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Old 3rd February 2005, 10:41 PM   #1
pjpoes is offline pjpoes  United States
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Default use of wood as enclosure

Ok I have read about how mounting your pcb's to certain kinds of wood coated in certain kinds of resins sounds better than your typical metal enclosure. Im curious about this, and if anyone has any experience.

First some questions, what kind of woods are usually used for this? What kind of Resins or finishes are used. I read that they used natural resin coatings made from wood resins. They also mentioned that this stuff was the same as is used on violins and such. Where can I get such resin finishes, or do I need to make this stuff myself?

Now finally, for my specific application. I just finished two different headphone amps, and I want to try mounting them into a wooden enclosure, like Grado does. Both are designed for portable use and run on two 9v batteries. One is commonly put into mint tins, the other is really too large, but still pretty portable. Both are biased into class A operation, and sound quite sweet, I must say. As far as what I can do on my own, I have access to a wood shop with a router, saws, etc. However we dont have any real unusual tools. I was thinking I could get a block of something, say mahogany, route out the inside of the block, and mount it that way. However, this isnt the most precise, and I dont expect the results to be great. Anyone have any ideas that might make this better. Another Idea I had was a clam shell sort of case, routing out the inside of two small blocks, and then screwing them together, making it a complete case.

Thanks for any ideas or clues here. Im probably being silly to put such amps into a wooden enclosure, but Im looking for something different. Thanks for any help.
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Old 4th February 2005, 12:33 AM   #2
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Try a Google search for tonewoods. I'm hard pressed to state what a reason might be for a circuit to sound 'better' mounted to a certain wood, but I do it myself.

(My reason is more pragmatic: I have a lot of woodworking tools, and next to no metalworking tools.)
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Old 4th February 2005, 01:12 AM   #3
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Two things to bear in mind with wood enclosures. Heat and EM screening. Wood can't really cope with either of those things on it's own. But if you can work round those problems, then the world is your oyster, and there is nothing better than a fine piece of wood. As for exotic finishes that change the sound, I am sceptical, but hey, if you have the money to spare, give it a go.

As for techniques, for the small amount of wood you would be using, you can afford to make a few trials, and see what works best.
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Old 4th February 2005, 02:02 AM   #4
eLarson is offline eLarson  United States
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Here's a link to get you started:
http://www.pantheonguitars.com/tonewoods.htm

As Pink mentioned, there is no screening of interfering signals whatsoever from wood. If you are thinking of a high gain circuit, consider some sort of copper to shield you from EMI, and then keep it a fair distance away from the magnetic field of the transformer.
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Old 4th February 2005, 02:05 AM   #5
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I just heard about this "wood affecting the sound" business. I have to say that it is one of the single most rediculous things I have ever heard. Followed (closely) by hi-fi wall outlets.

I am making a nice walnut fron for my new amp, but it will be in a sturdy steel chassis.

BTW: most woodworking tools work very well with Aluminum.
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Old 4th February 2005, 02:28 AM   #6
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Old 5th February 2005, 12:16 AM   #7
pjpoes is offline pjpoes  United States
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I have to be honost, I am extremely skeptical of how wood could effect the sound, I could only give wild guesses. I first became intrested when I read the C37 laquer deal. I read all these people trying it and using it, thinking, thats insane, how could it possibly effect sound, even slightly. I have no idea if it does, Im not about to spend that kind of money on a little tincture of the stuff. From there I found a sight where I guy built a gainclone like amp, mounted it to a piece of wood coated in natural resin based laquer, and found the sound of it to be better. He sell's these as completed amps, and listed a studio and Cabasse speakers as two companies who are clients of his for these amps.

I have been building most of my amps onto wooden bases for the same reason another member mentioned, I dont have many power tools to use to cut aluminum. I also have lots of wood around, and not much metal. I was always pleasantly suprised by the sound of these cheasy little amp's, but at the same time, I never would have associated mounting them onto wood as having anything to do with it. I have a GC in the works along with these two headphone amps, and I wanted something attractive to mount them in. I had read about the tone of wood with electronics, and thought I would give it a shot. I have some Koa, Bubinga, and Curly maple blocks sitting around, which are too small for anything else, that might work perfectly for these projects. I was just curious if anyone had more experience with it here. Also, I know that wood offers no RFI or EMI shielding of any sort. Its funny too, cuz I use shielded wire inside my amps often, yet will have them mounted in such a way that they are completely unsheilded. Anyway, I seem to live in an area that is without radiation, as I hardly ever pick anything up. At worst I sometimes pick up trucker radio waves, and I have to say, mostly on cheaper components like my computer speakers, and no so much on my main stereo.

On this site, which I have refrenced a few times, the guy mentions his experience with wood effecting tone. He mentiones its effect it has on guitars. This is an old trick for anyone who has played guitar. Though I hate the idea of stripping the finish from a guitar usually, specially cuz most people dont refinish them propperly, I have done it to three of my guitars. I have a Gibson ES-135, a Chandler Telepathic 57', and a Martin acoustic. All of these came with standard laguer finishes, and all of them I became tired of. I wore the finish off the neck of my Marten and Chandler, so I decided that I didnt like the slick finish anyway. I sanded off the finish on both guitars and then cleaned the wood best I could. I then refinished it with a violin laquer I got from a local violin maker. He makes it himself, and is unfortunatly now gone, so I have no more source for the stuff. I later cracked the finish on the Gibson at a gig and had the finish taken off by gibson. I then refinished that one with the same laquer. I have to say, every single guitar now sounds warmer, richer, and has longer sustain. To me, this is sensible given that we are talking about an instrument in which the actual wood of the instrument plays a role in the sound, by design. We also have comparably larger vibrations because of the strings, which could resonate wood more effectivly. By that same token, Im guessing, that the oscillations and slight minute vibrations which take place in a cuircit could potentially transfer into and resonate the metal enclosure. Same could happen in revers, enviromental vibrations return back through the enclosure into the board. People do use spikes and cones, and hear differences. They feel that thicker stronger, better dampened cases effect sound. They also feel that adding dampening material can effect sound. By this same token, I suppose that you could simply embrace these resonations and use ones that are more musical, such as those in wood. Like I said, this is simply a guess as to why it might effect the sound for the better, or at all.
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Old 5th February 2005, 01:35 AM   #8
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Try this little test with one of your amps:

