JT:
>Is wood warping not a problem?<
It can be a serious problem, unless your design takes the warpage into account. This is why in my previous post, I suggested that you _don't_ use wood as the primary structural members in your chassis design, and you _do_ use some sort of floating mount system that allows the wood parts and non-wood parts of your chassis to expand and contract at their own natural rates, without unduly interfering with each other.
>Especially with hot running amps like zens and alephs the large temperature variations can't be good.<
Even a preamp will run into problems with a poorly-designed wooden cabinet, if its operating temperatures are high enough. The chassis of my top-line preamp is a solid machined aluminum billet with integral heatsinking, and the general chassis temperatures range from 45 to 50 degrees centigrade, depending on the time of year.
>Anybody have this problem?<
Over the past 14~15 years, we've shipped literally hundreds of amplifiers with wooden cabinets. With the earlier designs, when I wasn't sufficiently aware of the structural issues with wood, I had to replace a number of cabinets which incurred warpage, cracking split joints etc., and the ultimate reason was inexperience and a lack of thought during the design phase (aggravated by the high levels of heat and humidity during Japanese summers).
My current cabinet designs use only well-seasoned woods, all of the mounting reference points and structural stresses are dealt with by the metal chassis and not the wood, and the mounting of the wood to the metal is accomplished by a floating system which allows a fairly wide independence of movement between wood and metal. To date, none of these newer cabinet designs have had any warpage problems.
hth, jonathan carr
>Is wood warping not a problem?<
It can be a serious problem, unless your design takes the warpage into account. This is why in my previous post, I suggested that you _don't_ use wood as the primary structural members in your chassis design, and you _do_ use some sort of floating mount system that allows the wood parts and non-wood parts of your chassis to expand and contract at their own natural rates, without unduly interfering with each other.
>Especially with hot running amps like zens and alephs the large temperature variations can't be good.<
Even a preamp will run into problems with a poorly-designed wooden cabinet, if its operating temperatures are high enough. The chassis of my top-line preamp is a solid machined aluminum billet with integral heatsinking, and the general chassis temperatures range from 45 to 50 degrees centigrade, depending on the time of year.
>Anybody have this problem?<
Over the past 14~15 years, we've shipped literally hundreds of amplifiers with wooden cabinets. With the earlier designs, when I wasn't sufficiently aware of the structural issues with wood, I had to replace a number of cabinets which incurred warpage, cracking split joints etc., and the ultimate reason was inexperience and a lack of thought during the design phase (aggravated by the high levels of heat and humidity during Japanese summers).
My current cabinet designs use only well-seasoned woods, all of the mounting reference points and structural stresses are dealt with by the metal chassis and not the wood, and the mounting of the wood to the metal is accomplished by a floating system which allows a fairly wide independence of movement between wood and metal. To date, none of these newer cabinet designs have had any warpage problems.
hth, jonathan carr
Hallo Vince,
sometimes i forgot to switch them out and so
they heatup all the night maybe for 24 hours.
The wood isn`t really hot next day.
In my case the wood isn`t in direct contact to the heatsinks. I put some teflon rings between heatsink and aluprofil. Also there is a airgap
between sink and wood(5mm).
Wood can handle easily 200gradC.
You should oil or paint inside also to close the structur.
Andreas
sometimes i forgot to switch them out and so
they heatup all the night maybe for 24 hours.
The wood isn`t really hot next day.
In my case the wood isn`t in direct contact to the heatsinks. I put some teflon rings between heatsink and aluprofil. Also there is a airgap
between sink and wood(5mm).
Wood can handle easily 200gradC.
You should oil or paint inside also to close the structur.
Andreas
shielding
if you're worried about EMI/RFI, just line the inside with TI-Shield or copper sheeting (available at a hardware store probably). i've heard TI-Shield is especially good. the heat dissipation and other physical properties of wood are a legitimate concern however, though lining with metal helps in this regard. i would probably not use wood for any component that tends to heat up a lot. i'm thinking of pouring some concrete into the base of my CD player that i'm modifying though.
if you're worried about EMI/RFI, just line the inside with TI-Shield or copper sheeting (available at a hardware store probably). i've heard TI-Shield is especially good. the heat dissipation and other physical properties of wood are a legitimate concern however, though lining with metal helps in this regard. i would probably not use wood for any component that tends to heat up a lot. i'm thinking of pouring some concrete into the base of my CD player that i'm modifying though.
http://www.mgchemicals.com/products/841.htmlgeoffwa said:
I haven't used this myself, but it is probably better than regular nickel paint.(which I've used to shield guitars)
Thomas B said:
At the frequencies you're dealing with (0-20KHz for arguments sake), it's not going to make any appreciable difference.
