[Jens]

The chassis is one part that often forces a compromise for practical reasons, especially with conventional power supplies requiring large transformers.

Much as I like the idea of having a wood enclosure rather than a metal one, I worry about the lack of RFI shielding. 

So I think if you're gonna do this, you need to do what I think it was Jens who did with his GK-1 ... coat the inside of the wood panels with copper foil so he was able to make up a Faraday shield, yet only had a very thin layer of copper whose properties would not have "upset" the pure wood case much.

Regards,

Andy

Actually, I have not used copper foil in my GK-1R. It is housed in a standard Monacor enclosure made up of steel and aluminum sheets joined at the corners by ingenious alu profiles.

However, I find the current discussion very intriguing and follow it with avid interest, although I have not ventured into this field myself - yet 

[Srajan Ebaen]

Jules,

wood and audio. The only thing I have to go by, thus far and from personal audition, are the fantastic results at Ocellia and PHY-HP I wrote about recently. I've been aware of "alternative" enclosure approaches but never had an opportunity yet to listen to those for myself. However, I have talked to designers who have done certain experiments and there seems to be sufficient data available to suggest that besides a good circuit, a stout power supply, impedance matching between speaker and amplifliers etc etc, resonance control (micro as, developed inside the component - and macro, as encountered in-room from the speaker and environmental interaction) plus subtle material influences on electron propagation seem to be more or less "open frontiers" still.

Lloyd Walker is a true fanatic who happens to make products most everyone agrees work. He eliminates plastics wherever he can and is a big believer in rock maple for resonance control. He also was a controls engineers who got nuclear and petroleum plants online - this in reference to those who poo-poo this whole subject as unfit for real engineers and write off those who investigate these matters as self-proclaimed "golden ears" who imagine to hear things where none are to be heard. Yamamoto creates a wood/resin "composite" with qualities resembling Bakelite for its amplifier decks. More and more speaker companies use plywood rather than MDF for enclosures.

And so on. There are plenty of examples and many of them cannot be argued to have production cost savings behind them.

Because my visit to Southern France was so eye/ear-opening; and because its characters believe heavily in the MDI = avoid synthetics credo; I'm simply inclined to take them quite serious. Which then opens the discussion to include Morecroft and Duelund and bee's wax capacitors and denuded resistors encapsulated in wood  and "nekkid" DACs a la Altmann and so forth. There's wood-enclosed headphones as Sony and audio technica make. The list keeps going.

Plus, there's the aesthetic angle. If two amps sounded identical, and one was clad in steel and the other in curvacious woods, I'd prefer the woodie hands down. Wood lends itself to subtle or intense sculpting to go beyond the ubiquitous straight-edged rectangular boxes. I prefer health food to canned food, wool to synthetics, fresh juice to pasteurized. Why not extend that "organic" theme to audio, even if it did nothing sonically (except not to sound worse)? Alas, there's reason to believe it could sound audibly better. If so, why not experiment?

[andyr]

I think the thin layer of copper brings us right back to the concerns re. eddy currents voiced on page 2 of this thread, and are what I am talking about avoiding through the use of non-conductive materials in the proximity of conductors carrying signal.

I wonder how important RFI shielding is in the analog domain (except for small signal carrying conductors such as those from microphones and phono cartridges) - even for switching amps that are properly designed.

regards,
Russell

Two things here, mate.  IMO:

1. a thin layer of copper foil must have much less "metal effect" (read "eddy currents") than the normal 2mm thick sheet of metal.

2. I think RFI shielding in the analogue domain is v. important. Although I agree this is probably a "religious" argument (ie. there is no universal truth).  However, it's easy for me to experiment - simply use unshielded ICs to connect my preamp to my power amps!    Or - as you say - even worse, use an unshielded phono cable from tone-arm to phono stage.

I've done this - and I believe in shielded ICs.    (IMO, if it affects the low-level phono cables greatly, then it affects high-level ICs less ... but it still affects them.)

Regards,

Andy

[andyr]

Actually, I have not used copper foil in my GK-1R. It is housed in a standard Monacor enclosure made up of steel and aluminum sheets joined at the corners by ingenious alu profiles.

However, I find the current discussion very intriguing and follow it with avid interest, although I have not ventured into this field myself - yet 

Sorry for tarring you with the "roolly weird" brush, Jens!    It must've been Kyrill who went to all that trouble?    I know it was one of you European fellows! 

Regards,

Andy

[kyrill]

ah well

I release my precious secret. Yes i used very thin copper foil 100 % glued with organic glue on waterbasis. (hand the foil a bit rough and it breaks.) and connect it to ground.This is what i did for the AKSA. For the preamp i use aluminum kitchen foil ( less vulnerable than the copper foil i used) one sheet thick connected to ground ( a 3mtr long copper pipe hollow, actually ordinary plumber stuff used for water transport, hammered into my garden, ground water is at 2 mtrs deep)

I made holes in the wooden enclosure ( sides and bottom) but these "windows"are closed because of the aluminum foil inside
this is ( as i follwed the insights of Altmann) to lessen or even eliminate enclosure "cavity resonance" Also wooden enclosures will have cavity resonances which will add in a wrong way these vibs into the rest of the more musical vibrations. You can lessen vibrations but not avoid them, in no way even NOT with infinite mass, but you can choose the pretty ones ( wood, carbon based) or the bad ones ( metals plastics)

the lonely tube up top is a lovely Siemens CCA ( NOS) a 7308 alternative

[Gordy]

Two hopefully helpful comments...  In reference to chassis's affecting sound quality, Steve Nugent once described one of his mods to the P3a dac as sounding similar to removing the dac from it's chassis, only more so.

