrape .. dig ) hou4b!mat
,.. .,, ,,, ..,***_*.