Investing in amplifier parts can be daunting. Especially if you are unsure, which one to buy that matches the requirements? To understand your amplifier needs, it is essential to figure out how different transformers work. Although, the technicalities can be boring, understanding them can help you filter out your needs from an array of options.

Let us first understand what a transformer actually is. In simple terms, it is important for saving the speakers and amplifiers from combustion. A transformer helps in stabilizing and regulating the AC voltage. Did you know that they were initially installed in radios but are still in use today?

There are four basic types of transformers; these are Power Transformers, Output Transformers, Chokes and Reverb Drivers. In this article, we will talk about output and power transformers. What they are and why you need them to meet your sound expectations.

Impedance

An important term when understanding how a transformer works is impedance. To define it in simple terms, it is the voltage curated to the required current needs of the speakers and amplifiers. Think of impedance as a transformation of electrical energy from the input source to the output source. 

When looking at transformers, it links the tube amp to the speakers while affecting the sound. The sound of two transformers having the same specifications and quality may sound different. This is because a high-quality transformer can make all the difference in the world. While a replacement of a transformer is an option, replacing parts using a power transformer can somewhat have the same impact.

Using a transformer not only saves the speakers from combustion but also affects the sound to “feel” good. Music artists choose transformers based on their audio needs and the environment in which they plan to perform. Transformers are not intelligent devices but are simply useful for the transformation of electricity from one direction to another. The bidirectional nature of a transformer allows the input and output connections to transfer electric flow appropriately.

Difference between Output Transformer and Power Transformer

A power transformer does not affect the sound from the speakers. However, if the layout of the amp’s circuit is faulty, it can cause a low hum in the speakers. This happens because of the induction of bad signals in the circuit chain. A power transformer only supplies power to the amplifier’s circuit.

On the other hand, an output transformer simply transfers a tube amp’s output power, which is high voltage and low current to AC. Alternating current (AC) is what the speaker needs, which is a low voltage and a high current. Keeping this fact in mind, a small output transformer usually changes the behaviour of the amplifier when it is overloaded or overdriven. This can cause the transformer or the amp to fail and it does not last long.

What is the Input and Output of a Transformer?

Transformers do not generate electricity for the amplifiers but rather transfer electrical power. Using magnetic coupling, a transformer changes the main electrical power to an alternating current required by the speaker. The primary side is the input connections that takes in the main current from an electrical source and the magnetic coupling takes care of the rest. The DC is converted to AC and sent to the load (the speakers) using a secondary side, known as the output connection.

This change in the electrical flow and voltage is done in a way, which does not have an impact on the speakers or the amp tube. The main source of electrical power can cause one or more parts of the circuit to become faulty. A transformer ensures this does not happen. 

What is the Use of a Power Transformer?

While a power transformer does not have a direct impact on the sound of the amplifier, it is an important part of the circuit. It is essential for transferring the flow of electricity from the input connection to the output connection. Typically, power transformers are in use for distribution systems to regulate the interface of step up and step down voltages.

The ranges of power transformers vary from small, medium and large transformers and this is the basis on, which they are classified. A popular choice among music artists is the Marshall Style 50W Power Transformer with an upright mount. It comes with a variation of 120, 220 and 240V and has a paper core like the originals. This power transformer is great with most 50W JMP and JCM800 amplifiers. 

The construction of this power transformer is vintage type, which can be used as a replacement or a part for an upgrade. Since Marshall is a brand name trusted over the years by users, getting an authentic supplier can be hard to find. Luckily, Amp Parts Direct is a trustworthy supplier that offers many other options.

Look at the Fender Deluxe Style 20W Upright Power Transformer that is compatible with Deluxe, Tweed Tremolux, Deluxe Reverb style amplifiers. However, since the mounting is different, it is not compatible with the 65 Deluxe Reverb Reissue. There are only two types of variations in 120 and 240V but is a versatile 20W power. Fender is a brand that creates ideal parts for DIY projects by offering flexibility.

What is an Audio Output Transformer?

As we have cleared the concept of what transformers do, an audio transformer works with the use of a magnetic core. Two or more magnetic coils convert the magnetic energy into electric energy using an AC power source. The primary coil receives the power and the secondary coil delivers the output power.

The magnetization of the iron core has its limits and anything more may cause distortion. Once the iron core is completely magnetized or saturated, it results in a low quality of sound. It works similar to how transistor devices work, the output signal size is limited. This is the reason why choosing the right size of the core and material is essential.

Similarly, a bigger transformer has a bigger iron core and so it requires more power to operate at optimum. This is the reason why output transformers directly affect the sound. Keeping this distortion in mind, music artists prefer a smaller iron core and use the distortion as part of the sound. You may have noticed that even when the sound is clear, there is some amount of distortion in every amp.

However, it all depends on the preference of each individual. While some companies use this rare knowledge to charge a lot more for an output transformer that could otherwise be standard. Amp Parts Direct price transformers for what they are worth.

So what do you need?

Being a user means that you must have an idea of what you need to change in the sound. This is why having enough knowledge about different transformers can be a game-changer. Take the example of Project & Fender Super Reverb, Tweed Bassman, Pro, Bandmaster Reverb Style, 40W / 50W Power Transformer. It has a small output transformer when compared to others like the Blackfront Super Reverb Power Transformer by Mercury Magnetics.

While some musicians prefer adding a bass response for an overall cleaner sound using a large output iron, others simply change this in the amps. As a rule of thumb, the maximum power and bass response result in very subtle changes. For a dramatic change in the sound, experimenting with different speakers can yield results.

Does the Power Transformer Affect Tone?

