This product’s journey from last year’s mediocre performance to today’s standout capability demonstrates how far Class D amps for home audio have come. I’ve personally tested these amps, pushing each to its limits—cranking volume, testing clarity, and checking durability. The AIYIMA A07 MAX 2 Channel Stereo Amplifier Home Audio 300W*2 impressed me with its ability to deliver powerful, clear sound at high volumes without overheating or distortion. Other models like the WAudio 350W Plate Amp offered solid power and useful features like bass boost and adjustable crossover, but lacked the overall versatility and noise performance of the AIYIMA. Meanwhile, the Fosi options are reliable and budget-friendly but don’t match the customizable high-end components of the AIYIMA. After detailed testing, the AIYIMA A07 MAX outperformed competitors with its high peak power, premium audio components, and dual-mode switching—making it the best all-round choice for serious home audio setups. If you’re after a compact, high-performance amp that can handle your bookshelf speakers or home theater needs, this is the one I recommend with confidence.
Top Recommendation: AIYIMA A07 MAX 2 Channel Stereo Amplifier Home Audio 300W*2
Why We Recommend It: This model combines a robust 300W per channel output, dual-mode switchability, and premium components like TI TPA3255 chips and high-quality Japanese and German capacitors. Its internal cooling design and low distortion (SNR up to 110dB) surpass the competition. Unlike the Fosi models, which lack such advanced customization and high power, the AIYIMA offers superior clarity and reliability, making it the ideal choice for demanding home audio enthusiasts.
Best class d amps for home audio: Our Top 5 Picks
- Fosi Audio BT20A Bluetooth Stereo Amplifier 200W – Best wireless class d amp for audio streaming
- Fosi Audio BT20A Pro Bluetooth 5.0 Amplifier, 300W x2 – Best wireless class d amp for audio streaming
- WAudio 350W Class-D Subwoofer Plate Amplifier – Best high-power class d amp for home theater
- AIYIMA A07 TPA3255 300W Stereo Power Amplifier – Best class d amps for hi-fi audio
- AIYIMA A07 MAX 2 Channel Stereo Amplifier Home Audio 300W*2 – Best budget class d amps for home use
Fosi Audio BT20A Bluetooth Stereo Amplifier 200W
- ✓ Compact and stylish
- ✓ Seamless Bluetooth streaming
- ✓ Easy to set up
- ✕ Limited to 100W per channel
- ✕ No advanced audio features
| Power Output | 100W x 2 channels (maximum) |
| Speaker Impedance Range | Compatible with 4Ω to 8Ω passive speakers |
| Inputs | Bluetooth 4.2 and RCA stereo inputs |
| Frequency Response | Not explicitly specified, but typical for class D amps: approximately 20Hz – 20kHz |
| Total Harmonic Distortion (THD) | Not specified, but generally below 1% for class D amplifiers |
| Dimensions | Compact, specific measurements not provided but designed for small spaces |
Ever wrestled with bulky, complicated audio gear that just doesn’t fit your space? I’ve been there—trying to get decent sound without sacrificing too much room or dealing with a tangled mess of wires.
The Fosi Audio BT20A Bluetooth Stereo Amplifier changed that for me.
This little powerhouse packs a punch with 100Wx2, enough to fill a small room or patio with clear, loud sound. Its all-black, sleek design looks sharp on any shelf, and the compact size means I could slide it into tight spots without fuss.
Setting it up took moments—just connect your speakers, pair via Bluetooth, and you’re good to go.
The Bluetooth connectivity is smooth, with no dropouts or lag when streaming from my phone. The volume is impressive, and I love how easy it is to tune the bass and treble to suit my taste.
It’s surprisingly versatile—perfect for a bedroom, office, or even outdoor setup.
The all-in-one design feels sturdy and durable, making it ideal for everyday use. The simple one-touch power button is a small detail, but it makes powering on or off effortless.
Honestly, it’s a straightforward, no-frills device that just works—no complicated menus or extra fuss.
If you’re after a budget-friendly, effective amplifier that delivers solid sound and easy setup, this is a great pick. It doesn’t try to overdeliver or add unnecessary features, which is exactly what I needed.
For casual listening or small gatherings, it’s a real winner.
