Catalinbread Dirty Little Secret Mk III Overdrive


The Catalinbread Dirty Little Secret Mk III is essentially a Marshall in a box!

From classic Super Lead and Super Bass (JTM45) type tone. Cleans up as you back off guitar volume – just like the real thing

Battery operation or 9v-18v Negative Tip DC Power. Approx  5 mA draw

(2 customer reviews)

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Catalinbread Dirty Little Secret Mk III

The Catalinbread Dirty Little Secret Mk III “nails that classic Marshall tone” because it gives that Plexi sound and response.

The Catalinbread Dirty Little Secret (DLS) is an overdrive pedal bringing you the sound and response of a classic Marshall amplifier.

Its always-on design transforms any amplifier into those raging British stacks.

You can get a great clean sound just by rolling your guitar’s volume knob back! That’s the way the old-school Marshall players did things!

Forming the core of your guitar sound, embellish the sound by adding boosters, fuzzes, filters, and other overdrives

Just like you would in front of a real amp.

Classic Marshall sounds from the Dirty Little Secret

Supercharging the sound of rock and roll. The house lights dimmed. All you could see through the hazy darkness was the array of red pilot lights shining from a backline wall of Marshall stacks.

In the absence of your own personal wall of Marshalls, the Dirty Little Secret is the perfect secret weapon in your tone arsenal.

The Dirty Little Secret has a well-deserved reputation for replicating the sound and feel of a classic era Marshall amplifier.

The JFETs used for the Dirty Little Secret are now discontinued. As our stock begins to dwindle, we knew we had to find ones still being manufactured.

Rather than re-voicing around these new JFETs, we decided to push the envelope and provide an amazingly robust feature set.

This isn’t just ‘a’ Marshall in a box, it’s the most versatile and dynamic Marshall-style overdrive out there!


The pedal mode dynamically reconfigures the tone controls

Whether in SL or SB mode, the tone circuit is exactly the same as found in Super Lead and Super Bass Marshalls. It behaves and interacts the same way as on their amp counterparts.

• Full-featured bass, middle, and treble tone controls. These provide precise adjustments for a multitude of tones and to match your amp and guitar.

• Preamp controls the gain or amount of overdrive. The new DLS is tuned for a bit more gain than most Plexi Marshalls actually got. Super Bass mode is tuned to have less gain then the Super Lead mode to get more of that early Marshall response.

• Master knob controls the output volume. For the best response out of your DLS, set the Master volume so that the sound with the DLS engaged is a bit louder than your bypassed sound.

• Your guitar’s volume knob is a part of the Dirty Little Secret’s control surface. Even in Super Lead mode with the Pre-Amp cranked, you can get a perfectly clean sound by rolling back your guitar’s volume knob.

The Mk III

This is the latest evolution of the Catalinbread Dirty Little Secret. It is the most dynamic Marshall-style overdrive out there.

It has two distinct voicings.”Super Lead” and “Super Bass”are switchable via an internal slider switch.

A full three-knob treble-middle-bass tone control complement reproducing exactly the tone circuits of the Super Lead and Super Bass amps.

You can read more about Catalinbread innovation here. Also, find out about the full tech spec of the Caltalinbread Dirty Little Secret using the highlighted link.

Super Lead

The “Super Lead” mode gives you the great rock sound of a Marshall Super Lead amp. Awesome harmonics, touch sensitivity, cab thumb and kerrang.

Higher gain than the Super Bass mode, Super Lead mode is perfect for use with humbucker-equipped guitars. Its gain range goes from classic Plexi all the way to modified JCM800 levels.

Just like a great Plexi, you can go from clean to scream with just a twist of your guitar’s volume knob. Like a Super Lead, its voice is all about thump and upper-midrange kerrang because this is THE rock sound!

A Marshall Super Lead’s circuit cuts out a lot of low end in the first gain stage. The Super Bass or older Super Leads passed a lot of bass through.

