DK Design VS.1 Reference mkII - Optimization

Audioari1, I'm not disputing the effects you hear, and I would like to learn more about the electromagnetic bounce effect (EMBE) to which you attribute the difference in sound. There a dozens and dozens of amplifiers, preamplifiers, and CD players that use aluminum cases and covers, and I have never before read about the deleterious effects of aluminum as it exacerbates EMBE. If EMBE is a cause of less-than-ideal sound, and if it's effects are so apparent, it seems to me there would be far fewer components utilizing aluminum cases for improved shielding.

With your help, I'd like to understand this better.

I'm assuming you have read somewhere about the electromagnetic bounce effect, how it bounces more readily off some materials than others, and how it relates to the performance of audio components. Since I'm trying to learn more about physics and audio, any link or reference to an article/study about electromagnetic bounce effect would be appreciated.

Have you ever considered taping a sheet or two of ERS paper (ERS blocks EMI/RFI) to the inside of the cover of the DK and listening for any difference?

I have not tried ERS paper, but one manufacturer that supplies a lexan cover instead of an aluminum one is DartZeel. Their amplifier, as you can see in a lot of literature, is supplied with a clear cover specifically for that reason.

Maybe shoot an email to DartZeel to explain this effect in more detail?

Also, while I believe that almost all components sound better with the aluminum cover off, this effect is especially prevalent in the DK amplifer where the difference is quite dramatic.

07-07-06: Audioari1
I have not tried ERS paper, but one manufacturer that supplies a lexan cover instead of an aluminum one is DartZeel. Their amplifier, as you can see in a lot of literature, is supplied with a clear cover specifically for that reason.

I did some research on the Dartzeel website, and they do use a clear cover, although it is made of glass (according to their white paper).

Interestingly, they do mention the benefits of a glass cover over a metal cover:

And contrary to metal, glass is totally transparent to magnetic fields, thus avoiding the inherent magnetic loop that metal would induce over the power supply transformers. Last but not least, the internal housing is much less polluted my magnetic ghosts

Ironically, the Dartzeel amplifier's case is made of aluminum:

The case of your machine is ezclusively machined from AW-5754-ALMG3 alloy aluminum. offering a remarkably even surface and hardness

Why use a glass top and an aluminum case if aluminum is an issue for reflected EMI? EMI doesn't know about direction...it radiates 360 degrees...not just up. Why not make the case out of ceramics, plastic or carbon fiber? There are a few non-magnetic, non-reactive material.
Since aluminum is non-magnetic, I'd still like to learn how it could induce a magnetic loop.

By removing the cover you will have changed the mechanical mass of the entire chassis.Vibration and it effects on the circuitry will also have been changed. Vibration influences can greatly alter the spectral balance. The amp has been retuned within its own environment. Tom

Tom, Your explanation is as good as any I've seen for the reason this amp sounds best with the top off. Tubes are microphonic to some degree and the less vibrations (from any source) the better. Removing the top would certainly eliminate one potential source of vibrations. I've done this with some CDP's/Dac's and pre-amps.

I just don't understand these electro-magnetic 'waves'comments.

Apparently the amp generates a lot of EMI which must then be disappated in some fashion and taking the top off facilitates that disappation. But if the amp is creating the EMI in the first place, and its harmful to the signal, it seems to me as if the damage is already done.

If the EMI is externally produced it seems that having a non-ferrous case, including top, would be beneficial in keeping it out of the amp. I also don't understand the 'wave' concept, I can understand EM fields of changing intensity, but 'waves' which bounce back and forth off some surfaces but not others? Are you aware of any science which supports this?

Tvad, Audioaril, Tom, anyone - please help me to understand this.