Path: utzoo!news-server.csri.toronto.edu!cs.utexas.edu!asuvax!ncar!elroy.jpl.nasa.gov!sdd.hp.com!zaphod.mps.ohio-state.edu!rpi!uupsi!sunic!isgate!krafla!thsa From: thsa@rhi.hi.is (Thorvaldur S Arnarson) Newsgroups: comp.sys.acorn Subject: Re: Archimedes keyboard (and Acorn badged monitors) Keywords: monitor Message-ID: <2866@krafla.rhi.hi.is> Date: 4 Mar 91 19:37:29 GMT References: <1991Feb19.160812.20483@cns.umist.ac.uk> <2313@cybaswan.UUCP> <1991Feb21.143445.22959@fwi.uva.nl> <2618@root44.co.uk> <1991Feb24.105353.2791@abekrd.co.uk> Reply-To: thsa@rhi.hi.is (Thorvaldur S Arnarson) Organization: University of Iceland (RHI) Lines: 56 In article <1991Feb24.105353.2791@abekrd.co.uk> garyb@abekrd.co.uk (Gary Bartlett) writes: [stuff deleted ] |One thing that does annoy me with this monitor though (which may also be true |of the Acorn-badged model?) is the fact that although it advertises as having |stereo speakers accessible through the Scart connector, it doesn't tell you |that the two signals it requires are SUM and DIFFERENCE signals --- ie one |signal needs L + R, the other L - R --- most annoying! --- you can't just wire |in your Archimedes' sound output direct (well you can but it does weird |things when you pan the sound from left to right). Does anyone make an |adapter? | | +-------+ | | | | L ------> -------> L + R | | | | R ------> -------> L - R | | | | +-------+ | | |Gary The cirquit below might do the job. If all resistors are equally large the amplification is 1. The OP amps are usually packed 4 in a simgle IC so this shouldn't be too bulky. R o---/\/\/\--o---/\/\/\--o o--/\/\/\--o | | | | | |\ | | |\ | L o---/\/\/\--o---| >-----o----/\/\/\--o---| >----o----> R+L -+|/ -+|/ | | 0 0 R o-------------------------/\/\/\--o--/\/\/\--o | | o--/\/\/\--o | | | | | | | |\ | | |\ | L o---/\/\/\--o--| >-----o--/\/\/\--o--| >-----o-------> R-L -+|/ -+|/ | | 0 0 + denotes the noninverting input 0 denotes ground Good luck. -- Regards, Thorvaldur S. Arnarson