An Interview with Sergio Hamernik of Mercury Magnetics Part One

Can you tell us how the Mercury Magnetics Company got its start?

Well, its roots as a company date back to the early 50’s. The guy I bought it from was an old General Electrics transformer Engineer who was working there pre-World War Two. He then went on to do a bunch of design work for the war effort. iIn the early 50’s he hung a shingle and became self employed. The Mercury came out of his passion for Mercury cars, he always drove a Mercury since the late 40’s – he loved those cars. He moved from the East Coast to the West Coast and found that there was a lot of military and aerospace work. A booming economy in the early 50’s gave him a lot of business.

I met him in the 1970’s when I was an Engineering student and an audio enthusiast. He built a lot of custom transformers for me and we always had a huge debate because he hated audio. For anyone that ever studied electronics, namely vacuum tubes, the poor audio industry was always looked down upon: subjective, run by kooks, people who don’t know what they are doing, and people who have no idea how to make the right thing. So audio was always the illegitimate stepchild to the rest of the industry. He sort of characterized that because I had to do the actual designing which was a relief to him because he considered all of this audio stuff, especially guitar tone, to be nothing but voodoo and completely nonsensical. He couldn’t understand what made it tick and how musicians thought and reacted. I had a music background along with my technical background so I was able, with the aide of my experience of guitar playing and recording studios, to have a good understanding of what made a decent tone and how an amp should behave. If you are a real touch player than it is about the speed of the amp and the note separation and things like that. Most transformer people I dealt with just didn’t want to bother with it. So he bugged me for about ten years to buy his company because he figured that I was the only one qualified to take it over.  

That is where I took off with my guitar amp connection, because I worked as a hired gun for a bunch of these studio heads and pro musicians. And what usually would happen is if an amplifier blew out, namely if a transformer went out, if I bought a replacement transformer or anything that was an equivalent and it was not the original then the tone blew out. It didn’t matter what resistors or caps or tubes I used, I couldn’t rescue the amps. So I would end up out of pure necessity having to do more hands on work with transformers. You end up becoming an expert after a while when no one else wants to bother with them. I started in 1980/81 collecting all of the specs for all of the vintage amps all over the world because no one seemed to be paying attention to such things. In the 1970’s everyone was quote unquote “upgrading to solid state,” so less and less people were interested in tube gear. Less and less cared so a lot of people would hire me because I was the only guy who preferred to work on tube equipment and magnetics and so on. So having that kind of background made quite a demand, especially during the early 80’s when the boutique amp market was just starting to realize they needed better transformers.

When did Mercury really become involved with making transformers for guitar amplifiers?

Well, I worked for people on a one-to-one basis, under sort of confidential arrangements with certain rock stars that just didn’t want to be bothered with having their name being flaunted around or capitalized on or to endorse things. All they wanted was to have their amps run right for recording or projects, even for touring. So my background with Mercury in the early 80’s was catering to the guitar heroes of the 60’s and 70’s, whose technician would fix their amp and they would loose their tone because they realized that their output transformer was replaced. It would completely change the character of the amplifier.

So word got around rather quickly that I was able to repair, rewind, and restore the original transformers. And the whole “Tone Clone” thing came from artists who had an irreplaceable amp, the amp that made them history back in ’66 or ’67. They really didn’t want to bring it out and tour with it, so I would end up cloning their original transformer that they fell in love with. We would make several amps for them or they would assign their techs to drop in the transformers so they would have, for example, six amps that would all sound the same as that first perfect amp. So they could take it on tour and not worry about it breaking down or being stolen and keep the prized original back at home.  I worked with Ken Fisher, the whole Trainwreck thing, a lot of these guys early on, even Alexander (Dumble) and all of that. They wanted to keep thing confidential and not brag about or let too many people know who their sources were because there were few and far between transformer sources, even back then, that catered to the guitar amp market.

Also there was a natural dumbing down beginning in audio and all that was post World War 2 momentum. A lot of ex-military parts that were high tolerance parts, the formulations of iron and copper and so on, we designed to win the war effort. So the 50’s and 60’s enjoyed the benefits of that, but by the late 1970’s and definitely in the 1980’s steel manufactures started to change recipes to make the iron or the materials much more affordable. You can hear the difference between a late 60’s Marshall and a late 80’s Marshall and a Marshall today. It really documents what changes and, unfortunately, they made those changes more out of economy than anything else. The amps were loud but they didn’t really catch on to the fact that their tone was disappearing because they were changing their recipes.

See, the iron that I use is custom formulated for us. I buy enough so that all of our iron is literally from American iron ore that is processed here in the USA. It is 100% American built to the original recipes. Some of the drawbacks to it? Well, some of the iron rusts more easily; today the big break throughs are in any of the transformers you see that have a silvery or a shiny core to it. Those have ingredients that are anti-rust. They aren’t worth a damn for tone but they keep the rust from building up on the core and will sometimes preclude the need to dip it in any kind of varnish or resin like we did traditionally. So it helps to make cheaper transformers but at the sacrifice of decent tone. One of the reasons why I am emphasizing transformers is because there is so much documentation even dating back to the mid 50’s where engineers and technical people were really writing these scathing reports of how awful transformers are in the audio industry. Tubes are designed to be dead clean, run linear and they are efficient voltage amplifiers. These darn transformers when tubes are plugged into them have this tendency to distort and we can’t have any of that, even harmonic distortion – especially even order harmonic distortion. Which is the whole point of what we are looking for when we overdrive our amps, to emphasize those harmonics that were frowned upon by the engineers of that time. That’s why Solid State was so openly embraced in the 60’s because it eliminated the output transformer and took out a big piece of the audio budget for HiFi.

