The original Vox AC15 was designed by Dick Denney in the mid-1950s (in early 1956 by most accounts). It was voiced to hone in on the natural midrange frequencies present in the tone of an electric guitar. As bands were getting louder and moving into larger concert halls the AC30 was created by doubling the dual-EL84 output of the AC15 to a quartet of EL84s. Biased correctly, an AC15 puts out just over 15 watts while an AC30 puts out just over 30 watts.
Shortly after the creation of the AC30, guitarists began asking Dick Denney and Tom Jennings (the owner of Vox) for an amp with a brighter tone. As a result, Vox created the Top Boost circuit. It was first available as a factory add-on and later as a standard feature. For guitarists used to the tone stacks on Fender and Marshall amps, the Top Boost circuit can be very strange. The bass and treble controls are extremely interactive and their respective locations determine how much midrange is present in the tone. Cranking both the Bass and Treble creates a scooped midrange while dialing them back offers a flatter tonal response. Additionally, the added treble in the Top Boost circuit can make it very finicky with overdrive pedals—leading to harsh papery or buzzy tones.
The sound of an AC15 or an AC30 pushed into distortion is a beautiful thing; think of the soaring lead tones of Brian May or the chimey grit of Peter Buck or the Edge. While 15 or even 30 watts might not sound like a whole lot of power, pair them with an efficient Celestion AlNiCo Blue speaker (or a pair of them in the AC30) and these amps can be surprisingly loud.
Given the option, I'd use a dimed Vox AC30 or AC15 Top Boost for 90 percent of my distortion needs. But alas, my band plays in your average corner bar, not arenas. So, what is the Vox player to do if they want to get that amazing, chimey distortion without annoying their respective spouse, band mates and neighbors?
Having had the luxury to try tons of overdrives through various Vox amps, I've compiled the following list of five ODs you have to try. Each of these overdrive pedals will pair beautifully with your Vox Top Boost amp—no matter how loud (or quietly) you play.
Crowther Hotcake
Just as the go-to overdrive for a blackface Fender is an Ibanez Tubescreamer, the Crowther Hotcake and the Top Boost circuit were made for each other. With plenty of output and neutral EQ, players can dial in some grit or just use it at the front end of the amp with extra volume. Lots of players talk about “transparent” overdrive pedals; the Hotcake does a trick that few other overdrives can. Try this: Set the Level on the Hotcake to around 2 o’clock and the Drive and Presence to minimum. Now click the Hotcake on and off. You likely won’t be able to hear a difference in your tone with the pedal off or on. Of course, we buy pedals so that they make a difference in our tone. Now slowly roll up the Drive control and feel how the dirt from the Hotcake becomes one with your Vox.
The Presence control on the Hotcake is perfect for dialing in (or out) high end. I tend to prefer it fully counter-clockwise for single coil and Filtertron pickups and up around 11 o’clock for humbuckers. I also tend to increase the Presence as I push the Drive knob higher.
The Hotcake also happens to come with one of the nicest buffers in the pedal world. It’s one of those things that isn’t noticeable when it’s there, but is will when it’s not. However, with the buffer in there, you will need to run the Hotcake after any vintage-style fuzzes or other pedals that are sensitive to buffers or require a direct interaction with your guitar.
The only caveat is that one needs to have the volume knob on the amp to at least 10 o'clock for the Hotcake to shine—that and the distortion can get a little bass-heavy and unfocused as the Drive is raised above 1 or 2 o’clock. It’s not the pedal for getting the Vox tones at bedroom levels, but the magic of the Hotcake lies in how it becomes one with the guitar and amp. It works almost like a Fuzz Face in how well it cleans up as the volume rolls back. It’s the ultimate gigging pedal for the Top Boost circuit.
Paul Cochrane Timmy
Yes, both of the first two pedals come from men named Paul. The Timmy is the streamlined little brother of the Tim pedal (named after the Enchanter of the same name in Monty Python’s Holy Grail). People call the Timmy transparent, and if used as a clean boost, it certainly can be. But once you start to turn up the grit, the Timmy stops being transparent and starts being awesome. It brings a Marshall-esque grind to the party and can summon fire like its Holy Grail namesake. Part of what makes the Timmy such a great match for the Top Boost circuit are the tone controls which cut bass and treble as you turn them up. So if your amp starts to sound fizzy as you crank the Timmy, you can dial out the fizz by turning up the Treble control. Likewise, turning up the Bass control will help to tighten the bottom end and keep things from getting boomy. The Bass control is also pre-distortion so turning it up will clean the pedal up a little as well.
