Processing Pre or Post STL?

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hurleysm
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Processing Pre or Post STL?

Post by hurleysm »

Hey Genius People,

Quick question........we are currently in the process of getting some new transmitters and this will give me the opportunity to move some components around as to where they sit in the broadcast chain.

At the moment the chain is as follows: Studio - Direct Fibre Link - Processor (Optimod) - STL - Exciter/Transmitter

My question is do you think processor should move to the front of the chain after the studio before the Fibre link which is transparent & does not alter the signal at all, leave it where it is, or after the STL at the transmitter site?

Thoughts and reasons why would be super helpful.

Many thanks all :)

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Shane
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Re: Processing Pre or Post STL?

Post by Shane »

Is the STL a composite STL? If so, this looks ok as it is. I might consider adding some kind of level rider ahead of the fiber link. Different story if this is not a composite STL or if we were talking about an AM station.
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hurleysm
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Re: Processing Pre or Post STL?

Post by hurleysm »

Hey Shane,

Thanks for the reply.......

The STL is composite & I do have an Aphex Compellor pre fibre just levelling things out, i forgot to put that in the chain info.

My thought was I might move the processors Pre fibre after the Aphex for the simple reason of accessibility as they are slightly older optimod's and do not have remote access. That way it's easier to make adjustments & keep an eye on things without having to journey out to the mid point site where the STL & processors are.

Appreciate any further feedback you may have :)

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Deep Thought
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Re: Processing Pre or Post STL?

Post by Deep Thought »

If you do that make sure the A/D conversion is 192k sample rate.
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hurleysm
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Re: Processing Pre or Post STL?

Post by hurleysm »

Deep Thought wrote:
Mon Jul 23, 2018 1:43 pm
If you do that make sure the A/D conversion is 192k sample rate.
On what part of the chain?

I know the outputs from the studio's in analog to the Aphex, and the outputs from that is 44.1 KHZ Analog to.Then from there it goes into a D/A before going down the point to point fibre to the STL & processing site.

I'm prob missing the point which is why I knew to ask all the clever people here hahahaha

Nathaniel Steele
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Re: Processing Pre or Post STL?

Post by Nathaniel Steele »

You need a composite signal into the STL, so to pass a composite signal you need 192Khz A/D conversion.

Otherwise you would have to process it in the optimod and out as L/R Audio (do they even have audio out on the back of the 8100, been a while since I looked), and then you'd need a stereo generator to generate the composite signal to feed the STL. This would not be an Ideal solution IMO

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Re: Processing Pre or Post STL?

Post by DaveSt »

I have been lurking here for a while and have finally decided to register. So hello everyone! it is good to find a forum with some friendly professional discussion.

Answering the question, by far the best connection from an audio processor to the transmitter is composite. You really don't want to drop back down to L/R. If you do use the L/R output on the processor then you lose the overshoot correction which the Orban is so good at. Here, we have always said that you get the processor as close to the transmitter as you can. The composite STL is (should be) fine, but best not to move it any further back.

hurleysm
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Re: Processing Pre or Post STL?

Post by hurleysm »

Nathaniel Steele wrote:
Mon Jul 23, 2018 2:21 pm
You need a composite signal into the STL, so to pass a composite signal you need 192Khz A/D conversion.

Otherwise you would have to process it in the optimod and out as L/R Audio (do they even have audio out on the back of the 8100, been a while since I looked), and then you'd need a stereo generator to generate the composite signal to feed the STL. This would not be an Ideal solution IMO
Hey Nathaniel......

Right got what you mean, So when it gets to the mid point STL site the output from the point to point fibre is is composite. It goes from the fibre receiver into the optimod and then from that into the STL.

Do you think there is any advantage moving the position of the processor to before the fibre here at the studios (just so it makes it more accessible for tweaking / adjustments) or after STL at the transmitter site or just leave it as is?

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Re: Processing Pre or Post STL?

