I think I misunderstood Tom's point. I thought he was suggesting that removing the top increased vibration due to a less rigid case structure (which is the case in automobiles...coupes being more rigid than convertibles in the same models), when it appears Tom was suggesting that removing the top decreases case vibration. Sheesh, I'm confused.
I don't know whether to remove my Magic Fingers motel bed from my listening room, or to keep it in. |
07-06-06: Audioari1
One tweak that I tried that makes a BIG difference is playing the amp with the cover off. When the cover is on, electromagnetic waves bounce off the metal and back into the amplifiers circuitry. When the cover is off, you will be surprised how much better it sounds. And you know the difference in sound is attributable to the electromagnetic waves bouncing off the top cover? How do you know this for certain? Could it also be possible that the amp runs cooler with the top off, and therefore the bias is at a different level than when the top is on? Having done bias measurements on my Class A/B solid state amps immediately upon removing the top cover (after the amps had been on for several hours), and then measuring again 45 minutes later when the amps were cooler, I know for certain the bias was different...and the amps sounded different. |
07-08-06: Theaudiotweak
Hey guys my thoughts were that removing the top changed the vibrational pattern and therefore the sound...for the better or for the worse. Indeed. |
And it makes logical sense that the electromagnetic bounce effect is at play here. In any case, whatever you want to call it, the DK amplifier sounds substantially better with the top cover off, try it and see for yourself.
Audioari1 (Threads | Answers) Honestly, electromagnetic bounce effect sounds like pseudo-science to me, but if the DK sounds better with its top off, then top-off it shall be! |
07-06-06: Audioari1
One way to achieve the best sound and still have a cover for your DK is to have one made from Lexan. It is a clear material, so the cover will be see through, but it wont have the electro-magnetic bounce effect like the aluminum cover does. Aluminum is non-magnetic, just like Lexan, so there should be no difference in performance between these two materials. Plastic (Lexan) encourages static electricity, so it seems to me the aluminum cover would be the better choice. |
Audioari1, can you provide a link to an article discussing electro-magnetic bounce effect? I have done a search for "electro-magnetic bounce effect" and found nothing. I have found several articles discussing electromagnetic field radiation, and ground bounce, but these are two separate phenomenon, and ground bounce is controlled by the adjusting size of wire traces. Here's the article |
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? |
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. |
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? |
If you believe it sounds better with the top off, then that's all that matters in your system. |
I'll lay heavy odds that a 9awg power cord of any brand would be noticeably better on the DK than a 12awg cord. |
Also, the previous owner, Daniel Khesin, was not a big believer in power cords, although he heavily emphasized upgradingthe tubes.
Audioari1 (Threads | Answers) Mr. Khesin's opinion doesn't carry much weight these days. |
