Treble Boosters

The treble booster effect pedal has been a key component in Brian May’s signal chain since the beginnings of Queen. His interest was inspired by the well-defined sonorous clean tones of Hank Marvin and the sustain and overdrive characteristic of Rory Gallagher. A treble booster performs these two related functions by adding gain to the input signal and by selectively boosting upper mid-range frequencies. This is particularly necessary when using Tri-Sonic pickups which have an indistinct and somewhat flat response without a treble booster but come alive to exhibit a pleasingly shrill and flute-like tone when boosted. In the YouTube video below, published in April 2023, I explain how treble booster effects pedals work, I show you eight variants associated with Brian May then assemble a KAT Treble Booster Plush kit. The video duration is 16m 41s and is divided into two parts and thirty chapters.

The pictures above shows a selection of the myriad of commercially available treble boosters. There are some very good replicas of the revered Dallas Rangemaster made famous by Eric Clapton, Richie Blackmore and others and they all have subtly different output characteristics. The simplicity of the circuit lends itself well to production by the hobbyist effect pedal builder and both Greg Fryer and Nigel Knight have produced circuit diagrams to assist DIY experimenters (see links in the Further Reading section below).

KAT Project Simple TB Circuit Schematic (PDF, 45 kB)Download

I prefer to buy professionally-made versions because, aside from their expertise in guitar effects, Nigel Knight and Greg Fryer buy in bulk quantities of each component, test them and only use those which fall into tight tolerances to precisely control the output curve and reduce noise in use. All the treble boosters in the picture above except the VPW Rangemaster are hand built. Subsequent discussion is limited to three examples: the KAT RED-18 strap mounted treble booster, the BMG Treble Booster Classic designed by KAT for retail by Brian May Guitars and the Fryer Plus, Touring and Deluxe series.

BMG Treble Booster Classic (2019)

The BMG Treble Booster Classic offers Brian May tones from the three eras of Queen: the germanium transistor Dallas Rangemaster used in the 1970s, the orange label, silicon BC149 transistor Pete Cornish booster installed on his pedal board throughout the 80s and an original 1998 Greg Fryer strap booster. To design the device, Nigel Knight measured reference responses of these units for gain, noise floor, peak frequency boost, peak frequency width and slopes. He then exhaustively A/B benchmark tested the prototype and made minor component changes or additions to hone the responses to get them as close to the originals as possible, while retaining the core circuit design throughout.

https://shop.brianmayguitars.co.uk/bmg-accessories/bmg-tb-classic.html
https://deacyamp.com/collections/products/products/bmg-treble-booster-classic

BMG Treble Booster Response Curves (PDF, 175 kB)Download

Considering that it offers three boosters in one unit and given the meticulous research and development effort underpinning its production, it represents good value at £249. Check out Frank Campese playing a seldom heard Queen track on demonstration videos using a BMG Special and a Vox VBM-1 amplifier with his BMG treble booster classic:

KAT RED-18 Strap-Mount Treble Booster (2018)

The KAT RED-18 strap-mount treble booster was developed by Nigel Knight for Brian May prior to Queen + Adam Lambert’s 2018 Las Vegas residency to exploit a wider tone range from the overall system after he installed a KAT Superpot into Brian’s Red Special guitar and because Brian was using a different frequency band for his radio system.

https://deacyamp.com/collections/products/products/brian-mays-kat-red-18-strap-mount-treble-booster

The units are designed to offer a little more drive than Brian’s original strap mounted boosters to exploit the extended control range offered by the KAT Superpot. It can be adjusted to provide up to 32.5 dB of gain, although they are factory set to 31.5 dB. The KAT RED-18 units feature a fixed integral output lead fitted with a connector for the market leading UHF wireless radio systems. The output lead includes a 180 degree curved strain relief sleeve at the end to support the connector at its most vulnerable point, where it loops into the transmitter pack. The input lead guitar jack assembly is pre-formed into a curve that hugs the shape of the guitar. The curved assembly also houses the ferrite core that forms part of the RF rejection system.

