Updated by Bobby
Updated on April 25th, 2022
Checked product availability and replaced preamps that are no longer available. Added the Rocktron ValveSonic Plexi and the Positive Grid BIAS Rack.
QUICK HIT: A rackmount guitar preamp curation and guide that includes our favorite rack-style preamps (some of which double as effects processors) for modern guitarists.
Before we get into rackmount guitar preamps, it's important to discuss what a guitar preamp actually is. Most people understand a guitar amplifier as one piece of equipment. In reality, a guitar amp - which often comes in the form of a combo amp - is three different parts:
- Power amp
- Speaker cab
Therefore, a preamp (rackmount or otherwise) is only one of those three pieces and is not the same as say, an amp head, that combines a preamp and power amp into one unit. A preamp needs a power amp and some kind of speaker to run, otherwise it won't be much more than a super-heavy paperweight.
In this article, we've rounded up what we believe are the best rackmount guitar preamps for modern electric guitarists. For whatever reason, there are a lot more bass and acoustic guitar preamps available in rack (and pedal) form, which meant that the electric guitar varieties were a bit hard to track down. Some of the products we were able to find have been discontinued (like the Marshall JMP-1) but are still popular on sites like Reverb and eBay.
We've jumped back and forth between recommending products on Reverb and Amazon, and will make mention of which products are discontinued.
More about our process for selection and inclusion is explained at the end of this article.
For now, let's jump into the preamps, starting with our two favorites.
Best Rackmount Guitar Preamps and Processors (top 3 picks)
Rocktron ValveSonic Plexi Tube Guitar Preamp
Positive Grid BIAS Rack Amp Match Rackmount Preamplifier
Avid Eleven Rack
1. Rocktron ValveSonic Plexi Tube Guitar Preamp
The ValveSonic could be thought of as Rocktron's take on a Marshall Plexi pedal, yet with a full compliment of preamp controls, and multiple gain stages. It produces a vintage distortion and tone with some brightness and a lot of power, reminiscient of the JCM800's of past decades.
We like it for anyone who is a fan of classic rock, and wants a British-voiced amp with some added control.
You get two channels, as well as a bright, gain and drive control. You could either put it in front of a power amp, or go directly in a recording interface/mixer.
IDEAL FOR: Fans of classic rock and/or Marshall amplifiers
2. Positive Grid BIAS Rack Amp Match Rackmount Preamplifier
If you've used Positive Grid's software or mobile apps, the Bias Rack is essentially a hardware version of those applications.
As you might expect, it integrates with the applications allowing you to download amp models and sounds to go alone with the onboard controls which are quite extensive in their own right.
It's a lot of digitized tone - which you might need to get used to if you're coming from a tube background. However, we like the flexibility of the Bias Rack and would certainly recommend it for those who already like the Positive Grid products.
IDEAL FOR: Modern tones, onboard distortion, and versatility
3. Avid Eleven Rack Preamp and Processor
The Eleven Rack is manufactured by Avid, who also built the Pro Tools software and will, in some cases, package the two products together. In its own right, the Eleven Rack is one of the more advanced guitar preamps and processors available on the market, providing a massive amount of sounds and functionality that make the DigiTech GSP blush.
It's a useful unit for both studio and live setups, with plenty of control via the large LED front panel or MIDI i/o on the back of the device.
Here's a closer look at both the front and back of the device:
You can model the amp type, cabinet type and even the microphone and its positioning, all of which sounds incredibly authentic, if you don't mind the stigma of digital amp modeling and effects. Because there's no denying, this is an entirely digital experience. It's a good experience, but digital nonetheless.
Here are just a few of the amp models you'd have access to:
Folks who want a higher-quality, better-value version of the DigiTech GSP will be really happy with the Eleven Rack and will have plenty of different tones to experiment with.
If you're a Pro Tools fan the stock should go up even more.
Line out, main outs and an output to amplifier all give you plenty of different ways to integrate the unit into a live or studio rig, making it capable of handling all ranges of complexity. What it all comes down to is how you feel about the centralization of digital power. It's not for everybody.
IDEAL FOR: Heavy distortion and recording
Assessing Cost and Value in a Rackmount Guitar Preamp
It's difficult to determine value when buying one of these preamps because the use and integration of such a unit is always going to be contextual. This is why we don't recommend something like the Rocktron Widowmaker (no longer in production) to everyone. Because, quite simply, it's not going to be a high-value purchase for folks who want to sink money into something other than modern distortion.
This is a big part of how we determine value for any piece of guitar gear, but especially for something like a preamp.
We look at where the manufacturer invested the most resources and who they're marketing the product to. If the preamp is tailor made for a certain type of player or situation, we make sure to recommend it in that context.
Here are a few examples that would apply to rackmount guitar preamps:
- Emphasis on tube-driven tone or digital circuits
- Strength with distortion, clean tones or both
- Universally helpful features like multiple channels, effects loops and MIDI i/o
We've weighed these aspects for each product in this list and used them as measuring sticks to figure out what type of guitarist we'd recommend these pieces of gear to and in what situation(s) they would they be the most helpful.
When we can find a suitable preamp that keeps cost low, and/or checks off a lot of our boxes for a particular type of player, we can suggest that product as a high-value option in that context.
FAQ about Rackmount Guitar Preamps
Q: Can I run a preamp directly into a set of speakers?
A: The short answer is no. If you have powered speakers, you might be able to configure something workable. But, generally speaking, this is never something we recommend since a preamp simply won't be able to deliver enough volume.
Q: What is the difference between a preamp and a power amp?
A: Power amps handle volume and the actual amplification (increasing strength) of the signal, while preamps are responsible for EQ and tone-related adjustments.
Q: What kind of power amp should I couple with a rackmount guitar preamp?
A: In most cases we've used and seen preamps paired with power amps from the same manufacturer, particularly with Marshall and Mesa guitar preamps. However, it's possible to mix and match depending on the manufacturer of each unit. Your best option is to decide on a preamp, then contact the manufacturer for help with specs for a suitable power amp pairing.
Q: Is it better to just go with an amp head (preamp/power amp combo)?
A: It's largely preference, though having the two separate will often mean a better quality preamp and power amp with more versatile control between the two.
Q: Can I run a preamp into a combo amp or amp head and bypass its preamp?
A: If that combo amp or amp head has a send/return loop, you can send a line level signal from your preamp into the return input on your amp head or combo amp and then use it only as a power amp, meaning you'd control master volume and presence from the amp head or combo and everything else from the external preamp.
Comments and Questions
Have questions about the rackmount guitar preamps listed here?
Maybe you have a question about a different preamp or think there's one we should add to the list?
Drop us a note in the comments section and we'll check it out. You sharing what you know is a great way to help us keep these lists updated, so feel free to sound off if you've got info on a great rackmount preamp that we aren't privy to.