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Optimod 8100 de-emphasis circuit for "test jacks"

O

OKCRadioGuy

Does anyone have some notes on the proper de-emphasis circuit for the Orban 8100's test jacks? I'm assuming the best way might be to use a matchbox and bring it up to line level. So, would anyone have a de-emphasis circuit for the balanced circuit version instead of the test jacks? Either way.... I'd like to use the 8100 for the aux transmitter at the studio and provide an air monitor for the jocks (old guys that like to hear compression while talking) because we are now in a HD delay, etc.

Thanks!
 
It shouldn't be too difficult to roll-off the high end. It need not be absolutely accurate as it's a monitor feed for the Jocks.
You may be able to use an RDL model ST-EQ3 to amplify the signal up to a +4 level and to de-emphasize the audio.
 
Remember the test jacks output is approx 4.4v peak (8.8v p/p) !
From centre pin of jack connect a series resistor, and from other side of resistor capacitor to ground/jack shield.
De-emp audio is across the cap.

For 50us de emp, resistor = 5k, and cap = 10nf.
For 75us de emp, resistor = 7.5k, and cap = 10nf.

Paul.
 
Single pole low pass filter 750ohms series and a 0.1uf shunt (after the resistor) or 7.5k and a 0.01uf. It's in the Optimod 8100 manual . We also modify HE matchboxes with a deempasis circuit.


A response from Kim Sacks when i inquired awhile back.
 
oldiesstation said:
Single pole low pass filter 750ohms series and a 0.1uf shunt (after the resistor) or 7.5k and a 0.01uf. It's in the Optimod 8100 manual . We also modify HE matchboxes with a deempasis circuit.


A response from Kim Sacks when i inquired awhile back.
Click to expand...

Kim actually added the de-emph circuit to my 8100 via an additional set of RCA jacks on the rear, leaving the test jacks intact!
 
The opamp feeding the test jacks and paralell stereo encoder is a tl072.
I would personally not load this output too much as distortion increases as loading is reduced from 2kohm.

De emp values of 750 ohm and 0.1u seem a bit heavy for that opamp's limited current drive.

Paul.
 
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