Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site crystal.UUCP Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!decvax!genrad!teddy!panda!talcott!harvard!seismo!uwvax!crystal!bill From: bill@crystal.UUCP Newsgroups: net.audio Subject: Re: Adding a buffer amp Message-ID: <392@crystal.UUCP> Date: Fri, 11-Jan-85 19:52:29 EST Article-I.D.: crystal.392 Posted: Fri Jan 11 19:52:29 1985 Date-Received: Mon, 14-Jan-85 02:45:30 EST References: <38@angband.UUCP> Distribution: net Organization: U of Wisconsin CS Dept Lines: 37 > > At any rate, one article about putting a buffer between a preamp output > and your cables appears in issue 4 of the 1977 Audio Amateur magazine. > Unfortunately, you must buy the entire year of 4 back issues for $10 > (Box 176, Peterborough, NH 03458, USA). The same people, wearing a > different hat, also sell for $17.50 a kit KH-8 called the "Morrey Super > Buffer", including parts and board, but not the instructions, which > appear only in the original magazine article (Old Colony Kits, Box 243, > Peterborough, NH 03458; VISA, MC 603 924-6526). > The Audio Amateur (TAA) is an interesting mag for anyone interested in how to put audio equipment together (with or without taking it apart first -- they do a lot of rebuild articles). I highly recommend it. The Morrey super buffer uses a 531 op amp, I believe. TAA ran Walt Jung's articles on op-amp selection for critical audio uses; he thinks the 531 is a stinker. It also requires an output transistor. I would suggest building a simple non-inverting buffer, with a voltage gain of 3, using an NE5534 (single) or NE5532(dual) op amp -- it directly drives 600 ohm lines, and is very quiet. (Signetics or TI; the 553[24]A version is a low-noise selected version, but the non-A ones are usually about as good) Jameco or DigiKey sells the TI version, I believe. Runs $3 - $5, depending on the usual things. I have several friends who use these for pro-audio stuff, and swear by them (and the '071, below). Walt Jung's Audio IC Op Amp book (Sams) has lots of circuits, but apparently not all of them are very good. Another choice would be the TI bifet op amps, the TL071 family (low-noise), available for around 75cents from Action Electronics (see ads in Radio-Electronics). Need an output transistor, however. -- William Cox Computer Sciences Department University of Wisconsin, Madison WI bill@uwisc ...{ihnp4,seismo,allegra}!uwvax!bill