chassis material considerations

Keyoke · 7th December 2006, 12:58 AM

So I've built the PCBs, and tested the thing with some cheap ratshack fullrange drivers, and everything is working perfectly.

Now it's time to build the enclosure.

How big of a deal is a metal case v.s. one built out of wood when it comes to EMI and grounding issues? Is it better to have an alu bottom to place the boards on, and just ground to the chassis, or does it matter?

What about on the back panel, where the RCA inputs are panel mounted? Will the lack of a 'groundable' material cause interference or other problems?

Since I'm using an LM3875 based design, and simple non-switching PSU, EMI should be _less_ than say.. oh a class D, right? I mean.. I shouldn't have to worry too much about placing the amp too close to say, a AM radio tuner (not that I listen to AM radio all that much...)

v-bro · 7th December 2006, 01:35 AM

A well designed PCB should operate fine in a wooden enclosure, it's you who should place ground leads 'near' the signal leads and you'll still be fine with a wooden enclosure....

I prefer aluminium becase it's easy to manufacture for me, and brings a larger ground plane (I DO like to use class D).

Some audiophiles place wood in their book of favorables.... for many 'reasons'....

I'd say if you like the looks or find it nicer to handle... go for wood...

DJ Exprice · 7th December 2006, 01:42 AM

I would say that you can do both! Wood and metal. I tried it and honestly mine came out like a piece of crapola, but I've seen what it can be and I was speechless!

Try that.

v-bro · 7th December 2006, 02:00 AM

These you can build with a workmate and some metal or wooden bars and beams....

DJ Exprice · 7th December 2006, 05:21 AM

Quote:

Originally posted by v-bro
These you can build with a workmate and some metal or wooden bars and beams....

Those are NICE!

Nordic · 7th December 2006, 06:30 AM

Google is your friend.

Now is time for my flame bath...

Take the very same amp build it into a metal box, give it a good listen, then build it into a wooden box. Do the same.

I am willing to bet you almost anything (its realy a shame I'm a poor man) the wood enclosed amp, will knock the socks off your metal case.

I have been reading about this phenomena for a while now, and have been doing some tests of my own. (doesn't anyone want to die and leave me a scope in their will?) I am pretty sure the changes shoud show on a scope.. thats how diffirent the sound is.

The very materials you use will affect the sound. Get rid of plastics and steel, when you need standoffs, stay with brass, aluminium or wood.

http://www.soundstage.com/maxdb/maxdb111998.htm

I linked a nice article by Doug Blackburn, and will try to find some of those I read in the past as this is a topic I was getting the guts together to start.

I_Forgot · 7th December 2006, 09:08 PM

Quote:

Originally posted by Nordic
Google is your friend.

Now is time for my flame bath...

Take the very same amp build it into a metal box, give it a good listen, then build it into a wooden box. Do the same.

I am willing to bet you almost anything (its realy a shame I'm a poor man) the wood enclosed amp, will knock the socks off your metal case.

I was going to say something but I think I'd rather go take a nap.

I_F

Leolabs · 8th December 2006, 02:07 AM

Copper or Aluminium-my favourite but hard to obtain and expensive in my area.

Steel or Zinc-popular but not solid enough.

Wood-A piece of art,require much effort on designing the PCBs and wirings.

Geoff H · 9th December 2006, 08:59 AM

I have just scanned over that link to the sound stage article, expecting to find a suggestion that electronics are subject to micrphonics. Some are, ie the good old EF86.

I have never seen a reference to solid state micrphonics, except in the case of dry joints, or a faulty part. Now I accept that could be due to my ignorance, or lack of knowledge.

That article refers to mechanical or acustical resonance as if it were electronic.

I'll stick by my time old method of sturdily mounting PCBs on aluminium, and to keep out stay fields, shield the case in some manner. If you choose timber, line it with foil.

That article, is to me, proof you can not believe everything you read. It's your choice to go along with it, or dissagree with it, but please think about it.

Geoff.

