How to Buy a Digital Amplifier on eBay

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How to Buy a Digital Amplifier on eBay

The first time audio became amplified was right after the introduction of the phonograph. Sound that was reproduced had too much interference and distortion, which resulted in very poor sound quality. With the development of converters in 1950, engineers were able to reproduce higher-quality audio. Yet background noise still existed, and scientists scrambled to develop advanced technology that produced pristine audio signals. Since the analogue to digital conversion still did not replicate the type of sound quality sought by audiophiles, stereo component manufacturers worked for over two decades to create truly digital audio signals. During the 1980s, digital stereo systems became the standard for audiophiles, though it was not until a few years later that digital amplifiers were produced to be compatible with a stereo speaker.

Audiophiles who shop for digital amplifiers should consider eBay as their number one shopping destination. eBay is home to myriad digital amplifier sellers, some of whom may offer nearly mint condition amplifiers at discounted prices. This is because eBay sellers may change their mind about the brand of digital amplifier that they want or they have decided on a different stereo system design. Before shopping for digital amplifiers on eBay, buyers should learn how digital amplifiers work, the advantages of using a digital amplifier, and what to consider before buying a digital amplifier on eBay.

Overview of a Digital Amplifier

Digital amplifiers are the latest innovation in a rapidly changing industry. This type of amplifier, which is often referred to as a Class D amplifier, creates an audio signal that remains digital from its inception until the signals reproduce. Consumers who want to buy digital amplifiers on eBay should first learn how digital amplifiers work and the advantages they provide to audiophiles.


Digital audio initially required the use of expensive sound systems that were mostly operated in scientific laboratory settings. A large number of computer chips were required to transfer digital signals from the point of origin to one or more speakers. Technology advancements have dramatically reduced the number of chips required to process digital signals, and hence, digital amplifiers have become accessible to the general public, especially online at eBay. They are no longer the sole domain of high-powered music acts and world famous symphonies.

How Digital Amplifiers Work

Digital amplifiers sold on eBay receive analogue signals and convert the signals into a digital format that varies by pulse width. While manufacturers produce design variations, Class D amplifiers are considered Pulse Width Modulator (PWM) designs. Digital amplifiers receive digital input from a source, typically in a linear pulse code format. The amplifier then converts the linear pulse format into a PWM, which produces a high voltage signal that filters to duplicate the original digital signal. The digital output signal synchronises with stereo speaker terminals to reduce background and machine noise.

Advantages of Digital Amplifiers

Technological advances have produced digital amplifiers that are much more affordable than they were early in their development. Only a few computer chips are required to mass produce digital amplifiers, which means the size and weight of the machines available on eBay have declined as well. Reduced sizes equates to reduced power waste and less heat release. What was once a low power conversion rate, now consistently exceeds 90 per cent. Consumers who want a Class D amplifier included in a home cinema system no longer have to make special requests, since digital amplifiers are routinely included in the systems. Digital amplifiers also provide extra power for mobile phone internal speakers.

What to Consider When Buying a Digital Amplifier

While some consumers place budget constraints at the top of their shopping criteria list, affordability should be considered only after an analysis of a digital amplifier’s performance. To judge performance, buyers can look at three technical, but easy to understand, performance concepts.

Matching Amplifiers to Speakers

When trying to match a digital amplifier with a set of stereo speakers on eBay, choose a digital amplifier that produces power two times greater than the speaker IEC power rating. A stereo speaker that possesses a normal impedance of eight ohms and an IEC power rating of 350 watts requires a digital amplifier that produces 700 watts for an eight-ohm load. With two speakers, the digital amplifier should produce 700 watts of power per speaker channel. First-class stereo speakers sold on eBay should be able to handle excess of an amplifier’s rated power if the amplifier delivers the peak with no distortion. Buying a digital amplifier that has extra "headroom" assures buyers that only undistorted power releases from the digital amplifier to the stereo speakers.