Play some very sublte music, where you can hear every detail. While it is playing, have someone tap on the amplifier, gently but firmly, so you don;t hear the impact directly. Most importantly, do this while you cannot see them. Perhaps put the amp in a different room than your speakers.

Can you hear the tapping sound coming through your speakers?

Perhaps you could with a tube amp, as they are very suseptible to "microphonics" where the internal structure of the tube vibrates, but there is no such free-standing structure in a transistor. With tubes, you want to keep the structure from resonating at all, not enhance the vibration. Much like a speaker cabinet, you want it to be dead to vibration (high-mass, lower resonant frequency). I think if anything you would want the same in an amplifier suseptable to vibration.

Comapring it to a guitar is liek apples and oranges. A guitar body is supposed to vibrate. That IS the amplifier for a guitar. (I must say, it was nice reading your post. Very well wriiten. Made me think about why I love woodworking.)

Let us know what you find.

My point it, if large scale vibration doesn't impact the sound, then these chassis resonances probably won't either. Also, I think if solid-state amps were so suseptible to vibration, pro-PA amps would not last nearly as long as they do.

Just my 2cents (why don;t keyboards have cent symbols on them?)

-b
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Old 5th February 2005, 04:43 PM   #9
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Like I had said before in my post, it was a wild guess. I do not believe that it could have that effect, but I figured I would make a guess, based on what I had been reading. I do agree though, wood working is something special. There is a gross pleasure I take in watching a piece of raw lumber become a thing of beuty as you sand and polish the piece, apply coat after coat of finish. Not to sound too strange, but I really do find something sexy about a fine piece of wood propperly finished.

I figure at this point, I will give it a shot, if I hear a difference, cool, if not, so I have a pretty little amp enclosure. So I found a few things out about this. First thing I found was that Stradaverei(Sp?) were not finished as his said but rather finished with something known as a French Polish. After the fall of the French Polish and oil finishes people began using nitrocellulose, which is the natural wood fiber finish. However they would finish it off with shellac I guess. Today instruments are finished with either a nitrocellulose or water based varnish. Unless of course they are one of the many instruments finished in a cheap finish, inwhich case its probably polymer based. I am buying a quart of the french polish stuff for 12 bucks. If nothing else, I will have a nice finish to use on stuff.
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Old 5th February 2005, 04:59 PM   #10
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I stepped up from regular cinch plugs and chassis parts to versions with Teflon isolation, stepped up from regular cable to ones with Teflon.
After that i tried to find a way of attaching copper clad to Teflon boards, at the time that Teflon pcb's were solely used in the aerospace industry.
(think of how to have something stick on a material used for non-stick pots and pans).
I grew up with rolls of Teflon foil in DuPont boxes in my dads plant, it did not surprise me that Teflon is still adding advantages in many fields.

Now, Teflon isolated plugs, cables and pcb boards are standard, regarded as having a positive influence on sound.
Microphonics influence sound, several amplifiers have been built with pcb's mounted with dampeners.
For tubes different material damping slide-over rings are sold, even in wood, with prooven results.
Some have built amplifiers using wooden boards, with wire wrap or direct soldering techniques.
There is one famous guy in Germany who has been building turntable arms of wood for a long time.

Given that wood has been the best acoustic material for a very long time, who is to say it may not have a positive effect on sound when used for amplifier casings.
Like with a lot of other applications it may be that a combination of various materials, including wood, may lead to better results.
I am still often amazed about the physical properties of wood.
Much of the woodwork in my 1935 house that i am renovating is still as good as new, some wooden furniture have survived ages. I built a sailing boat in wood with fiber roving reinforced epoxy lamination. It is an easy building material, longlasting, light and outperforms most others.
With violin building the kind of lacquer on the violin has a tremendous effect on its sonic signature, i do not recall anyone ever examining effect of lacquers or resins on amplifier sound.
Known however are the fools who wrote on CD's with different marker pens supposing it influenced CD sound.
Turned out they were not such fools. These marker pens have been professionally marketed now for years, even CD washers.
I am sure not going to spend my time coloring CD's but i respect the ones that do.

On top of that wood looks good, i was impressed by Italian wooden amplifier design in the 90's.
I do not agree that microphonics only apply to tube amplifiers, it has an effect on solid state too, and has been proven.
The effect is a lot less, and each needs to decide whether its worth the bother.

I dont bother, for the same reason that i do not spend time and money on cable stuff.
But i am a metal guy, i love to build heavy casings that shine and look like Fort Knox.
Visually the things you can do with wood are unlimited compared to metal. Making a casing out of a solid piece of wood with routed openings for the right kind of alloy heatsinks sounds great.
For the kind of wood you might check with wood types used for audio stands, a lot of research has gone into that.
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