{"id":5381,"date":"2012-07-30T08:00:10","date_gmt":"2012-07-30T12:00:10","guid":{"rendered":"http:\/\/www.engineeringradio.us\/blog\/?p=5381"},"modified":"2012-07-29T19:42:59","modified_gmt":"2012-07-29T23:42:59","slug":"orban-optimod-8000","status":"publish","type":"post","link":"https:\/\/www.engineeringradio.us\/blog\/2012\/07\/orban-optimod-8000\/","title":{"rendered":"Orban Optimod 8000"},"content":{"rendered":"

A piece of vintage gear from the late 1970’s, the Optimod 8000 was and still is a good sounding box.\u00a0 I have often thought that these processors would make an excellent internet audio processor using the test jacks on the back of the unit.\u00a0 The audio on these jacks is unbalanced and has 75 \u00b5S pre emphasis.\u00a0\u00a0 It would be easy enough to make a de-emphasis network and create balanced audio with a 10K:600 ohm transformer.\u00a0 Some experimentation may be required with the transformer primary impedance value.\u00a0 Orban notes that not less then 1 M\u03a9 impedance should be connected to the test jacks.\u00a0 For the internet station looking to copy the “FM radio” sound, this unit would do the job nicely.<\/p>\n

The 75 \u00b5S\u00a0 de-emphasis network would look something like this:<\/p>\n

\"75<\/a>
75 microsecond de-emphasis network, unbalanced to balanced audio conversion<\/figcaption><\/figure>\n

In this case, the values for the de-emphasis network are fairly critical, therefore 1% or better tolerances for the resistors and capacitors is required.<\/p>\n

Even better, an LPFM or some other radio station on a budget could acquire one of these for relatively little on eBay or somewhere else.\u00a0 With a little TLC, most of these units can be rebuilt and put back into service.\u00a0 I would recommend that some type of limiter be used in front of it, such as a Texar Audio Prism or CRL SEP-800.<\/p>\n

Some classical music stations prefer these units.\u00a0 I have noticed that they have a nice,\u00a0 mellow, open sound.\u00a0 Not at all fatiguing and yet still offer a nice easy 10 dB gain reduction.\u00a0 There is also a modification that can slow down the release time on the gain reduction.\u00a0 More gain reduction, AKA compression, can be had with something else in front of the unit.<\/p>\n

The best part about these units, there is no rebooting, no processor lock ups, software glitches or any of that non-sense.\u00a0 Additionally, a quick look at the front of the unit shows very few user controls, making it almost impossible to screw up and sound bad. They are well built and so long as the electrolytic capacitors are changed out, fairly bullet proof.\u00a0 Other processors, not so much.<\/p>\n

\"Optimod<\/a>
Optimod 8000A under test<\/figcaption><\/figure>\n

This is an Optimod 8000A that I decided to put through its paces.<\/p>\n