Read Time 17 Minutes
The ZT Lunchbox
I first saw the ZT Lunchbox amplifier in a company advert. Reading the claim that the amplifier was capable of pushing a 200 watt signal through a 6.5″ speaker, I wondered how the amp sounded, and whether it could live-up to the flurry of glowing user reviews that cropped up online.
Months later, I played a gig where the opening band consisted of two horns and a full rhythm section. To my amazement, the guitarist of that group, using only an un-mic’d ZT Lunchbox amp, cut through the live mix with a rich and balanced tone that belied the amp’s small speaker size. My perception was that the tones I was hearing could only have come from a much larger (and frankly more expensive) amplifier than the lunch box sized amplifier I saw sitting on a chair next to the drummer.
The study of how one perceives sound is a branch of science called psychoacoustics, which is not only an area of interest to the CEO and lead designer of ZT Amplifiers, Ken Kantor, but also is a key design component behind ZT’s innovative line of new amplifiers that include the Lunchbox, the Lunchbox Acoustic, the Club and the Lunchbox Junior.
In this interview, Kantor discusses a variety of topics including amplifier design, modeling, tube amps and what makes his amplifiers unique.
Interview with Ken Kantor
You have an extensive background in speaker design that includes work with psychoacoustics. How did you get into audio design and psychoacoustics (and what role does psychoacoustics play in your current work)?
Wow, those are some huge questions! Let me try to break them down.
How I got into audio design:
Sound has fascinated me ever since I was a little kid. Whether it was raindrops splashing against the window or being swamped in high pressure waves packed into some “enormodome,” my ears have always been my favorite erogenous zone. (Well, perhaps it’s a tie….)
I played trumpet in school band. I took lessons on drums and guitar, and music theory. But it soon became obvious: I was a crappy musician. A passion for something doesn’t automatically translate into an aptitude for it. But, what I did have was an aptitude for the technical side of things. I started tinkering with audio equipment and instruments, repairing and building things. It was a way for me to stay close to music, and be useful to my more talented musician friends.
At the time, I had only a rudimentary knowledge of electronics so, of course, my “designs” were really primitive. For several years, it was mostly glorified circuit bending, not really design in the way I think of it now. For example, I added a master volume to my amp, I built fuzzboxes out of the amp stages of transistor radios, added effects to wah pedals so they could be foot controlled. Gradually, I began to realize that to make any real progress, to be able to experiment with new ideas, required me to learn electronics. I did this throughout high school, but getting an EE degree is what really made the difference. Even after a few semesters, I found myself doing design work for local audio companies and the more you learn, the faster you learn.
How I got into psychoacoustics:
In the early sixties, as music started to get really loud and solid state came on the scene, amp designers tried various things that, overall, just didn’t sound very good. At this point in time, in my opinion, instead of pushing forward to understand what great tone was about and learning how to achieve it, designers and manufacturers either fell back on the tube amps of the past, or pressed forward with tonally-challenged solid state designs. As a result, musicians were forced to choose between great tone, on one hand, and power, reliability, size and convenience on the other. Of course, in 95% of the cases, great tone is going to win.
But, I was never satisfied with those compromises. I decided to try and understand what went wrong. What was it about the classic designs that engineers were missing? Hey, those engineers were not stupid so I figured there must be something missing in our fundamental understanding of audio. That’s where psychoacoustics comes in. Big word, but all it means is the formal study of how humans perceive sounds. Jumping in to that, perhaps I could find some better clues to the mystery of what sounds good, what sounds not so good, and why.
What role does psychoacoustics play in my current work:
Over the years, I have designed dozens and dozens of audio products. Psychoacoustics has become completely infused in the way that I think about amps and speakers. They help me set the technical goals for a new product, and guide countless decisions during the development process. It’s a huge help to be able to predict what people will prefer in advance, and fine tune it as you go along. It helps increase the chance of making a better sounding product out of the box.
The Lunchbox amp is a product that is, tonally, greater than the sum of it’s parts. Many guitarists get caught up in dogmatic thinking about amps and tone, but, by and large, some don’t understand the relationships between the individual components that create tone. Can you explain how you optimized the individual components (amplifier, speaker and cabinet) into a unified whole and the relationship between them in the signal chain?
Well thanks! The key thing to understand is that the Lunchbox’s response varies from note to note (depending on how it is played, what the pitch is, the level, etc). When we studied the behavior of the finest amps available to us, a pretty esteemed crowd, we found that they all had one thing in common: they all had these subtle and complex interactions. They had a slightly different response with every change in signal level, every nuance of the input signal. This allows players to learn them, to “play” them to get rich tonality beyond the basic voicing. That’s what we tried hard to achieve, and I believe it is one of the major things that experienced players respond positively to when they try the Lunchbox,
It’s also a very tightly integrated product. In that regard, it is a wholistic re-thinking of the guitar amp – a clean slate. A great amp is not simply a matter of combining such and such with such and such to get, “The Tone”. The key thing is for the parts of the amp work together to handle the signal in exactly the same way as a fine vintage amp, but using totally different tools. So, the parts were not optimized individually. They were optimized together, as a system. The power supply can react based on what the power amp is doing, the preamp can adapt to the tone settings.
