Quote:
Originally Posted by Diabolical Artificer
I'm guessing in the 50's most speakers were 16 ohm and the "new" transistor amplifiers of the 60's early 70's were designed for a nominal 8r speaker Z so maybe these were sold then to save loss of power Op or similar.
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My recollection is that it was considered unwise to use these kinds of speaker impedance matching transformers with early solid-state amplifiers. I am not sure about this, but one potential problem may have been that at very low frequencies, they offered only a very low impedance to the amplifier, not a problem with most valved units but potentially destructive for some solid-state units.
I suspect that a major use for these transformers in the 1950s and 1960s was in connecting say a 15-16 ohm speaker of the hi-fi type to the external speaker outputs of typical radio receivers and radiograms, which were typically designed for speakers in the 2.5 to 3 ohm range. With limited AF power available, often around 3 watts, impedance matching was worthwhile.
Some of the Wharfedale cabinet speakers of the era were intended for such use as well as with hi-fi systems. This advertisement for the W3 is indicative:
The W3 was a 15 ohm speaker, so use of the WMT1 autotransformer would have been advisable when it was to be fed from a domestic radio receiver optimized for say 3 ohms.
Quote:
Originally Posted by Diabolical Artificer
One last thing, I had a trannie PA amp that has an OPT between OP stage and spkr terminals, one sec for 100v line but also for 4 and 8 ohm spkr's, it sounded superb.
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A classic example of a transistor power amplifier equipped with an output transformer intended to match a wide variety of loads was the Quad 50E.
Cheers,