What you should consider when purchasing a tube preamp

• Choose a high signal level: Tube preamps have signal levels. When you boost up the gain, your instrument strengthens the signal sent to the next device in the chain. Try to select a higher signal level, as that would make it easier for other devices to receive and manipulate the signal. There are some tube preamps that offer a fixed boost, but you should always go for the ones that allow for a variable boost, in order to match better with a greater number of devices.

• Check for volume control: Yet another important factor to consider is the volume control. The volume is a different functionality from the boost gain, despite being seemingly similar. While the gain boosts up the strength of the signal going into a piece of gear, the volume control remains passive and only contributes in increasing the signal strength right before the output. The volume is the amplitude of the signal going out of a piece of gear.

• Ensure the correct impedance: There are different types of tube preamps, and you must be very careful to choose the right product which offers the correct impedance for other parts as well. This is because mismatched impedance can cause losses in the signal to such an extent that it will become very difficult to work with. The general rule is that you should go for a low impedance source to be connected to a high impedance input device, and not vice versa. (If the source has high impedance and is being fed to a low impedance device, the device will get a severely reduced signal. That's something to be avoided.)

In short, be sure that you check the specifications carefully, and only then make your purchase.