Can I remove the tops from all rack gear?

[Cableaddict]

I am constantly battling the weight of my racks, as I often do 1-man shows.

One of the biggest sources of weight is the steel chassis of each piece of rack gear. (Including my racked computers.)

I'm thinking of simply removing the tops and replacing them with plastic, maybe with one thin aluminum cross bar for torsional strength. I'm even considering drilling-out large-ish holes in the rest of the chassis, also then covered in plastic.

I can certainly be done in a way that's both mechanically & electrically safe. - But I'm wondering about EMF & other possible noise issues.

SO:
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With something like a good mic pre or DAC, using a typical torroidal tranny, is the steel top actually needed for shielding?

If so, might I get away with just leaving a shield around the tranny itself?

Any other concerns, such as high gain op amps?
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- And the same question holds for my rack PC's. EMI won't affect THEM, but I've read that switching power supplies generate a lot of EMI, or back EMF, or somethingerother.... (Yes, I'm not an electronics expert!)

I currently have no top on my PC's but I also keep them at the top of each rack. Could drilling-out holes in the bottom of the chassis possible cause interference with my preamps & DAC, below?


THX.

 

[jean-paul]

With something like a good mic pre or DAC, using a typical torroidal tranny, is the steel top actually needed for shielding ?

I think you answered your own question. using sensitive equipment without shielding is asking for trouble.

The proposed solutions are no real solutions as you trade in one problem for another problem. Maybe scaling down to smaller but equally or even more powerful pc's is a way ? Micro or mini sized computers are way less heavy. Or you build a DIY blade system like Build-a-blade with mini ITX boards in one case. Saves a lot of weight.

Problems/challenges are best solved at the root of the problem. Please do not even try to make large holes in steel enclosures.

 

[Enzo]

I don't worry about the transformers a much as I would about the whole sensitive audio circuit board picking up noise.

Do you have any power amps in your rack? Going to a amp with a switcher (SMPS) power supply will save tons of weight. A 1500 watt power amp that weighs 7 pounds is easy to find.

 

[chris661]

Interesting. What do you need all those computers for?

If you've got budget, I'd recommend giving a digital desk a try. I got one a year or so ago, and love the fact that I don't need to move racks of compressors, EQs, etc.

Chris

 

[Cableaddict]

Interesting. What do you need all those computers for?

If you've got budget, I'd recommend giving a digital desk a try. I got one a year or so ago, and love the fact that I don't need to move racks of compressors, EQs, etc.

Chris

I use the computers for everything except mic pres. Basically, a digital desk, except I can use any plugins & vsti's I want, PLUS any other Windows-compatible software: Lots of VSTi's for my keyboard controller. Plus DJ software. Plus "intelligent keyboard" software. Plus all my charts. Plus a karaoke machine when needed. Plus .......

I use Reaper as the host, since it's very efficient & stable.

I carry three PC's with me, because I like to have two full versions of Traktor running, plus one PC for safety / redundancy.

 

[Cableaddict]

I don't worry about the transformers a much as I would about the whole sensitive audio circuit board picking up noise.

So... what does that mean, in terms of my question? Does the chassis have to be a completely enclosed shield, or can I open up parts of it?

This is serious, not some theoretical question.

Do you have any power amps in your rack? Going to a amp with a switcher (SMPS) power supply will save tons of weight. A 1500 watt power amp that weighs 7 pounds is easy to find.

I already have Lab Gruppens. No problem there. (Better not be, for $4600 a pop!) Plus the amps & speaker processing are in a separate rack. Believe me, after 10+ years of tweaking and custom fabrication, there is not a single ounce left to be saved, except for the subject of this thread.

- And my poor old back is killing me.

 

[JMFahey]

Believe me, after 10+ years of tweaking and custom fabrication, there is not a single ounce left to be saved, except for the subject of this thread.

- And my poor old back is killing me.

Then face reality, there is not an ounce to be saved.
Sorry for your back.

 

[chris661]

Any chance of running the whole thing through a powerful laptop instead of the rackmount PCs you have?
I'm typing on something that's 3 years old, but has 16gb RAM, a 3.4GHz quad-core processor, runs on battery and folds into a compact shape for transport.
The latest stuff is really really powerful.

Chris

 

[Cableaddict]

Any chance of running the whole thing through a powerful laptop instead of the rackmount PCs you have?
I'm typing on something that's 3 years old, but has 16gb RAM, a 3.4GHz quad-core processor, runs on battery and folds into a compact shape for transport.
The latest stuff is really really powerful.

Chris

No. Laptops are terrible for this kind of work, for several reasons.

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Well, I have yet to see an answer that actually addresses my question specifically. I appreciate ANY response, I guess, but I really don't need a bunch of people telling me "oh, that seems like a bad idea" or "oh, you should just save weight elsewhere."


Is anyone out there that actually knows exactly where EMI, etc is generated, and exactly which parts of a circuit are susceptible to it?