Post by Nathaniel Steele »

The signal INTO the optimod will NOT be composite, it will be discrete L/R (or mono) Audio. Dave ST sum's it up nicely
DaveSt wrote:
Mon Jul 23, 2018 2:30 pm
Answering the question, by far the best connection from an audio processor to the transmitter is composite. You really don't want to drop back down to L/R. If you do use the L/R output on the processor then you lose the overshoot correction which the Orban is so good at. Here, we have always said that you get the processor as close to the transmitter as you can. The composite STL is (should be) fine, but best not to move it any further back.
And honestly, yes its a pain, but how often do you really adjust your processing? I always follow "Make a tweak and listen for a week"...well maybe not a week , but you make one change, and listen for a while before making any others.
Last edited by Nathaniel Steele on Mon Jul 23, 2018 3:56 pm, edited 1 time in total.

hurleysm
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Re: Processing Pre or Post STL?

Post by hurleysm »

Hey Guys,

Thank you so much for all the info thus far.........

So the opinion so far seems to be don't move it back in the chain, if anything the actual best thing to do would be to move the Optimods from the mid point relay station where it goes from fibre to STL & put it right before the lovely new shiny RVR Transmitters. As someone said earlier having it at the closest point to transmission......

Would everyone agree with that assessment?

Nathaniel Steele
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Re: Processing Pre or Post STL?

Post by Nathaniel Steele »

IF you have a composite only STL (IT connects with BNC Coax Cable) then your best bet is to leave it like it is now, you can't put it on the other side of the STL, because:

You don't then have a composite signal to put INTO the STL

and

You couldn't run the Composite Signal INTO the processor

The composite signal should go the shortest possible path to the transmitter, which in your setup is going to be through the STL (which we can think of as a long wireless composite cable for all intents and purposes).

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Re: Processing Pre or Post STL?

Post by Lee_Wheeler »

If the Optimod has analog or AES outputs (I assume it is something newer than an 8100) you can move it in front of the link no problems. You indicated that you are getting a new transmitter and I don't think there has been an exciter shipped in the last 15 years that can't take an analog or an AES signal and then use its built in stereo generator at the transmitter site. The only trick is to make sure to get the pre-emphisis correct.

You can toggle pre-emphisis on and off at all stages and it is easy to either get no pre-emphisis or double pre-emphisis if you aren't paying attention.

...Lee
Last edited by Lee_Wheeler on Tue Jul 24, 2018 5:54 pm, edited 1 time in total.

DaveSt
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Re: Processing Pre or Post STL?

Post by DaveSt »

hurleysm wrote:
Mon Jul 23, 2018 3:31 pm
Hey Guys,

Thank you so much for all the info thus far.........

So the opinion so far seems to be don't move it back in the chain, if anything the actual best thing to do would be to move the Optimods from the mid point relay station where it goes from fibre to STL & put it right before the lovely new shiny RVR Transmitters. As someone said earlier having it at the closest point to transmission......

Would everyone agree with that assessment?
If the composite STL is working well with good signal and no multipath, there is nothing perceptible to be gained by moving the processor to the transmitter. If you were to do that you would need to use the STL with discrete L/R in and out which may not be possible. The best advice is to leave it as it is.

hurleysm
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Re: Processing Pre or Post STL?

Post by hurleysm »

Hey All.......

I'm going to go out to the mid point site over coming days to confirm what optimod models are there & the connectivity on the rear panels but I have a feeling from memory that they are 2200's

Image

The 2 new transmitters for the 2 stations are RVR TEX2500's http://www.rvr.it/en/products/fm-trasme ... ex2500lcd/

I have also checked at the studio end what connectivity there is and the Aphex levelers that sit before it goes down the fibre do have AES digital in's & out's along side the analog XLR's.

It would seem so far from the wise collective here that it's probably best to leave them where they are unless anyone can think of a good argument for either moving them to the front of the chain after the Aphex (for ease of access) or to the back on the chain before the new transmitters at the tower?
Last edited by hurleysm on Tue Jul 24, 2018 2:24 pm, edited 1 time in total.

Nathaniel Steele
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Re: Processing Pre or Post STL?

Post by Nathaniel Steele »

Doesn't the 2200 have a serial port for remote control? You could put an IP to serial converter at the midpoint for remote control, if you have IP access at the midpoint.

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