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Hi there, welcome to my blog - La Revolution Deux. It's an odd name - but I like it! Here you will find all the info on my various DIY Guitar effects builds, amplifiers and guitars. Everything from a humble Ibanez tubescreamer to the holiest KLON Overdrive.

You may also find a few effects builds that I am looking to move on - usually in exchange for other effects/gear/cash. You can always check my ebay account to see what I've got up for grabs.

Have fun, enjoy the blog - Fred Briggs :-)

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Feel free to get in contact with me about anything you see on this blog or with any general questions about guitars, amplifiers and effects, I'll be happy to answer! Just click the button above to email me directly or alternately my email address is fredbriggs2007 [at] googlemail [dot] com

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Saturday, 14 July 2012

Catalinbread - CB30 Overdrive


So, on the topic of "Voxy" sounding boxes here's another - the Catalinbread CB30. Most of you who read this blog regulary will know that I do like Catalinbread pedals; they always sound good and their aesthetic appeal and build quality is top notch. Unsurprisingly the CB30 is no different.

Here's the description from the Catalinbread website;

"The CB30 is designed to give you jangly, dynamic, responsive overdriven tones, just like it's British 30 watt counterpart. The tone controls work exactly the same way as the actual amp, where the more the treble and bass increase, the more scooped the mids become, making it capable of being quite hollow and jangly. The CB30 can be dialed in for that immediate attack, compressed mid range honk, finished by the shimmery high end jangle, an elusive sound for many players. Like all the foundation pedals in our line it sounds excellent on its own, or when stacked with other pedals (no really, just wait until you put a treble boost in front!)

As owners of the real deal know, the amp has an amazing touch sensitivity, with the ability to go from clear and chimey, to that unique overdrive character with just your picking dynamics. The CB30 has the same response, and cleans up extremely well with your guitar's volume control. The CB30 is true bypass, and comes in a rugged silkscreened case, has black aluminum knobs that feel great, and are easy to see on stage. If you're looking for an expressive, chimey overdrive, we think you'll enjoy the CB30 for years to come."

Here's a demo video of the Catalinbread CB30 in action;


Here's a schematic from mmolteratx;


It's similar in structure to the Catalinbread Dirty Little Secret and Formula No 5; a dual mu-amp design with a tonestack taken from the amplifier family it's looking to emulate. There are a few interesting little additions to this circuit though - C6 & R2 form a gain lowering feedback arrangement for higher frequencies and the 470pF C7 really restricts low end signal from exiting that first mu-amp stage.

Some people have complained that the CB30 lacks a little gain, I'm not sure it does but here are a few mods and suggestions which will allow you to pump up the available gain without removing too much of that Vox character;
  • Reduce the value of R1 (maybe 10k),
  • Increase the value of C4 (47n or higher),
  • Increase the value of C7 (1n-10n),
  • Remove R7 or just reduce it's value,
  • Make Q5 a jfet gain stage instead of just a buffering stage.
NOTE - these modifications will alter the frequency response of the pedal somewhat, it's about tweaking it to your taste while attempting to retain that Vox character!

Another favourite modification I like to use with mu-amp type circuits is an increase in supply voltage, it nearly always has a positive impact on the tone of the circuit. Pumping up the voltage from 9 to 18v opens up more dynamic headroom and pushes the gain up just a touch. Even though when playing mu-amp circuits at 9v they feel like an amplifier the higher you go with the voltage the more convincing they get. Push the voltage up to a limit of 25v as that is the limit for 2N5457 jfet type devices, any more voltage than that and you'll cook 'em!

Here's the freestompboxes.org forum topic for reference; http://freestompboxes.org/viewtopic.php?f=7&t=13691

6 comments:

  1. Not sure how much Voxification this really offers but it is a great overdrive particularly to add some sparkle to a dark sounding amp. It also works really well in conjunction with other pedals again adding clarity and definition if place at the end of a long effects chain.

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  2. good day friend.
    I wonder if I find the layout to transfer term with the list of components or something like tonepad site.
    thank you

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  3. Any idea what the value for r13 is? Unless I'm missing something I can't see a value for it.

    Love the blog, by the way, Mr. Briggs :-)

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  4. Figured it out, it's 10k if anyone else was interested

    ReplyDelete
  5. is this site still being updated, or do you have a new site ?

    :)

    ReplyDelete
  6. I put this together and noticed that the bass pot seems to work backwards unless it's supposed to be a bass cut. I don't think the CB30's bass control reacts like that.

    Regardless of that, the tone stack is very interesting as the treble and bass interact and affect each other. This circuit sounds great.

    ReplyDelete

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