Click here for the review in Acoustic Guitar magazine.

This week’s interview is with Gerry Humphrey of Humphrey Amplifiers. Mr. Humphrey’s amps recently made their debut at Dream Guitars. In a world of solid state acoustic guitar amps, the Humphrey Espresso really stands out. Beneath the beautiful hand crafted wooden cabinet beats the heart of a high fidelity tube amplifier. Paul, Al, and I took this sophisticated new tube amp for a spin, and found it highly accurate, full of great tones, and a delight to use.

Humphrey Amplifiers Espresso

Could you tell me a little about your background, and how you got into designing boutique acoustic amplification?

I’ve been in love with music, particularly the guitar, as long as I can remember, Steven. As a 12 year old, my first tube amp was a little Marshall 10W that I used to terrorize the neighbors! Of course, it wasn’t long before I was ‘encouraged to play acoustic instead.

Later, my chosen career path had me graduating from college in Scotland as an electronics engineer and jumping into the world of hi-tech — where I stayed for almost 30 years. My very patient wife and family stuck by me as promotion also meant several relocations, with the USA welcoming us 20 years ago.

Most recently I was an executive at a Fortune 100 company, but for the last couple of years I wasn’t truly enjoying what I was doing. That’s very important to me – life’s too short to spend it working on something that doesn’t inspire you.

I’ve always had an itch to start my own business, and when a good friend told me of his frustration at not being able to find the perfect amp, I did some market research and found there could be a real opportunity for the ‘right’ design.

What is your connection to luthier Brian Applegate?

We’re fortunate to have him as a neighbor. Brian was the good friend ‘that planted the amp seed about 5 years ago. He gave us the idea in the first place – the initial concept was his, and knowing my engineering background and love of the guitar he encouraged me to take a serous look at it. Brian not only gave me encouragement, he also offered advice and support as I fleshed out the initial design and the multitude of prototypes that followed.

He was our initial test-case too. We knew the circuit design wouldn’t be right until Brian was happy. That entailed countless tweaks, modifications and even a few total redesigns before we saw him grinning like a Cheshire cat when doing a sound check. That process took months, sometimes with multiple tests on the same day, but more typically one or two days apart. We called it ‘death by Brian’ 🙂

Following that, we left a couple of prototypes at his shop and he was kind enough to bring in his own customers to try them out. We’d hoped to get some constructive feedback, expecting to make some design changes. Instead, we got orders. We were blown away by the response – and apparently the customers were blown away by the sound. I guess we knew we were really onto something good at that point.

If a product, any kind of product, is going to be successful, it has to solve a problem.
Here’s the problem: Brian not only makes very beautiful acoustic guitars that sound incredible, he plays too, so he obviously has a very good ear for tone. When he needed amplification, although having various acoustic amps, microphones, PA’s etc., he found the closest he could get to the sound he really wanted was when using an oversized electric guitar amplifier, dialed down to keep it in a very narrow clean zone.
It sounded pretty good, but didn’t quite fit with the image or the surroundings.

He wanted the warmth and fidelity that only a tube amplifier could offer, but in a package that was more suited to a hand-built acoustic guitar, and didn’t look out of place in his living room.
With that in mind, I spent a lot of time looking at what’s available in the market, what people were actually using and asking lots of questions. Many people make compromises when it comes to amplification, playing their custom acoustic guitars through sound-systems & amps that effectively strip the rich and complex tones.

Some, like Brian, struggle to find the setup that lets them hear just how their guitar sounds, only louder.

Espresso Control Panel

A lot of folks actually enjoy the challenge, develop sophisticated setups using particular pickup systems and/or mics and swear by a specific brand/model of amplifier. Mostly, they’re happy with the result, for a time anyway.

What we wanted was a ‘living room friendly’ tube amplifier – one that was designed specifically for acoustic guitars. Sounds reasonable – after all, the best (and most expensive) stereo hi-fi amplifiers still use vacuum tubes today.

