Where's your processor?

[Justin Speck]

An item on the newspage today says that Spin are having test transmissions from the studio "to test the Optimod".

So, where do stations locate the processor? At the studio or at the transmitter site and why?

Discuss.

J

[Tabasco]

Spin and many other modern stations have their processor at the transmitter site, unfortunately!

This is because if you're using a digital link, that link runs discrete left and right, not composite stereo.

Now that in itself doesn't preclude placing the processor at the studio, as most processors will output L and R as well as composite.

But if, like Spin, you're using a digitally-compressed link, that link won't handle processed audio very well, and a lot of the processor's fine work in peak limiting will be messed up.

It's still possible to do it, by putting an overshoot-compensating limiter.stereo coder at the site (as one station I work at does), but that means extra expenditure of about E 2000.

If the processor is at the site, it can feed the tx directly, using it's own optimised stereo coder.

Pity, as processors look cool. I think Orban and Omnia should give a free front panel, with simulated displays, purely to fit in the rach at the studio!

[Justin Speck]

Without wishing to nial my colours too firmly to the mast I'm inclined to agree that the closer the processor is to the transmitter the better.

I'm afraid I come down on the side of transmitter engineers rather than studio engineers - at least if the processor is at the transmitter site no one in the studio is tempted to fiddle with it. I know they have front panel locks or password protection but these luvvies do like to tweak don't they?:)

[Tabasco]

Well I kind of agree, but it depends.

If you're using an uncompressed digital link, and invest in a decent stereo coder at the tx site (like the Orban 8218 - I mean in that league) then there's no problem in citing the processor at the studio.

remember the link has to be protected/limited too, so the practicce some stations have of running the audio into the link via a relatively cheap compressor/limiter will only detract from any good work the processor will do.

But if the STL is digitally compressed, then the processor has to be at the tx.

BTW: Moseley now do a version of their Starlink (uncompressed) STL which passes composite stereo! If that works well without adding any overshoots it will be a godsend.

rgds

[Nick]

As far as I'm aware Q102 had a processor in the studio to do the initial processing, and then at the TX end of the digital link, there was a Peak limiter, stereo expander, then the Stereo Coder, and a Composite processor, all separate.

I think that's probably how many stations do it.

[Tabasco]

That was a load of Aphex kit, Combinator, Dominator, etc.

Didn't sound very good when I last heard it.

But the best way to do it is have the processor just before the transmitter or, as long as the link is linear digital or analogue, have the processor at the studio and a decent overshoot-compensated stereo coder at the tx site.

Of course, a digital link should always be linear, not compressed. Bad artifacts can be audible otherwise, wherever the processor is.