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April 2024
Vol. 23, No. 7

Ask Charlie...

A Little More About Amps…

by Charlie LoachSeptember 2014

Hello Troubadourians! Back in July I shared a brief treatise on tube amplifiers. I also mentioned that I would talk about non-tube amps in a later column. Well, here we go… There are actually several sub-classes of non-tube amplifiers that include solid-state amps, digital modeling amps, and hybrid amps, amps that are essentially solid-state or digital modeling amps that contain an actual vacuum tube in the preamp stage to make them sound overall more tube-like. Let’s look at each of these amp types in their most generic forms to give you an idea of how they differ from each other and from tube amps.

Solid-state is just a fancy marketing term for transistor-based amplification. While tube amps have been used for amplifying guitars since the 1940s, the first transistor-based solid-state guitar amp, manufactured by Kay Musical Instruments, wasn’t commercially available until 1962. Because transistors perform pretty much the same function as vacuum tubes in that they amplify a small signal into a larger signal, many early solid-state amplifiers were based on similar circuit schematics as the tube amps of that era. Just substitute the equivalent functioning transistor for a vacuum tube and, viola! You have a solid-state amp. Right? Not quite… It’s really not as simple as that because while they were designed to be electronically similar in basic functionality, tubes and transistors sound very different when exchanged for each other in the same amplifier circuit. The tonality of early solid-state amps was described as being cold, sterile, dry, and metallic when compared to the tonality of the tube amps that guitarists were used to hearing. Additionally, as you turn a tube amp up, as it approaches the point of saturating the tubes, it begins to distort in a very musically pleasing way. By comparison, as the early transistor amps were turned up to the saturation point, they usually sounded quite brittle and nasty, sometimes exhibiting overtones that weren’t even remotely musical. Okay, while some of you are probably thinking, “Cool! How very punk!” “I’ll bet that is just what I’m looking for,” trust me when I say that I’ve heard some old transistor amps turned up loud and they’re neither punk nor pretty to listen to. As Huey Lewis once said, “Sometimes bad is bad.”

Fortunately, modern solid-state amps have come a long way now that amp designers have realized that to achieve a tube-like tone from a transistor-based amp you have to approach the design much differently than assuming that a transistor behaves the same as a tube in the same circuit. And the tone of most of today’s quality designed and built solid-state amps rival the richness and warmth of the best tube-based amps. Some could even be considered to be better than their tube-powered cousins in that they are usually much lighter weight and, because of their different electronics, are far less susceptible to the power issues that can plague tube amps.

Hybrid amps are essentially an attempt to make solid-state amps sound more tube-like by using an actual vacuum tube in the preamp stage of the circuit. The majority of the tone generation and shaping in an amplifier takes place in the preamp stage of the circuit. The power amp stage then does the heavy lifting of sending the sound to the speakers. The signal levels in most tube preamps are very similar, even in high-gain amps like Mesa/Boogies and Soldanos. The difference in loudness comes from the power amp stage. As I said in July, the “sweet-spot” for the power amp will be a higher level — louder — for a higher powered amp than for a lower powered amp. The thing is, a tube-based power section will contribute its own character to the final tone whether or not you are able to turn it up to its “sweet-spot.” The concept for most hybrid amps is to simply use the tube preamp to create that ‘tube tone’ and then utilize a generic solid-state power stage to amplify that tone and hope we don’t notice. We noticed. Not that this is a bad amplifier architecture, but they usually don’t sound as ‘tube-like’ as you might think, or as you’d want them to.

Digital modeling amps are just what they seem; digitally modeled guitar sounds that offer the player a multitude of amplifier sounds that can be controlled, altered, programmed, stored, and recalled almost at will. In theory, the tones available in a digital modeling amp are only limited by the software in its DSP’s (Digital Signal Processor) or by the imagination of the player who is configuring the tones and program algorithms. Early modeling amps fell somewhat short of this ideal concept though, and most sounded more like a recording of a good guitar amp than an actual guitar amp. This isn’t surprising as the genesis of modeling amps was as a software plug-in for digital recording systems. Using them in a live context often yielded similar results as the hybrid amps described above; a good sound but sort of fake sounding compared to a real tube amp. Fortunately, this technology has vastly improved the realism of the tonality and tube-like feel and experience in both studio and live performance contexts. The first to market these amps was Line 6 and they are still the industry leaders as far as the variety of their offerings but companies such as Decibel Eleven and Kemper are challenging their lead.

Solid-State amps have now evolved and improved to the point where many die-hard tube amp fanatics are finding that it is often easier, cheaper, and more reliable to perform and record with some variation of the amps described above than it is with their favorite tube amp. I have to say that even I, a proud player of an awesome sounding — and very heavy — Mesa/Boogie Mark IV, have been tempted to crossover to the dark side of solid-state amps by a very fine sounding Quilter Steelaire amp. There are also environmental concerns with the manufacture of vacuum tubes and with the only viable market for them being musicians and hi-end audiophiles, the price of quality vacuum tubes will only go up and their availability will only go down as time progresses. If you have a good tube amp, hold onto it, maintain it, and it will continue to serve you well. But you may consider investing in a high quality solid-state amp just in case…

Need to know? Just ask… Charlie (

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