When you make the decision to upgrade your home recording setup, your first step is, of course, a large diaphragm condenser microphone. Number Two on the list is a quality preamp. Now, you can argue with me on that, but I’ll get petulant and stomp my feet! Even if you’re already using a mixer – which has a preamp built into most channel strips – you can likely do better. (Read why you need a microphone preamp)
The Focusrite ISA One Classic single-channel preamp is as close as you will get to recording with Sir George Martin, the legendary producer of the Beatles, Jeff Beck, America and many others. The ISA transformer-based preamp design traces back to a circuit that Rupert Neve developed for a mixing board that Sir George commissioned for his AIR Studio.
There is one word to describe the Focusrite ISA One and that’s Class. Capital C intended.
The Three-Second Summary: Run, don’t walk, if you’re looking to add a preamp to your setup. The ISA One is the real deal.
The ISA One is a single-channel microphone preamp with line and instrument direct-inject (DI) capabilities. As a professional piece of equipment in construction and performance, this is not a simple plug-and-play device.
Some knowledge of analog signal chain is necessary, since it is a classic analog device. The quick tour is that your microphone plugs directly into the ISA One, and the ISA One connects to your recorder input. Since this is the 21st Century, that likely means a computer, and therein may be the challenge for some.
Analog output from the ISA One uses a balanced XLR cable, a regular mic cable with three pins inside. Let’s look at some common home recording setups in practical terms and how the ISA One fits.
Whether your mixer is USB or analog, you can connect the XLR output from the ISA One to a channel on the mixer. Since the ISA One output is now boosted to line level, the ideal connection will use an XLR female to ¼-inch TRS (tip, ring, sleeve) adapter cable.
You may be able to connect using an XLR-to-XLR cable, but for gosh sake, make sure your gain control is turned down all the way. Your mixer has a preamp between the XLR plug and the rest of its electronics. This job is now being done by the ISA One. In fact, it’s possible that the mixer preamp will spoil some of the great sound you’re gaining with the ISA One.
Mic to Digital Interface:
Connecting to a digital interface is essentially the same. If line level input is available, that’s your best option. Popular and affordable interfaces, such as the Steinberg CI-1 or the M-Audio M-Track, include ¼-inch TRS inputs, your preferred option.
Again, you may be able to get away with an XLR-to-XLR connection, however signals may be high and distortion unavoidable. Proceed with caution.
Mic to Sound Card Input:
If you’re plugging a studio mic directly into a typical computer sound card with a 1/8-inch phone jack, you’re probably not at the point you can fully appreciate the ISA One. However, you can plug your mic into the ISA One and use whatever adapter you were already using between the mic and computer before.
As with the other methods, connecting to a line input, if one is available, is preferable. You will probably not get a good result connecting to a mic input.
Digital connections require the optional A/D converter upgrade. We’ll stick with the basic ISA One here.
This is a preamp that not only sounds good, it may breathe new life in equipment you already own. That might seem like a pretty extravagant claim, but one on which the ISA One delivers. Sound quality is as much about taste as anything. However, there is a reason why classic equipment is, well, classic. Things just sound ‘right’ sometimes, and plugging a quality mic into the ISA One will sound ‘right’ to a lot of users.
Preamps fall into two categories of design and intent. On one hand you have transparent preamps. These boost the mic signal while trying not to alter the sound of the mic in any way. Other preamps can impart character. For example, tube preamps add what’s described as “warmth,” which is usually a controlled distortion.
The ISA One is a character preamp. The overall effect is natural, but in fact the signal is changed and flattered. This goes back to the classic circuit design that was good enough for Sir George. Vocals will cut through with clarity, but without being harsh or aggressive.
Inexpensive mics do sound better through the ISA One, so even if your condenser mic isn’t the top-of-the-line, you will still benefit from this preamp. I don’t want to bore you with talk about microphone impedance. There’s a good chance I’d fall asleep as I did so. However, consider that a mixer has, usually, a one-size-fits-all preamp. The impedance is what the impedance is, and any mic you plug into it has to live with that.
The ISA One has four impedance settings. Match them to your mic. Or not. Flick the settings until you hear something you like. One mic may now sound a little different at each setting. Your chances of finding a setting on the ISA One that delivers magic is pretty good.
And this box isn’t through delivering yet. It’s also a quality DI unit, able to take instrument signals and converting these to line-levels with clarity and low noise. The DI functions can be used independently of the main preamp, meaning you could record voice and guitar in one pass, yet through separate signal paths. To my knowledge this is unique for a single-channel preamp, and in fact makes it a quasi-two channel preamp.
This is a solid, substantial piece of equipment, built into a metal box and weighing 8.6 lbs. (12.5 lbs. for shipping). Controls are smooth and solid and plugs are professional quality, well-mounted into the box.
Much is made of the circuit quality and components. Thirty years ago, when this preamp design was in its halcyon days, it cost along the order of $14,000 in today’s terms, and it was used in some of the most elite pro studios. By all accounts, the electronic components are comparable. This speaks volumes to both the build quality and the value the ISA One represents.
I took a look at 44 online user reviews of this preamp. Only two gave scores below 3.5 out of 5. With that kind of result, I suspect those two users more than I suspect the ISA One.
Interestingly, several reviews describe the ISA One as a transparent preamp. It’s not by any stretch, but this is a compliment to the way the preamp flatters the output of the microphone. It’s a very natural character that is musically useful. Users who love it, and that’s over 90% of them, really love it.
If you’re at the point you want that extra bit of polish on your voice work, the ISA One preamp is the best thing you can do after purchasing a reasonable quality condenser mic. Chances are that you will immediately notice something much better about your sounds, even if you can’t put your finger on exactly what it is. Well, what it is is classy and right.
Have you had an experience with the Focusrite ISA One? Leave a comment. Argue with me about preamps. Feel free to share this article and subscribe below to receive new posts right to your inbox. We’re committed to providing passionate, high-quality discussions of home recording topics, and hey, if a preamp falls in the forest… we need to hear from you, or the preamp falls in vain!