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wood vs metal

post #1 of 11
Thread Starter 

does the material that the enclosure of a diy amp is made up of matter? i see lots of good looking metal amps, but i really prefer wood. is there a reason not to encase in wood?

post #2 of 11

Price, weight, thermal dissipation, fireproof concerns, manufacturing proccess, etc. Do you need a better answer?


Edited by squallkiercosa - 10/31/13 at 2:29pm
post #3 of 11
Thread Starter 
Quote:
Originally Posted by squallkiercosa View Post
 

Price, weight, termal dissipation, fireproof concerns, manufacturing proccess, etc. Do you need more answer?

well weight isnt much of an issue, the rest i would like elaboration on....

post #4 of 11

Thermal (heat) dissipation: Power dissipation performance must be well understood to ensure that any given device is operated within its defined temperature limits. When a device is running, it consumes electrical energy that is transformed into heat. Most of the heat is typically generated by switching devices like MOSFETs, ICs, etc. As power consumption increases, components like linear voltage regulators can heat up during normal operation. Some heat is okay, however when things get too hot, the performance of the linear regulator suffers.

 

The ambient air temperature TA for cooling the devices depends on the operating environment in which the component is expected to be used. Typically, it ranges from 35°C to 45°C, if the external airflow through a fan is used and from 50°C to 60°C, if the component is enclosed. The interface resistance θCS depends mainly on the interface material and its thickness and also on the surface finish, flatness, applied mounting pressure, and contact area. Reliable data can be obtained directly from material manufacturers. With all the parameters defined, θSA becomes the required maximum thermal resistance of a heatsink for the application. In other words, the thermal resistance value of a chosen heatsink for the application has to be equal to or less than the previous θSA value for the junction temperature to be maintained at or below that specified .


The following are the various important parameters in selecting a heatsink.
1. Thermal resistance θSA
2. Airflow
3. Volumetric resistance
4. Fin density
5. Fin spacing
6. Width
7. Length


The thermal resistance is one parameter that changes dynamically depending on the airflow available. Airflow is typically measured in linear feet per minute (LFM) or CFM (cubic feet per minute). LFM is a measure of velocity, whereas CFM is a measure of volume. Typically, fan manufacturers use CFM because fans are rated according to the quantity of air it can move. Velocity (speed) is more meaningful for heat removal at the board level, which is why the derating curves provided by most power converter manufacturers use this. Typically, airflow is either classified as natural or forced convection. Natural convection is a condition with no external induced flow and heat transfer depends on the air surrounding the heatsink. The effect of radiation heat transfer is very important in natural convection, as it can be responsible for approximately 25% of the total heat dissipation. Unless the component is facing a hotter surface nearby, it is imperative to have the heatsink surfaces painted to enhance radiation. Forced convection occurs when the flow of air is induced by mechanical means, usually a fan or blower. 


Edited by squallkiercosa - 10/31/13 at 2:12pm
post #5 of 11

Fire retardant material: it's not a question of whether a fire/heat can damage a structure, but a question of when. It simply takes longer to affect fire-resistant materials. Metals like aluminum or steel aren't combustible instead, they tend to buckle under intense heat. 

post #6 of 11

Sustainability: This debate over which one is better, wood or metal has been going on for quite some time, with no clear winner.

 

Wood is a renewable resource: it is recyclable, biodegradable and less expensive than steel. It has a lower embodied energy than steel. In this definition from Wikipedia - embodied energy is the sum of all the energy required to produce goods or services, considered as if that energy was incorporated or 'embodied' in the product itself. Building sustainably requires being just as diligent in picking the products while considering the impact on the environment in making the product. Both the steel and wood industries have had environmental challenges, e.g.- the clear cutting of forests and strip mining iron. Both industries have made improvements in helping the environment recover. The wood industry is adopting the best practice standards developed through the Forest Stewardship Council. Around the world, steel production is changing to decrease the amount of CO2 emitted, energy used to produce and replanting areas mined.

 

Wood is not a thermal conductor like steel, wood acts as a thermal bridge which means exterior and interior cladding can go up right against the wood with out any insulation between. 

Wood absorbs moisture promoting mold growth and dry rot when leaks occur. it burns at low temperatures. While wood can be recycled, it is limited in its reuse for structural uses.

The cost of steel runs about 3x the cost of wood for the same size member.

 

While embodied energy studies the making of a product, I can’t seem to find the durability factor online.  Some might disagree, to me the more important factor to the environment is how long something lasts before you need to address replacement or repair.

post #7 of 11
Quote:
Originally Posted by squallkiercosa View Post

Metals like aluminum or steel aren't combustible

This isn't true, as you will discover if you connect a wisp of steel wool across the terminals of a battery. Aluminium too will catch fire in a regular atmosphere if heated to a sufficiently high temperature, such as when a warship is struck by a missile.

Of course, this is just nitpicking, as neither of these materials will catch fire under normal conditions... ...you probably know this already.

w
post #8 of 11

Thermal dissipation aside i would add EMI suppression (Metal box works, wooden box dosent), and maybe possibly acoustic damping would be better with wood. I.e. less vibration transmitted to internal components, probably more critical with tube based amplifiers.

post #9 of 11

Well I got a portable amp with a full aluminum casing and I'll have to say that without a dedicated built EMI shield, they still get a bunch of interference... which makes it only occasionally used on the go.

post #10 of 11
Quote:
Originally Posted by kalbee View Post
 

Well I got a portable amp with a full aluminum casing and I'll have to say that without a dedicated built EMI shield, they still get a bunch of interference... which makes it only occasionally used on the go.


More likely one of those interference antennas attached to the casing, allowed the camel into the tent. Once the interference is inside the chassis, it's a lot harder to deal with.

 

Interconnect cables, speaker cables, headphone cables, power cables and control cables all can act as interference antennas.  It takes a skilled designer to not let them into the casing.


Edited by Speedskater - 11/4/13 at 6:24am
post #11 of 11
Quote:
Originally Posted by Speedskater View Post


More likely one of those interference antennas attached to the casing, allowed the camel into the tent. Once the interference is inside the chassis, it's a lot harder to deal with.

Interconnect cables, speaker cables, headphone cables, power cables and control cables all can act as interference antennas.  It takes a skilled designer to not let them into the casing.
Continuing on I suppose batteries are a big offender too. There's totally no interference when the batteries are taken out!
...
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