A: The control provides harmonica players with the ability to quickly adjust volume during performance without having to be close to the amplifier, AND to get close to the amp to make adjustments without worry. This is useful for many reasons, such as setting the maximum volume attainable without feedback, adjusting for quieter harps (Low D comes to mind,) or "backing off" a bit when filling behind anothers' solo or vocal.

The control positions the knob where it is not prone to "accidental adjustment." This can be a real problem with on-mic controls as you constantly re-adjust your cupping/holding hand position. You can move the control from mic to mic easily, making it far less expensive than adding built-in controls to individual mics.

A: Many years ago, Switchcraft (manufacturer of many connectors for audio and radio frequency use) made the "Nr. 329" volume control shown at right. Today, it is a prized collector's item, and good examples sell for as much as $300. I wanted to reproduce the functionality of this control, but in an even smaller package and with better structural design.

A: The control places a variable resistor, or "potentiometer", often referred to as a "pot", between the amp and microphone. The schematic diagram to the right shows how this is accomplished, and is the way both the Switchcraft control and my design work. The resistor places some load on the microphone, just as the amplifier itself does.

A: Yes. I can provide a Switchcraft Type 44 adapter as shown at right for this purpose. In addition to the adapter, you need a cable with a standard 1/4" connector for the amp end and a Switchcraft female connector at the other. This will connect the volume control to your cable. You can buy these cables through HarmonicaMasterClass. I can also make custom cables with any connectors you like. I charge $20 plus $1.25 per foot.

A: This is the Switchcraft 332A. I sell these for $14.95. I also make custom controls and adapters with your choice of connectors - see the Mods and Adapters page.

A: If your microphone is low impedance and you play through a PA, the best solution is my low impedance XLR volume control. If you use your low impedance mic with a harp/guitar amp, then you also need to use an impedance matching transformer. The product shown to the right is what you need. And if you want a combinated impedance matching transformer/volume control with your choice of connectors, I make those too - see the Mods and Adapters page.

If your microphone is a high impedance mic I can make you a custom volume control. Some high impedance XLR mics have the mic signal on Pin 2, some have it on Pin 3 - so you must be able to tell me what you have, or send me your mic. You also must choose the kind of connector you want on the cable/amp side - Switchcraft or 1/4" female are common choices. See the Mods page for more info.

I make adapters like this one shown on an Audix Fireball V mic - XLR at one end, switchcraft at the other, an impedance matching transformer in between.

A: The short and honest answer is "yes". The most important modifier is "for the better" and an equally important one is "but not much." Crystal element mics like older JT30's are likely to be most affected; dynamic (including controlled magnetic and controlled reluctance) mics aren't as affected. In any case, the impact is minimal, and many players don't notice any change. If you do, generally you can usually re-adjust your amp settings to compensate. There are many factors involved in amplified tone, the most important of which is technique! Other key ingredients are the amplifier and the microphone. Your technique will not change for better or worse, and your amp and mic combination will still exhibit their unique characteristics. You can also contact me about custom controls for special mics.

Tone is affected as the volume is reduced, by reducing the high frequency response. When you overdrive your microphone into its distortion range, some of that distortion is comprised of high frequency signals. Reduction in volume will "take a little edge off." I personally like this - when I reduce the volume it is because I am trying to stick out less, usually when I'm filling as opposed to soloing.

Solid state amplifiers tend to reproduce microphone distortion with a gritty, hard edge - losing a lot of the warmth associated with all-tube designs. The installation of a volume control will take just a little of this edge off - making the sound (in my opinion) much more pleasant.

Note that the human ear is naturally less responsive to both high and low frequencies as volume is reduced as well. This is a documented phenomenon known as the "Fletcher-Munson Curve." Some of the reduction in highs comes from the control, but some comes from this as well.

In the end, I say "Try it, you'll like it". And if you don't, I offer a money-back guarantee. Just return it within 7 days and I will refund your money.

A: Easy. Just set up your amp and mic with the volume control installed. Set the control to full volume and adjust your amp for the loudest sound you want, along with the tone you want. If you already have a very dark tone, you may want to turn the treble, gain or presence controls up a tiny bit to restore any lost brightness. Voila! You're all set.

A: While it is true that a higher resistance pot puts even less load on the mic at full volume, there are significant disadvantages to using higher values. Most importantly, a useful volume range is available within only about 10 degrees of knob rotation. This makes it very difficult to make quick, subtle changes. I have seen schematics of circuits with additional components designed to offset this narrow control range problem, but these circuits have their own negative side-effects. The 100K pot (the same one, by the way, Shure ships with every 520-DX Green Bullet mic - the best selling harmonica microphone in the world) provides useful control over its entire 270 degree travel.

As a rule, crystal mics are the most sensitive to the load placed on them by the amp and volume control. Solution: turn the amp up, dial up the treble and mid to compensate. If you're using a Bassman-style amp, consider substituting a 5 M-ohm resistor for the 1 M-ohm resistor wired across the input jacks. This resistor ALSO places a load on the cartridge and can reduce the performance of a crystal mic; the 5M resistor has less negative effect.

I do build custom controls with 1Mohm pots. Dave Barrett and I have tested them. We agree they are absolutely the wrong solution for any dynamic, controlled magnetic or controlled reluctant elements. If you have a crystal or ceramic element, you might prefer the 1M version. Note the pot I use for this control has a 1/8" nylon shaft and therefore is not as rugged as the 1/4" aluminum shaft in my standard controls. However if you avoid "slamming" it against the "full" and "off" stops it should last a long time. Princing info at the bottom of the Mods and Adapters page.

In the photo at right, notice that the center connector (actually a rivet) stands above the remaining surface, even with no solder at all.

A: Yes, it can be disassembled. I would not recommend trying this without contacting me for some techniques to prevent damaging the unit.

But I think once you see one, you'll rest assured that it won't fail in the first place. I truly believe it will last a lifetime without requiring any service. I use mine all the time and believe me, I don't want it to fail! I wanted to be sure it would be mechanically strong enough to endure the rather severe torque loads it might ancounter in normal use, and I sure didn't want any chance of a connector coming loose, spinning in the housing.

The photograph below shows an "exploded parts diagram." The Switchcraft connectors have a knurled portion at the neck of the smaller threaded diameter. I machine the hole in the aluminum end-caps hole smaller than the diameter of this knurled portion. I then press the connectors into the end-caps with an arbor press, mechanically locking the connector to the end-cap. It can not spin! And to ensure it can't back out either, I add a nut, and a drop of Loctite® for added security.

These assemblies are then press-fit into the aluminum barrels. This makes for an extremely strong joint. A drop of Loctite® is applied to these joints before fitting as well, just to be sure.