Back in the late 1960s, Vox went to Thomas Organ to have solid-state amps built and they were very proud of this state of the art amplifier. I met a few of the musicians from the late 60’s that were sponsored and using those type of amps that were built locally.  Literally, the plant is only a few miles away and the tone was so awful that they used the enclosure and the boxes and they put their old tube gear inside them when they played because they were unbearable. As you can tell the vacuum tube industry is alive and well, we have given the solid-state industry at least 40 years to catch up and surpass tube tone, and they haven’t.

Part of the confusion is that people think it is because of the tubes that their tone sounds that way. There are what we call “output transformer-less” amplifiers in the HiFi world, where they basically parallel a bunch of power tubes together till they get down to 16, 8, or 4 ohms. There is no output transformer, so you literally connect your speaker to the tubes. If you ever do an audio demo of that, you will find that while it works, it sounds nearly solid state. The output transformer is what provokes a tube into giving the characteristics that we find desirable as far as tone. The engineers didn’t want the tubes to distort, as they are very clean voltage amplifiers. But when you have a reactive element like a transformer, you irritate the tubes into getting this harmonic distortion to come out.  The difference between a good and mediocre transformer is based on how it works and syncs with these tubes to produce the kind of tone or distortion we are looking for. It is not as easy as winding some wire around a steel core, if it was than we would not be having this conversation.

How does a Mercury transformer made today compare to the transformers made in the golden age of amps (the 50’s and early 60’s)?

One of the biggest mistakes that today’s amplifier market makes, especially hobbyists and do-it-yourselfers make, is to blindly copy every aspect of an amplifier hoping to get a piece of that golden tone. But it is random, and hit or miss with not a lot of study, or they are self taught. Our approach with the transformers was to duplicate; we use the best grade components like they did in the 50’s and 60’s. We wind every layer and every turn as if it were a circuit in itself. In fact, on our website you can download an output transformer circuit equivalent, a schematic drawing that is a representation of an output transformer. Most people think it is an audio circuit, its leakage reactance, its leakage inductance, or its capacitive reactance. These things are fairly complex, and all these numbers have to be right in order to get what we want as musicians to have it sound right.

So to answer your question, we really do follow the recipe to a point. We don’t repeat any of the mistakes and inconsistencies that were prevalent, for example, if you were into Fender tweeds or late 60’s Marshalls. We would literally have to rent or borrow dozens of amplifiers to find that one or two that had that sound, and the rest of them did not. There were so many inconsistencies, and a lot of these inconsistencies had to do with sloppy tolerances on the transformers. For our transformers we simply extract the best parts and the virtues of these original transformers and take out all of the things that were obstacles. We took a cost is no object approach, and made it equal or better and added consistency. If you bought a particular transformer five years ago and then you buy the same one today you want it to sound the same.  You don’t want good batches and bad batches, which were problematic of the original production. I removed the issues of inconsistency out that didn’t affect the tone in any positive way.

For example, the controversy between paper tubes and nylon bobbins: in the vintage years they used both, so people think that somehow, some magical quality comes from using a paper tube winding form over a nylon bobbin. Tonally it made no difference at all, but the paper tubes were widely out of tolerance most of the time because the paper tubes were actually a few feet long. They would wind multiple coils on these long sticks then use a saw or blade to cut off the various coils. But in order for these tubes or coils to come off of their winding forms they had to have an angle to them. So the first coil would be larger in diameter and the last coils were smaller, and each of these made a greater difference than the paper. When we switched to using nylon bobbins the tolerances were within 3000’s of an inch of each other, as opposed to as much as a ? in from the paper tubes. If you ever take apart a really old transformer that is pre 1970 sometimes you will find wood wedges that are jammed between the paper tube and the core because that piece of paper was too wide and too sloppy to fit into the core correctly. They would force a wedge in there so the darn thing wouldn’t rattle. Which one made for the best tone, well it was the luck of the draw.

I was lucky to have all of these stars that had these amazing sounding amps. They went through the hassle of culling and choosing and picking that one special amp that inspired them, and that they recorded with, and when I analyzed the transformers sometimes I would find happy accidents or little anomalies that would that set this transformer apart from standard production. So when you look online at our list of tone clones they are from the hand picked best of the best. Say someone comes in with a 50 watt Marshall that they love, and it sounds amazing, so we rewind it and it becomes our benchmark. Then, say two weeks later or a year later, someone brings in something that is even better, then we will use that. We upgrade and switch to the best possible sounding transformer. There are little subtitles and changes between them, but they make a hell of a difference on the final tone.

Continued in part two.