You can surf the web all day and find plenty of opinions on whether or not analog audio gear is worth the high cost or effort. I have been critically listening to audio for 15 years, and I can say one thing for certain - analog and digital effects are NOT the same.
I recently stumbled across as a great article where several UAD plugins were compared to their real-world analog counterparts. The samples are level matched and the plugins and hardware were dialed in with the same settings. Click here for a link to the article.
Of the seven audio clips provided in the blind tests, I immediately picked out the analog version 6 out of 7 times - the second Maag EQ comparison I flipped back and forth on. Try for yourself by listening to the soundcloud clips in the article - just don't scroll down too far at first or you will see the answers on the same webpage.
What was I hearing that made the analog versions stick out? A few things. For now let's just focus on the big ones - width or 3D depth, and also the range of audio/clarity of the high end.
A good part of what makes analog sound analog is actually bad, at least on paper. Noise, crosstalk, and differences between left and right channels may sound like good ways to ruin your recordings. But - in small amounts these normally undesirable elements do something great to the audio. One of the biggest differences between the digital and analog files was the width. Anytime the left and right channels of a stereo source are different, your brain is going to perceive it as wider or more separated. If the left and right channels were identical, the sound would be perceived as 'in the middle' or mono. The fact that running audio through analog gear introduces imperfections and differences between the left and right channel of a stereo mix imparts a width and sense of full 3D-ness that digital simply does not.
Another difference between today's best plugins and hardware is the fact that analog generates more upper harmonics well beyond the Shannon-Nyquist frequency. Analog is not limited by a finite sample rate like digital audio is. This means a few things - first of all there is absolutely no digital aliasing generated when adding analog effects since most of the noise can stay well above the range of human hearing, rather than get folded back into the audible range of the mix (We're not about to discuss oversampling today, but I hear you guys). Secondly - and I don't understand how or why - when I boost super high frequencies above 20kHz in analog recordings, it definitely does something to the sounds I can hear down in the audible range. It's hard to put my finger on, but the harmonics from 20kHz to 40kHz or so being present or not makes a difference to the clarity of the audio. I'll need to put some files up of my own later to show you what I mean.
Anyway, just those two factors - width and high end range - account for a lot of what I hear when comparing the files.
Are they close? Hell yeah they're close. Today's plugins are REALLY good, especially ones from UAD that run on their own dedicated DSP card. But, even still, they simply ARE NOT quite the same. Close, but not identical. Native plug-ins tend to be even more different from their analog brethren when I compare them to what they're modeled after.
It is entirely possible to get great results mixing and mastering with plugins. I definitely reach for plug-ins on every master for certain functions like limiting and surgical EQ. However, if you demand the best possible sound out of your music; the most width, the most clarity, the most punch, the broadest frequency response - you still have to go with analog, even in 2017. For producers working entirely in the box, adding some of that analog magic at mastering may be even more important. Plugins are 90% of the way there, but for the most demanding musicians, that last 10% matters. It comes at a high cost, as most mastering quality hardware has a price tag of $1000 or more. Sometimes much more.
So, the next time you see some argument on a forum about 'are plugins better than analog' or vice versa, understand that they each are awesome in their own way, but they are NOT the same. Plugin companies who tell you they're identical in sound are just trying to take your money. They're close, yes. But, **it is not possible, at least yet, to exactly recreate the effects of analog hardware in a plugin**. Period. Go back and read that again. If it was, it wouldn't be possible for me to consistently pick out the analog audio in level-matched, blind shootouts like these. When the plugins completely have me blindly guessing 50/50, I will let you know.
I recall seeing an interview with house producer Moodymann a few years ago. He asked the audience if they wanted to know the secret to getting 'that sound' - the sound of a professionally produced, top-notch recording that sounds like it came from an expensive studio with thousands of dollars of gear. He then said they wouldn't like the answer: thousands of dollars worth of gear that never goes on sale, citing the $5000+ Manley Massive Passive EQ specifically in his example. He's right. To get 100% of that top-notch sound, you can't fake it. You can only hope to get close.
However, he also tells the audience "it ain't what you got, it's how you use it".
Both are valid points.