Triad Magnetics is one of the world’s foremost manufacturers of transformers for audio, musical instrument, and industrial applications. Founded in 1943, Triad is based in Perris, California and offers thousands of off-the-shelf transformers, as well as the ability to create custom designs. Guitar amplifier buffs know Triad from their use in vintage Fender and modern-day amplifiers. Triad became a foremost supplier of audio transformers during the mid-1960s and the rise of color TV (which used Triad transformers extensively), and today offers a wide range of models for consumer and professional audio equipment, as well as other commercial and industrial applications.
Just what is a transformer anyway, and why are they so important for audio?
A transformer is a device that literally transforms one form of AC voltage to another. A transformer is comprised of two coils of wire and an iron or other core. It works like this: an AC voltage feeds into the primary winding of the transformer, a coil of wire wrapped around a core, to create an alternating magnetic flux in the core. Another secondary winding is also wrapped around the core and has an alternating voltage induced in it by the core (by electromatic induction). Depending on the number of turns of wire in the primary and secondary, the voltage will either be stepped up or stepped down to the voltage that needs to be passed on to the rest of the circuit. Transformers can range from huge industrial models to tiny components mounted on PC boards.
A transformer that increases the voltage is known as a step-up transformer, and one that decreases it is a step-down transformer. In a step-up transformer, the number of turns on the secondary is greater than the number of turns on the primary. For a step-down transformer, it’s the opposite.
Some common examples in audio: a power transformer changes the incoming voltage from the wall (for example, the 120 volts AC from US wall outlets) to a voltage that’s usable by an audio component. The output transformer in a power amplifier converts the high-impedance signal coming from the output stage to a low-impedance signal that can drive a loudspeaker. A moving coil phono step-up transformer converts the extremely weak voltage from a moving-coil cartridge to one that’s strong enough to be fed into a preamplifier. Without getting too far into the weeds, other types of transformers can serve to facilitate balanced inputs and outputs, provide electrical isolation, eliminate ground loops, or block unwanted DC while passing audio signals.
A classic paper section output transformer, as used in guitar amps and other devices.
In high-end and pro audio and in the guitar amp world, a lot of voodoo is thrown around regarding the sonic characteristics of transformers. Do toroidal transformers sound “better?” Do certain transformers have a desirable “sound” in guitar amps, and are there “magic” materials that gave vintage guitar amps their mojo? I spoke with Bill Dull, president of Triad Magnetics, and Triad’s engineering manager Lazaro Rodriguez to shed light on these and other subjects.
Frank Doris: Please tell us a little bit about Triad’s history.
Bill Dull: Triad’s an 80-year-old company and was founded in 1943 in Southern California by three guys, hence the name. There was a sales and marketing guy, an engineering guy, and a finance guy. As a result of being in Southern California, they got involved in the recording industry and film and television pretty early on.
Bill Dull, president of Triad Magnetics.
FD: It seems like there could have been a parallel development then – as Triad made advancements in technology, that might have driven what the product manufacturers were able to develop, or was it vice versa?
BD: It's probably more vice versa. Typically, what happens even today is that customers come to us with requirements, and then we try and figure out how to meet them. That's what spurs a lot of innovation and development: OK, so we might need to work with our suppliers to create new materials to be able to operate at that frequency, or we need to develop new types of winding techniques to be able to meet the requirements.
The Triad Transformer Manufacturing Company back in the 1950s.
BD: [For example, you may know about the] first 100-watt guitar amp power transformer, [developed] for [Fender’s Dual Showman amplifier and surf guitarist] Dick Dale. I don't know that that was necessarily any kind of huge technological innovation on Triad’s part as much as from Leo Fender saying, “Hey, I got this guy who plays guitar and wants to play 'em louder than our typical 10-watt,” But most of the [early-1960s] amplifiers were pretty low-power. [Dick Dale’s requirements ultimately led to the development of the Fender Showman and Dual Showman amplifiers of the early 1960s – Ed.]
