Compact All-In-One Chassis Design with good ventilation. And low noise, Not a Schemat - diyAudio
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Old 27th February 2004, 10:17 AM   #1
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Default Compact All-In-One Chassis Design with good ventilation. And low noise, Not a Schemat

This is a rather quick sketch of an all-steel design with single-90mm fan forced ventilation and vents upon the underside and back of the chassis.

Paint is my friend :P

Anyway thought I would spread the idea...Hopefully I can use it or someone else can use the layout.

I have thought of rebirthing the old idea with valve amp chassis design where the valves are placed horizontally for both better heat dissipation and compactness as I have placed the KT90's on the bottom directly underneath the 6SN7's and faced them 'towards' each other..

The 6 large green boxes at the front of preamp are PIO.. and all transformers are Torodial Plitron...

All those wittle yellow pixellated resistors are to accomodate components...both resistors on blocks and capacitors.

This is not usually my idea of a schematic :P It's a block diagram (stretching it)...

With a heap of steel and a couple of KT90's this chassis could very well work...

I was hoping to see if this design would work against or for noise in both preamp and amp sections.

The sacrifice for a compact design is that the power supply cannot have a large base, therefore electrolytes must be used...

Cheers.
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Old 27th February 2004, 09:32 PM   #2
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Hi there...that picture....looks like the map of my local bus station......am working on it !

Hint. Keep electrolytics away from any heat areas, otherwise they will have a short life.

rich
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Old 28th February 2004, 04:51 AM   #3
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Default Mind the stupidity of the sketch :P

VERY rough sketch over what I think will be the Airflow
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Old 28th February 2004, 05:14 PM   #4
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Fifth revision of the chassis sketch..

I have added a total of 6 electrolytic (got it right now-was tired :P)
caps in series for double volt ratings and a pair of chokes.

Furthered the distance from each Transformer and as the input
stage is furthest away from the power supply while being in the
same chassis I am quite happy to go ahead with a more specific &
accurate (by a mile) paper sketch to stamp out a steel base
for this revision :P

I have changed my mind about the all-steel chassis instead having
an aluminium case ontop of a steel one-piece base with all holes
drilled, so I don't really need to worry about magnetic interaction
(too much).

14th revision of the power supply :P

It's quite a simple power supply when you think about it.

C1 is two 100uF Jensens in series, so is C2..

C3 however is a single pair of 220uF Jensens in series to make
110uF.

All caps are 'rated' at 1200v... Should be enough :P

Here is the PSUD simulation.

Cheers. I think this will be my last post upon this matter.
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Old 28th February 2004, 05:17 PM   #5
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Chassis (HAH)
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Old 28th February 2004, 10:56 PM   #6
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Hint:

Design the electronics of the amplifier before you start worrying about the layout.

I suggest that you re-think mounting the tubes in the horizontal plane.
While this improves the cooling (on one side of the tube only), it puts great stress on the internal structure.
There is a reason why nearly all amplifier designs have the tubes mounted in the vertical plane with their bases down. Mounted that way, the heating of the glass envelope and the internal elements is symmetrical.
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Old 29th February 2004, 02:24 AM   #7
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Which is exactly why I chose KT90's instead of KT88's....

The KT90's are a very long and cool operating tube from my understandings when placed at KT88 limits...

But even so, I can get plenty of power 50watts, out of a pair..

So that's 100-130 watts dissipation between the two... big deal.

Please tell me otherwise if i'm wrong

I could always place the 6SN7's at a diagonal position so they're also further from the surface of the KT90's...

I understand what you say, the internal structure of the KT90's would become heat stressed as all the heat moves to one side of the tube, the one facing up... which could turn a plate or grid red.

I'll give the 6SN7's placement another think...

Thanks for the heads up, that's what I'm here for.

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Old 29th February 2004, 02:44 AM   #8
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Hi,

Quote:
The KT90's are a very long and cool operating tube from my understandings when placed at KT88 limits...
At the end of the day the dissipated heat will still be about the same, possibly even more.

The length of the KT90s is certainly not an advantage either when mounted horizontally putting more stress on the bases too.

I'm not saying you can't operate these tubes safely this way, just that the reasoning behind it seems flawed to me.

If you want to run them cooler, why not build in a fan at the bottom blowing air against the bulbs?
Any fan from a broken computer PSU would do nicely and if that's too noisey, add a rheostat to set the rotational speed.

Just a thought...

Cheers,
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Old 29th February 2004, 02:51 AM   #9
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Quote:
Any fan from a broken computer PSU would do nicely and if that's too noisey, add a rheostat too set the rotational speed.
or even easier run the 12vdc fan on 6vdc. That makes it real quiet and it still moves air :-)
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Old 29th February 2004, 02:55 AM   #10
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Yeah it looks like it I may have to have two fans...

SO another 90mm, that brings it up to a total of 30dB or thereabouts.

The fans that I have, have a rotational speed (aka RPM) of 2400...

So I don't think I'll see much noise as it is, it is a completely silent fan at 12v already...

Of course once I put a dust/hairball grill on infront the noise is going to go, up up up and away!

Depends also upon the distance between the fan and the grill, Maybe I can make up a 'tunnel' bracket so I can space it a tiny bit between the opening of the chassis, to further reduce noise.

Thanks guys

:P
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