Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.1 6/24/83; site whuxl.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxl!houxm!whuxl!wjm From: wjm@whuxl.UUCP (MITCHELL) Newsgroups: net.audio Subject: Re: Balanced Lines & Shielding Message-ID: <147@whuxl.UUCP> Date: Mon, 6-Aug-84 15:14:30 EDT Article-I.D.: whuxl.147 Posted: Mon Aug 6 15:14:30 1984 Date-Received: Wed, 8-Aug-84 08:10:08 EDT Organization: Bell Communications Research, Inc. Lines: 49Yes, most broadcast equipment uses 600 ohm balanced lines (this means that neither side of the line is connected directly to ground, but rather that the line is driven through a transformer and the center tap of the transformer is grounded: _________________ line 1 hot out ___ ) ( )_____ ( ) | common ___( ) )_________________ line 2 Center Tap is grounded to signal ground. Advantages: One can use relatively inexpensive wire (although shielded cable with the shield grounded is still preferred in hi-fi applications or wherever there is a problem with RFI. Disadvantages: Unless your equipment is "semi-professional" (and thus designed with balanced inputs and outputs), you'll have to buy N+1 transformers, 1 for the driving preamp and N for each of the remote amps, and hi-fi transformers are EXPENSIVE (why do you think McIntosh amps cost so much, the output transformers are one reason). Ron Natalie has the right attitude about RFI - the only way to stop it is to keep it out in the first place. Connecting cables should be shielded, and the shields should be solidly grounded (to earth via the 3rd wire of the AC line cord, or a convenient cold water pipe). It may be desirable to only ground the shields at one end, to prevent ground loops that can pick up 60Hz hum. While we're on the subject of connections, I agree that gold plated RCA jacks are preferable to the tin variety. Whatever the material, the cables should be unplugged periodically and the plugs twisted (hold the plug, NOT the cable!) to remove any corrosion that may have built up on the contacts. Does anyone have any experience with 'Tweek', a fluid which is supposed to improve connections, inhibit corrosion, and cure whatever ails you :-) ?? It is a small tube of colorless fluid that is applied to contacts. Note to Dick Dunn: I don't necessarily endorse transmission lines for speaker wire, however, I would like to minimize the DC resistance (which means at least 16 gauge, 14 gauge if you have a high power (> 100w/ch) amp) of the wire, and I don't think a low inductance configuration is going to hurt. Personally, I'm using Monster Cable on my JSE-1's and I'm quite pleased with the transient response - there is an improvement over the standard 14ga SJ cord I was using. Regards, Bill Mitchell (whuxl!wjm)