The reason the Super Lead cuts so much bass is to keep things tight when the amp is turned up, which is what the SL mode does.

It tightens the bass response at the classic Marshall frequency point. Also, it turns up the gain potential giving a hot, fast responding, gainier sound.

Sounding absolutely fantastic with humbuckers but with Fender-style guitars a player may prefer a fuller response.

Super Bass

The “Super Bass” mode gives you the tone and gain structure of a Marshall Super Bass. This is very similar to a JTM45, JTM50/100, or very early Plexi.

This mode is voiced to really hone in on that elusive in-between “not quite clean, not quite dirty” response that old tube amps are so good at getting.

Using Marshall amp-geek language, the difference between the SL and SB mode is akin to split-cathode vs. shared-cathode configuration on an old Marshall.

Split-cathode has a high-pass response starting around 700hz,  while shared-cathode lets everything through.

But the SB mode is not just for single-coils.

This is the mode you want if you’re trying to get that classic AC/DC sound, big open crunch that’s not too gained out sounding. Hendrix fans will love this mode. It was voiced with that sound in mind!

Without a fuzz in front of it, think The Wind Cries Mary. With a fuzz in front of it, pull out your live Hendrix recordings!

Plug in a Fuzz Face!

Fuzz pedals sound great with the DLS because of its voicing. Especially two-transistor based fuzzes like the fuzz face.

Plug a Strat into a Fuzz Face into the new DLS in SB mode and you’ll see what we mean!

Its voice is deeper bass, and an emphasis on the lower midrange,  sounding especially great with Fender style guitars.

This is precisely why it works so great with fuzzes like the fuzz face. Super Leads cut too much bass right up front and have too much gain. So, a fuzz face ends up sounding farty and pinched sounding instead of a huge, full sound.

Fuzz Face and Marshall fans will know what we’re talking about.

Reconfiguring the tone stack – the SL / SB Mode

The voicing mode switch doesn’t just add a bit more bass to make it a “Super Bass” or something simple like that.

It completely reconfigures the tone stack and key first gain stage parameters to give an authentic Super Lead or Super Bass type response.

The treble-middle-bass tone control complement exactly reproduces the tone stack circuits of the Super Lead and the Super Bass amps.

So when you switch from SL to SB mode, the tone circuit gets reconfigured to the Super Bass circuit.

A bit of history.

Early Plexi Marshalls and JTM45s also had the “Super Bass” tone stack. This was later changed in the Super Lead amps to emphasize the upper mid-range frequencies , because guitarists in the late sixties wanted a more aggressive cutting sound.

Compared to the SL tone circuit, the SB tone circuit shifts the bass response lower and gives a somewhat more “scooped” sound than the SL mode.

It’s actually not really much more scooped but the SL mode adds a lot of upper midrange cut to give that classic Super Lead kerrang response.

Both SL and SB voices are compelling so we wanted to be able to give you access to both!

There are a lot of great Marshall tones lurking in this pedal. Enjoy


  • Complete redesign with two Marshall modes.
  • Super Lead and Super Bass to suit your sound.
  • Fantastic clean-up with your guitar’s volume control.
  • Ideal for stacking with fuzzes, ODs, and boosts.
  • Exact tone stack circuits from SL and SB amps for a true-to-amp response.

Technical Specifications

  • 2.34″ x 4.39″ pedal
  • Battery operation or 9v-18v Negative Tip DC Power.
  • Approx  5 mA draw

Additional information

Weight .18 kg
Dimensions 11 × 6 × 5 cm
Analogue or Digital





5 mA



Pedal Type


Power Connection Type

Centre Negative

Silicon or Germanium



9V – 18V

EAN 13





Dirty Little Secret Mk III

2 reviews for Catalinbread Dirty Little Secret Mk III Overdrive

  1. Stuart I (verified owner)

    Highly Recommended

  2. Vel S (verified owner)

    Excellent item

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