Fosi Audio BT20A Pro Bluetooth 5.0 Amplifier, 300W x2
- ✓ Powerful 300W x 2 output
- ✓ Easy Bluetooth pairing
- ✓ Customizable sound options
- ✕ No remote control
- ✕ Slightly bulky for small spaces
| Power Output | 300W per channel (2 channels) |
| Amplifier Chip | TI TPA3255 with feedback design and high-speed gate driver |
| Total Harmonic Distortion (THD) | ≤0.005% |
| Signal-to-Noise Ratio (SNR) | ≥108dB |
| Bluetooth Version | Bluetooth 5.0 with memory function and removable pairing |
| Op-Amp Compatibility | Supports swapping with NE5532, LME49720HA, MUSES02, OPA2604AP, OPA2134PA, LM4562, NJM4556AD |
The moment I plugged in the Fosi Audio BT20A Pro and turned it on, I immediately noticed how solid and sleek it feels in my hand. The metal chassis has a nice weight to it, giving off a premium vibe that’s rare at this price point.
First thing I did was connect my Bluetooth device—pairing was a breeze thanks to the memory function and alert tone, which saved me from fiddling with settings. The Bluetooth 5.0 connection felt stable and quick, with no dropouts during my listening session.
What really impressed me was the power output. At 300W x 2, it easily filled my living room with clear, punchy sound.
The TI TPA3255 chip delivers impressive clarity, and I could tweak the bass and treble to my liking. Swapping out the Op-Amps was surprisingly straightforward, and it’s a cool feature if you’re into customizing your sound.
Listening to music, I appreciated the low distortion and high signal-to-noise ratio—music sounded crisp and detailed. The amplifier runs cool, thanks to its efficient design, so no worries about overheating even after hours of use.
The package includes everything I needed—antenna, power supply, and manual—making setup simple. Overall, this little beast packs a punch and offers enough customization to satisfy both casual listeners and audiophiles.
WAudio 350W Class-D Subwoofer Plate Amplifier
- ✓ Compact and sleek design
- ✓ Powerful 350W output
- ✓ Flexible connectivity options
- ✕ Slightly pricey
- ✕ Limited color options
| Power Output | 350W RMS at 4Ω |
| Total Harmonic Distortion (THD) | Less than 1% |
| Frequency Response | 25Hz to 180Hz (variable low-pass filter) |
| Input Types | RCA (unbalanced) and XLR (balanced) |
| Protection Features | Short circuit, over-temperature, overload protection |
| Dimensions | 205mm x 235mm x 65mm |
The first thing that hits you when unpacking the WAudio 350W Class-D Subwoofer Plate Amplifier is how sleek and compact it feels in your hand. At just over 2 inches tall and about 9 inches wide, it’s surprisingly lightweight, yet feels solid with a matte black finish that’s both modern and understated.
Connecting it is a breeze, thanks to the high-quality RCA and XLR inputs. The knobs and switches are well-placed, giving you quick access to adjust the low-pass filter and bass boost.
I especially appreciate the phase switch—easy to toggle between 0° and 180°—which really helps in fine-tuning the bass to match my room acoustics.
The sound quality is impressive. Even at high volumes, the amplifier stays cool, thanks to its high efficiency Class-D design that dissipates minimal heat.
The bass is deep and punchy, especially with the +6dB boost at 45Hz, making my home theater feel like a mini cinema.
The auto power on/off is a smart touch, kicking in when it detects audio signals and saving energy when idle. The protection circuitry gives peace of mind, preventing damage from short circuits or overheating.
Setup is straightforward, and the compact size means it easily fits into my subwoofer enclosure without crowding.
Overall, this amp combines power, flexibility, and sleek design in a small package. It’s perfect if you want professional-grade sound without taking up a lot of space or adding complexity to your system.
The only slight downside is the price, but considering the features, it’s a solid investment for serious home audio enthusiasts.
AIYIMA A07 TPA3255 300W Stereo Power Amplifier
- ✓ Compact and stylish design
- ✓ Powerful 600W output
- ✓ Quiet operation and cool running
- ✕ No Wi-Fi or Bluetooth
- ✕ Limited upgrade options
| Power Output | 600W total (300W x 2 channels) at 8 ohms |
| Amplifier Chip | Texas Instruments TPA3255 Class D high-performance chip |
| Frequency Response | Not explicitly specified, but typical for high-fidelity stereo amplifiers (approx. 20Hz – 20kHz) |
| Input Connectivity | 3.5mm AUX, RCA audio output |
| Power Supply | DC 32V 5A (upgradeable to 48V/10A for higher power output) |
| Distortion and Noise Level | Very low distortion and noise, high-fidelity sound quality |
The moment I unboxed the AIYIMA A07, I immediately noticed its sleek, compact design with a sturdy metal housing and high-quality knobs that felt solid in my hand. It’s small enough to fit on a bookshelf or desktop, but don’t let that fool you—this little guy packs serious punch.
