Stereo Tool

We've been toying with Stereo Tool on air for a little while now and paid for the advanced clipper licence. It's currently running on an old Pentium D unit we have lying around and doing the job quite nicely.

However, we've got presenters that would like to listen "off air". No matter what we do (including pulling the soundcard buffer size right down), we can't get the delay down low enough. It's close but not quite there.

Other items in the transmission path include a Audessence Procoder-3 (doing RDS and MPX with a quoted delay of 7ms), a 1.5GHz STL link (an Elenos ELR100-A which I'm lead to believe is analogue FM) and the exciter (it's only a 25W rig).

I'm starting to think it's probably the hardware doesn't quite have enough "grunt" to do low latency processing. For that reason, I'm asking if there's a recommended hardware specification we should look to meet. I know we're looking for a fairly beefy multicore processor but are there any other recommendations (including soundcards) we should look in to for lower latency processing?

First, make sure that you're using ASIO, otherwise you easily get a few hundred (!) ms extra latency.

For both audio quality and (given the numbers that you just posted) also latency I would really suggest that you do everything inside Stereo Tool. So the Stereo Tool output would go directly into the transmitter.

In general, read this post for info about needed hardware (both pc and sound cards are covered):
viewtopic.php?f=22&t=4922

If you do this and you use the composite clipper in Stereo Tool, you can easily get multiply dB's louder (and much brighter) output than in your current setup.

Latency can be set as low as 17 ms, but it won't sound too good. For better quality, you need at least 28 ms, which might be too much for your dj's. Stereo Tool can generate a lower latency (~ 11 ms) monitoring output, but for that to work you need to send it to the same sound card as the FM output (it must be one card for ASIO). In many cards you can use the analog output for FM and the digital output for monitoring. Alternatively, for many cards (I know that this is true for the Marian cards), if you plug in 2 cards and connect the clocks, the ASIO driver will see it as one card, so that's also an option.

You can give up and generate a fake "on air" signal for the DJ's headphones. You may have an old analog processor you could use or get something from ebay.