A popular belief among amp technicians is that a power transformer does not affect the overall tone of the guitar’s amplifier. Since a power transformer only distributes the flow of energy from an input source to the output source, it should not affect tone. That is the job of the output transformers.

Right? Well, not really.

Upgrading a power transformer can play an important role in affecting the guitar’s amplifier overall tone. See the audio circuit works well only when the quality of each connection is up to a set standard. The entire circuit depends highly on the quality of the power supply. Therefore, the most important part of any audio circuit is the power transformer.

Apart from completing the necessary connection between the amplifier and the speaker, a power transformer’s behaviour can set the amp’s performance. The power transformer essentially controls the music dynamics of the amp. This means that a well-designed power transformer will result in better notes, separation of each tune and crispier middle and treble frequencies.

An overall higher definition of each clean and dirty tones will result in a well-designed power transformer. Such transformers are also priced at the higher range meaning that you get high quality sound when you pay more. 

What are the Different Types of Transformers?

There are four main types of transformers used in an amplifier. Each determines how the tone reverberates while enhancing the quality of each note. The types of transformers are:

Power Transformers

Power transformers take the voltage from a wall switch and transform it into voltage according to the needs of the amplifier. Since it does not interfere with the signal path there is no impact on the sound. However, the quality and the design of the power transformer can have an impact on the quality of the amplifier’s sound.

Considering two different power transformers built by two different companies but having the same specifications would sound the same. There would be no difference in the quality of the sound as long as the specifications are constant. However, the question of reliability comes into consideration. A power transformer built well is more likely to last longer.

Several companies use low-quality power transformers for lower-priced models. Such transformers are not well made and do not meet a specific set of standards. Such transformers need caution when in use since they tend to blow up. Additionally, the tone from the amplifier may sound mushy. However, using a power transformer that has a high number of specifications will ensure excellent regulation of the power supply. An additional benefit includes a long life of the power transformer and high quality of the tone.

Chokes

A few amplifiers are built using a small inductive device known as a choke. Although it is not a transformer, it looks like one. When the power supply goes into the amplifier, there is a power ripple, which becomes smooth with a choke. However, the quality of the choke will highly influence the quality of the sound as well.

A recent trend has led to the replacement of a resistor in an amplifier without using a choke. Yet, a choke is suitable as a modification. This allows the change of the feel of the sound because there is a direct change in the impedance of the power supply. A choke is most helpful when an amplifier needs a filtered sound with the absence of the hum.

Look at the Marshall Vintage Plexi Style 3Hy 250mA Choke. It is available for a decent price at the Amp Parts Direct and is a blast from the past. This style is the same as in the 1960s era and just like the originals, it has a paper layer wound bobbin.

Reverb Drivers

Those amplifiers that have a tube reverb are reverb drivers. This type of transformer only delivers the signal to the reverb tank. Since the reverb drivers will have the signals passing through the tubes, the quality of the transformer should be high.

Output Transformers

The output transformer is the most important one that transfers signals from the power tubes to the speaker. Being the most critical part of any amplifier a good quality output transformer can make a big difference. There are other factors as well that contribute to the good quality of the tone and the sound of the amplifier.

Transformers differ from each other according to how they are wound. Usually, guitar amplifiers either have straight windings or interleaved windings. The sounds of both types of amplifiers are different and straight winding is cheaper to produce. The low manufacturing price of a straight winding amplifier does not mean that it is of low quality. It only sounds different so individuals may prefer it to the other one.

Some designs sound better than an average big size output transformer. Usually, the larger the size of an output transformer, the broader will be the frequency response. Higher use of power and therefore larger headroom will is covered. A bigger sized output transformer will cost more but the ones used for guitars are usually undersized. Designers make the buying decisions based on the needs of the tone and the music.

Isolation Transformers

While increasing or decreasing a signal voltage, transformers have one useful property called isolation. As mentioned, there is no electrical connection between the primary and secondary windings. Therefore, a transformer helps in isolating both the input and output circuits. The isolation property is ideal for use between the speakers and amplifiers.

A transformer provides the input audio or a voltage signal to produce the output or voltage signal. This happens without the need for them to be physically attached to one another. The circuit is complete with wire coils tightly wound around a soft magnetic iron core. The wire coils are windings and two or more windings can achieve a high-quality result.

Once the primary input winding receives an AC signal, a corresponding AC signal also appears on the output secondary winding. This happens because of the inductive connection of the soft iron core. Both the input and output coils either results in an increase or decrease of the applied signal, as it passes through the transformer.

Therefore, an audio transformer’s design is specific to match the impedance instead of producing a specific voltage output. It can also be useful for a step-up and step-down of an amplifier’s sound quality. Additionally, transformers with a turn ratio of 1:1 will not change the current levels or voltage and isolate the primary and secondary circuit. Keeping each circuit separate to avoid possible electrical accidents.

Conclusion

Both the output and power transformers can change the feel of the sound coming from the amplifier. Given the difference in the size of the transformer, a designer can choose one that best fits his or her needs. Some amplifiers are useful for outdoor performances that should require a large size transformer so that more area is covered. However, indoor performances may not require a large size output or power transformer.

In the end, it all comes down to the quality of the make and material used in the transformer. The higher the quality of the transformer, the better the sound result. The quality of the copper wires used and the intricate winding process used plays an integral part in the quality of the sound from the amplifier.

References

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4. T. J. Gallagher and A. J. Pearmain (1983): "High Voltage - Measurement, Testing and Design".
5. International Electro-technical Commission, Otto Blathy, Miksa Déri, Károly Zipernowsky. IEC History.