I had several discussions yesterday with people who want to buy a few dozen PC's to run Stereo Tool. The information that I gave them is probably interesting for others as well, and beside that, other users may have more tips. So I decided to create a new forum section and post the info here.
Note: The text below is aimed at FM stations, that use all the settings in Stereo Tool (including declipper, natural dynamics and FM composite clipping).
If possible, go for the Marian Trace Alpha. (Marian Trace Pro if you need AES/EBU digital input). Both are PCI-based, if you want a PCIe-version, you'll need the more expensive Zeraph AD2.
They may be hard to obtain though - don't wait too long with ordering. Alternatively you could go for the ESI Juli@, which is slightly less 'tight' (you'll probably loose a few % in loudness, 0.5 dB or so).
This is the single most important thing to run Stereo Tool.
I haven't checked prices recently, but I would go for an i5 or i7 (from the viewpoint of Stereo Tool there's no real difference between the two, i7 has Hyperthreading but Stereo Tool does not benefit from that).
For a CPU benchmark see: http://www.cpubenchmark.net/cpu_list.php
Click on a CPU, and in the details page you'll find the single thread rating.
Example: My now 4.5 year old development laptop:
Intel Core i7-2630QM@2.00GHz 5564
On the details page http://cpubenchmark.net/cpu.php?cpu=Int ... GHz&id=873
you can find that the single thread rating is 1313.
I can run a complete preset, including Declipper, Natural Dynamics and FM composite clipping on this system with a bit of headroom. If I enable the Stokkemask (ITU-R.1268) mode of the composite clipper, I need to lower the Quality slider to 85% to be able to run it - with very little headroom.
Edit: This was the case with version 7.30. With 7.40, I can easily run the whole preset including Stokkemask with sufficient headroom.
Edit 2: With version 7.71 the CPU load on the highest used core for a complete preset including Stokkemask is about 45%.
Quality slider effect on the CPU load: At Quality 0% the CPU load would be exactly 50% of that at Quality 100%. So with the Quality slider set at 85%, I need (50 + 50 * 85%) 92.5% of the CPU load when running at 100%, which means that to run at 100% I would have needed 1081 / .925 = 1168. So for version 7.30 of Stereo Tool with all these options enabled, the result of the above calculation for a CPU should be at least 1200.
Due to the update above, a value somewhere between 900 and 1100 should be sufficient. Note however that future changes might increase this value again.
In version 7.70, the used CPU load is 45%, with single thread rating 1313 (however, I ran the Passmark software on it, and found 1441, so I should use that value instead). This means that the amount of CPU used is 1441 * .45 = 648. So, you would need at least 700.
Take one of the new Haswells you get:
Intel Core i7-4790K @ 4.00GHz - Single thread rating is 2532. So the expected CPU load on the highest used core is about 700/2532 = 28%.
Single thread ratings are usually roughly the same for the same models of i3, i5 and i7, so unless you're planning to run a large number of Stereo Tool's on a single pc, you can often buy a much cheaper CPU. Stereo Tool currently (!) uses 2 cores, so there's little benefit in having more than 2 cores. Except for one thing: If you want to achieve low latency, you need to have 2 cores that are dedicated to running Stereo Tool, and core 0 is usually used for drivers. So, you want to avoid using core 0 for processing, which means that having 2 cores isn't sufficient. If the cores are fast enough you can run Stereo Tool on a single core, but then the latency will also be slightly higher.
Note: These values are estimates, system speed is also determined by other things such as the motherboard, memory, etc. But it gives a good indication.
For stability, get an SSD harddisk or a memory card. I heard from someone in the military that they use memory cards instead of SSD harddisks because - according to him - SSD harddisks tend to fail more often than those (simpler) memory cards. You need a cardreader, and I don't know how reliable Windows is with this.
Size isn't important, as long as you can store the OS and Stereo Tool (approx. 1 MB) on it. You can get a 60 GB SSD harddisk for about 45 euro / $60.
There are multiple sizes of memory chips; the bigger ones get less hot so get those. There's no difference in speed or price.
In most motherboards, if you place memory in multiple banks, the CPU can access them in parallel, effectively doubling memory speed. So, it's better to get 2 1 GB cards than 1 2 GB card. See your motherboard manual.
The amount of memory is not really relevant, it needs to be enough to run the OS, and have a few hundred MB left to run Stereo Tool. Depending on the OS, even 1 GB suffices in most cases.
Try to get a CPU that doesn't get insanely hot. What I heard (but I have to look into it, I basically only read a post from someone on my forums), is that the new Haswell chips use less power and hence get less hot. They are also insanely fast. Haswell chips are the i5/i7 4xxx numbers.
want to go for a redundant power supply. I have never experienced a failing power supply, but I know that many hardware processor boxes have redundency.
Make sure that you use good quality fans. If anything breaks in a pc, in my experience, it's usually the fans. The fans are the only moving parts in the pc.
Stereo Tool runs on:
- Windows 95/98 (no 192 kHz FM output)
- Windows XP (SP2 needed for 192 kHz FM output)
- Windows Vista
- Windows 7
- Windows 8
- Linux (tested several flavors)
- Mac OS X
Turn off everything you don't need (especially automatic software updates that cause reboots).
If you're going for Windows, audio is easiest to setup under XP and the performance with the GUI open appears to be slightly better. But it's not officially supported anymore.
Many people have already reported running Stereo Tool on Windows without a single glitch in multiple years. The Linux and Mac versions are new and have not yet been tested this thoroughly, although I don't expect any issues. Once Stereo Tool runs, when you don't touch it it only repeats the exact same action over and over again; it doesn't allocate or release memory, it doesn't use the harddisk, so there isn't much that can go wrong - this is very different from how most software works.
Don't put in things that you don't need that will increase the temperature. Especially avoid video cards etc, they tend to get hot and there's no need at all to put one in - since nearly all motherboards have a built-in video output.
These pc's aren't exactly the cheapest, and many stations run with much
cheaper E8xxx and E9xxx series without any issues. Lowering the Composite clipping strictness a few steps won't really cause any issues, and if you're running at latency 4096 you can also reduce the Quality slider a bit. But if you want to use everything and have headroom for potential future enhancements then I would go for something faster.