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How to choose a preamplifier for a power amplifier?

Let's take a moment to discuss the biggest challenge that audiophiles face when it comes to creating the perfect sound...

How to choose a pre-amplifier for a power amplifier
How to choose a pre-amplifier for a power amplifier

A typical setup for achieving top-notch sound quality at home involves a component system with separate preliminary and power amplification blocks. Despite its apparent simplicity, connecting a preamplifier and a power amplifier can be tricky, and even choosing both components from the same brand doesn’t always guarantee great results. Find out about the potential pitfalls, the benefits of a tube link in the circuit, installation mistakes to avoid, and what to focus on in our latest article.

1. It all starts with the gain...

1. It all starts with the gain…

A preamplifier’s primary function in a system is to align and enhance the signal from the source before sending it to the power amplifier. One common error is introducing a preamp that cannot properly boost the signal, or worse, overloading the power amp with a signal that is too strong. It’s crucial to ensure that the gain parameters of the preamp match the sensitivity of the power amp input to avoid any issues.

2. Parameters of input and output voltages are the most important selection criteria.

2. Parameters of input and output voltages are the most important selection criteria.

Another important electrical factor to consider is voltage when looking at performance characteristics. The output voltage represents the maximum capacity of the preamplifier, while the input voltage is the level at which the power amplifier can maintain its specifications. If the input voltage surpasses the output voltage, the devices won’t work well together, resulting in poor sound quality. The same applies if the preamplifier’s output voltage exceeds the power amplifier’s capabilities, leading to distortion.

3. Input and output impedance need matching

3. Input and output impedance need matching

Let’s now assess the input and output impedances of the devices. To ensure good sound quality, it’s important to set up the resistance of the electric current flow path like a “ladder”, with the power amplifier’s input impedance higher than the preamplifier’s output impedance. If not, the preamp will be overloaded and we won’t get that desired “brilliance”.

4. A balanced connection is almost always a good thing.

4. A balanced connection is almost always a good thing.

Most of the time, when devices are constructed with balanced circuits, it’s best to utilize XLR connectors for connecting them. A stronger signal level being transmitted ensures improved immunity to interference within the circuit. It’s recommended to steer clear of switching between a power supply with RCA outputs and a power amp with XLR inputs by using adapters – it’s not ideal.

5. Cabling is important - and it is most important in the area of ​​power supply to the power amplifier.

5. Cabling is important – and it is most important in the area of ​​power supply to the power amplifier.

Audiophiles often allocate a large portion of their budget to interconnects, but in reality, network cables, particularly those used for high-current power amplifier circuits, have the most significant impact on sound quality.

6. The bandwidth of devices is the primary criterion for assessing performance characteristics. SOI, signal-to-noise ratio, dynamic range are secondary.

6. The bandwidth of devices is the primary criterion for assessing performance characteristics. SOI, signal-to-noise ratio, dynamic range are secondary.

When assessing the performance of audio components, most enthusiasts focus on factors like SOI, signal-to-noise ratio, and dynamic range. However, nowadays even basic Hi-Fi equipment offers a decent level of performance in these aspects. What really sets High End technology apart is its impressive bandwidth, with a frequency response ranging from 0 to 1 MHz, ensuring a truly exceptional audio experience.

7. Selecting components from one brand is not a panacea. Everything is decided based on the results of the audition.

7. Selecting components from one brand is not a panacea. Everything is decided based on the results of the audition.

Sometimes, it’s just not feasible for a company to launch a stylish pre-amplifier and a stylish power amplifier together. That’s why there’s a simple rule to follow – evaluate the specifications, then listen, listen, and listen some more. In many high-end installations, it’s quite common to come across pre-amplification and power amplification components from different companies.

8. The weight of devices in 99% helps to evaluate the capabilities of their power supplies

8. The weight of devices in 99% helps to evaluate the capabilities of their power supplies

Indeed, there are instances where the device’s weight is increased by attaching a cast iron plate to the underside of the body. However, this anti-vibration technique is not commonly used. In the majority of cases, the weight of the device is attributed to power transformers, both for power and pre-power functions. As the power reserve has never been a concern (as stable power always enhances the sound quality), the principle is straightforward – the heavier each component is, the better.

9. A tube preamp can really elevate the sound.

9. A tube preamp can really elevate the sound.

Are you longing for a smooth and soothing sound that you can enjoy without getting tired? Maybe it’s time to think about adding a tube preamplifier to your system. When implemented correctly, a tube-based cascade can enhance the openness and naturalness of the sound.

10. Maximum attention to eliminating vibration should be concentrated on the preamplifier.

10. Maximum attention to eliminating vibration should be concentrated on the preamplifier.

Power amplifiers typically have a considerable weight due to their large power transformers, which actually helps with their anti-vibration properties. However, a lighter preamplifier could benefit greatly from having anti-vibration mounts installed.

11. Power filtering is indicated for the pre-amplifier and not for the power amplifier. The same applies to the regeneration of the supply voltage.

11. Power filtering is indicated for the pre-amplifier and not for the power amplifier. The same applies to the regeneration of the supply voltage.

Don’t go overboard with power filters – and be cautious with power regenerators. Typically, it’s recommended to connect high-current devices (such as power amplifiers) straight into a wall socket, making sure to use a good power cord (or else you might lose some dynamics). However, you can still try out different preamplification setups, and maybe think about adding an electricity filtering system for that part of your setup.

12. It is better not to place the pre-amplifier on the power amplifier (as in the promotional photo) - overheating is possible!

12. It is better not to place the pre-amplifier on the power amplifier (as in the promotional photo) – overheating is possible!

Most promotional photos show the preamplifier sitting on top of the power amplifier. However, it’s not recommended – check the manual for the minimum clearance needed for proper heat dissipation. Typically, it’s around 20-25 cm, so make sure to give enough space between the devices on the rack to prevent overheating.