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Microphone Choices: NITS and CHIGGERS—THE NASTY DETAILS INSIDE:

1 February 2012 12,322 views No Comment

SWAPPING OUT FOR CRYSTAL, PART 1

by Fritz Hasenpusch

I’ve got to admit that the squad of post-holiday helper elves still on duty down here in the MICROPHONE DUNGEON were more than a little concerned with the working title of this installment of THE MIC BENCH. They’ve requested that I state for the record: This is about harpmics that utilize piezo-electric/Rochelle salt elements—or that we’ll be using these high impedance devises. They’ve also asked me to request that the DEA please stand-down at this time. Thank you…

During our last visit we looked at the aspects of compatibility between components when installing a CONTROLLED-MAGNETIC or CONTROLLED-RELUCTANCE element into your harpmic. On this visit we’ll run down the checklist of requirements and methods when installing the other perennial heavy hitter in the Harp Kingdom, the CRYSTAL element. Take a look at the image below…

Examples of full-sized CRYSTAL elements you may encounter include—from left to right with top and bottom views: BRUSH DEVELOPMENT; Early ASTATIC ’30′ as found in the Model ’30′ “Biscuit”; SHURE pre-R7 as found in “Brown Bullet” models; SHURE R7 as found in 707 models.

The first point on the checklist: Do you really need a CRYSTAL element in your arsenal of Harpmics? Will a CRYSTAL element provide you with an indispensable sonic tool otherwise unattainable? Are you willing to deal with their temperamental and fragile nature?…

The CRYSTAL ELEMENT GRAVEYARD… Many pro Tin Sandwich jockeys will answer in a flash with a thunderous ‘YES!’. There are many Harpsters who choose to use nothing else.

Onward…

Let’s concentrate on what has been by far the most widely used CRYSTAL element in recent Harpdom history: The full-sized ASTATIC elements, most notably the units designated 101 thru 151…

In terms of physical dimensions, these elements—measuring 1.95″ or 1 15/16″ in diameter—will fit in any and all of the familiar “bullet” mics from both ASTATIC and SHURE. As they were stock factory equipment in all the ASTATIC mics fitting the “bullet” description this is no surprise. However, they WILL NOT fit many of the popular ASTATIC “canister” mics by virtue of their diameter (The ’10′ and some of the DN models). Any of the SHURE “bullet” mics—from the 7A thru the 520 “Green Bullet” models—would be candidates for the swap. In addition, TURNER base station mics present another hosting possibility for the full-sized ASTATIC CRYSTAL elements. The TURNER ’200′ and ’400′ series mics have enough interior diameter to make a swap possible, and have made TURNER “chops” (the mic head separated from the base’s neck) more common. Be aware that tight tolerances may make proper gasketing for these a problem. We’ll deal with that, too.

Whatever your choice for the mic body that will serve as the CRYSTAL element’s delivery vehicle, very specific precautions need to be observed when installing these tender beasts. If you don’t want your CRYSTAL to become a statistic, please take note…

THE INDISPENSABLE HEATSINK: Generally speaking, extreme temperatures are the enemy of most audio electronic components. With CRYSTAL ELEMENTS they mean certain death. Too often these fragile flowers are dead before ever seeing duty to the Tin Sandwich simply because of exposure to excessive or prolonged heat while being soldered into the wiring of an intended harpmic. Enter the HEATSINK. A HEATSINK is any material or method utilized to wick-off heat from a subject item. In our case, it’s the heat applied to the wiring terminals or ‘lugs’ of our subject, the CRYSTAL element.

Our image below shows a spring-actuated heat sink made of aluminum from Radio Shack…

Placed between the heat source (soldering iron) and the base of the subject terminal, it will help regulate/minimize the amount of heat entering the element’s capsule and possibly doing irreversible damage to the Rochelle Salt CRYSTAL within. I’ve found this design to be effective, but clumsy to handle due to its thin/flat configuration.

Something more ergonomic and manageable would be an advantage at the MIC BENCH…

CAN YOU SAY “HEMOSTAT”?

Hemostats—or hemostatic clamps—are small needle-nose plier-like mechanical devises commonly used to stem blood flow (“Hemo” from the Greek for blood) during medical procedures. Their scissor-like action and looped handles utilize interlocking teeth to hold their forward plier components in a fixed position at a level of pressure determined by the pressure applied to the handles. They can be purchased new through crafts and technical supply sites or found through medical surplus sources (my fave).

Here’s an example of the smaller, finer versions…

Here’s an example of the larger, modified versions…

Beyond medical applications, Hemostats can be used to remove fish hooks, manage and handle tiny mechanical components, and—Hallelujah!—as very workable heatsinks. It’s a fact that the stainless steel they’re constructed of isn’t as efficient at conducting heat and therefore not as effective at wicking-off the soldering-generated simmer as aluminum. Still, I’ve never lost a patient due to “heat stroke” when using them. Just be aware that they aren’t a guarantee, they’re a precaution.

CUSTOM-FITTED HEMOSTATS: They’re not just for vampires anymore! Some CRYSTAL elements have soldering lugs that are very short and as a result have eyelets that are extremely close to the element’s body. The ASTATIC MC-151 is a prime example of this…

Modifying the gripping jaws of the Hemostat on a sharpening stone or bench grinder to fit the limited margins available is the answer, producing a multi-use custom tool that can be utilized over and over again.

An especially versatile model is the customized CURVED Hemostat…

HEMOSTATS IN PLACE, YOU’RE READY TO SOLDER: Just remember that the Hemostat is there as a barrier to impede damaging heat from entering the CRYSTAL element via the base of the soldering lug. MAKE CERTAIN you’re positioning the Hemostat between the base of the soldering lug and the terminal you will be soldering, applying your soldering pencil’s tip to the wiring eyelet positioned ABOVE the Hemostat ONLY!…

Printable Version

We’ll be showing ELEMENT INSTALLATION, GASKETING and wiring procedures in detail, with pix to illustrate key points as we continue SWAPPING OUT FOR CRYSTAL, PART 2!

THE NEXT TIME WE VISIT…

THE MIC BENCH

 

 

For pictures and descriptions of most of the microphones listed visit http://www.harmonicamasterclass.com/vintage_collection.htm

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