Hi, Andy,
I did read that HP comment a long time ago but relegated it to the overflowing cupboard where all sorts of other peculiar ideas reside.
I respected, still do, HP very highly because of his very critical nature. He was, still is, in the end only interested on how it sounds.Close to impossible, the way HP is that he would follow a "snake's oil"trend EG. did you ever come across an eccentric Englishman by the name of Peter Bent? I seem to remember he was writing about hi-fi in the 80s and he was always talking about ways to eliminate static, or EMI, or put the "life force" into the music ... etc..
Yes, I did and I did not had enough faith in him obvously, to repeat the findings you mention. They did not make sense to me. Two of his "recommendations" which I am afraid I have never tried, although they stick in my mind are as follows:
* for each one of your fuses, use a violet/purple fibre-tipped marker pen to place a mark on each end (this is assuming your fuses are held in a PCB-mounted holder and are pushed from the top, sideways. If the fuse is held in a spring-loaded chassis-mount fuse holder which connects to each end, put the mark on the side of each end-cap).
* if you have any batteries located near your cartridge, make sure you wrap some sticky-tape around the circumference, at one end.
Go figure!!
Why I mention this is that your recommendation to use a wooden case which is maybe one inch thick and well damped with tar or bitumen etc. to me smacks, somewhat, of "Peter Bentism".
Be careful, he still may be right. But maybe he is not, in both examples above it does not seem rational, doen't it? nhjmmm ( that is the neighbour's cat spinning and walking over my keyboardBut I'm open to enlightenment which is why I'd be interested in a more detailed explanation of why you recommend wooden cases. Perhaps you could answer the following Qs:
1. Why wood up to 1" thick? I wood have thought if you are trying to have as non-resonant an enclosure as possible, then thin wood - maybe only 1/4" thick - would be better?
Did I say 1"inch? I must have forgotten that an inch is 2,25 centimeters. For a small case this maybe too thick, but..the ideal enclosure is NO enclosure. Their design is decoupled from and are not part of the amp's schematic. So why are they?
To shield, that is a very good and in transparent systems a MUST. That is the benefit. For the rest they have (again only in highend transparent systems) 2 very nasty disadvantages and wooden cases only one.
and yes you are right and no you are not right in making the wood as thin as possible because there are two "resonances with opposing needs
*a) vibrations.Then, the thinner is better as the vibrations stop earlier, there is less mass and so less energy can be absorbed by the mass . An official technical term in English exists for "the time a vibration needs to completely halt.
*b) with a certain thinness of the enclosure wall it starts to resonate by itself as a whole, with a maximum in the middle of the plane. it becomes a sound instument like a guitar. This also happens with thin metal plates.
So if you make wood too thick unless very dense and thick, it has a negative effect not so much because they vibrate too (but less) but because it is out of sync with the music itself. This is an uglier kind of "grunge" than grunge which is perceptably in sync with the music. And no I do not believe sitting away 13 to 14 feet from my amp, my ear will acctually make me hear the sound emanating from the amp's enclosure, like I can hear from badly designed speaker enclosures You hear it amplified by the pre- (much more) and poweramp (rest will follow, I am taking a shower now:)
Ok,
Another reason for not too thin wood is the mass of the amp. It needs structural support. Especially since my wondering what kind of sound do transformers have, i made the choice to abandon the toroïds and go back to the "ei" (?) trafo's Well two of those ( i have them in the house) for Aksa 55 together weight over 10 kilo's add up the heatsink and you have a very heavy amp.
So to make a choice between resonances and vibrations and you still can carry your amp if you have too, make it not too thick (unless very thick and dense as possible, so it almost does not react, like enclosures from stone), and make it not too thin 
Then you damp it as much as possible because these wooden vibrations/resonances reach the amp's pcb, trafo's and heatsink. So they start to move and that is BAD. They are all metallic like and embedded in multiple chaotic but very real presence of all kinds of electrical and (sub) local magnetical fields. And you know what happens if you move any kind of metal in an electical or magnetical field. The effects will find their way amplified in the music. These are: less focus, less warmth, less space and less tube (life) like as if the current coming from the wall has more grunge. Also for DACS this is bad. As digital systems need a precise clock as possible, which is somehow based, somewhere in the system on a crystal oscillator. In fact a very fast moving (bouncing) crystal. Mechanical resonances will influence this bouncing only in a disturbing way. It is not a bad idea to mechanically isolate the crystal from its surroundings or damp it.2. If damping wood is a good idea then why wouldn't a metal case with the same tar/bitumen damping material applied, be just as good?
Good question. Wood by itself does not generate a magnetic or electical field. It only effects the amp indirectly by sharing its vibrations with the physical structures of the amp. A metal case does this too but adds on top of this its own influences on the electrical and magnetical fields.3. What are these "musical signal energies" that you mention? Are you saying the music signal flowing along the PCB tracks and the component leads - ie. the electrons - have an affect on the metal case (because electrons flow in metal but don't in wood)?
Yes as explained above. In the domain of electrical physics the influence of dry wood (not wet) and cotton for instance is neglible, Maximum field coupling happens with metalsOr are you talking about the external sound waves originating from the speakers which hit the amplifier case?
And coupled with a " shaky"floor..
I hope to explained these too indirectly influence the innard working of the (pre)amp 4. What about shielding the inside of the wooden cases with aluminium kitchen foil?
The less mass the shielding has, the better. I don't know how good this foil is, and don't under estimate how difficult it is to realise good thorough shieldingRegards,
Andy