Damping Factor

Due to inertia, many stereo speakers vibrate after the digital signals have ceased. Audiophiles call this phenomenon “ringing” or “time smearing”. The speakers produce sound waves that do not resemble the original digital signal. Digital amplifiers exert control over stereo speakers, which reduces or eliminates the ringing. Damping refers to a digital amplifier’s capability to control stereo speakers. The damping factor, which measures amplifier control over speakers, is calculated by dividing load impedance by amplifier output impedance. If a stereo speaker load impedance measures at eight ohms and the amplifier has an output impedance of 0.01, then the damping factor calculates to 800. Speaker cable impedance may also influence the damping factor. Any damping factors over 1,000 are considered high, and buyers should stay away from any digital amplifier-stereo speaker combination sold on eBay that exceeds that level.


Ohms measure the level of resistance. Manufacturers typically construct digital amplifiers to operate with either four, eight, or 16 ohms of resistance. Optimal stereo system performance is achieved whenever speaker resistance load exactly matches digital amplifier resistance load. Many audiophiles prefer digital amplifiers that have eight ohms of resistance because too much resistance can lower the power delivered from the amplifier to the speakers, and too little resistance creates more power, which can overload speakers and damage the digital amplifier. Buyers who search for digital amplifiers on eBay should confirm ohm levels with prospective sellers.

How to Buy a Digital Amplifier

Before using eBay to find a digital amplifier, buyers should follow a few rules to ensure that they purchase a high-quality digital amplifier. First, listen to tube and solid-state digital amplifiers to become aware of the sound quality difference between the two primary types of integrated digital amplifiers. Check the stereo system speakers for the minimum and maximum power requirements. There is no reason to purchase a digital amplifier that falls below or above the speaker minimum or maximum power requirements. Speaker-digital amplifier compatibility also means that buyers need to know the nominal impedance specifications for the system speakers.

After collecting the pertinent speaker data, research digital amplifiers by reading audiophile magazines and going online to manufacturer websites. Read the informative eBay guides that describe how the components of stereo systems integrate to provide high-quality sound. During the buying process, request to take home digital amplifiers for test runs. Play live recordings on the test-run digital amplifiers to receive a more accurate depiction of sound quality. Compare at least three digital amplifier models before making a decision. The final decision should be based on sound quality, price, manufacturer’s warranty, and retailer service.   Above all, make sure any digital amplifier under consideration is truly digital.

Buying Digital Amplifiers on eBay

Educated buyers who come to eBay in search of digital amplifiers can find a wide variety of sellers to match their shopping criteria. The best way to find the right digital amplifier sellers is to type keywords into eBay’s powerful search engine, and then navigate through the search result pages until you find the right seller. Type specific keywords into the search engine to reduce the number of search results. For instance, type "Sony digital amplifier" or "Pioneer digital amplifier" to reduce the amount of time that you spend on an eBay search. Moreover, specifying a brand name gives you a better chance of finding a seller who offers a high-quality digital amplifier. Once you find the right seller, go to the seller’s product page to review the accepted payment methods, delivery terms, and return policies.

Know the Seller

During your seller search, consider sellers who have earned eBay’s Top-Rated Seller designation. These sellers have established reputations for selling high-quality products and offering generous return policies. Buying a digital amplifier requires you to test it out a few times before deciding if it truly is the right amplifier for you. Therefore, only consider top-rated sellers who offer return policies that exceed 30 days. You can also review customer feedback that eBay compiles on seller product pages. Look for sellers who have received positive feedback over the last year for selling electronics products. Once you forge a business relationship with an eBay seller, check if the seller runs an eBay Store where you can purchase products directly.


Sound amplification has come a long way since the phonograph was invented at the turn of the 20th century. Since the direct audio transmission from phonograph to speaker, audiophiles have discovered other ways to improve amplification and sound quality. For decades, sound amplification meant stereo receivers sending analogue signals to one or more system speakers. The true sound amplification breakthrough came to pass with the discovery of digital audio signals. This allowed manufacturers to produce digital amplifiers that project more power, without adding distortion and background noise. Sound that emanates from digital amplifiers is much more superior than any other amplification method.

The high sound quality projected by digital amplifiers means more consumers than ever are plucking stereo components off of retailer shelves. High demand often leads to inflated prices, which shrewd digital amplifier shoppers avoid by buying their amplifiers on eBay. The leading online auction site brings digital buyers and sellers together in a virtual marketplace that can help buyers save money. To save money, eBay buyers should collect all of the data required to match a digital amplifier with their stereo speakers. Then, they should test run a small sample of digital amplifiers to discern which one provides the ultimate in listening enjoyment.

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