Do Digital Effects Defeat the Purpose of Tube Amps?

How well do digital effects and guitar amps with tube circuits get along? The stigma associated with digitized guitar pedals - and the processors thereof - would say they don't mesh well. In some cases, that may be true. However, the question here is, does having a digital device in your signal chain - particularly before your amplifier - downgrade the tone or the "organic-ness" of your signal? 

Answering this question is difficult because it's highly situational and depends on a long list of variables that can change from rig to rig.

I'll bypass those variables by speaking generally about a number of truths related to tube amps, digital effects and what happens when we use them both in the same signal path. We'll dig through the following ideas:

• The reliability of tube-driven tone
• The differences between analog and digital effects
• The differences between good and bad digital effects
• The optimal way to pair digital pedals and tube amplification

In this situation, the tube amp takes precedent. Our priority is to preserve its tone and to make the digital processors work around it instead of overriding it. We want to feature the analog tone of the tube amp and use the digital processors to compliment that tone. 

Tube Amplification Seldom Requires Supplement

While there can be debate between digital and analog effects (which one is better in certain situations), it should be understood that the tone of a tube amp is almost always superior to that of a solid state amplifier. Therefore a tube map needs far less in the way of modding and effects layering. In fact, many solid state amps are modded to sound like popular tube amplifiers. Take the IK Multimedia software suites for example:

Notice the Fender and Mesa Boogie amp heads. Those are digital models made to replicate the tone of popular tube amps. You'll also see this with the Line 6 amps, particularly the Spider series, and the new Fender Mustangs that allows you to dial in and save different amp models and presets. These presets have, almost exclusively, been established by actual tube amps.

In other words, tube amps are extremely reliable on their own. They rarely need supplemented or modded to sound like something else. They are the source of almost all popular guitar tones of our time and of years past. 

Understanding this is important if and when you go about layering them with any kind of effect- particularly digital.

You should also be careful to make a proper distinction between effects and amp modeling.

Amp Modeling Over Tube Amps is a No-Go

Using any kind of digital amp model - like the ones you see in amp modeling software or multi-effects pedals - over the natural tone of a tube amp is almost always a bad idea. Your goal is to compliment what's already there, not to cover it up with a cheap imitation of something else.

Consider this screengrab from the DigiTech RP500 owner's manual. All of these settings are just amp models:

This sort of thing is great if you just want to try out and tinker with a bunch of different sounds. It's bad if you already have a Fender '65 Twin Reverb. Avoid plastering these kinds of digital effects or "models" over your good, physical tube amp.

Up To The Task of Both Clean and Distortion Tones

Another thing to keep in mind is that with most tube amps you probably won't need a distortion pedal, digital or otherwise. When an amp has both a dirty (gain) and a clean channel, this allows you to dial in your distorted tones along with whatever clean sound you want to use.

This is why it's helpful to have amps with multiple channels and a channel switcher. Take the Mesa Boogie Dual Rectifier for example: 

The Mesa Dual Rectifier has three different channels that essentially do the work of three different effects pedals. Typically you would set these channels to the following responsibilities:

1. Clean signal (basic three-band EQ and presence control)
2. Light distortion
3. Heavy distortion

With a tube amplifier, the more responsibility you can delegate to the amp itself the better off you will be. That will save you some money and give you a better tone than you would get from an external pedal, especially when you're talking about distortion or overdrive.

The dirty channel of a good tube amp is almost always preferable to what you'll get out of a digital distortion pedal. 

But what about delay, chorus and other effects that you can't get directly from a tube amp? This is where digital pedals can - in some cases - be a decent pairing with a tube amp. For example, the responsibilities of your rig might be delegated something like this:

• Clean base signal: Tube Amp
• Overdriven tone: Tube Amp
• Distorted tone: Tube amp
• Modulation: Digital pedals
• Delay: Analog pedals
• Compression: Digital rack processor

That's just a hypothetical, but it illustrates how a tube-driven rig might find a happy marriage with certain digital elements. It's all about playing to the strengths of each device. To develop these best practices a little more clearly, we need to talk more about the pedals.

Let's start with the difference between analog and digital effects.

