ROG BRITANNIA Mods... please help

[mania448]

Hi guys!
I need some help to mod RunOffGroove BRITANNIA
I love this pedal but in this moment I'm using it more like a distortion, so I need to decrease High and Bass content
I've noticed that I cannot set Treble, Bass and Brilliance anything but minimum with high Gain setting because it is too muddy or shrill in flat or other position
So I'm trying to get a more flexible EQ... and also to tame it in high and low frequency


According to 1776effects schematic, I've tried various mods with no appreciable result
http://1776effects.com/wp-content/uploads/2015/03/Britannia-BOM.pdf

First I increased C2 from 2n2 to 4n7-6n8
Changed C5 from 470pF to 270pF (to have more control over high)
Increased treble pot from 100k to 250k
increased bass pot from 50k to 100k
My EQ is still unusable except with controls at min
Please, any suggestion? I have to look in other sections of the circuit?
I would like to get a good distortion with usable EQ and balanced tones
Thanks
Excuse me for my English

[GibsonGM]

I think you need to define what type of sound you really want, Mania...the "Brittania" pretty much does one job, and has its sound, IMHO.   It would not be very hard to put together a different distortion that does what you need, if you can explain the sound better!   Provided there are no build errors, you SHOULD be having "the Brittania sound"....

Perhaps bypassing the tone stack completely, with just a piece of wire, would help?  You could then run the output into an EQ pedal to better tailor the tone....I personally would try an EQ after it anyway, to see what there is to see.....

Others will probably come by with better advice than this, but I'm one who will just build a new pedal if I'm not getting what I want....maybe a Marshall Guv'nor would do you well? 

Welcome to the forum, by the way!  

[antonis]

maybe a Marshall Guv'nor would do you well? 

Excellent choice..!!!
(with a little boost..)

[mania448]

Thank you so much GibsonGM!
Yes, the Britannia pedal has its own distinctive and wonderful sound...
Until now I used it for what it was designed but I realized that I love it at high gain settings also... then using it as a high gain distortion even if it is not designed specifically for this.
The sound is really ok apart for the Bass and Treble section... I cannot set the controls anything but min position.  Other settings make the sound too confused and muddy in bass or shrill in high frequency.
Unfortunately with the mods I tried, I was not able to darken the sound and to dry low.
Simply I will try what you said... I will completely disconnect the EQ section and add a 6-band equalizer after!
Before switching to another project, I wanna try this because I believe it can be worth it.
I will let you know how it works
Thanks again 

[GibsonGM]

You're welcome...I would just "jumper over" the tone section, with a wire...you do want to have the 'rest of the circuit after the tone stack'!   You may need to adjust other things, as well, since without the tone stack there, the signal will be of a greater magnitude!   You may want to insert a pot to control the level to the following stage, if necessary.  Or just turn the drive back...

I hope it was not a build error that caused the tone controls to act as you described...I would imagine that ROG set them up to work well...that confuses me a little.   Oh well, let us know what happens!

[PRR]

> I need to decrease High and Bass content

There's Low and High cuts in there--- but they hardly touch the audio band.

Suggest you try major changes of cap values. Here's a starter plan which should be obviously different. You may wind up going 2X 5X even 10X up -or- down from these values depending what you want to hear (and not-hear).

[GibsonGM]

Wow, those are pretty whacked out (original) values!!  I should have gone to the schematic, but I got lazy 

[Transmogrifox]

There's Low and High cuts in there--- but they hardly touch the audio band.

[EDIT] Oops.  I was not able to view the image from the other location (blocked by router filtering rules).  Now I see -- PRR is correct.

I do think messing with c9 is likely t make it more muddy.  See my final comments about clipping after the tone control.
[/EDIT]

Second opinion:
Bass = 50%
Treble = 0%, 50%, 100%


Treble = 50%
Bass = 0%, 50%, 100%


3rd Opinion:
Duncan Tonestack Calculator agrees with my LTSpice simulation, AND this general EQ curve is very near to the standard Fender style tonestack, so it most certainly is working in a normal guitar-relevant zone.

The problem is likely due to another clipping stage following the tone control.  You may want to move the tonestack to the end of the effect and apply some hard-wired EQ of some sort in place where the tonestack currently resides. 

This circuit really doesn't lend itself well to cranked high-gain sounds because of this topology.  I also find these kinds of tube amps sound like trash when cranked also.  They're sweet when set on their sweet-spots.

Might have more success finding a Mesa gain & voicing topology.  Those were designed for tight and well-balanced sound at high-gain settings.

[PRR]

> I do think messing

You may be right. And there is a LOT of stuff going on in here, so re-tweaking may be a time-sink.

I just offered it as a 4-bit 10-minute thing-to-try.

[Transmogrifox]

I just offered it as a 4-bit 10-minute thing-to-try.

Yup, pretty cheap and easy.  Especially on a breadboard.

Better to try it and show me wrong than to listen to me and miss a simple fix.

[J0K3RX]

For the hell of it maybe run a jumper from lug 2 of the treble pot to lug 3 of the volume pot and see how the tone controls respond like that? If it sounds good then perhaps mod the opamp circuit to be an MXR micro amp.. 

[GibsonGM]

> I do think messing

You may be right. And there is a LOT of stuff going on in here, so re-tweaking may be a time-sink.

I just offered it as a 4-bit 10-minute thing-to-try.

This is why I was like...."Guv'nor, yup"....sometimes it seems easier to just pop together something new rather than try to rebuild the old design.

Just the amp/clipping section of a Guv'nor is a hell of a distortion, IMO!  And easy to cobble together as a building block.  Add your own EQ/tone controls...

[mania448]

Hi guys!
Thank you all for the replies.
Just tried to completely bypass the equalizer, moving it to the end of the circuit
Just after final IC1B (removing C20- 1uF cap)
Now there is a Treb-Mid-Bass passive EQ with Master Volume control after it. I succeeded to find right values of pots and caps for my taste... Also minor changes in the Low cut/Hi cut filters (after previous treble control... C8-C9-R10-R11).
The passive EQ at the end of circuit makes me loose a lot of dB now... I cannot match clean volume.
Any suggestion to increase output? Buffer?
Increasing Master volume value doesn't work (I started with 100k)

[GibsonGM]

You could add a transistor gain stage, just like the last one in the Big Muff Pi.   Or an opamp gain stage....lots of ways to go with that!

See - you're redesigning the thing, LOL...  I knew you would..  I hope it sounds great when you're done!!