In the late 1950s the three founders sold Triad to Litton Industries, and Litton was gearing up for the space race at the time. The more engineers you had, the more likely you were to get a contract from the government. Triad was actually involved in the Apollo mission and things like that. In the 1970s and early 1980s, semiconductors were coming on board and switch-mode power supplies were being introduced. People were predicting the end of these sort of analog, linear-type power supplies that [had been in use]. A group of investors - bought Triad from Litton and formed this new company called Magnetek to manufacture switching power supplies. And Magnetek owned Triad until 2003 when we were sold to a Taiwanese transformer manufacturing company that had be building Triad’s product for 15 years prior. They hired myself and Lazaro shortly thereafter. And the rest of us have grown with the company again for the last 20years.
I grew up in the industry, so I was familiar with Triad, but not as familiar as I am now. Even with our history [we’ve] sort of latched onto some of our legacy in a lot of ways just out of passion more than practicality.
FD: That could describe the entire audio industry. “More passion than practicality!”
BD: For sure. The good news is the companies that owned us, the Litton and Magnetek, were big companies and they were very professional and kept very good archives. So, we have a lot of historical documentation on how parts were built and materials that were used and intellectual property information. But some big holes of it have mysteriously disappeared. All of our Fender files are gone.
More images of the Triad factory showing various stages of transformer manufacturing.
FD: For readers who aren't technically inclined, could you give them a quick explanation of what a transformer does?
Lazaro Rodriguez: Essentially, a transformer transforms signal levels from one level to another level. If you have a step-up transformer, for example, one-volt signal on the primary and the turns ratio is 1 to 10, then you get 10 volts on the secondary. The current is also transformed proportionately. Let's say you have one volt, one amp on the primary, now you have 10 volts, and one-tenth of 1 amp of current on the secondary. When the current flows through a primary winding that is wound around a magnetic core it produces a magnetic field. This magnetic field is concentrated by the magnetic core. The magnetic field is then induced onto the secondary winding. That's how you are able to create the voltage and current transformation from the input to the output of the transformer.
That's important for a lot of reasons, specifically in audio transformers, because normally, source impedances don't match load impedances. So, in the case of a speaker, for example, they're typically considered low impedance devices, and by low impedance, normally that means low voltage, high current, where high-impedance [devices are] the opposite: high voltage, low current.
In order to match the source impedance to the load impedance, a transformer is used. The turns ratio of the transformer is one of the key elements in impedance matching. The reason you want to do impedance matching is because you can get maximum power transfer from your source to your load. Normally that's the end goal.
BD: The signal has to be some kind of “on and off” [AC] signal, like a sine wave or pulses or something. If you just have a DC current, a transformer does nothing. It's the fact that the magnetic field is turning on and off at some frequency. That actually drives the atoms in the secondary winding to be induced for the current to flow [and create] voltage.
Power in equals power out (without considering losses), so all you're really doing is just transforming that voltage and current to better match the transfer of power from source to load.
Lazaro Rodriguez, Triad's engineering manager.
BD: For a pro audio transformer, typically [operating from around] 20 Hz to 20 kHz, that's a pretty wide range to [have to] design a transformer that has to work well across that entire range, versus a power transformer that's operating at only 60 Hertz.
FD: How would you design a transformer with a wider frequency range? There have been high-end amplifier companies it insist on ultra-wide bandwidth. What actual materials would make a transformer have a wider frequency response?
LR: Typically, there are two considerations when it comes to designing a very large bandwidth-type transformer. To get a wide frequency response, we normally try to control capacitance and leakage inductance on the transformer, and also [the] resistance [of the coil windings,] because all of those are considered series impedance. Whenever you have any series impedance to your source, you're effectively dropping voltage across that impedance. Impedance It's also proportional to operating frequency. The higher the frequency, the greater your impedance will be. That is one of the limiting factors when it comes to being able to design a transformer that can operate in the megahertz. Ideally the capacitance would be zero, but in reality, that's not practical.
