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Author Topic: Matching transformers for Audio Matthew Taylor Expert Film Handler Posts: 186 From: Essex, UK Registered: Mar 2004 posted 06-15-2005 06:15 AM                     Reading through the archives, I see that the best way of connecting a stereo cell to an amplifier is via matching transformers. Does the output from a matching transformer still have to go into a preamp? What benefit is a matching tranformer?  |  IP: Logged Josh Jones Redhat Posts: 1207 From: Plano, TX Registered: Apr 2000 posted 06-15-2005 04:05 PM                        Yes, it still has to go to a preamp. The purpose of the impedance matching is to reduce the signal loss caused by the missmatch. Along with signal loss comes non-linearity in frequency response, namely, loss of high end (treble) JJ  |  IP: Logged Gilbert Travin Expert Film Handler Posts: 101 From: Villeurbanne / France Registered: Jan 2004 posted 06-16-2005 01:56 AM                        Hi ! a matching transformer has several advantages : - balanced input eliminates noises (particulary noises produced by Ac power @ 50 Hz or 60 Hz, etc.) - the transformer eliminates cell DC component (*) - it works at low impedance (*) You can see also Gordon's answer in an earlier post BUT a good transformer MUST be shielded to avoid interference inductions !  |  IP: Logged Pete Naples Phenomenal Film Handler Posts: 1565 From: Dunfermline, Scotland Registered: Feb 2001 posted 06-16-2005 04:24 AM                     And good ones aint cheap either!  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 06-16-2005 06:29 AM                     http://www.sowter.co.uk/ was the supplier to Dolby for the older CP100-50-200 optical preamp transformers as well as the MPU  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 06-16-2005 10:50 AM                       Those old Dolby transformers were just good enough to do the job shielding wise. The Dolby MPU was always touchy about where it was mounted in relation to hum fields. There are better shielded transformers, but prices go up rapidly for good electrostatic shielding. Even though the original question was about matching transformers, they are most often used today for absolute isolation from one piece of audiovisual equipment to another.  |  IP: Logged Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 06-16-2005 10:59 AM                     Sometimes also used to connect a balanced line to an unbalanced device; more often done with valve (vacuum tube) devices, I think more modern inputs tend to be transformerless.  |  IP: Logged

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