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The EA 2503 is a custom made audio output transformer. The 2503 has been designed by Ed Anderson to replicate the transformers found in the vintage API recording consoles from the 1970's. In the console, this transformer was mainly used to balance the output signal on the 325 cards which were post fader, booster amplifiers. The 2503 was also used as the balancing output transformer in nearly all of the 500 series modules like the 550, 550a, 550b and more. The vintage 2503 is probably most renowned for it’s part in the unique sonic character of the coveted API 312 card. The 312 was originally designed as a “plug-in” mic preamplifier, booster amplifier or line amplifier. With the combination of the 2622 input transformer, the 2520 discrete operational amplifier and the 2503 output transformer, you have one of thee most sought after microphone preamplifiers ever designed. The circuit is ever so simple and the components far from perfect. The inherent phase shift and distortion, are what make it all sound so special. The 312 circuit is very easy to build in quite popular in the DIY community. Many different PCB’s can be found in the Prodigy Black Market forum. Many thanks to Ed Anderson, who has spent countless hours over 3 years to make the EA 2503 available to us. To quote Ed, “this reproduction is the closest match to the original of any transformer I've seen”. The EA 2503 has flying leads and can be mounted directly to a PCB The physical layout matches its predecessor and also the popular CMOQ-2 series of transformers

Additional information and photos:

EA left, Vintage right

Vintage 550a eq

PDF specs

		This product is proudly manufactured in the USA

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