FD: When toroidal transformers first came out, they were a big deal, and obviously they're in use today. What are their advantages?
LR: There is better coupling between the primary and the secondary side. I think I would say that that's one of the advantages of a toroidal versus a traditional “EI” type transformer. [EI transformers are so named because their core resembles the letters “E” and “I” – Ed.] The leakage inductance is also considered a parasitic, and normally you would not want it to exist in a transformer because it also acts as a series impedance to your source. And as you go up in frequency, that increases proportionately with the frequency, and you're dropping more and more of that signal across that impedance. Toroidal transformers normally have lower leakage inductance compared to the EI-type transformers.
A toroidal power transformer, so named because of its torus-like shape.
FD: Some people talk about the “sound” of a transformer. I would think in an audio application you wouldn't want it to impart any kind of “sound,” which I suppose might be a distortion or a coloration, but as we know, a lot of the vintage pro audio gear is revered for their sonic personalities.
LR: You wouldn't believe how many people we get who tell us, no, no, no, we don't want hi-fi! They want it to be crappy. They want the distortion – it's a very complex thing happening that adds “color” like leakage, inductance, winding resistance, etc.; all this together amounts to the coloration that we normally refer to. If you want [a product] to be ultra-high fidelity, ideally when you put a transformer into the circuit it should be sonically invisible. In other words, you don’t want the transformer to have any influence whatsoever. We do get [requests for] those once in a while, but for the most part, [pro audio] people don't really want that.
BD: At certain places on the frequency curve, they want a little less high end. It's funny, it feels like you could control some of this with EQ, but I don’t know, they're very specific [that they want it to happen in the transformer].
FD: A lot of this desire for a transformer to have a sonic personality might be considered “voodoo,” even though there's a technical reason for everything, and people get fixated on the voodoo. I’m guilty of this. I have a 1965 Fender Princeton Reverb (guitar amplifier) and I would never part with that amp, and I hope it's passed down to every member of my family for a thousand years. Part of the mystique for guys like us is having a vintage amp with original power and output transformers.
BD: Regarding an amp that has the original transformers in it versus a replacement: my understanding is a lot of these amps weren't necessarily designed for professional use. They were designed for some kid who wanted to play guitar. There are lots of [stories] about how notoriously cheap Leo Fender was, trying to get things as low-cost as possible and make them as cheap as possible. So, when you start looking at a transformer, which would be one of the more expensive components in the amp, you’re going to start [thinking], how can we build this with less steel? How can we use less copper? All of those things that contribute to the cost. So, the transformer's going to have run hotter and maybe be more lossy [in terms of technical performance]. So the “sound” or whatever is going to be what people are looking for, but it’s also not going to be as robust of a transformer. So, they're going to potentially fail, especially if they're abused.
And then there are so many different ways to balance [the internal] impedances [and the] turns ratio. There’s side-by-side winding, concentric wiring, sandwich winding, different core materials, bobbins, and insulation materials, i.e. paper and Mylar. The simplest, easiest way to make a transformer that puts in a certain voltage and puts out a different voltage is pretty simple, but it may not, [because of] capacitance, leakage and inductance, perform the same [as another design]. You could have two transformers that are rated identically that actually work differently or even are wound differently, but they still take the same voltage in and [pass] the same voltage out.
Examples of shielded audio transformers.
FD: There's a certain amount of art involved, then? Or “accidental” art?
BD: Yeah. Sorry, but I think some of the people that are reissuing transformers are doing it by [thinking], all right, let's count the number of turns and let's look at the number of layers [of insulation] and stuff like that, and we'll kind of reverse-engineer this. But, because the same materials don't even exist that were being manufactured in the 1950s, you're not going to get the same results. You have to have ways to measure the original performance versus the new performance.
