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Old 26th June 2006, 01:12 PM   #1
jarthel is offline jarthel  Australia
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Default help with chassis layout

I am making a headphone amp and I have bought a similar chassis like this one: http://www.thlaudio.com/image/miscIM...-PRAL-1cB.jpg.

The top plate and the sides are together. While the bottom plate and the front and back are together. So the chassis cover is shaped like a "U".

I need to mount a choke and 2 output caps (for the amp) on the top plate. The B+ supply circuit is mounted to the top plate. But the transformer is mounted on the bottom plate. The B+ is tube-based so holes will need to be made on the top plate.

The amp which is on a PCB is mounted to the bottom plate.

I have several wires going up and down (and vice-versa) the chassis:

1. B+ supply down to PCB
2. PCB up to output caps (output caps are ASCs)
3. transformer secondaries up to the B+ supply.

some possibilities:

1. The wires that are going up and down are long enough so that I can easily remove cover. My concern is that the long wires might affect the sound especially for the output cap.

2. the things are supposed to be mounted on the top plate are now mounted on a sheet mounted on an "L" shaped piece of sheetmetal screwed to the front and back.

I do not need to run insane length of wires with this one. Only downside is that I need to create holes on the top plate so I can insert the output caps and potted choke. Downside is that the holes needed can't be made easily.

3. Mount most of everything on the chassis cover. Again a sheet it attached via L shaped sheet metal screwed to the side.

The PCB will be upside-down. I know the input tubes can't be mounted in any position. Still finding out if the output tubes can be mounted upside-down. the datasheet is in Russian so I have asked the resident expert on the answer.

so the transformer will be mounted upside-down. The amp requires a seperate heater transformer (the main transformer doesn't have the necessary secodary for it), so this will be mounted upside-down as well.

To relieve some pressure on the L shaped sheetmetal, I was planning to mount some wood blocks with a sheetmetal attached on top to support the transformers. Of course the wood block + sheet metal would be just the right height.

With option 3, I need to have some wires running up and down again:

1. wires going to the output stereo jack
2. wires from the input jacks to the input of the amp
3. wires coming from the AC input going up to the transformers.

since the bottom would be bare, I was thinking of using RCA jacks to mate the wires.

something like this
| (from top)
|
|
V (male RCA)
V (female RCA)
|
|

the female rca will be mount on a sheetmetail with spacers. While the male RCA will be supported by a tube so it is pointing down straight.

The idea is that when I put on the cover, the male and female are perfectly align. one could say it's like they are having sex.

I haven't tried using RCA jacks for AC just from what I've seen, I have a feeling there's enough copper there to support 240VAC.


Thanks for the help.
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Old 26th June 2006, 01:57 PM   #2
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Location: Sussex
Hi,

The link you posted doesnt work, might get a few more replies if it did

Craig
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Old 26th June 2006, 02:03 PM   #3
jarthel is offline jarthel  Australia
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http://www.thlaudio.com/image/miscI...e-PRAL-1cB.jpg
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Old 26th June 2006, 02:25 PM   #4
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Try:
http://www.thlaudio.com/image/miscIM...e-PRAL-1cB.jpg
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Brian
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Old 26th June 2006, 03:35 PM   #5
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Join Date: Sep 2003
Location: Paris - France
jarthel,


>> ~So the chassis cover is shaped like a "U".

In your case all components and circuit board should be mounted
on or under the "chassis cover U"

Holes for the tubes, and PCb installed on supports all attached to top plate ;
in this case the PCb will be in the right way, with tube supports upward just under
the holes

The bottom plate should serve to close the chassis only, but no
components attached on it.

Take a look at one of these:
http://www.jogis-roehrenbude.de/Lese...schreibung.htm
http://www.tubecad.com/2006/05/blog0063.htm

Regards.

Alain.
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Old 27th June 2006, 04:41 PM   #6
jayme is offline jayme  United States
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Join Date: Sep 2005
I have a similar chassis. I have decided that the best approach is to cut out most of the bottom (leaving a small lip around all of the bottom edges.

Then, attach the top-sides to the bottom-front-back. Thus, you have a rigid chassis that you can flip upside down when you are working.

Now, you can attach all components to the underside of the top, or even mount some directly exposed on top.

When I am done, I'll attach a mesh screen for the bottom to cover the hole.

The best part about this is that airflow is increased...

The difficult part (for me) is cutting thru 16 gauge steel...
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