PS I-forgot, you said in your footer, by Charles Darwin.

gbyleveldt · 9th December 2006, 01:28 PM

Quote:

Originally posted by Nordic

Take the very same amp build it into a metal box, give it a good listen, then build it into a wooden box. Do the same.

I am willing to bet you almost anything (its realy a shame I'm a poor man) the wood enclosed amp, will knock the socks off your metal case.

*SIGH*

7th December 2006, 12:58 AM	#1
Keyoke diyAudio Member Join Date: Jan 2004 Location: Virginia	chassis material considerations So I've built the PCBs, and tested the thing with some cheap ratshack fullrange drivers, and everything is working perfectly. Now it's time to build the enclosure. How big of a deal is a metal case v.s. one built out of wood when it comes to EMI and grounding issues? Is it better to have an alu bottom to place the boards on, and just ground to the chassis, or does it matter? What about on the back panel, where the RCA inputs are panel mounted? Will the lack of a 'groundable' material cause interference or other problems? Since I'm using an LM3875 based design, and simple non-switching PSU, EMI should be _less_ than say.. oh a class D, right? I mean.. I shouldn't have to worry too much about placing the amp too close to say, a AM radio tuner (not that I listen to AM radio all that much...)

7th December 2006, 01:35 AM	#2
v-bro diyAudio Member Join Date: May 2006	A well designed PCB should operate fine in a wooden enclosure, it's you who should place ground leads 'near' the signal leads and you'll still be fine with a wooden enclosure.... I prefer aluminium becase it's easy to manufacture for me, and brings a larger ground plane (I DO like to use class D). Some audiophiles place wood in their book of favorables.... for many 'reasons'.... I'd say if you like the looks or find it nicer to handle... go for wood... __________________ Max. cone displacement can be several foot on any speaker!Too bad it can be done only once......

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7th December 2006, 01:42 AM	#3
DJ Exprice diyAudio Member Join Date: Mar 2006 Location: San Francisco, California	I would say that you can do both! Wood and metal. I tried it and honestly mine came out like a piece of crapola, but I've seen what it can be and I was speechless! Try that.

7th December 2006, 06:30 AM	#6
Nordic diyAudio Member Join Date: Sep 2005	Google is your friend. Now is time for my flame bath... Take the very same amp build it into a metal box, give it a good listen, then build it into a wooden box. Do the same. I am willing to bet you almost anything (its realy a shame I'm a poor man) the wood enclosed amp, will knock the socks off your metal case. I have been reading about this phenomena for a while now, and have been doing some tests of my own. (doesn't anyone want to die and leave me a scope in their will?) I am pretty sure the changes shoud show on a scope.. thats how diffirent the sound is. The very materials you use will affect the sound. Get rid of plastics and steel, when you need standoffs, stay with brass, aluminium or wood. http://www.soundstage.com/maxdb/maxdb111998.htm I linked a nice article by Doug Blackburn, and will try to find some of those I read in the past as this is a topic I was getting the guts together to start.

8th December 2006, 02:07 AM	#8
Leolabs diyAudio Member Join Date: Dec 2004 Location: Bukit Mertajam	Copper or Aluminium-my favourite but hard to obtain and expensive in my area. Steel or Zinc-popular but not solid enough. Wood-A piece of art,require much effort on designing the PCBs and wirings.

9th December 2006, 08:59 AM	#9
Geoff H diyAudio Member Join Date: Oct 2006	I have just scanned over that link to the sound stage article, expecting to find a suggestion that electronics are subject to micrphonics. Some are, ie the good old EF86. I have never seen a reference to solid state micrphonics, except in the case of dry joints, or a faulty part. Now I accept that could be due to my ignorance, or lack of knowledge. That article refers to mechanical or acustical resonance as if it were electronic. I'll stick by my time old method of sturdily mounting PCBs on aluminium, and to keep out stay fields, shield the case in some manner. If you choose timber, line it with foil. That article, is to me, proof you can not believe everything you read. It's your choice to go along with it, or dissagree with it, but please think about it. Geoff. PS I-forgot, you said in your footer, by Charles Darwin.

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