The Timmy also has a three-way clipping switch. The down and middle positions offer two flavors of symmetrical clipping while the up position is asymmetrical. I prefer the up position for playing the Timmy through a Top Boost-equipped Vox. To get started, set all of the controls at noon. Click on the Timmy and feel your Vox get a little more throaty and authoritative. If you have really hot pickups, you might want to roll back the Gain. If you have low-output pickups you might want to crank it a little more. If you have too much high end, you can push up the Treble control counter-clockwise to bring things under control. No matter where you set the controls, the Timmy is perfect for bringing a little extra riff-friendly grit to the Top Boost circuit.
Bearfoot Emerald Green Distortion Machine
I know what you are thinking, “Isn’t the Emerald Green Distortion Machine meant to emulate the sound of a Vox? Why do I need it when I already have the Vox?” The short answer is that this is the one for the bedroom players, the guys trying to get the cranked Vox tone at levels that won’t wake the baby or annoy the folks in the next apartment over.
That’s not to say that the EGDM doesn’t sound great loud, it’s just that it kills at getting the sound of your dimed Vox at conversation (if not whisper) quiet levels. The Voice and Drive controls on the Emerald Green Distortion Machine are extremely interactive and the various permutations of them can run from early “British Invasion” tones up through Brian May lead tones and even beyond. The folks at Bearfoot suggest starting with all of the controls turned fully clockwise. I agree with this aside from leaving the Volume control at noon. The EGDM has a ton of output on tap and cranking the Volume control usually leads to a big jump between your clean tone and distorted tone. Now try various combinations of the Voice and Drive control and see how they impact each other. Once you nail the tone you are after, you can use the Treble control to brighten or darken the sound to taste. Thanks to this well-voiced tone control, the EGDM allows you to dial out the fizz without losing the chime. I’ve found that you need to cut the tone back inversely as you crank the drive.
For band level playing, I tend to keep the Drive well below noon and use the Voice control to match various guitars to my amp. At home, I keep the output volume low and then use the Voice and Drive controls to dial in everything from Beatles to Edge to Rhapsody. No matter where or how you use the EGDM, it’s always extremely dynamic.
Mad Professor Sweet Honey Overdrive
The Sweet Honey Overdrive is the odd duck in this list in that it doesn’t have a tone control. If you’ve been paying attention, you will have noticed that the prior three pedals work so well with the Top Boost circuit in part because they have tone controls that are able to reign in the bright Top Boost circuit. While the Sweet Honey Overdrive lacks a treble control, the unique Focus control allows you to voice the drive and the EQ curve to match the tone of your guitar and amp. With the Focus control to the left, you have to dig in harder for distortion and the tone is slightly darker. Moving the Focus control to the right, you get faster breakup and an increase in treble response. In my experience, the best setting for pairing with the Top Boost circuit is Volume at 9 o’clock, Focus at 7 o’clock, and Drive at or below 12 o’clock. Not unlike the Timmy, the Sweet Honey Overdrive creates a tone that is a little throatier than what you might expect from a Top Boost with a compression that is almost tweed-like. I’ve also found that as you move the Drive beyond noon it still sounds great but it loses the Vox-iness. Because of the thicker mids and throatier voice, I love using the Sweet Honey Overdrive when running a Strat or Tele into a Vox.
ProCo RAT
Last, but not least in the list is the ProCo RAT. It’s no secret that tons of pros have paired a RAT and an AC30 to very good effect. The RAT is the original high-gain distortion pedal and it uses a pair of LEDs to hard clip the guitar signal. Typically, LED clipping creates an almost buzzy type distortion that should be all wrong for pairing with the Top Boost circuit and its abundance of treble. But like the other pedals in this list, it once again comes down to a tone control that can cut the extreme highs without getting muddy. In my experience, the RAT gets rattier (buzzier) as you crank the Distortion, so I tend to keep it at or below 10 o’clock. With the Filter control also at 10 o’clock and the Volume at 12 o’clock you get a thick almost fuzzy tone that is perfect for lead playing. And the RAT is perfect for coaxing your Top Boost Vox into feedback. The RAT doesn’t clean up as well as the other pedals in this list and it also has a tendency to be noisy, but there’s just something about the way it pairs with the Top Boost circuit.