It starts with a preamp that presents the exact load that a guitar expects, and which allows it to respond at its best. The preamp readily handle the extreme dynamics coming from a guitar. When we very carefully examined the output of most guitars, we were astonished to find brief transients that were many time the voltage that would clip most preamps. Not in the good way that a player can use, but in a subtle way that robs the signal of some of its natural openness.
Next, the line stage is what handles the complexities of responding to the individual notes, the pitch, the playing style, note dynamics, etc. It also contains some really unusual, proprietary tone controls. Instead of just boosting and cutting the sound, they actual morph through a huge range of curves as you turn them. You have a much better chance of getting exactly what you want, plus there are ways to set them to get lots of bass boost without muddiness, lot’s of treble without harshness, etc. Casual players won’t notice this, but it is there.
Just as the line stage is about the individual note, the power amp and power supply work together to determine the overall dynamics of the amp, and its overload characteristics. A huge amount of time was spent on this, getting things to “bounce” just right, sag as needed, open up when called for.
Finally, the speaker is tightly integrated into the electronics. Good luck replacing it with a “better” unit! This speaker is understood by the amp, and performs as ideally as possible, from tone to protection. I’m a speaker guy, so this was a matter of pride!
Living in NYC, I see a number of people carrying ZT bags around from gig to gig. The small amplifier idea is really great, but why did you decide to focus the company on being “The World Leader in Compact Amp Technology”?
When I looked at the landscape prior to starting ZT, I realized I could buy some great sounding amps that were large and heavy and I could buy any number of smaller amps that either sounded bad, or were very limited in output and flexibility. Most brands seemed to put their best chops into their large and expensive amps, and left their small amps as entry level or practice amps. Meanwhile, its a dynamic world, and portability is more important than ever. It was easy to realize that many musicians would have a place for a top quality, very small amp. That’s what we try to do.
Many guitarists have tastes that are specific and stuck in sixty-year old amplifier models and size requirements. Do you see a change in guitar players’ ears and expectations or do you have to cater to tastes?
I would not have made the Lunchbox if simply catering to tastes is what I wanted to do. We all know which amps from the past sound great. I’ve managed to collect a few stellar examples. We all know how to copy them to whatever degree our patience and budget allows. Does that mean that no new amps can equal or exceed them? What I have to do is satisfy guitar player’s tastes and, hopefully, exceed their expectations.
I have given a lot of thought as to why musicians, an extremely open-minded, intelligent and exploratory lot, get so dogmatic about technology. I think it has to do with being pitched so much crap for so long, without any plausible explanations about what benefits might actually be achievable. We had a lot a people come through our lab during the development of the Lunchbox, and all our products. We tried to bring in the most cynical, opinionated, hostile players we could find, and there were plenty. We learned a ton from them, and maybe they learned something, too. Several of those guys have turned into our biggest supporters. I get letters and emails just about every week telling me, “I only played your amp so I could show my friend what a piece of crap it was. Now I own two. I never thought I would ever own a transistor amp, let alone one with digital in it!” I’m not saying everyone likes the amp, or even wants to try it. But, I will say that very few people who try it actually wind up disliking it.
It would have been difficult to release an amp that size with a tube component. Was the decision to go solid-state solely a concession to size? As a related question, do you have any interest in tube amplifiers and/or would you ever consider making a tube design?
I have zero interest in making a tube amp. There are already plenty of great tube amps to choose from. I built my first tube amp when I was 11. It was never a consideration. ZT is all about bringing new things to the table, and hopefully raising the bar. Besides there are plenty of problems with tubes, and the future supply is far from assured. Yes, I follow that scene closely, and I know about all the chatter, but the clock is ticking. So, c’mon, somebody has to work on the problem of transcending tubes, including tonally. Most designers have their head in the sand, and rely on knee-jerk buying habits.
I’m actually very opinionated on this subject. It seems to me that most of the people building and selling amps over the last few decades have basically given up in the search for tone. As I said before, they revert to the great sounding designs of the past. Or they start to believe in mystical totems, as simply adding a vacuum tube or an Alnico magnets or using point-to-point wiring automatically confers great tone. This is pervasively believed, and widely advertised. But it is ridiculous, if you think about it. Along with playing technique and a good instrument, tone comes from exactly what happens to the electrical signal on the trip from your guitar and your ears. It does not matter what kind of parts or output devices you use, if you use them correctly! The fact that people learned how to squeeze good sound from vacuum tubes before they managed to do it from transistors is interesting, but not crucial. What is crucial is what happens to the musical signal.
Do any non-musicial factors influence your design? As a related question, do you think that your design aesthetic has evolved over time or is there a constant target that you’re aiming for that requires different approaches and innovation?
