Behind The Gear: Whitestone Audio Instruments

A few months back, we sat down for a conversation with Kim Rosen, the famed New Jersey-based mastering engineer. Kim heads up Knack Mastering and has worked on Grammy-nominated releases from Bettye LaVette and Bonnie Raitt. Aside from her engineering work in the studio, Kim and her husband Dave are the brain trust behind Whitestone Audio Instruments.

Whitestone has quickly made a name for itself in the pro audio world with its P331 tube amplifier. The P331 has become a fan favorite in recording, mixing and mastering studios with avid users like Greg Calbi, Ryan Freeland, and Justin Niebank. In order to find out more about Whitestone and the inspiration for the P331, we had Kim hang around after our initial 20 Questions interview and had Dave join us to chat.

Let’s talk about how Whitestone got its start. What made you want to own your own gear company?
Kim Rosen: For me, analog processing is essential to the way I work. That’s not to say I have anything against digital processing. I use both analog and digital for their strengths. They’re really just tools to me. I tend to use digital for its precision and its ability to be “invisible.” Analog can’t touch digital when it comes to surgical precision.

However, I personally have a difficult time finding real “magic” in the box. While emulation has gotten better over the years, I want to be using the real thing – not an emulation of the real thing. I want to run audio through truly exceptional analog signal paths. I want to place pieces of gear in just the right order with just the perfect amount of gain from one unit to the other.

There’s an authenticity to the sound, a deep blackness of space and depth, a nuance that comes when you patch in just the right chain and settings for a particular recording. There is just something about the sound of a really beautiful tube amplifier interacting with other analog circuits. It’s real and I can feel it as much as I can hear it.

With that being said, while I love using analog gear, I don’t really know or care much about the internal workings of it. All I care about is how it sounds and if it helps me get to the finish line faster. That’s really liberating for me to say because I spent years feeling insecure about who I was as a mastering engineer because I wasn’t “into gear.”

When I went out on my own and started Knack Mastering in 2009 after spending the previous seven years mastering in someone else’s room, my husband Dave really put in the time to research and find the gear that would be a good fit for me. Dave knows how I like to work and how I like to hear things. We spend a lot of time listening to and discussing music and sound.

Dave Rosen: I quickly became fascinated with the gear. I spent the first half of my life in bands and in recording studios, which is how Kim and I met, but I had a lot more experience messing with guitar amps and pedals than compressors and equalizers. When I began researching the pro audio side of things, I went down the rabbit hole...  Deep. I would spend nights reading about tube circuits, old RCA consolette manuals, new production tube units… One article would lead to ten more and then to DIY discussion forums.

It all just flipped a switch in me. I said to Kim one night, “If we were to add something custom to your chain, what would you want? What could we build that you couldn’t just go and buy?” We came up with the idea for a tube line amplifier that would provide beautiful clean tube gain, but with the ability to tweak it in different ways. At the start, we weren’t thinking about it as a product to bring to market. It was just going to be a cool piece for Kim’s room.

To make a long story short, I never became a rock star. I’ve paid the bills as a marketing and creative director inside and outside the music business. I’ve helped companies launch products for longer than I’d like to admit. One of those companies was Wave Distro, who represents pro audio brands like Empirical Labs, Useful Arts Audio, Serpent Audio and a host of others. Kim and I had become close friends with Gil [the owner of Wave Distro] and his wife Teri over the years. When we showed him the concept for what would ultimately become the P331, he said, “Why would you keep it all to yourselves? If you build it… I’ll distribute it.” And so the journey began.

KR: And so the nightmare began [Laughs]! We had no idea what we were getting ourselves into developing a high-end audio product from scratch.

Were there any existing pieces that inspired your work with the P331?
KR: There are pieces of gear that I use that just make stuff sound better. Pieces like the D.W. Fearn VT7 or Pultec mastering EQs. So I guess you can say pieces like that inspire us. Gear that is so well designed and executed that just running audio through them makes it sound better coming out the other end.

Let’s talk about the development process behind the P331. Can you walk us through the journey it took from inception to production?
DR: We knew from the start that my experience messing around with guitar amps and pedals was not going to cut it for what we were looking to do with this line amplifier concept. We needed to find someone to help us and to be the electrical engineer for the project. Someone who could help bring what we envisioned to life without telling us “you shouldn’t do this or you can’t do it that way.” We ultimately found that person while picking up a MCI JH110 tape machine we bought up in New Hampshire.

KR: I was eight months pregnant and we drove five hours to pick up this tape machine from a mastering engineer up there. When we were checking out his room and talking, he told us he designed and built all his gear himself, even his converters. We were pretty blown away and asked if he’d be interested in working with us on this line amplifier concept we had. He told us he was too tied up with some alternative energy project he was working on in his barn, but there was a guy one town over that was “really smart and also into audio.”

DR: I reached out and on our first phone call I think I understood maybe a third of the conversation. I thought to myself, “Either this guy is full of shit, or we just found our man.” I’d love to tell you his name, but he prefers his name not be out on the internet. He works on various projects that need government security clearances and such. An interesting and brilliant guy for sure. We worked together over the next five years designing, testing prototypes, building revisions, over and over. We nearly gave up so many times.