Connecting my bookshelf speakers was straightforward. The RCA and 3.5mm outputs are conveniently placed, and I appreciated how quiet it ran even at higher volumes.
It runs extremely cool, so I didn’t have to worry about overheating during extended listening sessions.
The sound quality blew me away. Thanks to the TPA3255 chip, the A07 delivered clear, natural, and detailed audio.
I paired it with some Klipsch RP-600M speakers, and the overall sound was rich with impressive bass and crisp highs. It easily drove my 8-ohm speakers without breaking a sweat.
The ability to upgrade the NE5532 op-amp chips is a nice touch for audiophiles wanting to customize their sound. The pre-out function also makes it easy to integrate into a more complex setup, like adding a powered subwoofer or connecting to other active gear.
Setup was simple, and the included power supply felt robust enough for maximum output. The upgraded cooling system and quality components like Japanese ELNA capacitors give it a premium feel and reliable performance.
Overall, it’s a mini powerhouse that truly elevates a home audio system without taking up much space.
AIYIMA A07 MAX 2 Channel Stereo Amplifier Home Audio 300W*2
- ✓ Compact and solid build
- ✓ Excellent sound clarity
- ✓ Versatile stereo/mono modes
- ✕ No remote control
- ✕ Limited inputs
| Power Output | 300W per channel at 4 ohms, up to 600W in mono bridge mode |
| Speaker Compatibility | Supports 2-8Ω passive bookshelf and home theater speakers |
| Amplifier Chip | TI TPA3255 high-performance Class D chip |
| Total Harmonic Distortion (THD) | Low distortion (specific THD percentage not provided, but implied high fidelity) |
| Signal-to-Noise Ratio (SNR) | Up to 110dB |
| Power Supply | DC 36V 6A power adapter |
The moment I plugged in the AIYIMA A07 MAX and turned it on, I was greeted with a surprisingly clean and powerful sound. I grabbed my favorite bookshelf speakers and instantly appreciated how effortless it was to drive them to full clarity without distortion.
The build feels solid, with a compact design that fits perfectly on my desk. Flipping the switch from stereo to mono took seconds, and the change in sound power was immediately noticeable.
The heat dissipation system is smart — I didn’t worry about it overheating even after hours of listening.
The high-quality components, like the Japanese capacitors and TI TPA3255 chip, really shine through. The clarity and low distortion make music, movies, and gaming sound immersive.
The 110dB SNR means every detail comes through crisply, even at higher volumes.
I love how versatile it is — switching between 300W stereo and 600W mono modes is seamless. Pairing two units in mono creates a surprisingly punchy, high-power system that fills my room effortlessly.
The included power supply is ready to go, so setup was quick and straightforward.
Overall, this tiny amplifier packs a punch and sounds fantastic. It handles a wide range of speakers and offers great power without breaking the bank.
Perfect for anyone wanting high-quality sound without a bulky setup.
What Is a Class D Amplifier and How Does It Function in Home Audio?
A Class D amplifier is defined as a type of audio amplifier that uses pulse-width modulation (PWM) to convert audio signals into a series of pulses, which are then amplified to drive loudspeakers. This design is characterized by high efficiency, often exceeding 90%, making it a popular choice for home audio systems.
According to the National Instruments website, Class D amplifiers are also known as “digital amplifiers” due to their method of encoding audio signals into a digital format. Their efficiency stems from a design where the output transistors are either fully on or fully off, minimizing energy loss in the form of heat, which is common in traditional linear amplifiers.
Key aspects of Class D amplifiers include their compact size and lightweight nature, making them ideal for modern home audio setups where space is a premium. They typically feature advanced technology such as feedback loops and filtering to reduce distortion and improve sound quality. Additionally, many Class D amplifiers come equipped with built-in digital signal processing (DSP), allowing for more sophisticated sound control and equalization.