You can’t realistically play a circuit board. The mechanical and cosmetic design of an amp influences its playability and its appeal. It also influences how the speaker works, which is an important consideration. Roadworthiness is also critical. Much of the Lunchbox’s appearance is driven by function and economy, but we certainly had an experienced guitarist/industrial designer as a key part of the development team. We wanted the amp to stand out and be user-friendly.
In your opinion, what should people look for in sound reproduction (either professional or consumer use)?
Ha! I’ve written books worth on these subjects, as have thousands of others. I will say that the main thing is to trust your ears, but also know the various ways your ears can fool you in the short-term. Can I say, “Trust but verify?” Also, it’s so important to learn about whatever it is you want to buy, because there is just a ton of marketing bullshit out there, often spoken as if it were obvious fact.
The Lunchbox features an ambience control rather than a reverb. Can you talk about the relationship (or lack thereof) between the two and what are your thoughts about incorporating reverb into the design?
Oh, that’s easy. We designed in a chip as part of the digital architecture that had a reverb function. Unfortunately, before it came to production, the vendor deleted that function. So we were screwed. It was far too late for us to make an architectural change to the electronics, change the panel, etc. So, we built as useful an effect as we could using the DSP that was available to us. I think it is somewhat useful, but it’s not what we originally envisioned.
This is a very open ended question, but what are your thoughts about modeling?
Been there, done that. It’s clearly useful, but people expect too much from it. For mathematical reasons that are probably beyond the scope of this interview, you simply cannot model the directional characteristics of an amp, the sense of size and air it creates. You cannot fully model non-linearities very well. You certainly can’t model all the complex and unexpected interactions and microphonics you get in the real world. You can nail the basic tonality, but that’s all. In many situations, laying down a dense multitrack, playing a casual gig, it’s fine. But it won’t play like the real thing. It won’t respond to the player the same way.
Did the Lunchbox achieve all of your design goals and, in retrospect, is there anything you’d change?
Any entrepreneur or designer who says no to this is lying. Of course there are various things I would change. But, in the end, the product came out very much how I wanted it to. It surely could have been easier to get there!
The amps seem to be designed for guitarists to use live (rather than say a low wattage amp for recording), but you have videos on the ZT site of a number of different instrumentalists using it. Was that flexibility in application part of the design or an unexpected side benefit?
[It was] part of the design. Besides using the relatively neutral Aux Input on the amp, the reason there is a “Gain” knob is to allow the amp to accept a wide range of signals, and handle them fairly cleanly.
One thing that really knocks me out about the Lunchbox is how well it cuts through a live band mix. Even with that taken into account, do you have any recommendations for ways to increase the mid & high frequency dispersion?
Actually, a small speaker has wider projection than a large one, so the coverage of the Lunchbox is way better than a 12“. But if you want more, try putting as much reflecting area behind the amp as possible. It may sound counter-intuitive, but try it.
You have multiple products ranging from the Lunchbox, to the Lunchbox Acoustic to the Club and the Junior (as well as the Lunchbox cab). Do you view these products as tweaks on the initial design or are there enough differences among them that each is distinct in terms of design?
Oh no, not distinct. They are all based on the same DNA. Some share common parts. It doesn’t make sense to do each product from scratch, either economically or in terms of human resources or manufacturing. Besides, we wanted to create a ZT brand identity.
You advertised the bass amp a while ago, do you have any more information about when it was coming out, price point etc.
The design is done, and we are trying to work out cost and manufacturing issues. It certainly should be out early next year. We are working on the price, but ZT is not in the boutique biz. We try hard to make affordable stuff and the bass amp is no exception.
Let’s switch gears for a moment. Is there a story behind the company name?
With the major labels imploding, most guitarists who read this are probably independent musicians. What are the biggest challenges to starting your own company and would you impart any advice to people who are starting off with their own (self-employed) business?
I’ve done several startups now, from self-funded to venture capital backed. Not all have made it, but enough have. Most startups fail, no matter how carefully planned, well funded, not matter how smart the founders. So, expect to spend a year or two of 80 hour weeks constantly tending [to] a struggling new born.
A few other key points, which you ignore at your peril:
– Love the business, not the product. The product has to adapt to the customer, not you. I cannot stress this enough. Go to market with a business concept, not a precious design.
– Work at a successful company in the business first. Almost no hobbyists transition directly to successful business people, unless you are talking boutique, garage companies. Become a pro before you become a company starter.
– Do a business plan before you start. Period. No exceptions. If you don’t know how – learn.
– If possible, hire at least one key manager from the MI business, (that’s what it’s called, BTW; MI= Musical Instrument), and hire one who knows nothing about the MI business, but has other experience.
And finally, what’s in store next for ZT Amps?
Thank you so much for your time Ken! You can find out more about ZT Amplifiers by visiting their website at http://www.ztamplifiers.com. Stay tuned for an upcoming review of the Lunchbox Junior!