In the last couple of days I’ve been writing about the end of the analog preamp era and the beginnings of the digital preamp era. That’s sparked a lot of controversy and there are calls for me to either be lynched or certainly sent to my room for a few days. In my defense let me suggest I am NOT suggesting ANALOG is dead – it can’t be and never will be because you have to get to analog somehow to listen to it.
Here’s the thing: none of us should feel threatened by what I am writing. Why? Because reporting about what’s coming isn’t going to change anything other than your awareness. It won’t change the inevitable just because I write about it. I think I now have a clearer understanding of the poor soul who first wrote that airplanes would be replacing trains – or horses replaced by cars. He was probably hated. Isn’t there a saying about shooting a messenger or something? 🙂
To keep things in perspective, this tipping point we’re a part of in the history of high-end audio is a transition phase which every era change goes through. That means we’re not fully in either paradigm yet – we’re in the crossover period where much remains of one and the growth is seen in the other. This perspective is important to point out because of course there are many use cases where the old is still needed and the new doesn’t yet fill the gap. That’s normal. When photography transitioned from film to digital there was tons of film available everywhere – now it’s harder and harder to find until within a few more years it will no longer exist. That’s the nature of change.
Today let’s cover the output stage of our preamplifiers and note how similar they are and why that matters.
Yesterday I pointed out that all analog preamps have three main elements: input selector, volume/balance control, output stage. Digital preamps also have three main elements: input selector, digital to analog conversion+volume balance, output stage. I lumped together D to A conversion and volume/balance control because in fact they are integral to each other – a subject which I will cover in depth in this series.
So essentially analog and digital preamps are the same, certainly when it comes to the output stage. In both cases the output stage is a voltage amplifier – in many cases a simple op amp (something we covered many posts ago in a 9 part series). I promised many of you I wouldn’t get so technical on you in future posts so let’s keep this simple. A voltage amplifier simply makes a little voltage at its input a bigger voltage at its output.
Perhaps the biggest point to this post is this: a properly designed output stage on an analog preamp SHOULD be identical to the same on a digital preamplifier or DAC. It certainly is on any PS Audio design and it is on any well designed DAC I have ever seen. So why does that matter? Because it means from the perspective of the interconnect cable between the preamp and the amplifier and from the amplifier’s viewpoint, there isn’t any difference between an analog preamp and a DAC/digital preamp.
That’s a very important point to think about because if, from the viewpoint of the power amplifier, there isn’t any difference between an analog preamp and a digital preamp/DAC, then all we are left with is the other two elements in the chain, the volume control/conversion stage and the input selector.
Paul McGowan – PS Audio Intl.