Not being much of a handyman it took me a while before i built a reasonable enclosure for my clone. For a long while it merrily buzzed enclosure-free on my rack. The case looks a bit like Peter's, only it's a lot larger (ps inside), not very well made and far from cute. It's made out of 10mm alu but the base is wood. The chips are mounted on 20mm copper blocks to reduce the length of wiring between chip and binding post.
Now for the problem. I had some doubts that such an expanse of alu will aid the sound much, but seemingly all was well before i bolted the lid. With the top in place the sound took a major turn for the worse: an obvious midbass resonance and worse - an unpleasant grind on voices. The alu itself doesn't seem to be culprit, with the cover resting diagonally on top the sound is fine; it only gets screwed with the cover firmly in place. I briefly tried different materials like 10mm acrylic and PVC and the acrylic sounded quite unobtrusive. Unfortunately the only type i can get in 10mm is clear which i would rather avoid. The best solution is probably a cover with multiple large holes which won't allow the forming of a resonant cavity. Any suggestions not too difficult to implement are very welcome.
peter
Now for the problem. I had some doubts that such an expanse of alu will aid the sound much, but seemingly all was well before i bolted the lid. With the top in place the sound took a major turn for the worse: an obvious midbass resonance and worse - an unpleasant grind on voices. The alu itself doesn't seem to be culprit, with the cover resting diagonally on top the sound is fine; it only gets screwed with the cover firmly in place. I briefly tried different materials like 10mm acrylic and PVC and the acrylic sounded quite unobtrusive. Unfortunately the only type i can get in 10mm is clear which i would rather avoid. The best solution is probably a cover with multiple large holes which won't allow the forming of a resonant cavity. Any suggestions not too difficult to implement are very welcome.
peter
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What about wood? I also have plenty of tinted (black) acrylic. If you interested I could send you some
You migh talso try to attach something to the bottom of top alu panel. Don't tight the screws or use additional tension rod through the center of the box (from the bottom).
What are those small holes in top panel?
You migh talso try to attach something to the bottom of top alu panel. Don't tight the screws or use additional tension rod through the center of the box (from the bottom).
What are those small holes in top panel?
Good point. I tried several layers of cork in all corners to no effect. Foam tape will probably be similar.
Peter, you really don't want to know
Did them by mistake. I mostly do programming and mistakes there are quite a bit easier to fix than holes in metal. Dunno if damping the lid will help; the main resonances will certainly remain. If i could i would drill giant holes in it and combine that with damping. Wood, i still haven't tried. It will probably sound ok but may look quite out of place. It's very amusing how terrible the cover sounds; i would put up with almost anything just to avoid extra work, but this is just too much.Oh, and thanks for the acrylic offer. As much as i like shopping for parts from Canada, shipping a hulk of plastic half way (or is it full way?) accross the world exceeds even my madness.
thanks guys
peter
On my monoblocks I used 1/4" aluminum plates as bottom covers. One cover is under electronics section, the other, bigger under transformers. I didn't like the sound of those amps in the beginning, the sound was muffled and colored. Out of curiosity I removed the smaller cover and used a piece of solid maple wood, 3/4" thick, no spike, block of wood acts as footing.
The change in sound was tremendous, no more colorations, more space and detail. I like to use maple and I think that wood sounds better than acrylic. If you finish it nicely, top cover out of wood might look really good.
The change in sound was tremendous, no more colorations, more space and detail. I like to use maple and I think that wood sounds better than acrylic. If you finish it nicely, top cover out of wood might look really good.
I think that an all metal box - even aluminium - causes some kind of magnetic restriction that trashes the openness of the sound.