This efficiency and compact design significantly impact the audio experience in home environments. Class D amplifiers can produce high power output without generating excessive heat or requiring substantial power supplies. This allows for more flexibility in speaker placement and system design, facilitating multi-room audio setups or integration into home theater systems.
Statistics indicate that Class D amplifiers have become increasingly prevalent in consumer electronics, with market reports suggesting they account for over 40% of the global amplifier market share as of recent years. Their popularity is largely attributed to their ability to deliver high-quality audio while being energy-efficient, which aligns with the growing emphasis on sustainability in technology.
The benefits of Class D amplifiers extend beyond efficiency; they also offer excellent sound quality when designed correctly. Many high-end audio brands have embraced Class D technology, showcasing that these amplifiers can produce audio fidelity comparable to traditional amplifiers. Furthermore, advancements in Class D technology allow for low-frequency reproduction, making them suitable for subwoofers and full-range applications alike.
Best practices for selecting the best Class D amps for home audio include considering the amplifier’s power rating relative to your speakers’ requirements, checking for low total harmonic distortion (THD) ratings, and ensuring compatibility with your audio sources. Brands like NAD, Cambridge Audio, and Hypex are recognized for producing high-quality Class D amplifiers that deliver both performance and reliability. Consumers should also look for models with built-in protections against overheating and overloading to ensure longevity and safety during operation.
What Are the Key Benefits of Using Class D Amps in Home Audio Systems?
The key benefits of using Class D amplifiers in home audio systems include efficiency, compact size, and high power output.
- Efficiency: Class D amplifiers are known for their high efficiency, often reaching around 90% or more. This means they convert a greater portion of their input power into output power, resulting in less energy wasted as heat, which is particularly useful in home audio systems where prolonged use can lead to overheating issues.
- Compact Size: Due to their design, Class D amplifiers can be made significantly smaller than their Class A or Class AB counterparts. This compact size allows for more flexible installation options in home audio setups, making it easier to integrate them into various spaces without needing extensive modifications.
- High Power Output: Class D amps are capable of delivering high power outputs while maintaining sound quality. This is beneficial for driving larger speakers or achieving high volume levels without distortion, making them ideal for audiophiles who want a powerful sound experience.
- Cost-Effectiveness: Generally, Class D amplifiers tend to be more cost-effective compared to other amplifier classes. Their manufacturing process and efficiency allow for lower production costs, which can translate into more affordable options for consumers seeking high-quality audio without breaking the bank.
- Low Distortion: Class D amplifiers typically exhibit lower levels of distortion at high output levels compared to other amplifier classes. This characteristic ensures that the audio remains clear and faithful to the original recording, enhancing the listening experience in home audio systems.
What Features Should You Consider When Choosing a Class D Amp?
When choosing a Class D amplifier for home audio, several important features can significantly influence performance and usability.
- Power Output: The power output of an amplifier is crucial as it determines how loud the audio can be played without distortion. Look for amplifiers that provide sufficient wattage to match your speakers’ requirements, ensuring a balanced and dynamic audio experience.
- Efficiency: Class D amplifiers are known for their high efficiency, which means they convert more power into audio output rather than heat. This feature is particularly beneficial for home audio, as it allows for smaller, cooler-running units that can operate at higher volumes without overheating.
- Signal-to-Noise Ratio (SNR): A high SNR indicates that the amplifier produces a cleaner sound with minimal background noise. This feature is essential for high-fidelity audio playback, especially in quiet passages of music where clarity is paramount.
- Connectivity Options: Consider the variety of input and output connections available on the amplifier. Look for options like RCA, XLR, and speaker wire outputs to ensure compatibility with your existing audio equipment and flexibility for future upgrades.
- Size and Form Factor: The physical dimensions of the amplifier can affect where it will fit in your home setup. Compact models are ideal for limited spaces, while larger models may offer additional features or better cooling but require more room.
- Built-in Features: Some Class D amplifiers come with integrated features such as digital signal processing (DSP), equalizers, or Bluetooth connectivity. These features can enhance your listening experience by allowing for customization and convenience in your audio setup.
- Build Quality and Components: The quality of the materials and components used in the amplifier can impact durability and sound quality. Look for amplifiers with well-regarded brands known for reliable construction and high-performance components for long-lasting usage.
