Volume Pots & Knobs

• Good brands that have been recommended to me are Bournes and Clarostat. I use them exclusively in my own mics.

• Use 100 - 250k for Shure Hi-Z CM's and CR's

• Use 1 - 5 meg for Astatic MC-151 crystal elements

• I like the Clarostat RV6 military-grade pots for installation in tight spots. They are small and easy to mount (1/8" shaft). Good for Bullets, T-3's and others fitting in a tight space. But the prices have nearly doubled in recent months. These are great pots, though.
  
  

• For knobs, try the Kilo aluminum knobs. Small and durable. Fits 1/4" and 1/8" shafts.

Thanks Dave Kott, Keith Graham

Volume Pot Wiring Diagram

If you want the pot to turn in the opposite direction, pins 1 and 3 can be reversed. Be sure to always ground to the shell to avoid hum! I normally drill a hole inside the shell and attach a ring terminal with three ground wires - one to the element, one to the pot, and one to the connector.

Thanks to Keith at JT30.com

Shure CM/CR Polarity

Looking at the back of the element with the lettering facing you (and usually upside down), the hot is left and ground is right. There is usually a red dot on the plastic indicating "+".

Thanks Dave Kott

XLR-1/4" Wiring

Connect the XLR's Pin 1 to the XLR ground lug and to the 1/4" ground

Connect the XLR's Pin 3 to the 1/4" Tip

Everything you ever wanted to know about Shure Magnetic Elements

By the master himself, Dave Kott. It's a long and detailed article, read it HERE. Dave now has a website up as well, www.greenbulletmics.com

Thanks Dave Kott and Bluesharp.org

Preamp tubes - improve the sound of any tube guitar amp in an instant!

Preamp tubes are rated in percentage of output. The higher the percentage, the hotter the tube. If you can't turn your amp up past 2 before it begins to feed back, then it's time for a tube change. They're not that expensive, so you might as well get an assortment. They're self-biasing and any tube can go in any preamp socket. The order will definitely make a difference in the amps tone, so experiment. Look for American-made tubes like Tung-Sol, RCA, Sylvania, and GE. Avoid the Russian tubes if possible.

Tube Type	Percent
12AX7	100
12AT7	70
12AY7	40
12AU7	17

Thanks Dave Kott

Tube Equivalents

12AX7	ECC83, 7025, 5751, V4004
12AT7	CV10662/455, CV8154/9859, CV4024
12AY7	6072
12AU7	ECC82, E82CC, 12AU7WA, 6189, 5814, 5814A, 5963, 6067, 6680, ECC802(S), 7316, 7730, B329, B749, CV4003, M8136, 7801

 

Microphone Frequency Response Test

I pulled out all my favorite mics and performed a crude test to try and determine which mic was king. The winner? See for yourself. GO HERE

How to Mount a Switchcraft 2501 MP Connector in a Shure Bullet Shell

It's a bit of a job, but completely do-able if you've got the proper tools. If nothing else, seeing what's involved in the process will help you appreciate what your favorite mic builder goes through to work on your mics. GO HERE

JT-30 Screw-On

Ever wonder what the screw-on in a JT-30 looks like? I had to replace one recently. It's press-fit, with no threads on the mic end. I had to drill it out a little at a time until I could break it loose with some vice grips.

Harp Mic Shopping

Chris Richards has created a nice buyer's guide/owner's manual for harmonica mics. You can download the file HERE. In addition, here's a few things to think about:

Whether you're just getting your first mic or you're an old pro that's moving up from the store-bought variety, there's a few things you should know about purchasing a harmonica microphone. Here's a short list of things to consider when mic shopping.

Shell - Buy a shell based on fit, tone, and aesthetics. You'll need a shell that you can cup tightly without giving you a hand cramp, yet one that has enough metal and internal space to give you good tone and shielding. The two most popular are the Shure 520 and the Astatic JT-30. Try them out to see which one fits your hand the best. There are lots of others, but these two are by far the most popular. I have smallish hands, and the Astatic T-3 and Shure 707 shells are a good fit for me. In my experience, the thicker the metal in the shell and the more air space behind the element, the better the mic is going to sound. Just like a speaker cabinet! Some folks think of a mic like a boxed musical instrument, and create them from tonewood. Check out Greg Heumans's work at blowsmeaway.com sometime. Amazing! When it comes to looks, some folks like a mic that looks like it's been in every juke joint from here to Chicago, others go for flash and stage appearance, still others just want a good, durable paint job or chromed finish.

Element - The most important component in the mic. Again, two basic ones: The Astatic MC-151 crystal and the Shure Controlled-Magnetic (or Controlled-Reluctance). Crystals are a bit cleaner and have better cut, CM's are more ballsy and bassy, and distort easier when cupped. Crystals are tender, and may not survive a drop to the floor. Old crystals are VERY tender! CM's are very tough and will survive the next ice age. There are others. The vintage Shure R3 and R7 crystals are the best sounding by far, but it's rare to find one in working condition. There are a few good dynamic elements, but they require a transformer and a magnet, which makes the weight of the mic go up. Some folks like the Astatic MC-127 ceramic element, which sounds similar to a crystal.

Store-bought vs boutique mics - If you can avoid it, don't go to a music store and buy a new harmonica mic. The elements in the new Blues Blasters and 520DX mics are inferior. The 520DX has a dynamic element which is prone to feedback, lacks good bass, and is too clean for Blues. The $3 Japanese crystal (no kidding) in new Blues Blasters is tinny, and sounds like a toy microphone. Definitely go with the older CM's or a NOS (new old stock) crystal if you can. If you own a new Blues Blaster or 520DX, they can be improved! It won't cost you an arm and a leg either. Any mic builder can add a better element for you. If you have a decent soldering iron and a little soldering experience, you can do it yourself!

Vintage - If having a nice, old shell is important to you, then by all means go for it. But if you purchase from ebay, don't expect the mic to be working when you get it, especially if it's an old JT-30 or Brown Bullet. If the ad says the mic is untested, that is secret code for "it doesn't work". Here's a tip - if you're buying a JT-30 or other vintage crystal mic on ebay, ask the seller to shake the mic. If it makes noise like a maraca, the crystal is gone (the crystal is made of salt and eventually breaks down). If it doesn't rattle, that's no guarantee it will work, but your odds are somewhat better. Brand new 520 and JT-30 shells are available, and they are exactly the same as the old shells. Personally, I gig with a variety of old and new mics.

Project mics - Building mics is fun. But if you want to do it yourself, get ready. It's addicting! If you buy an "as is" vintage mic, you will have to add an element ($50-250), a volume control and knob ($20 for a good one), a gasket, connector, cable adaptor, and grill cloth. If you want the mic painted, your local auto body shop can do it for you for about $30-50. If you want something special, talk to the painter at your local custom chopper shop. Can you spray-paint your own?, Forget it. Your hand oils and sweat will eat the paint away in no time.