That’s why the Espresso amplifier incorporates a lot of hi-fi design methodology.

I was very pleased to learn that your amps employ EL84 tubes. Most people associate that tube type with the great Vox amps of the 1960’s and early Marshall 18 watt amps. How did you come to use this tube in the power section, and what does it offer that other tube types do not?

I love those amps, and the sound they get from the EL84’s. With an electric guitar of course! They’re set up to overdrive the EL84 tubes, pushing them to saturation point, giving the resulting sound a kind of ‘chime’ – the type of distortion that’s very pleasing to the ear.

If you don’t overdrive the EL84, in other words, you keep in the ‘clean’ zone, it’s wonderfully clear sounding. Some people say it sparkles or shimmers or words to that effect, but it’s a very subjective thing. Fact is, the ‘clean zone’ is ideal for the power level of this amplifier and the dynamic range of an acoustic guitar.

I did a lot of reading and a lot of testing and concluded not only that EL84’s were best suited, but that the JJ Electronics manufactured EL84’s, supplied by Eurotubes were the best sounding.

Your choice of speaker is quite unique. Could you tell me about it, and what led you to choose it?

Everything about tube amplifiers for electric guitars is designed, intentionally, to change the sound of the guitar in some way, including the speaker. Guitar speakers are made to breakup at a particular volume, or change the shaping of the frequencies produced in some manner – that kind of thing.

Espresso

What we needed was a speaker that didn’t color the sound at all, one that simply produced an image of the signal driving it: a hi-fi speaker. Actually, it’s a 2-way speaker with a horn for the high-end and an Eminence 10” for mid/bass.

To make sure the 15W output from the amp didn’t come anywhere close to overdriving the speaker we looked for one that was built to handle much higher power levels, but with characteristics that would be ideal for the dynamic range of an acoustic guitar. There were a few technical specs in particular that we were looking at as we did our research, and then there was the testing . . .

It was both interesting and comforting that the lab test results matched with the choices made by our volunteer guinea pigs. The number one choice, by far, for clarity, transparency and ‘authenticity’ lined up with the one our measurements suggested would be best.
However, as time allows we’ll continue to look at other speakers to see if we can make improvements or simply offer options for customers.

Your cabinets can be built in a variety of optional hardwoods, which of course have different densities. Have you noticed any significant tonal changes when using, for example, walnut compared to maple?

Not particularly. If there are any, they’re very subtle. If anything, the parts that could alter the tone are the speaker baffle and the back-panel, but they’re made from 14-ply baltic birch so there’s not really any tone altering that happens there.

Type of wood obviously makes a huge tone difference in guitar construction. Consider the structure, the thickness of the wood compared to the width & length. It’s all designed to amplify and shape the sound.

In our cabinets, the top, bottom and sides of the box frame are made from 3/4” hardwood panels, dovetail jointed and glued. Relatively small panels, thick wood, very solid construction, not prone to vibration, that won’t alter the tone to any discernible degree, is what we’re aiming for.

If someone wants an Espresso with an effects loop, is that a possibility? What other options do you offer?

The short answer, Steven, is yes. There’ are some circuitry changes that need to further be refined before we’d release it, but that option is definitely in the plans for the near future.

We’re getting requests for different input/output configurations: dual channels; mic/instrument; XLR in; AUX in for iPod , balanced DI out, etc. To satisfy those, we’re working on a kind of ‘universal’ plug-in for the inputs, and we’ll address output needs on an individual basis.

On the inputs – we’d be able blend the channels at individual levels but we’d still be limited to a single tone stack with the space on the current control panel. Eventually, we may move some of the controls to the side or back to allow for more space.

Part of the initial concept was to keep it simple and clean, focusing on the quality of the sound, and having specific sound/tone tweaks satisfied through external boxes, pedals etc.

