First off, I know there are many compressors out there.  But does anyone know of a compressor which can be obtained cheaply for for free which works in a similar way to the Sontinus one?
 
This is very much my go-to compressor as it sounds good to me and the GUI just makes sense to me.  Does anyone know of one with a similar GUI?  I've tried the one bundled with Reaper, but it's not the same!
 
Thanks!

Try kotelnikov, its very nice and free. I dont know compressors with similar gui

Ok, I will check it out, thanks.  I will probably just need to bite the bullet and learn a new compressor!

If you're using Reaper, or another DAW with a DX/VST wrapper installed, you could also use the Sonitus Surround Compressor, and just ignore the other channels. It has a very similar GUI.

ptheisen
If you're using Reaper, or another DAW with a DX/VST wrapper installed, you could also use the Sonitus Surround Compressor, and just ignore the other channels. It has a very similar GUI.

Thanks, I must have missed that one as I've not spotted it amongst the plugins in my Sonar Pro menu.  I will look out for it!

Thread on a DX wrapper: http://forum.cakewalk.com/How-to-Use-Cakewalk-DX-and-DXi-in-Studio-One-Really-m3696738.aspx
 
Unfortunately, the compressor is one of the few plugins that didn't work for most people in other DAWs. The good news is it does handle many other favorites, such as TTS-1, Sonitus Multiband Compressor, and MIDI FX. That thread also mentions some other DX wrappers.
 
But if you're going to buy a new compressor, might as well get a good one. Many will suggest FabFilter Pro-C, which you can't go wrong with.
 
Although light years beyond the Sonitus compressor, it happens to also be a good replacement for it, IMO, due to the way it overlays levels onto the threshold knob and the way you can visualize the knee versus signal levels. That was the Sonitus' best quality, that little bouncing ball next to the transfer curve that made it easy to set threshold and knee. Pro-C's kinda pricey, but that's the only downside.

Reaplugs are Reaper's stock FX, and they remind me a lot of Sonitus in that they're also no-frills, good quality.  Even better, they are FREE (and as VSTs, work in any DAW):
 
https://www.reaper.fm/reaplugs/

JonD
Reaplugs are Reaper's stock FX, and they remind me a lot of Sonitus in that they're also no-frills, good quality.  Even better, they are FREE (and as VSTs, work in any DAW):
 
https://www.reaper.fm/reaplugs/

Thanks. My main issue was that the Reaper plugins lack the graphical interface I've become accustomed to. I'll just have to learn to use them without! 
 
 

ptheisen
If you're using Reaper, or another DAW with a DX/VST wrapper installed, you could also use the Sonitus Surround Compressor, and just ignore the other channels. It has a very similar GUI.

Edit: Crap, I didn't read ahead far enough!
 
Additionally, even if you aren't using REAPER, you can download for FREE most of the plugins that come with REAPER, and while they don't sport sooper pretty UI graphics, they are pretty functional and will get the job done quite well and without much of a CPU hit.
 
https://www.reaper.fm/reaplugs/

after the sonitus compressor,
which is one of my most used plugs,
 
C1, by waves, is number two, 
and takes on the heavier jobs even better.
 
when using it at 44/48khz, Comp & Gate only, zero latency.
boom.