What’s the secret behind amazing guitar tone? Great fretboard skills, the best guitar and amp your budget allows, a cathode follower… Wait a second! A cathode follower? What’s that? And how does it make me sound better? Good questions, all of them. Now read on to find out more about this understated little piece of technology that’s hidden in many of the best guitar amps ever made, and to learn how its presence can make the difference between good tone and great tone…
“The biggest change from the previous models is not something you can see… but you sure can hear it!” said Rüdiger Forse, Hughes & Kettner’s Senior Product Manager, in an interview about the TubeMeister Deluxe 20 and 40 models at the 2016 NAMM show in Anaheim, California.
With this cryptic statement, he was alluding to these new amps’ fundamental sound. And he was right; these new models don’t just rehash an old formula.
There’s something fundamentally different about their tone.
One could say it’s more direct yet airier, warmer yet more assertive, beefier yet with bell-like chime. But whatever descriptive adjectives you want to use, TubeMeister Deluxe definitely serves up a refreshingly different flavor of sound.
And one of the main reasons why it ladles out such tasty tone is a much-loved and often talked about amplifier circuit called a cathode follower.
A cathode follower?
Although it’s a classic tube-driven circuit, a cathode follower never featured in the smaller TubeMeister 18 amp – but the TubeMeister Deluxe 20 changes all that.
This was evidently newsworthy: the NAMM show had been underway for just a few short hours, but word had already gotten out about this venerable circuit’s inclusion in a very modern amp.
Ask vintage amp enthusiasts about the cathode follower at your own peril. Many will get a little gleam of love in their eyes, and start gushing about how it’s the pack mule among tube circuits, with a mean kick that’s perfect for driving tone stacks.
Ask them to elaborate, and you’ll hear more than you ever wanted to know about less-than-unity gain, output impedance generally reciprocating transconductance, degenerative feedback, and a power supply rejection ratio somewhere around the inverse of the mu.
That’s interesting and all, but… er, what the hell does all that technical stuff actually mean?
What is this legendary cathode follower, and – most importantly – how does it make our guitar tone better?
The technical details
To put it (almost) simply, a cathode follower is an impedance conversion stage within an amplifier circuit that transforms a high-impedance signal into a low-impedance signal.
The latter is less susceptible to interference and can have a beneficial effect on tone. The explanation for this has to do with sine waves, synched oscillations and overtones, but we’ll spare you the details.
It takes a fairly firm grasp of electrical engineering to understand the intricacies of the theory behind the cathode follower.
For our purposes here today, suffice it to say that not every preamp circuit under the sun stands to benefit from an added cathode follower.
It’s a wise choice for some guitar amps, and a no-go for others. So how do we know when it’s a viable option? There’s only one standard to go by: tone is the measure of all things.
Do all amps have cathode followers?
There are plenty of examples of great amplifiers that do not feature a cathode follower.
Other amps have it both ways, with one channel that works with a cathode follower and another that does without. The Hughes & Kettner Coreblade, for instance, uses a cathode follower circuit to conjure clean tone, but the circuit’s role in shaping distorted sounds is limited.
Cathode follower = classic tones
Cathode follower circuits are said to lend the tone a special flavor, as a number of classic guitar amps would go to show.
A lot of this is down to the harmonics, generated by the cathode follower stage, that enrich the output signal. Early Fender Bassmans, the Marshall JTM and several Vox amps were all equipped with a variation on the cathode follower theme.
Although each amp maker used a somewhat different design or placement within the circuit, its presence certainly shaped the tone of these amps – and by extension, our perceptions of what rock ‘n’ roll guitar sounds like.
A Deluxe brown sound
In the TubeMeister Deluxe 20 and 40, the cathode follower stage is largely responsible for shaping the brown sound, as this most popular flavor of tone has come to be known.
TubeMeister Deluxe’s take on this tone is based on the tone of the TriAmp Mark 3‘s channel 2B, which in turn was inspired by the sound of a hot-rodded Marshall.
The texture of this tone is very intensive, lending an edge to the TubeMeister Deluxe 20 and 40 that makes them sound a lot louder than their 18/36-watt forebears, the TubeMeister 18 and TubeMeister 36.
They certainly pack a bigger punch than the added two and four watts, respectively, would account for.
A clear tonal upgrade
In any event, we’re talking about much more than just an upgrade here.
There’s something special going on inside these housings, and you can hear it as soon as you power up, plug in, and wail away.
They’re deliciously responsive to your picking attack and give you loads of dynamic range. And this response is very musical, with just enough natural compression to sound and feel good. Again, these amps come across as bigger, beefier and bolder.
Add a little zest to your guitar tone
In TubeMeister Deluxe, this boost can’t just be down to the nominal increase of two or four watts of power – so it has to be this circuit that’s adding the extra assertiveness.
The zesty flavor of tone the cathode follower delivers results in an amp that’s a pretty awesome combination of old and new – a time-tested guitar amplifier circuit, the cathode follower, paired with a tube-driven power amp, a power soak and the game-changing Red Box AE.
And that makes up a very solid FRFR package indeed (read all about the benfits of FRFR – that’s full range flat response – here). Take a bow, designers!
Classic tube tone, cooked up with the finest ingredients and the tastiest traditional recipes, all ready to go right out of the box: 21st century amps like these truly are a crossroads where tradition and modern-day innovation converge; where the cathode follower and FRFR coexist in the happiest of unions.
Are you bothered about whether your amp has a cathode follower? Does the technology behind guitar tone matter to you? We’d love to know, so let us know in the comments below… Because there’s plenty more tech talk like this to come from us if you want it!
Edit: 17 March 2016
We got such cool and interesting feedback on this blog that we decided we’d take the time to explain the evolution from the TubeMeister 18 – which doesn’t feature a cathode follower – to the TubeMeister Deluxe 20 – which does! Just click on this beautiful picture below to read our little TubeMeister 18 to TubeMeister Deluxe 20 case study:
First published: March 04 2016. Most recent update: March 17 2016.