The difference between digital and analog pedals is somewhat dependent on the type of effect you're dealing with. For example, an analog delay pedal uses something called a bucket brigade circuit to create echo sounds. The process looks something like a group of people passing a bucket of water (hence the name):

In a digital delay pedal, this process is replicated by a digital processor, meaning the above circuit is nowhere to be found inside the actual stompbox. For example, the PT2399 is a digital echo processor that you might find in a digital delay pedal. Notice it looks nothing like the analog bucket brigade circuit.

Digital processing chips are often viewed as a less genuine form of effect since analog circuits were the original design and used long before the digital chips showed up. In other analog effects (phasers, chorus, distortion, etc.) the circuit designs will vary but are always a physical circuit without any digitized parts. Broadly speaking, an analog pedal will often sound better (and cost more) than its digital counterparts.

Additionally, this does not mean that all digital pedals are bad or low quality. It doesn't even mean they can't pair and work well with tube amplifiers. Remember, as long as we let the tube amp do its job and don't get in its way, a digital layer doesn't have to detract from the pureness of the tube's tone.

When determining whether or not a digital pedal is "kosher," you should fall back on the same reputable conventions that you would in any pedal-buying situation.

The following stompboxes are digital, but enjoy a fantastic reputation:

• Boss DD Delay Series
• DigiTech Whammy Series
• TC Electronics Hall of Fame Reverb

As a general rule, you could also say that the simpler the effect (digital or not) the better off you'll be. For example, the Boss DD series simply deals with delay. When you get into more complex digital and multi-effects pedals, it gets harder to know exactly how your tone will be impacted. Typically speaking, as the roles of a pedal increases, the quality of its delivery on each task will decrease.

For example, when you look at Tom Morello's pedalboard, he has clearly employed some digital pedals but also has taken a less-is-more approach to each stompbox. His amplifier, a tube-driven Marshall JCM 800, is preceded by four digital pedals (the MXR Phase 90 is analog - I believe) that each handle a single effect. 

Again, it's important to remember that I'm making generalizations and all digital stompboxes will behave differently, depending on a number of factors. At the same time, I think we can establish some concrete conventional wisdom:

1. Staying away from distortion pedals is a good idea.
2. Though digital, Boss pedals are extremely reliable.
3. Digital pedals should be used as standalone effects, in a singular role (one for delay, one for chorus, etc.). In other words- keep it all separate.
4. A pedal's reputation precedes it. The reputation of a pedal is often reliable, regardless of whether it's digital or analog.

What about True Bypass?

True bypass is a type of guitar pedal technology that comes into play when a pedal is disengaged. A non-true bypass guitar pedal - even when disengaged - will alter your clean tone to varying extents. A true bypass circuit is designed to prevent this, acting like as a single, uninterrupted cable run when the pedal is turned off.

Here's a diagram of the technology:

The problem is that true bypass is usually only included with analog pedals. Digital pedals with true bypass are far more rare. 

Analog and true bypass circuits are often paired together in what we'd call boutique effects pedals. While these features can also be found in mainline products, they're hallmarks of the boutique pedal maker community, where you rarely find one without the other.

Most guitar players look for these two features in all their effects. 

Yes, Analog Pedals are Better Options

Which brings me to my final point:

Analog pedals are usually better options. They're typically better-made, better-sounding and are likely housed in a true bypass circuit. At the same time, it's important to balance this reality with the following:

1. There are plenty of great digital pedals that work well in front of a tube amp
2. Single-job stompboxes are preferable, whether you're talking digital or analog
3. Light effects layering is a better job for digital pedals than heavy modding or saturation of your signal
4. Avoiding amp modelers, multi-effects pedals and distortion pedals will generally mean you don't have to worry about losing tube tone.

Less is More: Cliche, But Very True with Tube Amps

Tube amps do a lot of heavy lifting on your behalf. And though cliche, it's quite true that less is more when it comes to analog guitar amplification. You don't need to add much to it. If you do, you can follow some simple best practices to make sure your amp’s tone is being showcased.

Your amplifier is arguably the most valuable tool you have when it comes to crafting tone (especially if you have a tube amp). Whether you're adding digital or analog effects, make sure those effects are taking a back seat to what the amp itself is producing.

Your Questions and Ideas

Do you have experience running digital pedals through a tube amp? How do you divide analog and digital responsibilities in your rig?

Share your story and your questions in the comments section below.

I prefer that to email, because it's much easier to answer our comments section, and it adds more content to the piece for those who might read in the future and benefit from the dialogue there.

Flickr Commons image courtesy of Bill Selak