DK Design VS.1 Reference mkII - Optimization

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.

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.
Newbee (System | Threads | Answers)

I sure can't, and that's why I'm not convinced EMI effects are the reason Audioari1 hears benefits with the DK top off. If Tom's vibration theory is correct, then why would the amp sound better with the top off? More vibration causing additional microphonics in the tubes? I have heard some claim that microphonic tubes...just below the threshold of causing ringing and echo...sound more spacious and open, and therefore "better".

Audioari1, in what ways does the DK sound better with the top off. Would you please describe what you hear?

Tvad, I'll take a stab at the vibration/top issue, by way of example. I have a CDP with case vibrations induced by the transformer. These vibrations are sufficient to rattle the tube innards which increases any potential they have to be microphonic. When I take the top off the CDP I'm eliminating one of the surfaces which facilitate the transmission of the vibrations. Often the audible (as well as physical) frequency (pitch if you will) and intensity of the vibration changes - usually lessens. Mass loading can have a similar effect.

If you have the best LN tubes and your unit has a low noise floor you might not actually change anything except reduce the audible transformer hum (not a bad thing at all), but if you have borderline tubes and a highish noise floor these vibrations can induce tube microphonics which can be audible. FWIW, I think there are better ways of getting 'spacious and open' than using microphonic tubes. :-)