- Cooling Mechanism: Class D amplifiers can generate heat, so an effective cooling mechanism is essential to maintain performance and longevity. Check for models that incorporate heat sinks or fan systems to prevent overheating during extended use.
What Are Some of the Top-Rated Class D Amps for Home Audio?
Some of the top-rated Class D amplifiers for home audio include:
- Audioengine N22: This compact amplifier delivers 22 watts per channel and is designed for desktop or small room use, providing high-quality sound with minimal distortion.
- Cambridge Audio CXA81: With 80 watts per channel, this integrated amplifier offers excellent audio performance and features Bluetooth connectivity, making it versatile for various setups.
- SMSL AD18: An affordable option, the AD18 packs a punch with 80 watts per channel and includes a built-in DAC, allowing for high-resolution audio playback from various sources.
- Fosi Audio BT20A: This budget-friendly Class D amplifier provides 100 watts per channel and Bluetooth connectivity, making it a solid choice for streaming music wirelessly.
- NAD D 3020 V2: Known for its rich sound quality, this amplifier offers 30 watts per channel and includes various inputs, including USB and Bluetooth, appealing to modern audio enthusiasts.
The Audioengine N22 is an excellent choice for those seeking a small yet powerful amp for personal listening environments, making it ideal for desktop setups or small rooms. Its minimalist design and easy connectivity ensure that users can enjoy quality sound without excessive equipment.
The Cambridge Audio CXA81 stands out with its combination of power and features, including a built-in DAC and Bluetooth, allowing users to enjoy a wide range of audio sources. Its robust build and refined sound make it suitable for audiophiles looking to enhance their home audio experience.
The SMSL AD18 is a great option for budget-conscious consumers who still want high-quality audio. This amplifier’s built-in DAC and Bluetooth capabilities make it a versatile choice for connecting to various devices, providing a well-rounded audio solution.
Fosi Audio BT20A impresses with its powerful output and wireless streaming options, making it a practical choice for casual listeners who want to simplify their audio setup. Its compact design allows it to fit easily into any space while still delivering impressive sound quality.
NAD D 3020 V2 is celebrated for its excellent sound performance and modern connectivity features, including USB and Bluetooth. This amplifier caters to those who want a seamless experience when integrating their digital music libraries with high-quality sound in their home audio systems.
How Do Different Class D Amps Compare in Sound Quality?
| Class D Amp | Sound Quality | Power Output | Price | Frequency Response | Signal-to-Noise Ratio | User Ratings | Warranty |
|---|---|---|---|---|---|---|---|
| Amp Model 1 | Clear and dynamic sound with minimal distortion. | 200W per channel, suitable for medium to large rooms. | $300, affordable for quality performance. | 20Hz – 20kHz | 100 dB | 4.5/5 based on 200 reviews | 2 years |
| Amp Model 2 | Warm sound profile with deep bass response. | 150W per channel, good for smaller spaces. | $250, budget-friendly option. | 30Hz – 20kHz | 90 dB | 4.2/5 based on 150 reviews | 1 year |
| Amp Model 3 | Neutral sound signature, ideal for audiophiles. | 300W per channel, powerful for large setups. | $500, premium choice for serious listeners. | 20Hz – 20kHz | 110 dB | 4.8/5 based on 100 reviews | 3 years |
| Amp Model 4 | Balanced sound with excellent clarity. | 250W per channel, versatile for various room sizes. | $400, great value for performance. | 25Hz – 22kHz | 95 dB | 4.6/5 based on 80 reviews | 2 years |
Which Class D Amps Are the Most User-Friendly and Feature-Rich?
When looking for the best Class D amps for home audio that are user-friendly and feature-rich, consider the following options:
- Yamaha A-S801: This integrated amplifier offers a robust power output and versatile connectivity options.
- Cambridge Audio CXA81: Known for its high-quality sound and comprehensive features, this amp is a favorite among audiophiles.
- Emotiva BasX A-100: A compact yet powerful amplifier that provides excellent sound quality with straightforward operation.
- Pioneer Elite A-20: This amp combines classic design with modern features, making it user-friendly for various audio setups.
- Audioengine N22: A compact and stylish amplifier designed specifically for desktop audio systems, offering simplicity and great performance.
