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TVP 7th January 2005 07:51 PM

Generic Open Chassis Design ...
Hey All ....

Is anyone interested in a generic chassis design effort ???

I've got an idea for a Amp Packaging system . Something that ANYONE can use . I've been lurking the audio boards for DIY projects and I noticed, everyone and thier brother has an idea for an amp circuit, but the hardest part about "any" of this is making it "real" . You know , the "package" . This is what I do for a day job :) Well ... Mostly PCB Design lately ....

I've been thinking of making a "rack" system , with modules to plug in and out for different amps and power supplies . More of a heat and power management "system" to build/test audio amps in ...

The cards would/could be the power supply and different amps for different users ... i.e. home theater , 100-200 watts x6 or x7 with 250-1500w subs ??? relay card for multi-room users ??? maybe a power supply for the car stereo crowd ??? a one size fits ALL scheme ????

My idea is to have an "orderable" or "buildable" cabinet. Maybe with SOME "custom" sheet metal parts built into a rack and card system . Then PCB's could be designed to fit this system . My idea here, I think, is CHEAP !!! ... OPEN, as in, free to the public DIY groups . EXPANDABLE , expendable , economical :)

YES .. I want my cake and eat it too !!!!! :)

it could be built up as 500 watts or upto 5000 watts ??? just get the bigger heat sink and fan kits ;)

let me know your thoughts .....


tiroth 7th January 2005 08:03 PM

I like the idea, expecially the notion of having the PSU be a component on the bus. But I doubt it is viable--have you seen the costs on these kind of plug in chassis? You could buy a complete BrianGT/Peter Daniel amp with chassis.

Check out what DIYcable is doing. Their chassis is nice and configurable, but not cheap. What you are asking for sounds a lot more complex.

lgreen 8th January 2005 05:09 AM

Go for it
Good idea! If you know what you are doing, that would help 99% of us out tremendously. Many of us are very interested in such a design, please tell us more!

It doesn't hurt to post your ideas and see if people are interested, give it a shot. I could use a few of these...

anatech 9th January 2005 01:24 AM

Interesting. An "open source" design. You may want to consider the power connections to be wired to handle the current. Considering the different size / power ratings the case could be 0 - 100W, 100 - 500W, 500 - ?W sizes. I don't think one size would fit all.

Wouldn't it be great to mix and match voltage amp stages?
Your power supplies may be dual mono, dual secondary, with or without separate voltage amp supplies. A slide in space for the power supply might fit that bill.

This could work.


TVP 10th January 2005 05:12 PM

2 Attachment(s)
Hey all .....

I'm heading down this path ANYWAY and I'd like to get ANY AND ALL idea's ANYONE might have !!!!! So regardless , IF you want one or not , feel free to chime in !!! AT LEAST "one" will be built !!! :)

I've designed over 150 chassis parts and 1000 PCBs . I've been at this for 20 years or so ... working with DC to 200 amps and multi-gigabyte digital paths ... mostly designing optical switching equipment lately . I feel that I have more than enough experience to handle this job . I also have a couple of close friends, couple that do the same thing I do, and they have expressed interest as well . Couple of them are more into Mechanical Engineering than I am . One in particular works for a fabrication rep firm :) This isn't something I just came up with and posted here ... I .. like ALOT of people here .... have built a few amps for hobby .. Just so happens I'm a audio/visual geek as well as a design geek .. So most of my toys are PCB based and packaged before built :) I've been playing with the chassis idea now for a couple of months ... thinking of something I need/want for my own use . I've been hunting for AMP schematics to get an idea of what kind of power is available to work a chassis around ... then I spotted this place .... figured others might like this idea too ???????

so as a starting place .... what does everyone want "in" this chassis ?????

My idea is an "open cage" to slide cards in ... as simple as possible and as few "pieces" as possible .. 19" rackable .. leaves 16.5" of inside the cage room ???

make the pieces in such a way that...
tops and bottoms are the same piece ..just flipped over ???
left and right sides are the same .. only flipped over ????

optional sides can be configured to make the chassis taller .. or the cards/modules wider .... i.e. 1", 2", 3", 4" wide top/bottoms, fronts and backs for the cards/modules that all have the same side used on both the left and right ... then a chassis side piece would have a matching card/module side piece ...

