Mercury Magnetics is the leader in guitar amplifier transformer manufacturing. I have personally used their iron in many repairs, restorations and custom builds over the years. It never ceases to amaze me when I use a set and listen to the amp after the project is complete. It’s almost like a blanket was taken off of the sound and you are listening with “3D glasses”. The feel of the amplifier becomes much more dynamic as well. In my opinion “your amp’s transformers truly are the heart and soul of your amp”.

In this exclusive interview with Sergio Hamernik (the man behind the scenes at Mercury) some basic questions that all relate to the tone and feel of a guitar amplifier. His answers are forward, straight to the point and insightful. Here is Part 1 of the interview.

300guitars: Why should guitar players care so much about the transformers in their amps?

Sergio Hamernik: When a player has to struggle with his amp then there’s really not much of a reason to play it. The tonal quality and performance of a tube-type guitar amp is largely determined by its transformers. Where there is great “tube tone,” you’ll always find “great sounding transformers” making it all happen!

Once you get past the player’s talent/ability, it’s all about the tone. If an amp doesn’t produce desirable tone, the window of inspiration closes and gets replaced with fatigue for both the player and the listener.

These days musicians who choose to play an electric guitar are only as good as their technical awareness and development allows them to be.

Transformers are the most important and most expensive components of guitar amp’s parts list. Also, they are the only components designed and built specifically for that amp, unlike the rest of the components – the resistors, capacitors and even vacuum tubes. These other components are considered to be “universal application” parts – meaning not just for making guitar amp tone. The electronics industry commonly uses these same components for medical, industrial, radio and many other applications. You certainly couldn’t fit or use guitar amp transformers for any of these other applications without offending someone.

Transformers are the key to providing that unique signature tone. It’s the transformers that differentiate one amp brand or sound from another. Here’s another way to look at it – all amp builders have to deal with the same limited choices from a small pool of vacuum tube manufacturers and other off-the-shelf component requirements (resistors, capacitors, etc.). This is NOT so with the transformers. Although there are plenty of generic transformer designs available that service the “power requirements” of an amp, you wouldn’t want to use these awful-sounding devices in your guitar amps. Likewise it’s not a coincidence that most of the best-sounding amp builders, modifiers, and repair techs begin their craft and finish it with enviable distinction, relying on their choice of transformers.

300guitars: Would you explain, in guitar player terms, what power and output transformers are?

Sergio Hamernik: Well, I really don’t like to lump all guitar players into one category. Making assumptions here (be it charitable or not) just doesn’t seem fair to me. Each player has their own level of interest and technical understanding on this subject. So I’ll split my answer into three different groups of definitions and let the player choose the one that suits them best.

In basic guitar player terms: It’s magic!!

In technician terms: A device applying mutual inductance in an efficient manner, so that circuits with different voltage/current requirements can correspond to each other.

In engineering terms: Transformers are electrical devices consisting of a magnetic-core and two or more coils (commonly referred to as windings) inductively coupled as circuits for the transmission of alternating-current energy from one closely coupled coil to another usually at a different voltage and current value. Transformers are also used for matching impedances between the signal generating source and the load.

300guitars: How does the power transformer affect the sound of your guitar? The sound comes from the output transformer right?

Sergio Hamernik: Yes the amplifier’s sound does come out of the output transformer, but where does it all begin? While an output transformer is vital to an amp’s ultimate tone, it simply can’t do it alone. The power transformer is the first step in building tone and in setting the standard of performance that the tubes and output transformer utilizes.

The output transformer depends on the power transformer for determining the maximum amount of power the amp can put out. The power transformer is also a major contributor for the overall feel of the amp. Such as punch through (the oomph factor), note attack, a perceived larger/wider soundstage presence and most importantly, the speed or reaction time of the amp’s audible response to the player’s sense of touch and playing technique. Tamper with that in any way by using cheap “dumbed down” power transformers and your audience may confuse your amp’s tone with the sound that is made by farting into a pillow!

A puny power transformer will deliver puny tone no matter how good the output transformer is. A good output transformer is also not intended to be a problem fixer or a turd-polisher. Garbage in is always garbage out. So please don’t shoot the messenger because the power tranny just ain’t cutting it.

Output and power transformers are actually close cousins. Doing similar tasks, one matches and isolates the speaker from the amp and the other one matches and isolates the amp from the power company. Peace keepers of a sort, preventing tubes from frying the speakers and preventing the power company’s energy from frying the amp and people connected to it.

300guitars: How does the output transformer affect the amps sound and feel?

Sergio Hamernik: An output transformer is the last component of the audio chain. The amplifier’s voice. The final word that reaches the speaker. Because all vacuum tubes were never really designed to distort intentionally, the weight of producing desirable amplified guitar tone falls heavily on the transformers. The output transformer’s job is to coax, extract and even irritate the power tubes into tone-friendly distortion. Ever wonder why solidstate amps have always played second fiddle to tube amp tone? Is that simply because of not employing tubes or of not having an output transformer? At the very least, it’s something to think about.

The output transformer determines how the amp sounds like from fully clean (sweet with a touch of sparkle) to fully over-driven (chainsaw) distortion, and everything in-between.

By the way, the term “clean” as used in guitar amp speak is a bit of a misnomer. There is no such thing as a distortion-free guitar amp. “Clean” simply refers to less distortion. There is an intimate inductive/reactive relationship between the output transformer (coils) and the speaker voice (coils) that also back-washes into the power tubes and influences that “clean to dirty” range of distortion. The quality of the output transformer determines how well the production of tone is executed by the amp – those notes that float between the strings which are created by overtones, chimes, bell tones, sustain, etc. Poorly made output transformers tend to gargle out, squash and mask those overtones.

The output transformer is also responsible for how efficiently the audio power of the amp transfers to the speaker (load). Ultimately, the player issues the final report card for the performance of the amp and the output transformer with comments like “clarity,” “articulation,” “loudness,” “break-up,” “grit,” “glassy,” “grind,” “dirty,” “woody,” “mushy,” “mashed,” “fuzzy,” “dark,” “cloudy,” and so on. There are hundreds of guitar amp speak descriptions and euphemisms out there which capture their emotional response (players and listeners alike) to what is coming out the amplifier’s window.

The mighty output transformer. Loved and hated by so many. Still one of the most misunderstood components of a guitar amp. 80 years and going strong. Go figure….

This is the end of Part 1.

Click here to read Part 2 of the interview with Sergio Hamernik of Mercury Magnetics Transformers.