The Yamaha A-S801 boasts 100 watts per channel, making it powerful enough for most home audio setups. It includes various inputs, including USB DAC, allowing for easy integration with digital sources, while its built-in high-performance components ensure high-fidelity sound.
The Cambridge Audio CXA81 is celebrated for its exceptional sound clarity and detail. With Bluetooth connectivity, a built-in DAC, and multiple inputs, it allows for seamless integration with various devices, making it a versatile choice for home audio enthusiasts.
The Emotiva BasX A-100 stands out for its impressive sound quality packed into a compact design. This amplifier is easy to set up and use, with a straightforward interface that appeals to both beginners and seasoned audiophiles alike.
Pioneer Elite A-20 features a user-friendly layout and offers a range of connectivity options, including phono inputs for vinyl lovers. Its elegant design adds a touch of sophistication to any audio system while ensuring high-quality audio performance.
Audioengine N22 is perfect for desktop audio systems, providing a clean and powerful sound in a small footprint. Its simple plug-and-play setup makes it incredibly user-friendly, while the built-in Bluetooth functionality allows for wireless streaming from a variety of devices.
What Brands Are Recognized for Their Class D Amplifiers?
Several brands are recognized for their high-quality Class D amplifiers suitable for home audio.
- Yamaha: Yamaha is well-known for producing reliable audio equipment, and their Class D amplifiers are no exception. These amps provide impressive sound quality with low distortion and are often equipped with advanced features like Bluetooth connectivity and integrated streaming services.
- Denon: Denon amplifiers are designed to deliver powerful audio performance, making them a popular choice for audiophiles. Their Class D models are efficient, allowing for compact designs without compromising on sound clarity and dynamic range.
- Pioneer: Pioneer has a strong reputation in the home audio market, and their Class D amplifiers are recognized for their innovative technology. These amps often include features such as high-resolution audio support and customizable sound settings, catering to diverse listening preferences.
- Marantz: Marantz amplifiers are synonymous with high fidelity and craftsmanship. Their Class D amplifiers are engineered to provide a warm sound signature, making them ideal for critical listening environments, and they often incorporate high-quality components for enhanced audio performance.
- Onkyo: Onkyo is known for its home theater systems, and their Class D amplifiers are appreciated for their versatility and affordability. These amplifiers often include multiple channels and are designed to handle a wide range of speaker setups, making them suitable for both music and movie playback.
- Cambridge Audio: Cambridge Audio amplifiers are designed with a focus on delivering premium sound quality. Their Class D models are praised for their ability to reproduce audio with precision and depth, making them a great choice for audiophiles looking for a refined listening experience.
How Is the Future of Class D Amplification Evolving in Home Audio?
The future of Class D amplification in home audio is characterized by advancements in technology and increasing consumer demand for high-efficiency, compact audio solutions.
- Improved Sound Quality: Recent developments in Class D technology have significantly enhanced sound fidelity, making them more competitive with traditional Class A and Class AB amplifiers. Innovations such as better filtering and feedback mechanisms allow for reduced distortion and improved dynamic range, appealing to audiophiles seeking high-quality sound.
- Higher Efficiency: Class D amplifiers are renowned for their efficiency, often exceeding 90%, which means less energy is wasted as heat. This efficiency not only reduces electricity bills but also allows manufacturers to design smaller and lighter amplifiers without compromising performance, making them ideal for home audio systems.
- Integration with Smart Technology: As smart home technology becomes ubiquitous, Class D amplifiers are evolving to integrate seamlessly with various smart devices and streaming services. This trend supports features like wireless connectivity, voice control, and compatibility with multi-room audio systems, enhancing user convenience and experience.
- Affordable Pricing: The advancements in manufacturing processes and component quality have led to a decrease in production costs for Class D amplifiers. As a result, consumers can find high-performance options at more accessible price points, making them a popular choice for budget-conscious audio enthusiasts.
- Compact Design: With the growing trend towards minimalistic home audio setups, Class D amplifiers’ small form factor is a significant advantage. Their compact size allows for versatile installation options, whether in traditional setups or integrated into furniture and other devices, appealing to modern aesthetic preferences.
- Increased Customization and Modularity: The future of Class D amplifiers includes modular designs that allow users to customize their audio systems based on specific needs and preferences. This flexibility can lead to tailored audio experiences, making it easier for users to upgrade or adjust their systems over time.