 

[indianajo]

Yeah I know where EMI is generated.
Guys driving around in pickup trucks with a CB with the transmit button glued down. Yelp Yelp Yelp Yelp, isn't Dixie barked by dogs a great song! (not)
Radio mikes, police radios, patrons with a 2 meter rig in their pocket, cell phones. besides the obvious SMPS supplies, chopper driven AC motors, lamp dimmers, refrigerator interrupters. The AM radio stations whose towers are 3 miles from my house.
Any high gain circuit will pick this stuff up. No condensor mikes, no mag phono cartridges, you might get away with no shielding. But not in my location with my equipment. I'm getting the AM radio stations on the 2 v 2000 ohm drive mixer to power amp cable, just by going from 2m cable to 4m. Had to put 68 pf across the amp input, up from 22 pf, to kill it.
Steel mesh is almost as effective as solid steel for RFI shielding, weighs a lot less. Home depot sells a 4'x8' sheet in the concrete section for about $10. Aluminum mesh is lighter, I don't know where to buy it cheap. Use SS star washers & screws to connect the case ground to the
mesh plate. coupla pounds gone, anyway.
I cut the home depot mesh with Weiss sheet metal shears.
If I gig, my instrument will be a 340 lb Hammond organ. Or a 300 lb console piano, real wood. That guy that plays a 400 lb upright piano for Kid Rock is my hero. (See the Graceland show from Soundstage) I'm thinking of buying an electric forklift before I audition.
Best of luck.

 

[ndcraig]

No. Laptops are terrible for this kind of work, for several reasons.

------

Well, I have yet to see an answer that actually addresses my question specifically. I appreciate ANY response, I guess, but I really don't need a bunch of people telling me "oh, that seems like a bad idea" or "oh, you should just save weight elsewhere."


Is anyone out there that actually knows exactly where EMI, etc is generated, and exactly which parts of a circuit are susceptible to it?

In a tightly stacked rack the bottom panel of the device above would act as your shielding. It is all at the same potential assuming your not isolating your chassis from each other and the rails with nonconductive spacers of some kind. It does seem kind of wasteful to have 2 layers of steel between devices!

You may want to have something non-digital adjacent to a sensitive analog mic pre or something -like a power amp between the PC's and the pre-amps for example.

I've also switched to this for most of my mobile rack computing needs:

Sonnet - RackMac mini 1U Rack Enclosure for Mac mini

Kind of like a cross between laptops and desktops -(Yes they run Windows and even Linux fine also) Two complete PC's with internal PSU's (no wall-warts) in one shallow rack-space was a major weight savings for me.

 

[jolathe]

Maybe you could bond a layer of conductive wire mesh to the bottom of your new plastic case top, and connect the edges of the wire mesh to the sides of the case to improve shielding.

 

[Cableaddict]

^ Aluminum mesh seems like a very good ides. I don't care what it costs.


Will definitely try it.

thanks for the idea.

 

[Cableaddict]

In a tightly stacked rack the bottom panel of the device above would act as your shielding. It is all at the same potential assuming your not isolating your chassis from each other and the rails with nonconductive spacers of some kind. It does seem kind of wasteful to have 2 layers of steel between devices!

You may want to have something non-digital adjacent to a sensitive analog mic pre or something -like a power amp between the PC's and the pre-amps for example.

This is very helpful. THANKS. - I was just going to post this very point. In my case, I usually leave a 1/2 rack space between units for cooling, but I imagine that still OK. All the chassis get shield-coupled at the racks. I could even use star washers to increase conductivity, though none of my ear sues floating chassis, anyway, and they all have a third pin on the socket.

Several of you mentioned taking extra care with the high gain circuits, which is really just the mic pres. I will definitely do so.

 

[Cableaddict]

BTW, that Mac Mini enclosure is pretty neat. It would never work for what I do (A liquid-cooled 8-core 5960x running at 4.2 GHZ is literally marginal) but it would be killer for a mobile DJ system.

 

[nikmartin]

Well, I have yet to see an answer that actually addresses my question specifically.

Is anyone out there that actually knows exactly where EMI, etc is generated, and exactly which parts of a circuit are susceptible to it?

Yes. I will first answer your question, THEN I will tell you how much crap you could shed, because you're probably the only one that's getting any value out of it.

I worked for a hardware manufacturer that is ul and FCC type certified. The chassis of your rack gear is a critical part of the shielding of your gear. The testing standards for type acceptance are very rigorous, and since gear needs a case for electrical safety anyway, we also use the case as part of the shielding. You know the little very fine stainless mesh gadgets gaskets you see around some computer parts like Ethernet ports and video cards? That computer would fail an emissions test without it meaning it would possibly cause interference to one of your pieces of gear without it. The metal chassis is a vital part of that. Now, if you remove all your lids, everything sounds fine, then get to a venue and a florescent transformer is taking a **** right above you, and emitting all sorts of noise, or every time a bouncer keys his HT to talk to the manager and your system starts squealing, youll know. The opposite is true to. You have an ADC running without a lid, and the venue takes your audio feed and amplifies it 200x, and now there's this very high pitched 'tick, tick,tick' coming from the mains, and nobody can seem to figure out what, it might just be your ADC emitting a bit of noise from a clock, crystal, filter, who knows. Bottom line is the chassis is a critical part of the shielding of your gear. Every component and copper trace in a piece of gear is susceptible to RF. Copper traces on PC boards are frequently resonant to RF, and without shielding from the case could do all sorts of weird stuff.

Now. About all this stuff you're carrying. If you play out live and need three desktop computers for running plugins, you're possibly doing it wrong. You got your way, and that's cool, because I have no clue about what you do live, but if you're a one man show and need all that stuff, you're gonna have to compromise, unless you are a one man Pink Floyd tribute band or something. ☺. 8lb 3000 smps amps exist., so do laptop's capable of running all your stuff.