We have a $30,000 piece of Audio Precision test equipment that allows us to do some really detailed testing on the performance of these [vintage] transformers. And even if we wound them exactly the same way as the originals, we can see that there are differences in the way that they perform, because of the core material or because of some of the insulation materials that have changed a little bit, or even the varnishes that were used. So you may have to make other adjustments to [a modern] design in order to better replicate [the originals]. I'm not tooting Triad’s horn [but] we've been learning over the last 20 years how these parts are designed.
FD: So, on the one hand you have advancements in materials that enable you to do things that couldn't be done in the 1950s or whenever, but on the other hand, are there materials that just can't be obtained anymore because of embargoes or scarcity or safety regulations.
BD: For example, we don't use lead solder anymore, because it's toxic. It's still available. We just choose not to. In the US, there were more paper mills than there are now. We've had to make some substitutions because of that. The material itself is still available, but it’s those industrial manufacturing capabilities have kind of disappeared in the United States.
Most of the material for the [core] laminations are still available. Recently we had some problems where the steel manufacturer “improved” the materials to make them less lossy. [The previous material] had a lossy performance that our customer liked, and all of a sudden we bought more, and now this material has been “improved.” It gave a much flatter frequency response. But the “improvement” was actually a bad thing for this one application, so we [had] to make adjustments to the design to account for that “improved” material and kind of downgrade it through the design effort.
Microphones have transformers too. Here's Triad's BV8-style output transformer for Neumann-type mics.
LR: This speaks to what we were mentioning earlier. [Many audio] applications don't really want these ultra-high fidelity-type transformers; they want the transformer to actually influence the signal that is going through them.
FD: But what about manufacturers of high-end audio components? I would think they would want a product with as little coloration as possible. Does your discussion imply that if you’re an audio manufacturer, you have to buy a couple or a bunch of different brands of transformers with supposedly identical spec and put them in the circuit and measure and audition them? Or would a manufacturer think, we’ll just design our own that’s custom-designed to our specs?
LR: Maybe a bit of both. There are companies out there that specialize in high fidelity-type transformers, so [a manufacturer] might go to them first before they can decide whether that's what they want or not. But yeah, a lot of this is really trial and error. You can't just simply say, OK, I want this transformer to work from this frequency to this frequency and be plus or minus two dB down. It's difficult to do that because there's so many variables. We have experience, and obviously that experience helps us get there more quickly, but just to simply say, hit the target, hit the bullseye at the first try, that’s difficult. It's probably unrealistic. It does take a few iterations to get to where you need to be.
FD: Even if you have a custom design, you have to put it in your product and see if it works.
BD: Exactly.
FD: How high and low a frequency response can a transformer have? Even if we’re not talking about audio transformers?
LR: We have [audio] transformers that are designed [to go down to] 20 Hertz, and that’s typical. We can certainly design for lower than that, down to 10 Hz.
BD: But I don't think I've ever heard somebody saying, “I want a one Hertz transformer.”
LR: Some of them go up to 100 kilohertz if not more.
Small size, big sound: an encapsulated audio transformer.
FD: Because there are people in audio who feel that even though the range of human hearing is nominally up to 20 kHz, there's stuff happening above that frequency that's important. In any case, I was just curious as to what the physical limits would be.
BD: There are transformers that operate at the gigahertz level now. This involves totally different core materials and things like that, to be able to have the core respond at those frequencies Class D amplifiers are an example of this, as the signal is turned into pulses and converted at a much higher frequency then the original analog signal.
Lazaro mentioned the use of lead, but there's another rumor about molybdenum being banned, which is not true.] Core material and nickel laminations still have molybdenum in them. I don't know how that rumor ever got sort of started but it's simply false. It's not a dangerous element when it's combined in nickel lamination in an inert form. It hasn’t been banned. And it's a pretty important component for high permeability cores.