That’s how many folks tweak do it currently, but there’s growing interest in having it ‘in the box’. We like to cater to any requests that we can because that’s what customization is all about.

Humphrey Amplifiers Espresso

Although not a hard request, another option that’s been suggested is a parametric equalizer/notch-filter. So far, we’ve resisted using any solid state & we’d prefer not to go there, so we’ve been working on doing it the old-fashioned way. It’s a pretty complicated filter network, and to do it right adds a big chunk of circuitry. Right now, we’re not happy about how it effects the overall sound, but we’ll keep working it.

Will you be expanding your line to include amps for electric guitar as well?

At some point, Steven, that would make sense. It certainly would be an easier design than our acoustic amp, because we had to figure out all the things that went into making a tube amp do what it does for the electric guitar sound, and then eliminate them.
Likely, the first step would be to design for archtops & hollow-body electrics — something that retains the clarity but introduces a more bluesy/jazzy tone to the mix.

But there are other more organic products we’d like to do first. Two things that are in the plans are an extension cabinet and a dual-channel pre-amp.

Interestingly, something that wasn’t planned until much later is a stereo hi-fi model, based on the Espresso 15. Something you could plug your iPod into and get great sounds out of. However, having stumbled into a discussion about it at a recent trade show, we now have a customer that wants a significant number of them, so we’ll be bringing it out a lot sooner than we planned.

It’s actually very cool – and it’ll give us a platform for the dual channel pre-amp too – so we’re pretty excited about that.

What does your tube amp offer tonally that a player cannot get from a solid state device?

A more life-like sound. That’s the bottom line. Yes, the tubes are a big part of it because of the physics of how they work, and how we perceive/process sound. A small, but very important point is that using tubes allows for a much simpler circuit (signal path) than solid-state, with fewer components and connections, and therefore less interference in the signal path. That’s a really good thing for acoustic instruments.

One key area that’s often overlooked in the typical tubes versus solid-state debate is dynamic range – what some folks describe as ‘touch’ or ‘feel’. What I mean by that is the way in which an amplifier responds to changes between soft strumming & hard picking. Tubes run on very high voltages (ours run higher than 300 volts), which means they can respond more rapidly to the strength of the note played. It gives the player a much more natural ‘feel’.

Those things, along with the cabinet design – unique venting & offset speakers – give you an experience that’s a lot closer to the sound of your guitar than any solid-state amplifier can.

Are your amplifiers point to point, hand wired?

All our amplifiers are hand-wired. We use military-spec (very heavy-duty) fiberglass board with turret-pins staked in the appropriate spots. The components are mounted on the board and silver-coated hookup wire is used to connect them to each other and to the tubes. Oh, and the solder has a high silver content too – all good things for signal integrity.

We looked at using the point-to-point method (components soldered directly to each other and directly to tube pins) and although it would have been easier, we decided quality assurance would be more consistent and reliable with the board/turret scheme.

Finally, do you have any other thoughts that you’d like to share with readers of our blog?

We may be a new name, but we’ve put a tremendous amount of time into ‘getting it right’ and we’re very excited (overwhelmed, actually) about the reception we’ve had so far, Steven.

Also, we’re really pleased to be working with Dream Guitars. I know from talking with several luthier friends that Dream Guitars is very selective about the products you offer your customer base – and for good reason. The reputation you have, in the market you address, is extremely high so you need to make sure they meet the high standards your customers have.

My last words (for now 🙂 Steven, would be to let your customers know that testing a Humphrey is very likely to cause a sudden increase in their ‘gear collection’. So far, all but one person that’s tried a demo has either ordered an amp or seriously plans to within the next couple of months. The lead-time is reasonable right now (around 8 weeks), but expected to grow pretty quickly.

Thanks Steven – great questions!

Humphrey Amplifiers Espresso

Humphrey Amplifiers are stocked by Dream Guitars, and can be special ordered to fit your particular requirements. Please call Dream Guitars for more information.