500 Rack Powersupplies

Two Capi 11 space racks here and a dual floor power supply.
Both fully loaded and no issues.

CAPI biggest baddest PSU of all !

I recently went through this rabbit hole myself...after dropping 180 bucks on the collective cases PSU & dc filter box....portable but no on/off switch ,can only power 8-11 modules, no light's for voltages, & it was noisey as hell with my preamps even with the extra 100 in that dc box, and a 5 foot xlr cable.... Dan said I could've gotten a defective one, as it's " the same one used on many api racks" but needless to say didn't work for me... in any case bought & assembled the Capi/GdiY 51x powersupply and couldn't be happier it's a Beast:)

I just got the jlm eleven rack with dual psu's. Will report back.

I'm unsure why you're using that language and tone. I still think my question is a legitimate one. Is there a specific reason there can't be a reliable power supply that is smaller, and more portable?

As I've said in other similar threads....after fiddle farting around with other racks with varying annoying issues I finally built the CAPI and can sleep comfortably at night again. CAPI all day long...

What language and tone? I answered the question.

If you want me to elaborate a bit, OK, I can do that.

The capacity and reliability of a linear power supply is directly related to the size of the transformer (gauge of wire in the coils, amount of iron in the core) and the size of the filter capacitors. These items are bulky, heavy (relatively speaking), and expensive (also relatively speaking). Transformers also generate heat, and you want to be able to dissipate that, as heat is not particularly good for the long term life of capacitors.

There are switching type power supplies that are considerably smaller and lighter for a given power output, but you don't want those powering your analog recording gear - switching supplies function in the RF range and as such the tend to act like little radio stations, spewing RFI into the environment. Computer gear is full of switching supplies, which is a big reason that computer gear often causes RFI noise issues. Switching supplies also often do not put out anything resembling a clean sine wave and those that do tend to be much more expensive. Most switching supplies put out either a square wave or a "psuedo-sine wave/modified sine wave" which isn't really a sine wave at all, it's a stepped wave. The vertical leading and trailing portions of these waveforms constitute harmonics reaching well into the radio frequencies - not what you want around analog audio equipment and you sure as hell don't want that stuff piggybacking on your power supply lines.

So what you need is a linear power supply with a good sized transformer rated at considerably more than the amount of current you're consuming (+50% is about right), feeding filter capacitors of high capacity and quality (there's a LOT of difference in quality between different brands and model lines of capacitors), feeding a quality voltage regulator circuit on each line capable of driving all the spaces in the rack at full load, plus a safety margin.

The power supply, while not "glamorous", is NOT the place you want to cheap out - a flaky power supply makes your entire system unreliable.

If the "kids" bit is what's bothering you, consider that it's coming from an old man who spent most of his life hauling heavy sound equipment around to live gigs - and I'd still be doing it if I hadn't developed a bad heart condition and arthritis in both hips. Hearing youngsters bitching about carrying around a couple of extra pounds has a tendency to somewhat tick me off.

You can get a small switcher but it will require extra custom filtering ala Danderlo's box. Your not going to find an affordable small foot print switcher that will equal Jeff's linear for the price not a enough demand in the general PSU world for the specific needs.
You want current ? Well that means linear and the size of Jeff's.
What JE is trying to say is you can't always get what you want!

I think my early 2000's remote recording rig was probably 150 pounds before you got into mic stands/etc. Couldn't take it on the subway.

I did move a futon on the Chicago L train once by doing it the moment they started running, like 6AM or something.  They weren't thrilled by two people lifting one over the turnstile, but we had the element of surprise in our favor.  

So I've been testing out a bunch of 500 series racks lately because I'm trying to launch a new 500 series product and want to verify compatibility. drbill has been helping me, too. Between the two of us we have:

API 500V with outboard linear supply
CAPI rack with outboard linear supply
Avedis R52 with internal linear supply
Purple Sweet Ten with internal SMPS
Rupert Neve Designs R6 with internal SMPS
Radial Workhorse with external SMPS

My conclusions thus far are:

1. Whatever my assumptions were regarding SMPS vs. linear and outboard vs. internal were wrong.
2. Not all modules have the same performance with every rack on the market, especially with regards to noise.  A module made with IC's might perform just fine, but a module made with transistors or tubes might not.  
3. One of these racks has weird modulated noise that sounds like an 8-bit video game. Before I name names I want to touch base with the manufacturer to find out if this is normal. If so, then I will not recommend this rack.
4. The quietest rack in my personal possession is the Purple Sweet Ten. It's about 20 dB quieter than the RND R6. I think it may be the quietest of the lot based on what Bill has provided to me.

I have yet to put these racks on my Prism dScope rig to take precise measurements. So far I've just been looking at RMS levels in my DAW. If someone smarter than me can give me some tips on the proper way to measure power supply noise using an audio analyzer like the dScope I'm all ears.

Has anyone compared the new API 8-sp Lunchbox to the Radial SixPack?  I'm tempted to pick up one of those because they seem to use the same line lump SMPS.  I assume their filtering scheme is similar.  Can anyone confirm?

After doing these tests I feel that the best future design strategy might be to provide my own regulation for positive and negative rails right on the 500 series product using LDO linear regulators.  That's the only way you can have some control over what's feeding your circuit.

Brad

Disclaimer:  I'm fully prepared to say some of these racks don't meet my minimum requirements for noise performance for the modules I'm testing with.  I will ultimately back this up with objective measurements.

I don't know this to be fact but have heard that Radial and API use the same brick SMPS. I know that company has made 2 versions. 500 series modules running on the older version are not as quiet as on the new version. They are also fairly load dependent. They need to be loaded a good bit to drop the noise. I just had a few of the 10 space Neve racks come thru and they were pretty respectable, as far as noise. It will likely also depend on what freq you are measuring at. The above mentioned bricks have a 65k switching freq. May not mean as much with a module that is 20dB down at 65k.

Given high frequency, it would be informative to have typical 20-20K bandpassed noise measurements along with full range (or 96K range) measurements, to see any difference in where various smps fall relative to one another, so it could be considered against any audible artifacts. Any more specific comparison of harmonic content outside of the normal non-distinguished THD %. Long day.....that's all I have for now.....