Also, in mgalusha's thread on his Burson Buffer preamp Occam calculated the thicknesses needed  for non-ferrous shields for about 40% attenuation here... http://www.audiocircle.com/index.php?topic=45068.20

[kyrill]

nice Gordy

so a (very thin) foil is enough for RFI freqs>>10khz

the 50/60 hz freqs are probably for blocking transformer interference which is BAAAAD

but distance is a much better attenuator
DIY ppl can safely bring the trafo in another (wooden) enclosure 2 feet away from the main amp

[Rom]

Hi Kyrill,


Looks like you made some more mod ( holes ) on the wood case.


Nice 


ciao
rom

[Kevin Haskins]

My requirements for validity are not those of a "close-minded" engineer.    They are simple and proven methods to determine false claims vs. true ones.   

Its simple, if there is validity to the claims that metal enclosures cause audible problems then there should be research, published in periodicals that are open to peer review that show it.    If the people making these claims publish, I'll pay attention to them.   When they don't, and their claims run counter to common physical laws, then I pretty much discount anything they have to say.   I don't care if they have a PHD in physics.    Why?   Because I've seen a lot of nutty people with degrees.   In fact, in proportion to their numbers, people with higher degrees tend to be nuttier than the average person. 

Its the only way to remove the wheat from the chaff.   I don't have time to test every claim, but if I see good research on it, then I'll take it into account.    I think that is a reasonable and measured approach and I'll continue with it.

[kyrill]

hi Kevin

why don't you trust your ears in the FIRST place?

[kyrill]

Hi Kyrill,


Looks like you made some more mod ( holes ) on the wood case.


Nice 


ciao
rom

Hi Ron
all my visitors ask who made that amp
thx for making

[Kevin Haskins]

hi Kevin

why don't you trust your ears in the FIRST place?

Because my ears are unreliable.   They give erroneous results as a test instrument.   Why?   Because they are attached to my brain. 

[kyrill]

but in the end customers want the best sounding gear, no?

[Kevin Haskins]

but in the end customers want the best sounding gear, no?

Yes... they do.   That is why I prefer methods that give proven results.   

[Steve Eddy]

Sorry for replying to such an old post, but hadn't read anything in this thread until today.

It is well known that we can hear around 20 dB into the noise floor, thanks to our excellent pattern recognition skills, but we can't measure signal that far into the noise.

We absolutely can measure signal that far into the noise and more.

se

[Steve Eddy]

Because my ears are unreliable.   They give erroneous results as a test instrument.   Why?   Because they are attached to my brain.

Hey now, we'll have none of that nonsense in here. Human aural perception is not only without limit, it is also utterly without error. So now just take your silly games and go play them someplace else.

se

[Steve Eddy]

By the way, here's a nice wooden case amplifier from the early part of the last century. The venerable Western Electric 7a.



se

[Daedalus Audio]

Very interesting thread, this will prompt me to revive some experiments with hardwood amplifier cases and panels.  I first started designing and building speaker systems for professional musicians amplifying acoustic instruments fifteen years ago. When I felt the design was close I did tests comparing cabinets built of braced Baltic Birch plywood and solid hardwood. All else was the same except for the cabinet material. These were listening tests with real instruments and professional musicians (among them Martin Simpson who fortunately lived nearby at the time). It was night and day, the hardwood was clearly superior, it came very close to sounding like the actual instrument, and I have to stress I’m not talking adding a wood resonance to sound like a generic acoustic instrument. There are differences in tonal qualities between a Traugott guitar , a vintage Martin or a Sobel even though these are all very high end instruments. With the hardwood cabinet we could easily hear the sound signature of the individual instrument, with the plywood it had more of a generic tone.  Over the years in both pro and home audio I’ve found that well braced solid hardwood is a very accurate and musical cabinet material for speakers and lately I’ve been experimenting with hardwood equipment racks getting good results, I’m not surprised that replacing a stamped steel box with wood can improve the sound.

[AKSA]

I do not enjoy the tone of some of these responses.  Say what you like, but keep it civil.  I will not enter into the debate;  it's a minefield, like religion or politics.  Everyone has a POV, but it should be put conversationally, nothing more.  Please keep all responses fair and rational.

Hugh

[andyr]

My requirements for validity are not those of a "close-minded" engineer.    They are simple and proven methods to determine false claims vs. true ones.   

Its the only way to remove the wheat from the chaff.   I don't have time to test every claim, but if I see good research on it, then I'll take it into account.    I think that is a reasonable and measured approach and I'll continue with it.

Hi Kevin,

I'm afraid I'm much less welded to "measurement" in order to believe than you seem to be but I'd like to ask your comment on one particular audio experience I had, which I believe cannot be explained by measurement ... yet it was unmistakeably a more inviting/involving/exciting musical experience.

A group of us was listening to several different amps driving some high-end speakers.  One amp (ss) was by far the best performer in terms of musical involvement.  No problem (that's not what I wanted your opinion on!  )

Then one of the group produced a SET amp.  When we hooked this up - and listened to the same CD - suddenly the chanteuse had moved several feet forward of the speakers and was palpably there, in the room!   

It was an eerie experience - so my Q to you is ... what on earth would you "measure" to explain why this tube amp was able to project the singer so much more into the room than the ss amps? 

That amp gave by far the most enjoyable musical presentation (but unfortunately really needed to be at least twice as powerful!  ) but IMO this cannot be explained by any measurements of distortion, frequency response etc.

Regards,

Andy