optimod composite clipper on a composite stl

[whit979]

Who has used the Optimod's Composite Clip Drive with an analog composite STL? Does it do anything? Should I just turn it off?

 

[fm-engineer]

The groups I have that use Optimod usually leave the composite clip drive set at 0.5 or 0.0
Each preset has a default setting. Most I believe are 0.5 dB. 0.5 will make you slightly louder than 0.0 or the off position. To my ears none of the rock or loud presets sounds right unless the composite limiter is at 0.5. That tells me that the presets were probably designed around the limiter. I would make sure the type of composite limiting is set to half-cosine and not hard. The hard clipping sounds and looks like (spectrum an) a typical diode clipper. The half-cosine sounds nice to me. Some time ago I actually read the US patent which explains in detail how it works. It's truly amazing how Bob Orban designed the half-cosine system limiter. He's a genius amongst us who will never learn a fraction of what he has forgotten. I'm not taking anything away from Frank Foti either. I think he figured out how digital DSP could sound like analog. My stations are about 50-50 Optimod and Omnia. I like both, but certainly prefer the half-cosine limiter in Optimod.

 

[LA_Guy]

Composite clipping done in front of a composite STL might make you LESS loud! Why? Because the 80 kHz lowpass filters in most analog composite STLs ring like the dickens-and the ringing/overshoots caused by clipped audio hitting these filters can make the peak flasher in your mod monitor go crazy! The proper place for composite clipping is just before the exciter-AFTER any composite STL!

 

[fm-engineer]

Composite clipping done in front of a composite STL might make you LESS loud! Why? Because the 80 kHz lowpass filters in most analog composite STLs ring like the dickens-and the ringing/overshoots caused by clipped audio hitting these filters can make the peak flasher in your mod monitor go crazy! The proper place for composite clipping is just before the exciter-AFTER any composite STL!

With diode clipping I may agree with overshoots, but with the Optimod half-cosine composite limiter the upper spectrum is clean. At 0.5 I have not witnesses what you describe. Any way you go it will_be_louder.
Legally? Maybe not based upon the mod monitor, but audibly, yes. You will hear harmonics that fall into the 38 kHz stereo area, but upper garbage is measurable to 100 kHz in most cases. About a year ago I compared the composite spectrum at the output of an Optimod 8500, and also 10 miles away at output of an analog Moseley 6030. After a 60 second peak average you could not discern any difference out to 100 kHz.. I then looked at 38 and 19 kHz phase and it was perfect. The new Moseley digital composite is the way to go if you insist on having the processor at the studio and still want to use composite clipping before the STL. I would not worry about the Orban at 0.5. I would try it and see if your STL overshoots.