[SpruceTop]

Originally Posted by Cuki79

Hi everyone,

I did not dare post that on SpruceTop's thread but this is totally related to his TA Amulet successful installation.

Inspired by SpruceTop, I have been trying to re-install my bass-side amulet lens... unsuccesfully. I could do better but not enough.

So before I run out of red tape, I decided to make a small experiment

I have a plastic plate with a surface exciter.

I sticked on it a K&K sensor (super glue) and an Amulet lens with red tape and over 12h clamping. Both sensor go into Hi-Z focusrite 2i2 inputs.

The exciter is fed with pink noise.



1) First experiment consist in comparing the K&K and the Amulet spectrum response. If you look at the left figure below, the K&K (Yellow) has more sub 100Hz content than the Amulet. The Amulet has more of everything above, expecially above 10 KHz.

2) Second experiment, I added weights to the Amulet (coins + double tape) or magnets to add pressure and improve bounds. I used all kind of neodymium magnets. (See pictures above)

My conclusion, is that the added weight effect on tone is minimal. I could get significant tone change by adding small neodymium magnets (5) to squeezet the amulet lens. Those small magnets are trong and lightweight, you can see on the right figure below, they added low and low mids... Exactly what my previous Amulet installation lacked.


NOTA BENE: The two spectra are different, because I pause the analyser at a different moment. Also I moved the plate between experiment 1 and 2 so the bundary condition for the hanging plate are different.

You can actually hear the difference



The sound sent to the exciter is pinknoise. Of course the plate response colors the tone already.

1) Amulet lens
2) Amulet lens squeezed by 5 small neodymum magnets

That is very consistent with what Spruce top has observed recently. A better bond provides better lows and low mids which eventually can make the tone control unnecessary...

The only question is: How can we get that great bond with red tape?

I have only 3 pieces left... I'd probably never get the answer.

Yes, indeed, the superglue's hard and thin mounting of the piezo disk supplies more bass content than the thicker, more pliable, red permanent tape mounting of the Trance Amulet. The Trance's less intimate mounting does, however, have more treble content and a lot of it is what you don't want to hear in an acoustic-guitar amplified tone. My epoxy mounting of Amulets lessens much of the nastier treble tones while increasing the bass content of the amplified tone.

As an aside on tone: Michael Laiacona, president and founder of Whirlwind Music, and who was the "M" in the original MXR company, once said to me facetiously to make a point after I commented on the frequency range of a loudspeaker not going above 16 kHz: Kenny, if you can hear anything above 13 kHz the Army will hire you for a million bucks a year to do something for them! His point was a lot of the content in the human hearing audio spectrum of 20 Hz to 20 kHz, especially the very high frequencies, is not necessary for forming our favorable appreciation of a sound source, e.g., an acoustic guitar. I use the trebly brittleness of a red permanent tape mounting of the Amulets as an example of how some of its treble content adds some annoying tone to the amplified signal. The epoxy mounting of the Amulets attenuates a lot of the undesirable treble tones while increasing bass content.