Dan D’Agostino of Dan D’Agostino Audio is one of the easiest designers to interview. Basically, you ask him a question, then ten minutes later when he's stopped talking about that first question, ask him another!. And he’s one of those rare people who speak in publishable sentences. He is also one of the sharpest amplifier designers around.
Since leaving Krell in 2009, D’Agostino (the man) has built D’Agostino (the brand) into one of the foremost new high-end amplification companies on the market, encompassing mono and stereo power amps, line preamp, an integrated design (with optional streamer) and now a phono stage. More is coming, too!
We approached Dan for an interview during the Munich High End, expecting a few words on the new phono stage. This is what we got!
AS: Let’s begin after the ‘K-word’ and before Momentum!
DD: About two years ‘before’, I was in Tokyo with my Japanese distributor and asked what kind of product he’d want. He started to describe a product that was beautifully finished, with no fasteners showing, with no tiny buttons that have little legends you can’t read; something that looks beautiful, and feels beautiful, and is not too powerful.
‘After’, my first thought was to build something big and mean – kind of the kind of stuff I used to do, only better! But then I said to myself, “I’ve already done that!” and I wanted to design something elegant and beautiful. But, I could never build an amplifier that is not powerful – I don’t see the point in it!
I had at home at the time all of the work I had done over the previous 30 years. For me, the one amplifier I had done in the past that really stuck out was the EV1. That was, I think the most musical amplifier made ‘before’. I wanted something that had the power of the EV1 but with that musicality. That was the goal of the Momentum – it took me a few tries to really get the circuit to do that.
I then started fooling around with proportions and what I finally came up with was 12” wide, 4.3” deep, and 18” long. That is pretty small. I got a machine shop to make me a case, but the problem was how to make a mains transformer that would give me the power I wanted. I proceeded to work with this gentleman who has a completely vertically integrated transformer factory. I gave him the specs, but the first transformer was much too small and not powerful enough, so I brought him the actual design and the shape that he had to work with, and after a couple of days he actually made this transformer for me that could fulfil the requirements I had.
Once I had that in hand, I knew how much room I had inside the case to put the rest of the electronics in. Well, the other problem I had was heatsinks, as I didn’t want to make it wider. Copper came to mind: I’ve been wanting to work with copper heatsinks for 35 years, so, I said “why don’t I get myself a piece of copper and build an amplifier on that piece of copper to see how it sounds” To my surprise, the copper did two things. First it allowed me to have a low profile heatsink as it absorbs heat energy 91% more efficiently than aluminium. What I didn’t realise at the time was its thermoreluctance – it retains heat. That threw me, until I figured that the thermal mass of the copper and the bias of the transistors.
Copper’s resonant frequency is much lower than aluminium. The amount of EMI is very closely damped by the copper, which made a difference in how the circuit worked. Then I started designing the power supply, the input board after that.
After eight or nine months, the Momentum was finished, just in time for the CES show. I started to assemble the four first amps, but there was so much clear coating on the cases, the heatsinks didn’t fit! I spent hours trying everything until finally, I went to my garage, got some carpenter clamps, put cloth around the heatsinks, tightened and tightened until ‘bang’ they fitted. This was five-thirty AM and we had to leave at six! I was worn out when I went to that show, but all four amplifiers worked, and they looked great.
Was the preamp a natural progression from the mono amps?
The Momentum gave me the opportunity to just wipe the slate clean. The same thing happened with the preamp. You know, if was to say that the only real negative comments about my career in the audio industry was I’d hear people say, “he makes the best power amplifiers in the world, but the preamps are so-so!” I knew that I could do better than that. I started working on something different, radical, and something that I knew if I could make it work, it would sound really good.
To that end, I kept on telling my partner that I would have it ready in three months. It took a year! But when I finally finished it, finished all the software and circuit boards working, I ran into the sound room to hear it. I knew what it was going to sound like – the circuits were like dreams to measure: very low distortion with extreme bandwidth, and I did that without feedback or any kind of compensation – but when I hooked it up and listened to it I finally knew I’d made a really good preamp!