Preamps have been an integral part of any studio (alongside microphones, of course!) since they first started.
Throughout the ages, there has been a dramatic shift in what is preferred as the ultimate choice, and ultimately concluded at the point we are now: what preamps should I use? Why? Is there that much difference?
Well, the answer to the first question is always subjective to your feelings towards a brand for example, or if you have used it before and liked the sound of it - but let me try and open the pathway for you a little more for you to make a much more informed choice going forward and let you decide with a much more settled mind by the end of this post, hopefully!
What is a preamp?
Microphones have a very small electrical signal by way of their make up. When the transducer (capsule) is subject to a form of SPL (sound Pressure Level), the signal is very small. A preamp is simply a way and means of converting the weak signal level from a microphone signal to a much stronger signal, with far more volume in order for it to be processed further.
You’ll find, whether on a mixing desk, an interface, or a dedicated preamp, there is always a gain dial for the input of a microphone for this purpose, to bring the microphone level up to a suitable level to process. Simply put, a preamp is an integral and necessary piece of equipment to have in order to allow the rest of your equipment (including your interface, which is why they have preamps built-in) to work at their standard operating level.
THD - What is it?
First of all, we must look at a scientific viewpoint specifically at what's called Total Harmonic Distortion (or THD for short). This is a very in-depth topic, so I will be brief and explain what it is and why it’s important without falling down the rabbit hole entirely, however, I do urge you to delve further into this as it applies to all parts of audio and can be extremely beneficial in the mixing realm.
Total Harmonic distortion is the harmonic content that is added to the source (the audio being listened to or recorded) once it has passed through the circuit. This, in the most basic terms, is what gives a preamp that ‘mojo’ or warmth, color, etc. that makes it so revered among the audio community. Microphones, preamps, compressors, etc. all incorporate some form of THD, usually at around 1% or lower. Simply put, the lower the THD, the more transparent and cleaner the piece of equipment is.
Neve 1073 preamps are revered for their colorful sound, due to the harmonic distortion caused by the input and output transformers. This enhances certain frequancies that sound pleasing and have given the 1073 legendary status.
We have advanced so far now that most interfaces will deliver a clear and clean signal path, usually with minimal coloration to the audio passing through. These are usually made up of digital chips in the circuit that are made by only 3 main companies in the world, thus the preamps of most interfaces are actually very similar if not the same across the board (plus or minus a few circuitry adjustments).
They are fine for the everyday recording artist, or home recording, but they can be limited in their sound, or offer very little in the way of flexibility or potentially at higher input gain, add more noise and dull the high end and low-end frequencies thus, adding unwanted color to your sound.
This is why dedicated preamps are in my honest opinion the better route. They provide much more flexibility and usually offer much more gain, far less noise, a much more transparent signal path, or a specifically designed color that is pleasing to the ear, and far more headroom thus allowing higher SPL before clipping.
Price is usually the next striking point with dedicated preamps, and of course, like with most things you get what you pay for, however here are some middle of the range options like the ISA ONE from Focusrite that offers a great preamp at a lower price.
The same can be said for some Warm Audio preamps, Golden Age Preamps, or Universal Audio. Definitely look into getting a dedicated outboard preamp such as by these examples especially for vocal recording - usually, they will house a dedicated DI input as well which is priceless for a good guitar or bass recording as well!
The ISA ONE is a brilliantly transparent and extremely high quality for a reasonable price for any home studio.
The variety of preamps is exponential. However, in this day and age, a group of preamps that are consistent, say for example the ones in your rackmount interface will serve well to record a large group of microphones at a high enough quality to suffer no discernable noise or unwanted coloration at low to medium gain needed to elevate the level needed to capture a good recording.
But with this in mind, a dedicated preamp will deliver much better sound quality, coupled with a specific sound in mind or superior sound quality in terms of transparency and ability to capture the raw sound of your source at a much higher level will far less noise, distortion or unwanted coloration or artifacts.
In any case, if you can, a preamp in the £300-400 at least for recording one microphone, this will elevate your guitar, bass, vocal, and acoustic recordings to a much greater place than where they are currently, and you can continue to build on your preamp arsenal, and discover your chosen poisons for the correct task as you grow your preamp knowledge and experience.