Four channel audio isolation using high specification Lundahl transformers Single Channel Audio Transformer Isolation
The Glensound External Transformer (ET) range was designed to help a specific outside broadcast customer who was having no luck in curing hum problems with cheap DI boxes. This customer was providing audio facilities in a venue away from the OB truck and there was sometimes hum being received at the OB truck on his output circuits. The input circuits of a professional audio device should of course be able to handle this situation but as our customer was a freelance contractor for the OB company he wasn't in the situation that he could tell his employer that their multi million pound OB truck had a rubbish audio desk. Our solution was to design a transformer isolating unit starting with a very good quality audio transformer from Lundal and adding a unique feature of a variable centre tap switch.
The unique centre tap switch allows the transformers' centre tap to be connected to either the devices' input ground, output ground or isolated from both. This switch alongside the use of the Lundhal transformer solved our customers' problems.
Although originally designed for use at the output end of an audio circuit the ET range can of course be used to reduce problems at the input end of the circuit as well.
Currently the range consists of single channel, dual channel & four channel rugged portable boxes, please contact us if you would like a 1RU rack or more channels in a portable unit as the modular nature of the design allows us to do this easily.
clip point > +28dBu into 150R
Noise (A weighted 20Hz -22KHz) 300R Termination -117dBu (in all switch conditions)
Input impedance 4.8k
Output impedance 106R
Insertion loss < 0.2dB @ 1kHz (100k load)
THD @ 1kHz +4dBu = < 0.02%
