Tuesday, June 3, 2014

Britannia - The new British Channel by Runoffgroove

In 2004 the Runoffgroove team released their famous "English Channel" pedal version for the VOX AC30 Top Boost amplifier. Their acclaimed JFET take on the tube overdrive sound was a big part of the amp-in-a-pedal mania that soon flooded the guitar world with boutique vendors releasing pedal versions of every amp known to man. What started as a unique way to generate the tube gain stage using silicon transistors was slowly replaced by new techniques which replicated the tube sound better but was not necessarily based on the original amp schematics. Using the new technique, Runoffgroove updated their schematics starting with the fabulous "Azabache" circuit to replace the "Professor Tweed" as the Fender style circuit. "Britannia" is their new approach to achieving the famous sound of the VOX AC30 Top Boost. The "English Channel" was a very good overdrive in my opinion. I built it in 2011 and I was quite happy with the results. I even compared it several times with a software version of the amp and I was always satisfied.

When the "Azabache"came out, I built it right away ("Tweed Palette" on this blog). Immediately it was obvious that the ROG team has made great progress in understanding the overdrive character of the tube amp, so it was no surprise that when they released Britannia, it instantly reached the top of my list.

I decided to go with the 1776 Effects PCB this time just to check out this path as I usually build the circuits on pref-board or vero. I was really pleased with the PCB because it was built so well, with so many small features to ease the work of the builder. I highly recommend these PCB layouts for everyone who is interested in building his pedals faster and safer. The features I really liked about the PCB:




  • Clear and logical layout.
  • Clear printing for each part, including pots, trimmers, grounds in/out and 9V supply.
  • Tips on the drain voltage for each transistor with the voltage values printed next to the biasing trimmers.
  • Location for soldering test points.
  • Great value


  • So, back to the VOX AC30 Top Boost story (from wikipedia):

    "The Vox AC30 was originally introduced in 1958 as “big brother” for the 15W AC15 model at Hank Marvin's (The Shadows) request because the AC15 was not loud enough with the screaming fans at Cliff Richard's concerts. Vox's original flagship amplifier. The Original first generation AC30, or AC30/4, had only a single 12" Goodman's 60W speaker in a "TV Front" cabinet, as opposed to the later, conventional twin 12" speaker configuration. The AC30/4 sported two channels with two inputs – hence the “4” in the model name. The amplifier used a GZ34 tube rectifier, three ECC83s (12AX7) for the Normal channel and it had EL34 tubes in the power amplifier circuit.

    In 1961 the "Top Boost" (or "Brilliance") feature became available as Vox's optional addition of a circuit that introduced an extra gain stage and tone controls for bass and treble (as opposed to the single "tone" control of earlier AC30s). The unit became so popular that its features were soon incorporated in newer AC30/6 models, and the controls moved from the rear panel to the control panel.
    The classic VOX AC30 Top Boost

    Vox AC30/6 amplifiers from around 1963 had already implemented the top boost, and therefore had 3 tone controls. People began to refer to these amplifiers as AC30TBs. In addition to the "Normal" version without the Top Boost, and the Top Boost version (which was a Normal version with the "Brilliance" unit added), Vox, with slight circuit modifications, created two more versions that were “voiced” in Brilliant (Treble), and Bass styles. Of all the different models that came around many consider the AC30 "Super Twin" to be the ultimate AC30, with a "trapezoid" shaped head and separate speaker mounted on a trolly."
    Brian May and his VOX wall of AC30 amps

    Those early 60's TB models became the tone of choice for many legendary musicians and bands. To name just a few, we are talking about The Beatles, The Byrds, Hank Marvin (The Shadows), Brian May (Queen), Vic Flick (James Bond theme), Rory Gallagher, Tom Petty, Noel Gallagher (Oasis), Johnny Greenwood and Thom York (Radiohead), The Cure, The smiths, Muse, R.E.M and almost every band who wanted that sweet British crunch. Vox was quite an amazing music company which developed many solutions for musicians and had VOX organs, VOX wah pedals, Vox guitars, VOX PA systems and each one of those lines became a legend of its own.

    More info can be found on the VOX website: http://www.voxamps.com/history/

    Inside the original VOX AC30

    The front panel and tubes of the AC30
    All I can say is that this amp-in-a-box completely blew me away and it rocks soft and hard at the same time. I love the range of the GAIN pot which really goes from completely clean to jangly crunch to ooomph power drive. The TONE controls are BASS and TREBLE which are super effective. With high GAIN settings and high BASS you can really rock hard a la Brian May, while low BASS gets and mid GAIN gets you to Rory Gallagher territory. Guitar volume is effective too. Putting a Treble Boost in front or a fuzz will give you ultra tonal flexibility. An additional overdrive on wither side will be super cool also. The coolest sound I got so far was with my Tele in neck pickup, volume knob on the guitar backed off a little and GAIN at noon. What a sweet smack in the face. I used my former ENGLISH CHANNEL enclosure and changed the knobs so the pedal looks quite similar, but underneath the hood it's a whole new beast.

    All this magic in a small PCB - The Britannia on the "1776 Effects" PCB 

    And the amazing pedal in a unique enclosure which used to house my English Channel

    The Runoffgroove page with all necessary info is found here:

    The 1776 Effects website:

    Below is a long demo of the pedal with my MIM Telecaster through a Dr. Z MAZ 18 cabinet.
    Just listen to the vast amount of sounds obtained by tweaking the guitar's volume knob, the GAIN level and the TONE controls. Just dime that GAIN knob and start those Tom Petty chords or those open arpeggios. Add a fuzz in front and you are in 60's heaven. 



    Don't miss out this great pedal. It quickly became on my top 5 all-time overdrive/tone pedals.




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