Friday, April 5, 2019

SONY ECM-250 serial number 3112 noise performance


Another ECM-250 has been found on eBay.de while trying to find a spare cable with dedicated mic connector.


It came in somewhat bad shape but it turns out that it sounds louder and will less hiss that the previous ECM-250 tested on previous posts which looked like new.


What was done to restore it?


Mic cleaned with a damp cloth.


The battery compartment (-) spring terminal had been cleaned with cotton buds and methylated spirit. Caution the battery polarity print is erased by methylated spirit.


The grill mesh had been carefully removed by pulling. It had been straightened, washed, dried overnight. The deteriorated ring foam around the small foam glued on the small electret capsule was replaced by cutting anew ring. Mesh then was careful reinserted while looking though a big magnifying glass near the grill.


The non original cable which gave a very bad plastic odor was removed and a Mogami mini star quad cable soldered. This took a long time. Sesame oil lubricant on ear buds was used to lubricate the cable, the grommet tunnel of the long rubber grommet if the connector so that this slightly thicker cable could slide through.


The broken plastic near the connector screw had been soldered with the aid of a small bit of paper moistened with UHU glue. The benzine somehow melted the plastic so hopefully now it has become one piece.


A Neutrik male had been soldered on the other side of the Magami mini star quad cable.


A cotton ear bud moistened on methylated spirit was used to wipe off remaining dirt marks from the mic body.


The mic with its one FET with output transformer single spended class A amplifier (very similar to Pleiades booster amps) now sounds big and brilliant.


When connected to a Pleiades (130Ω,40mH) gentle slope high pass filter, bass or mid heaviness disappears and a very natural and big sound, bright as a diamond is left to pass through to the following signal path stages:


Signal path:


Male voice singing The Power of Love - FGTH - SONY TCM-250 at 12 inch - Pleiades (130Ω,40mH), SONY TC-D5 Pro - Sennheiser HD 580


The impedance of a (130Ω,40mH) filter is (130Ω,2πf40mH)















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