KR: The goal from the start was to have something that could make recordings sound better without changing the intent of the mix. That’s always what I’m going for. How can I make this mix sound bigger and better without it feeling different? I want a seasoned mix engineer to get that master back and be like “I don’t know what the hell you did. It sounds like my mix, just better.” If this unit couldn’t help me do that, it wasn’t worth continuing to develop it.

DR: There was not much compromise from Kim on how things needed to sound and function [Laughs]. I became obsessive about the look, feel and ergonomics. From the start, we wanted the P331 to be simple and have this modern-meets-vintage look and feel. That’s what the unit is all about. Having precise, modern digital control over a Class A tube amp based around a tube from the 1940s.

I spent months ordering knob samples, meter samples... Debating between vintage-style bakelite knobs and more modern aluminum knobs. Not just for their look, but for their feel. How does it feel when you grab the knob? Ultimately, we decided on the custom aluminum knob with diamond knurl grip. They just feel solid and confident to us. We went back and forth three or four times with the manufacturer to get the feel of the diamond knurl just how we liked it and the satin finish just right.

While we were developing it and adding/scrapping features, we were also super fortunate to get advice from people like Paul Wolff and Dave Derr, whose collective experience is legendary. I mean, the reason the P331 is digitally controlled is because of a conversation I had with Dave while we were smoking outside a wedding one night. That one conversation changed a lot of the way I was thinking, and added a whole additional year to the development! But some of the final features that made their way to the P331 wouldn’t have been viable if I hadn’t had that conversation and decided to go down that path. The generosity of people like Paul and Dave sharing their knowledge and experience is one of the things we love about this audio community.

There’s so many successes and horror stories we could tell, but in the end, we finally launched the P331 Tube Loading Amplifier at the NAMM Show in California in 2018 and we were off to the races.

Was it a challenge to produce equipment with such a small team of people? Do you feel like that has become a strength for Whitestone?
DR: I still currently build and test each one myself on the bench and then it goes into the mastering room for Kim to test in-use before it gets a final calibration check and put into the carton.

KR: I listen to and test every unit in my room before it ships. Dave goes through the checklist and makes sure everything is functioning as it should from a technical perspective. Then he hands it off to me to make sure it sounds and functions as expected in the “real world.”

DR: For now, it’s a nice flow. If it becomes too much to handle as we continue to grow, we’ll have to adjust how we do things, I suppose. It’s getting kind of busy. Having Wave Distro handle our sales and distribution takes a big load off our shoulders. They handle all our sales, shipping and customer billing so all we have to do is focus on making sure each P331 is as close to perfect as we can get it.

The P331 Tube Loading Amplifier seems to have garnered a lot of praise in the time it’s been out. What do you think is special about this piece?
KR: You know, we designed and built this to be a thing I wanted for my work. I knew I liked the way it sounded and functioned, but to have other engineers that I so admire using it and telling us how much they love it kind of makes all the years of struggle worth it. People like Greg Calbi, Ryan Freeland, Chris Athens, Justin Niebank, Jeff Lipton and Maria Rice… So many more in the United States and all over the world. It’s crazy.

DR: It’s special because the audio path was designed simple and without compromise. I know it sounds cliché, but it’s just the way it is. The fully switched digital control along with very tight tolerance analog parts selection makes it incredibly left/right coherent. We calibrate every unit to have left and right channel matching to nearly three decimal points. What that does is helps create or maintain a rock-solid stereo image. Combine that with the inherent clarity of a well-designed, fully differential Class A tube amplifier designed around 6SN7 tubes AND the ability to control where the audio sits on the tube’s response curve. It all adds up to something pretty unique, and something that can help a mix sound bigger, wider, and deeper without changing its fundamental character. It goes right back to that original goal.

KR: I say this a lot... Compression and EQ aren’t always the answer. You can add the P331 to your mix buss or mastering chain and have a unit that gives you options that compression or EQ can’t provide on their own. I find it essential to have other tools in the toolbox when compression or EQ aren’t giving me what I’m looking for.

Kim, you’ve been emphatic about how the P331 impacts your work. Can you give us a couple of examples of tracks you’ve used it on?
KR: I’ve used it on nearly everything from rock albums like Belly’s Dove, mixed by Paul Q. Kolderie, and Flogging Molly’s 20th-anniversary version of Swagger that Ross Hogarth remixed. Then also on albums like Rhiannon Giddens’ There Is No Other and the new Meshell Ndegeocello record that’s coming out soon. One lives on Ryan Freeland’s mix buss and everything he does is pure magic. The Milk Carton Kids used a P331 in their vocal chain and on the mix buss for their latest album, The Lonely Ones. Greg Calbi is always telling us how he’s using it “on 80% of everything” he’s working on, including the latest Sheryl Crow album. It’s crazy, and humbling to know this creation of ours is being put to work on so many amazing recordings.

What’s next for Whitestone? Any plans for upcoming projects?
DR: We have a few projects in various stages right now. We’re hoping to have something new ready to launch by Summer NAMM in Nashville. Fingers crossed that it happens.

KR: We’re gluttons for punishment.

If you're interested in ordering the Whitestone Audio Instruments P331 tube amplifier, we're here to help! Please contact a Vintage King Audio Consultant via email or by phone at 866.644.0160.