I think that denis moorcroft developed this theory and consequenly uses acrylic for his enclosures and avoids metal of any kind as much as possible. He puts his O/P devices on quite thick ceramic heat tranfer washers to keep them away from the heatsink.
perhaps at least one non-metalic surface in an enclosure is essential ?
mike
I think that denis moorcroft developed this theory and consequenly uses acrylic for his enclosures and avoids metal of any kind as much as possible. He puts his O/P devices on quite thick ceramic heat tranfer washers to keep them away from the heatsink.
perhaps at least one non-metalic surface in an enclosure is essential ?
mike
Peter Daniel said:
I wouldn't count that out. Did you try those stones immersed in reisn in your monoblocks yet Mike?
not yet, you mentioned somewhere recently about simple crossovers sounding best and I'm reaping rich sonic rewards on that front at present.
Thanks for the idea.
When I've finnished I'll post my results in loudspeakers and get back to GC monoblocks.
cheers
mike
p.s. good luck with your commercial venture, the amp looks great ( I hope the wingers have not put you off the idea )
This was my first thought. Interestingly, when the cover sits on top askew, electrically touching the sides, the sound is fine. Alu should have no magnetic effect, other than that of eddy currents. I somehow feel that the audible effect is mostly the result of acoustical resonances. Peter Daniel's enclosure is much smaller which means higher resonant frequencies which are apparently less damaging and easier to control. Oh, and the cover adds another 3kg to the mass, probably not a good thing as well.
yes - I havn't quite got my head around this one yet - did you try it with the lid in place but electrically isolated from the box ? might be worth a try
if it is mechanical bracing should substancially help
somehow my guess would be to drill the large holes as you mentioned - sorry this is not an easy fix
perhaps non paralell sides would be the answer - I think one of the japanise companies, sony or pioneer have this theory.
if it is standing waves inside the box you could try a diagonal internal baffle to break them up
I am interested to hear what you find
cheers
mike
if it is mechanical bracing should substancially help
somehow my guess would be to drill the large holes as you mentioned - sorry this is not an easy fix
perhaps non paralell sides would be the answer - I think one of the japanise companies, sony or pioneer have this theory.
if it is standing waves inside the box you could try a diagonal internal baffle to break them up
I am interested to hear what you find
cheers
mike
Hi Peter,
I wonder how you ended up with lid material. Just today, I went to Sakura site and here's Yoshi Segoshi custom amp. Could it be that he had the same problem as you?
http://www.sakurasystems.com/show/yoshi's.html
I wonder how you ended up with lid material. Just today, I went to Sakura site and here's Yoshi Segoshi custom amp. Could it be that he had the same problem as you?
http://www.sakurasystems.com/show/yoshi's.html
What's a lid? 
An externally hosted image should be here but it was not working when we last tested it.
As a general contribution on case materials - Russ Andrews uses wooden enclosures on his custom amps, for much the same reasons as Denis Moorcroft, I believe. Russ even uses oak control knobs!
His ultimate amps use Torlyte cases (a very rigid, lightweight wooden structure - details at www.russandrews.com - follow the link for equipment supports).
Hope this of interest.
Colin
His ultimate amps use Torlyte cases (a very rigid, lightweight wooden structure - details at www.russandrews.com - follow the link for equipment supports).
Hope this of interest.
Colin
How about some kind of mesh? If you aren't stacking anything on top, it would be ideal. Enough holes for air flow and it's a "fabric" so it shouldn't resonate. Maybe the vinyl screen door material or grill cloth. I don't suggest aluminum screen door mesh as that may ring like a... well... a screen door.
On the same idea of holes, there are also a number of manufacturers of "perforated" plastic sheets. You could probably get some scraps from them as a a free sample for evaluation.
Or what about rattan like the kind in a chair. The bamboo is strong enough to support sitting so stacking would be fine, but not so rigid as to resonate. There would also be enough holes for cooling.
ensen.
On the same idea of holes, there are also a number of manufacturers of "perforated" plastic sheets. You could probably get some scraps from them as a a free sample for evaluation.
Or what about rattan like the kind in a chair. The bamboo is strong enough to support sitting so stacking would be fine, but not so rigid as to resonate. There would also be enough holes for cooling.
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