And then the technology of today makes your product better. I mentioned the test equipment, but I would also say that the discipline and manufacturing today is much better than it was 50 years ago. The winding machines are now CNC (computer numerical control) operated with really precision counters. What it allows for is a much more consistent product; you're not going to have as much variation from transformer to transformer. The coatings on the wire and things like that are improved, better than they were in the 1950s. A hundred years ago they were using woven silk jackets to insulate the wire.
FD: It cracks me up because vintage guitar geeks, and I am one of them so I am allowed to make fun of us, go crazy over stuff like cloth-covered wiring and carbon-comp resistors, and old Fenders had a plus or minus 20 percent tolerance on the resistors.
Here's a familiar site to anyone who's ever looked at a guitar amp chassis: a traditional-style power transformer.
BD: [For transformers also], a lot of the production testing that was done, historically, they put these wide tolerances, like you said. For example, plus or minus 20 percent on the inductance [specs], but that was based on a winding machine that might miss a couple of turns or a winder who might be [off] drinking coffee and lets the machine throw on a couple of extra turns or something. And that just doesn't happen anymore.
FD: Maybe not for audiophiles, but guitar players love the sound of certain kinds of distortions. Which leads to my “Dick Dale” question: when you're stressing a transformer, what happens to the sound? I know they can get hot and the insulation can melt. I've seen some horrible examples of transformers that leaked. What do you have to do to destroy a transformer?
LR: Temperature is the number one enemy, because all of the materials that are used in transformers normally have a temperature rating to them. If you stay below that rating, then the transformer will last, I wouldn't say forever, but a very long time. But some audio applications have a demand for distortion. The way you get distortion in transformers is by saturating the core. When you saturate the core, your impedance, which is what limits current to the transformer, is reduced. Once it's saturated, now you have a lot more current flowing through the wire. That additional current, which may be several orders of magnitude higher than what the transformer was designed to handle, is going to create much, much higher heat. If you double your current, you actually quadruple your power in the impedance or the resistance of the wire.
So, you can quickly heat up the wire if you operate in the transformer in saturation mode for a long period of time. That heat will accumulate over time. If you're operating in saturation mode for maybe an hour or so, it will go beyond the rated temperature of the wire and then you can cause the insulation to melt. Once the installation melts, then you can get a short, and if you get a short, then you get more current flow, and it's just kind of a snowball effect
FD: And you literally get a meltdown.
On another note, do you see any upcoming advancements in materials or manufacturing processes that might lead to improved transformer designs in the future?
LR: If there are, they will typically be incremental. It's not like the next day or tomorrow we’ll have something we’ve never seen before. It'll be more on the materials side, and [it’ll be] very slow. Transformers have been around for [more than] 100 years now, so it's not a new technology. Almost everything that has been said and done has been said and done already. But as Bill said, we're always striving to find ways to come up with winding methods that are consistent and to have that repeatability.
BD: it’s been around for at least 20 years, but maybe the technology of planar transformers is gaining more prevalence, where you print the coils on a printed circuit board and sandwich all these printed circuit boards between a core. These planar transformers can be used in some high-power Class D amplifiers.
FD: But as soon as we say there’s nothing new to be invented, I’ll be like IBM chairman Thomas Watson, the guy who said, “I think there’s a world market for maybe five computers.”
Does Triad primarily manufacture products for the audio world or do you make transformers mostly for industrial applications?
BD: Our business is primarily industrial and commercial customers. I would consider pro audio to really be more of an industrial market than say a consumer market. We manufacture equipment for the medical field, industrial automation, electric vehicles and alternative energy, and aerospace. Also, a lot of our products go into food processing equipment, like holding ovens and fryers and drink dispensers, which is fun to see when I visit my favorite fast food restaurants. But because of our passion and our legacy, audio is still an important market for us.. I love going to live performances and looking for gear that has a Triad transformer inside. It makes me really happy.
Header image: Bill Dull and Randy Eller at the 2025 NAMM show.
All images courtesy of Triad Magnetics.
