INTERNAL PREAMP VS. EXTERNAL PREAMP SYSTEMS
The Advantages and True Cost of Each
Most transducers (and this includes our Acoustic Lens Transducers) will need a preamp of some sort to properly match their signal output to the outside world (a sound system of some sort) without losing volume and tone. The reason for this is that most soundboard and undersaddle pickups have a very high input impedance, and this makes them susceptible to hum and buzz. Plugging them directly into a lower impedance input like those found on most amps and sound systems can also alter the tone, volume and dynamic range available from the pickups, in subtle or dramatic ways. To keep this from happening, you can have a preamp installed inside the guitar, or you can run the signal through an endpin jack and cable to an external preamp, and then through another cable from the preamp to your sound system.
What are the pros and cons of each?
If you have a preamp installed inside the guitar, the cables from the pickups to the preamp are short, maximizing the signal level and tone, and they can be well shielded to reduce or eliminate hum and buzz in your signal. The signal that leaves the guitar through the endpin is now properly amplified, buffered from any outside interference, and (hopefully) low impedance. You only need one cable (instead of two or more) to run from your instrument endpin to your sound system. A standard cable can be short or as long as you need, capable of running hundreds of feet with little or no loss of volume or tone. The cable can be moved and repositioned during a performance without any static, popping or cable handling noise. If you're planning to use the instrument with a wireless system, then this is the logical choice, because it presents a finished, useable signal to the wireless transmitter, with no additional hardware needed. This type of system does the most to protect and preserve the sound created by your pickups and transfer it safely to your amplifier or sound system. Both the Amulet stereo and Amulet M systems use internal preamps. This is one of the reasons that Trance Audio systems have become a staple of professional touring setups the world over; they provide clean, reliable signals, even in difficult venues.
So, what are the cons of this type of system?
An internal preamp needs a battery placed inside the instrument to provide the power, and that means that it needs to be replaced from time to time. Ideally, the battery life would be long, and you would want to know when the battery will need to be replaced, so you won't end up high and dry at an important gig. A good idea would be to have an indicator alert you with plenty of time to spare before a change becomes absolutely necessary, so that the battery could be replaced during the next string change, when it's easy to access. Many available systems with an internal preamp don't meet one or both of these requirements, which makes them less attractive to some players, and for good reason. Having the spectre hanging over your head of a battery going dead without warning during a performance is certainly enough to make even seasoned performers nervous!
Another downside is that multiple guitars each need a pickup and preamp installed which can be more expensive compared to external preamp systems. However, on the plus side each guitar is also completely operationally independent, which means that they could be used without relying on any other gear, such as a shared external preamp.
How does this setup differ from the original Stereo Amulet System?
The original Stereo Amulet System approaches this type of setup in a slightly different way. The extremely light internal preamp is professionally powered from outside the guitar via an external control box (no batteries inside the guitar). A special cable connects the guitar and interface utilizing a professional miniaturized 5 pin Canon connector (NOT a fragile, clumsy screw-on DIN connector as we've seen incorrectly mentioned time and again). This locking connector is the same type used on professional miniaturized audio equipment such as wireless transmitters, and is designed to withstand the rigors of professional touring. It is keyed to prevent any damage to the pins when connecting, and holding the cable with the cable lock button under your thumb allows for easy, immediate connection of the cable, even on darkened stages. The internal preamp is provided with professional level balanced power through this cable, and the low impedance buffered signals are brought back to the interface and on to the outside world. This keeps the components inside the guitar at an absolute minimum. This system can be powered by batteries or AC adapter, is very portable (everything fits into the guitar case if desired), and allows you to easily and quickly plug in at an open mic or jam session in mono or stereo using no more extra equipment, and without being a bigger commitment, than a system that needs an external preamp.
All Trance Audio products, including the original Amulet System and the Amulet M, utilize internal preamps. If you use a system that relies on an external preamp, then first and foremost, the pickup and the entire signal chain between it and the preamp must be carefully shielded.
Inside the guitar, this includes the pickups, the wire lead that comes from them to the endpin, and the entire endpin assembly. The cable that connects the endpin to the preamp is also a critical link; it needs to be a very well shielded and low capacitance cable, and these will cost more than a standard guitar cable. Because of the heavier construction of this type of cable, it tends to be stiffer and harder to keep from kinking and tangling if you move around on stage. It also can't be very long, because each foot of cable used between the guitar and external preamp robs your signal of volume and vitality. Even for very good cables, 10 feet would be the longest cable you could use without noticeable consequences. Less expensive cables will fare even worse in this application. Because of the high impedance, any cables used here will be much more likely to make noise (static or popping) when moved, and any problems with the cable due to wear or light damage will often show up as noise or hum. This type of system is more prone to problems and signal loss or degradation due to shielding or cabling problems, and is more likely to pick up interference from radio stations, neon signs, etc.
So, what are the advantages of this type of system?
If you use multiple instruments, an advantage here would be that you only need one external preamp, and can plug each of your guitars into it, as needed. Of course, you would still need to change the battery in the preamp from time to time, and would need to know when it needed to be changed to avoid being surprised at a gig. You may also need tools to open the preamp to change the battery.
What's the true cost of a system like this?
The true cost of a system with an external preamp would need to take into account all of these items needed for proper operation. Although sometimes a set of pickups alone may seem initially less expensive, once you factor in the cost of the pickups, the external preamp and the additional high quality cable to connect the guitar to the preamp (as well as the ensuing potential problems), the cost can be quite a bit more than you suspect.
So given all this, how do we approach these choices with the Amulet M system?
The Amulet M is a complete system, with an internally mounted high quality Dual Mono preamp. The endpin electronics package isn't some simple, stripped-down lower quality compromise; it faithfully delivers the same quality and reliability of performance that our customers have come to expect from our products over the years, and a few new twists as well. We decided early on that we would not offer an in-guitar system powered from a single 9 volt battery until we could meet or exceed the performance of our world-renowned Stereo Amulet system. The Amulet M system achieves that goal, and we invite you to compare our measured and published specifications to those of other systems on the market (if you can find them).
The battery life is very long (typically better than 100 hours) and the battery is easy to change when changing your guitar strings.
A battery life indicator LED is included with the M-V and M-VT systems. This sophisticated indicator draws virtually no power from the battery during normal operation (prolonging useful battery life), and flashes brightly at one second intervals when it's time to change the battery. And because we realize that you may not be able to change the battery right away, the system will still function very well for several hours or more after the LED begins to flash. After all, who doesn't procrastinate when it comes to changing these things?
The output from the high quality Switchcraft endpin is low impedance, and you don't need an additional (and expensive) cable to hook the guitar to an external preamp. You can use a standard guitar cable to connect to your sound system. The cable can be as long as you need without loss of sound quality, and handling or moving the cable will not produce static, popping or any other cable handling noise, even with lesser quality cables.
Finally, our prices reflect the cost for a complete system, ready to plug into your amp or sound system with no additional components needed or hidden costs. Our multiple options give you the flexibility to choose a system to fit your exact needs and budget.