Fun with Bluesbreaker

[cab42]

For the last period I have had a Marshall Bluesbreaker variant on my breadboard. I saw a JHS video where he compares different types of overdrive, and it occurred to me that I had never played, nor built a Bluesbreaker type pedal. I emptied my breadboard, found some schematics and started building.

I started out with a straight clone from ggg's schematic (http://www.generalguitargadgets.com/pdf/ggg_mbb_sc.pdf). Other than the usual swapped potmeter wires and a missing Vref connection,  it was a pretty easy build, and actually sounded great.

Then I compared it with some of its cousins:
Morning Glory (http://www.generalguitargadgets.com/pdf/ggg_mbb_mg_sc.pdf)
KOT (http://www.generalguitargadgets.com/pdf/ggg_mbb_kt_sc.pdf)
GGBB's Notorious OD (https://postimg.cc/cvX67422) found in this thread (https://www.diystompboxes.com/smfforum/index.php?topic=127457)
Stebens BBX (same thread as above) and
Mark Hammers Wattbreaker (https://www.diystompboxes.com/smfforum/index.php?topic=126135.0)

This is what I tried. Nothing particularly original , but it might be useful for someone. Comments and suggestion are, as always, welcome

- Changing resistors in the feedback loop of first opamp from 4.7k and 3.3K to 27K and 33K, like in the KOT (although the ggg shematic claims that some factory units came with these values). I liked the new values best, a more beefy sound, but I think I will put them on a switch like in the Notorious OD, as I can see the use of the lower values.
- Changed the 47p capacitor in  the feedback loop to 100p
- Changing input cap. I ended up with a 22n. I have a load of those and it always looks great with a tropical fish cap!
- Resistor in series with the gain pot. Tried a few values. It definitely needs one, but not too big (10K-50K). It makes the the lower part of the pot rotation much more useful. I will probably glue a 50k trimpot on the back of the gain pot, so a minimum gain can be dialled in. I have done that in my Rat.
- Fat switch as in the Notorious OD. That's a keeper! The 33n setting is SO good! I might lower the 100n a bit.
- Hard clipping diodes after opamp 2. I can easily see the point and it sounded good. But it was not what I was looking for!
- Soft clipping diodes in the first opamp as in the Wattbreaker. I could not hear much difference. Did I do something wrong?
- Presence control. The jury is still out on this!

I haven't tried any gain stages in the end yet. My test thing does not have a bypass switch ATM, so I don't know how loud it is compared to bypass. But there's a few to chose from. But couldn't I just use a stand alone booster after?

It will be pretty versatile with four pots and two switches. It will definitely be boxed and go on the board!

[GGBB]

- Changing resistors in the feedback loop of first opamp from 4.7k and 3.3K to 27K and 33K, like in the KOT (although the ggg shematic claims that some factory units came with these values). I liked the new values best, a more beefy sound, but I think I will put them on a switch like in the Notorious OD, as I can see the use of the lower values.
...
- Fat switch as in the Notorious OD. That's a keeper! The 33n setting is SO good! I might lower the 100n a bit.

My fat switch is always in the 33n position with KOT gain mode (27k & 33k).

If you go with the Notorious OD gain mode switch for the different resistor values, the "notorious" 100n fat setting becomes more useful with MG (4.7k & 3.3k) gain mode because there is a fair bit more bass roll off with the smaller resistors. Enough to make the gain switch actually sound like a treble boost - some may want it on a footswitch to use it for that purpose.

If you are interested - I have Notorious OD PCBs for free (you pay shipping): https://www.diystompboxes.com/smfforum/index.php?topic=127749.0

[cab42]

If you go with the Notorious OD gain mode switch for the different resistor values, the "notorious" 100n fat setting becomes more useful with MG (4.7k & 3.3k) gain mode because there is a fair bit more bass roll off with the smaller resistors. Enough to make the gain switch actually sound like a treble boost - some may want it on a footswitch to use it for that purpose.

That was my experience that it was more of a treble boost rather than a volume boost. A foot switch for that is a good idea!

PM'ed you regarding a PCB.