Power .....

my idea here is simple ... just a "spec" for copper bar stock cut to fit the width of the chassis ... isolation mount a couple of them
in the back of the chassis . Then we have a "clip" that is soldered to the back of the module/card/PCB in a "spec" area OR MOUNTED to the module for the point to point designers ... different clips for different width modules too ... 4" wide clips would be REQUIRED for the power supply .. .5" wide clips for your 50 watt amp module ??? Also an option for OUTSIDE power .. i.e. the rack can be ALL AMPS with a totally separate PS chassis ...

HEAT ....

find an "off the shelf" extrusion that mounts on the top and/or bottom .. mount as many as you need ???


how DEEP and TALL is the chassis ????? depends on ....
how much power (watts) ???
how much HEAT (BTU's) ???
how much room (real estate) do we/I need ??????
I don't think we need more than 12-14" deep ?????????
how big are the toriod xfmers ??? caps ???

I'm basing ALOT of my opinions on a Nikko Alpha 450, which I have ALOT of experience with .. only I'm assuming a MUCH HIGHER power density .. more like 2500 watts out of a
Smaller package size ...

Costs $$$$$$......

Here's the killer for the deal I guess .... I've been checking the PO's here at the "day job" for our proto chassis costs ... In qty 5-10...USING USA FABRICATORS AND ALUMINUM ... I THINK we can get the pieces around $5-40 per piece .. OBVIOUSLY , we/I need more module pieces than cage pieces , so there would be a price/qty break there .... this puts the target price around $200-350+ for a complete populated chassis . Using the China sources cuts the costs in half .. and TIN cuts another 40% ... and with say , qty 25, we can probably cut the cost another 35% !!!!!!!!! Hopefully, The design will be simple enough for the average home sheet metal guy, that he could build his own too !!!

BOM .... Bill of Materials .... IDEAS figured on the HIGH SIDE !!!!!

$50 $25 2 cage top/bottoms
$25 $12 2 cage sides
$112 $8 14 module sides
$60 $5 12 2" module top/bottoms
$16 $8 2 4" module top/bottoms
$6 $2 3 16" copper rails
$12 $2 6 isolation mounts
$60 $5 12 2" module faces
$60 $5 12 2" module backs ???? open ???
$10 $5 2 rack mount ears

$411 USA made, Aluminum ..... $150 Off shore Tin higher qty ???????

So YES, you CAN BUY AN AMP for what THIS chassis might/will cost ... I've been eyeing the cheap ($250) Crowns on eBay for quite some time too ... then I remember MY application is MY home .. 2 theaters , front and rear outsides , garage too .... those Crowns sure do get expensive when you have to buy 5 or so of them :\ which is what lead me to this idea in the first place ... I figured for the 10 cents a watt most people are spending on their home brews I could still end up way ahead ... My goal is $500 for a 2500 watt 6.1 amp , that's 250w X 6 @ 8 ohm with 500x2 for the subs ... that would be
3 x $250 and 2 x $500 = $1750 in CHEAPO USED Crowns !!!!

still wondering which DIY sub to do ;)..... the LAB , Rog's , JBL 4550?? ... decisions....decisions.....decisions....

tiroth 10th January 2005 05:24 PM

Well, TVP, knowing that you are a seasoned designer with a good idea of the costs involved, I think you will meet with success.

The most buy-in will likely be from gainclone type designs. If the form factor can accommmadate a decent transformer and X number of 3875/4780 amps I think that it will have the best possible mass appeal. Once you have that, you might either broaden your scope to some common discrete designs or just hope that people will adapt to fit your chassis.

I don't know what the sinking requirements are of the amps you plan to pack into your chassis but you might want at least one readily sourced heatsink profile that can fit in a "standard" module. Depending on this decision the same profile in a longer length might accommadate multiple designs.

lgreen 10th January 2005 06:13 PM

I agree
I agree with Tiroth, the design so far looks good to me.

For your slidable cards, keep in mind that a lot of people here like to make their own PCBs, so consider a way to allow for many size PCBs to work in the case, either slide in or fixed, with a common connector to connect them up.

