The active boost circuit favored by Eric Clapton and how to install it
In our previous two installments, we
explored the Fender TBX tone control and
ways to modify it. This month, let's take a
closer look at the Fender active mid-boost,
aka the “Eric Clapton mid-boost" circuit.
Originally called the “MDX mid-boost circuit,"
this device is a 12 dB active boost
circuit that first showed up in the 1983
Fender Elite Stratocaster. The MDX circuit
was developed by James Demeter and
John Carruthers to make single-coil pickups
sound like humbuckers—a typical '80s
thing. The Elite Strat concept only survived
for two years before it was discontinued
because of massive problems with Fender's
Freeflyte Tremolo System.
For me, the Elite Strat is the archetypal
'80s Strat, and I always smile when I get
one on the workbench. The Fender Elite
Strat served as a template for the Eric
Clapton Stratocaster, a model that made
its debut in 1988. Clapton liked the MDX
boost circuit (which he called a “compressor")
and told Fender to keep it for his
signature Strat. He also asked for more
“compression," which prompted Fender
to replace the Elite Strat's standard pickups
with Lace Sensor Gold pickups and
an updated MDX circuit that had been
tweaked to deliver a midrange boost of up
to 25 dB at around 500 Hz.
The EC Strat's features have changed several
times over the years, but the updated MDX
mid-boost remains unchanged, and you can
buy it for about $80 through a Fender dealer
to install in your own Strat. Fender officially
changed the name to “Stratocaster Mid
Boost Kit" (part #005757000). The set comes
with a prewired mid-boost PCB, a TBX tone
control, two pots, a stereo output jack, and
all the small parts you need to connect it to
Here's how Fender describes it:
The Stratocaster Mid Boost Kit
includes all the parts needed to
upgrade your guitar with the Mid
Boost Preamp used on the Eric
Clapton and Buddy Guy Strats.
The system replaces one of the
original tone controls with a variable
“Midrange Boost" control. The
Mid Boost knob adjusts gain from
0 dB (no boost) to 25 dB (for killer
mids). Great for clean and distortion
tones. The TBX tone control is
neutral in the middle position, cuts
treble in one direction and cuts
bass in the other direction.
If you want to install a mid-boost system
in your guitar, keep in mind that not only
do you have to install the PCB somewhere,
you also need space for a 9-volt battery to
power the preamp. There are many ways to
place these two components inside a Strat,
and naturally the ideal location depends on
a particular instrument and its routings.
The easiest way is to place the PCB on the
bottom of the Strat's electronics compartment
(below the pots) and the battery in the
trem-spring cavity. While this is the quick-and-dirty way, a more elegant solution is
to route an additional compartment for the
PCB below the neck and middle pickups.
This area is completely covered by the pickguard,
so you won't see it. There are many
variations out there, though, so do a Google
search to find the one you like best.
The DIY Approach
A lot of players want to install an active
boost device in their guitars but complain
about the high price of the Fender kit. If
you're willing to roll up your sleeves, check
out this very cool DIY project that I got from
Australian guitarist Ritchie Laird (reverbnation.com/ritchielaird). He developed a mod
for an active, EC-style mid booster that's
even more flexible than the Fender kit. Best
of all, it won't break the bank.
For this project, Laird uses an inexpensive,
onboard acoustic-guitar preamp called
the Belcat EQ-505R (belcat.com). You can
often find the Belcat preamp on eBay
for less than $10. And you can download
Laird's super-detailed, step-by-step instructions
from my site (singlecoil.com/docs/active_strat.pdf). I've had feedback from
players all over the world who've tried this
project, and they all loved it.
Next month, we'll talk about how you can
make your own version of the Fender Delta
Tone. So stay tuned for more Strat mods—and in the meantime, keep on modding!
Dirk Wacker lives in Germany and has been addicted to
all kinds of guitars since the age of 5. He is fascinated
by anything related to old Fender guitars and amps. He
plays country, rockabilly, and surf music in two bands,
works regularly as a session musician for a local studio,
and writes for several guitar mags. He is also a hardcore
DIY-er for guitars, amps, and stompboxes, and he runs
an extensive webpage—singlecoil.com—on the subject.