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Old 12th June 2012, 01:06 AM   #241
hurtz is offline hurtz  Germany
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Hi,

I have made plans for a stereo casing for the AMP, attached you will find the designs.

The main body will be made from 12mm MDF. However the backside of the case must not be thicker than 2mm in order to fit all the RCA jacks etc. Any idea what material except metal I could use? It'd be ideal if it was as easy to work with as wood..

The two little yellow dots under the big one are the LED's form the PSU. Everything else should be self-explanatory
The three black lines on the pictures with dimensions are the golden ratio and bisecting line.

Would be glad to hear your thoughts about this!

Concerning safety, the amp has a primary fuse, secondary fuses after the PSU and a temperature controlled (98C) fuse inside the toroid.
The power switch is rated for 100A peak current (capacitive, 10000 cycles) and 10A continous 1E4 and 6A 5E4 which I guess means the first 10000 switching cycles and respectivly 6A until 50000 cycles.
All connections of the mains wiring will be made by cable lugs.
Conections from toroid -> PSU -> AMP will be fastend with screw-down terminals.

Still since the casing is made of wood I'd like to hear your thoughts concerning safety!


cheers!
hurtz
Attached Images
File Type: png case1.png (6.2 KB, 335 views)
File Type: png case2.png (33.6 KB, 332 views)
File Type: png case3.png (8.6 KB, 326 views)
File Type: png case4.png (33.9 KB, 320 views)
File Type: png case5.png (46.3 KB, 329 views)
File Type: png case6.png (22.6 KB, 104 views)
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Old 12th June 2012, 01:15 AM   #242
! is offline !  United States
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Quote:
Originally Posted by hurtz View Post
Hi,

I have made plans for a stereo casing for the AMP, attached you will find the designs.

The main body will be made from 12mm MDF. However the backside of the case must not be thicker than 2mm in order to fit all the RCA jacks etc. Any idea what material except metal I could use? It'd be ideal if it was as easy to work with as wood..
There are a couple easy to work with materials that come to mind. Polycarbonate can be cut with standard tools but go slow to keep heat down, then if desired the cut edges can be sanded and even polished.

Aluminum is similarly easy to work with but the piece should be oiled so the cutting blade teeth don't clog up, and remember that it's electrically conductive.

The other option is to just use the thicker piece of MDF and drill the correct diameter hole, but drilling from the inside then make a 2nd inset hole of larger diameter (only big enough for the back side of the sockets, etc body to fit in it) with a drill press (using the depth gauge) so there is only ~ 2mm of material remaining between the bottom of the larger hole, and the other side of the board. However, 2mm of MDF is going to be fairly weak structurally. Some PVC based sealant could strengthen it but it seems like a hassle to do that, I'd sooner pick a different solid piece of wood instead of MDF.

Quote:
Still since the casing is made of wood I'd like to hear your thoughts concerning safety!


cheers!
hurtz
Since it is wood it doesn't need to be grounded.
Not much left to say about wood, good electrical insulator. Be sure to leave a few vent holes here and there to reduce cabinet air temperature.

Last edited by !; 12th June 2012 at 01:21 AM.
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Old 12th June 2012, 08:32 AM   #243
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I believe that MPX is more beautiful but more expensive...
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Old 12th June 2012, 10:48 AM   #244
AndrewT is offline AndrewT  Scotland
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Flat sheet of GRP.
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Old 19th June 2012, 02:19 AM   #245
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hurtz

newbie here, just joined the forum this past weekend. Learning a ton. I am however having a little trouble following the changes. Do you have an updated parts list for both the amp and power supply to correspond with the pcb layouts you have posted? I want to order parts and try this out. I've built amps in the past but this will be my first chip amp.
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Old 19th June 2012, 03:05 AM   #246
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I understand the amp, its the power supply I'm not so sure about.

R1,R2: 4.7k 0.5W
R3,R4: 1R 025W
R5,R6:??????????
C1-C6: Jamicon 4700uF 35V 20% 7.5mm
C7,C8,C11,C12, C13, C14, C15, C16: 100nF
C9,C10: 120nF
D3,D4,D5,D6 MUR820
LED1,LED2:???????? guessing basic led
RL1,RL2:?????????
FS1,FS2:????????? fuses? 2.5amp for 6 ohms right?


This is what I gather from this topic for the components of the power supply.

I'm not sure what the values are for:

R5,R6
RL1,RL2

Also FS1,FS2 are fuses right? I am running speakers with 6 ohms. Would 2.5 amps be correct?

Then last, basic LEDs?

Thanks to everyone on this board for all their help and knowledge!
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Old 19th June 2012, 03:10 AM   #247
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and I'm not thinking straight, RL1 and RL2 is just the names of the rails...
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Old 19th June 2012, 12:43 PM   #248
hurtz is offline hurtz  Germany
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The enclosure has turned out very well! I ended up using aluminium and cut two little plates where input and output is mounted on. I moved both heatsinks inside the casing now, and will later on test how much heat builds up inside and if venting is necessary.

Hi peazley,

here are the updated components lists.

A few changes though: Cs1/Cs3/Ci have now a 3.5mm pitch instead of 5mm om my PCB.

R5/R6 are 10k potentiometers adjusting LED-brightness. RL1/RL2 are 1W 1.2k resistors in series to limit voltage should the potentiometer be set to 0r. However I suggest increasing RL1/RL2 to 5k or something, since you don't want maximum brightness in any case and they get very hot.. Choose any colour you like.

C9/C10 150nF.

FS are the fuses however the correct value is somehow debated. However any value should blow if a short occurs.

cheers,
hurtz
Attached Images
File Type: png parts list amp v6.3.png (73.1 KB, 67 views)
File Type: png parts list psu+ v2.7.png (44.4 KB, 52 views)
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Old 19th June 2012, 01:15 PM   #249
AndrewT is offline AndrewT  Scotland
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35V electrolytics limit the transformer voltage that can be safely/reliably used.
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Old 19th June 2012, 02:09 PM   #250
hurtz is offline hurtz  Germany
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^ Yes good point I tend to forget that I only use 18V toroids since the next higher voltage I can access is 30V.
All components should be fine up to 22V toroids --> 31.1V DC

cheers
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