Isn't tin good for shielding? Maybe the interior could be subdivided by a tin or other shield to make a few isolated compartments?

kilowattski 10th January 2005 07:32 PM

It seems that any amplifier that needs any sort of heatsink will not work well in your scheme but the Gainclone and Class D/ Digital Amp crowd may find this very interesting.

TVP 10th January 2005 07:41 PM

Hey ...

Thanks for the vote for success :) ...

as for the heat and sinking it .. I was planning/thinking the "case" would do ALL of it !! i.e. the amps and power supplies would transfer the heat by mounting your "switches" (fets, xstrs,etc) on the body of the "modules" which would transfer it to the "case" ... the "case" could have a heat sink mounted on it .. top and/or bottom ... as needed . Idea here is , modular .... if your design only dissapates 10 watts of HEAT , then you probably don't need a heat sink AT ALL ... but if your building a 2500++ watt monster with only 85% eff and your burning off 375 watts ... then you'll proably want to bolt on a few heat sinks and fans to help dissapate it !!!!!

Of course ... I maybe WAY off base here and you guys WANT the heatsinks (and fans??) inside the modules ... then we can knock a couple of holes in the front and push or pull air from the rear ??????

hence the reason for posting all of this :) to get ALL the ideas out here and MASHED out :)

Since I'm a PCB designer ... I was planning on repackaging SEVERAL amp designs to fit the modules ... as many as people will let me use ?!?!?!?!? and I'm MORE THAN WILLING to "front" the effort involved as well .... like I've been saying ... I plan to build MINE FIRST !!!! :) So if you want your amp design to fit and want a FREE PCB for putting it "out there" LET ME KNOW !!!!

Tin and isolated compartments ....

metal is metal when it comes to EMI ... of course copper connects better ..but DOESN"T last worth a DAMN !!! Lead seems to work the best .. but DON'T TOUCH IT with your bare hands !!! I don't think I've ever seen a shielded cage used in ANYITHNG but RF ??? do you guys have a requirement for that ???? Most shields I've designed solder into the PCB too ... lately we've been using solderable clips for quick removal of the shields and access to tuners/pots under the shields ... I was thinking/ planning on the larger modules having a card cage system available in the future ... (for SMPS's and BIG amp designs??) but lets say , 3-5 PCBs in the 2" and up sizes .. then one slot could be used as a isolator slot . i.e. put a "blank" PCB or hunk of metal in there to isolate 2 areas ..

I was planning on a GENERIC OPEN PUBLISHED SPEC for the PCBs, to fit the modules . Then ANYONE can make thier PCB's fit ... I'm planning on a "perferated" PCB design with the correct outline and connections for the point 2 point designers ... tube guys ??? Some people hate card sliders ... some hate stand offs ... so I've been thinking of a scheme to use EITHER :) !!! for stand offs , people can locate and drill thier own mounting points . Using tapered seat screws you can still have a nice flat surface on the outside . PEM's don't lend themselves to DIY'ers :\
maybe have one set of standard mouting points too ... but holes cost money ????

I'm going to be meeting with my comrades and start the CAD work soon for the chassis ... once we get a couple of things ironed out .. costs can be NAILED down better !!!

mainly .. I think ... the biggest question is how big are the transformers you guys are using ??? torioids seem to be the best thing around ... 4x5x5" seems to handle 1000 watts ????
so plan on 2 of those deep ??? 2 farad worth of caps , couple of bridges ... so 4U = 7" high or 3U= 5.25" 3U is pushing it ?? especailly when you figure in the caps, probably have to lay them down ??? or build a bank with shorties ???




TVP 10th January 2005 07:54 PM

hey ...

why do you think the heat sinking won't work ??? I've used this scheme to dissapate over 500 watts of heat in SEVERAL designs , several times over the last few years ..... my only limitation is the fact that UL requires ANY exposed surface to be touchable ... which is max about 130 deg F ..... it would take ONE HELL of a load to heat up a OVER square foot of metal to 130 F and KEEP IT THERE !!!! right ???? add a SLIGHT breeze and it gets even harder to maintain that number !!! Now imagine if you added even the smallest heat sink !!! My 600 watt pioneer doesnt have ANYTHING near that amount of space , and no hope of air flow in my cabinet .. and no problems !!!



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