Exceptional circumstances aside (eg. you have something generating tons of RF radiating very near to the device),
there's going to be more "noise" from the power supply in the amp than from anywhere immediately outside.
Metal Chassis
I've had the opportunity to look into the chassis of a very high end preamp and found the chassis made from 2mm brass plates. To damp vibrations, the manufacurer stuck sound absorbent material sheets on the side chassis walls. On the internal metal tray supporting the pcbs, holes were drilled at certain locations and jammed with rubber pieces that looked like bottle stoppers. Some of the electrolytic smoothing and bypass caps were also wrapped with adhesive copper foil which I believe would help in RF shielding and some vibration damping as well.
Anybody tried this
ckt
I've had the opportunity to look into the chassis of a very high end preamp and found the chassis made from 2mm brass plates. To damp vibrations, the manufacurer stuck sound absorbent material sheets on the side chassis walls. On the internal metal tray supporting the pcbs, holes were drilled at certain locations and jammed with rubber pieces that looked like bottle stoppers. Some of the electrolytic smoothing and bypass caps were also wrapped with adhesive copper foil which I believe would help in RF shielding and some vibration damping as well.
Anybody tried this
ckt
wood use...
I'm building into a larger chassis right now, I hope to learn how much placing and spacing are critical paramaters for loading without cross-talking.
And seriously wondering what benefits might outweigh 'a proposed advantage' of dispensing with eddy currents that most transformers form in metal amp chassis, by simply eliminating [or isolating/grounding] metals which introduce sensitive inputs to signals sent from power transformers.
It has been said and done...that power supply in a separate chassis simplifies [always nice in a world of confusing interference] the elimination of hum.
Rolling, stamping and bending is quick and easy with the right materials and tools...this is probably why amp frames start with a sheets of metal that can quickly be made into chassis with necessary shapes and too often used...convenient ground everywhere. The only real problem with sheet metal chassis that I see is the eddy currents and ground loops. Clever [or star] grounding takes care of that issue though.
stuff to consider when using wood..screening or metal plates might for ground shielding [ground planes or local enclosure, reduced ignition chances with fire resistant coating [heat paint].
A very interesting topic to try to contribute to, many of the results on which to form an opinion seem a bit vague or wide ranging, fear of fire is likely a good cause for the metal convention.
When building countless stompboxes, I would regularly insulate any metals, preferring to start with wood boxes after a while, I'm pretty sure this helped contain bits of magic blue smoke [prevent shorts].
Wood grain is a beautiful color, machining with pliers anda hammer s'ugly.
With a bit of 'L-Beam' metal to form crossbeams, tube sockets and anything else can be mounted quickly and securely enough that tubes can be serviced, offers great ventilation too.
I'm building into a larger chassis right now, I hope to learn how much placing and spacing are critical paramaters for loading without cross-talking.
And seriously wondering what benefits might outweigh 'a proposed advantage' of dispensing with eddy currents that most transformers form in metal amp chassis, by simply eliminating [or isolating/grounding] metals which introduce sensitive inputs to signals sent from power transformers.
It has been said and done...that power supply in a separate chassis simplifies [always nice in a world of confusing interference] the elimination of hum.
Rolling, stamping and bending is quick and easy with the right materials and tools...this is probably why amp frames start with a sheets of metal that can quickly be made into chassis with necessary shapes and too often used...convenient ground everywhere. The only real problem with sheet metal chassis that I see is the eddy currents and ground loops. Clever [or star] grounding takes care of that issue though.
stuff to consider when using wood..screening or metal plates might for ground shielding [ground planes or local enclosure
A very interesting topic to try to contribute to, many of the results on which to form an opinion seem a bit vague or wide ranging, fear of fire is likely a good cause for the metal convention.
When building countless stompboxes, I would regularly insulate any metals, preferring to start with wood boxes after a while, I'm pretty sure this helped contain bits of magic blue smoke [prevent shorts].
Wood grain is a beautiful color, machining with pliers anda hammer s'ugly.
With a bit of 'L-Beam' metal to form crossbeams, tube sockets and anything else can be mounted quickly and securely enough that tubes can be serviced, offers great ventilation too.
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