In the video below, I demonstrate and discuss how Nigel Knight evolved Brian’s earlier KAT STB into the RED-18 strap-mounted treble booster to complement the additional control afforded by the modified volume potentiometer he designed and fitted, the KAT Superpot.

Brian May’s KAT RED-18 Strap-Mount Treble Booster & KAT Superpot

Fryer Treble Booster Touring, Deluxe and Plus (2008)

A popular set of treble boosters used by guitar players seeking to emulate Brian May tones are the Fryer TB Plus, TB Touring and TB Deluxe with their distinctive blue, red and purple powder coated cases. The TB Plus unit has been discontinued and replaced with the TB Super. This interview with Greg Fryer by Simon Bradley for Guitarist Magazine issue 309 in October 2008 covers the background of these effects pedals which were developed for the requirements of the WWRY stage shows:

https://www.musicradar.com/guitarist/greg-fryer-full-interview-244313

Fryer Treble Booster Touring (red) with 31 dB gain, offers a balanced sound with sweet harmonic detail and smooth treble definition, good definition and detail with sweet trebles, sparkling rhythm sounds when the guitar volume control is reduced.
http://fryerguitars.bigcartel.com/product/treble-booster-touring
Fryer Treble Booster Super (mid blue) with 34 dB gain offers good definition and detail with punchy rich mid range, fuller sounding and louder than the TB Touring pedal, but not as full sounding as the TB Deluxe. This unit evokes Brian May’s sound of the mid 1970s heard on A Night At The Opera, A Day at The Races and his live sound of the 1980s.
http://fryerguitars.bigcartel.com/product/treble-booster-super
Fryer Treble Booster Deluxe (purple) with 35 dB gain offers a punchy, rich sound with a balance between fullness and treble definition, evoking Brian May’s sound on late 1970s Queen albums News of the World and Jazz.
http://fryerguitars.bigcartel.com/product/treble-booster-deluxe
Fryer Treble Booster Plus (light blue) with 36 dB gain has been discontinued.
All the ‘no knobs, permanently plugged-in’ Fryer treble boosters can be powered by either a 9 V battery or 9 V DC adapter (2.1 mm diameter negative centre jack, 100 mA or greater current capacity).

Insider Insight (Greg Fryer)
If using a power attenuator (e.g. Marshall Powerbrake or Weber Mass) with a Vox AC30 amplifier, tonal losses can be compensated for to some degree by driving the amplifier with a higher gain treble booster than would be needed if operating them at full volume as Brian does on stage.

The definitive, professional review of this popular series of treble boosters was made by Jamie Humphries for Guitar Interactive magazine issue 40 (April 2016) using a BMG Super Red Special replica (23 minutes):

Expert Opinion (Nigel Knight, KAT)

Nigel Knight offers some insights into treble booster use with a Red Special guitar (adapted from text on the Brian May Guitars product page):

A treble booster should always be the first effect after the guitar in the signal chain. Even if a guitarist is using a UHF wireless radio system, the TB must be placed between the guitar and the transmitter pack. Most guitar amplifiers and effects are designed to offer a relatively high impedance load (at least 500 kΩ for effects pedals and 1 MΩ or more for amplifiers) but a treble booster is much lower at less than 100 kΩ.

When used to play Queen songs, a Red Special guitar will generally be used with two single coil Burns Tri-Sonic pickups in series (whether in phase or out of phase); this is in contrast to most guitars with single coil pickups such as the ubiquitous Fender Stratocaster which configure two pickups in parallel. This has the benefit of increasing the output level of the guitar, which helps drive Vox AC30 amplifiers into saturation. The downside is that it also increases the overall impedance of the guitar (to around 14-15 kΩ with two Tri-Sonics in series) which renders it more susceptible to ‘tone sucking’ if plugged into a low impedance load.

The guitar’s volume potentiometer provides the pick-ups with a constant high impedance load, whilst driving the treble booster with a variable impedance load. So, when the guitar volume control is turned down, the pickups see a high impedance load, but the TB experiences a low impedance input and thus doesn’t suck high frequencies and glassy clean tones result. When the guitar is played at full volume, the treble booster reduces high frequencies to yield pleasing distorted tones.