KoT mods for GGG Blues Breaker

[cousinpaul]

I recently acquired a second GGG Blues Breaker clone and decided to try some mods. My search led me to Analogman's King of Tone pedal (two modded BB's in one box). I did the cap and resistor mods but left off the presence control and hard-clipping diode-select switch. I didn't want to commit to mods I may not want to keep.

The results surprised me. Although the modded BB has a little more gain, the headroom is about the same. The biggest change seems to be in the midrange. It sounds a little more "present" in a good way (not ice-picky), making my stock BB sound a bit dull in comparison. Haven't gigged it yet, but I think I might like it.

If anyone's interested, you can PM me for the changes I made.

[aunchaki]

I'm interested in the differences between the stock GGG BB and the KoT (well, half of a KoT). I'd be interested in trying out such a project! The board looks pretty straightforward.

EDIT: I just ordered the PCB! Let's put together a Prince of Tone BOM!

[aunchaki]

Here's the GGG Bill of Materials for the BB. What should I exchange to bring me closer to KoT territory?

[rpjones]

Here ya go

http://revolutiondeux.blogspot.com/2...overdrive.html

Just click on the circuit diagram and it will open in a much larger window.
I built it as per the suggestions but didn't add the presence trimmer as I read that it didn't do that much. I sourced all the KOT correct diodes as well as the IC, which wasn't easy to find. If I did it over I probably wouldn't add the switch for the clean boost (removes diodes from the circuit) and probably would leave out the IS1588 diodes for the distortion, it sounds nice but I find myself just using the overdrive most of the time.

[cousinpaul]

La Revolution Deux was one of my sources. If you click on the schematic, there is a table at the bottom with GGG part numbers for all the changes. A good place to start would be R2- 27k and R3- 33k. You may not need any further changes.

[aunchaki]

Thanks for the input. This will be my Project of the Month!

[11 Gauge]

Originally Posted by rpjones

I built it as per the suggestions but didn't add the presence trimmer as I read that it didn't do that much.

This is a good call, IMO. At the very least, instead of hacking the board for a trimmer, you can get a tiny trimmer and install it in series with the cap, right on the pcb.

But IMO, if you need a "treble boost," just make the pair of .01uF tone caps smaller in value, or just the one that has the trimmer added. That is all that is happening with the trimmer - it isn't boosting anything. It's just cutting less treble. Try .0047uF, .0068uF, or .0082uF. If you have problems sourcing those caps, put two small caps in parallel.

Originally Posted by rpjones

I sourced all the KOT correct diodes as well as the IC, which wasn't easy to find.

The IC is super easy to find. It is the "new audio standard" for many electronics applications. It is super cheap, and has a much better gain bandwidth product than chips of yesteryear. Mouser Electronics has them for around 40 cents a piece. They even have a "L"-series chip that is "8 pins inline," like is used in the Boss pedals. So instead of putting goofy adapters in Boss pedals, you can use the 4580L. There's also a 4558L, 4559L (chip used in the Timmy), and 072L (made by NJM/JRC, and NOT Texas Instruments).

Anyway, the diodes don't require anything unobtanium to match what is in the KoT if you are willing to experiment just a bit.

...The ONLY relevant thing to the diodes is what is called the "forward voltage." This is the point at which a diode switches on. Germaniums switch on with less voltage, which is why they compress more, reduce volume more, etc. And something like LED's obviously require at least 1600mV (i.e. 1.6 volts) to "switch on" in order to light up!

So how to match the KoT diodes w/o having to get the same ones? Go find the freestompboxes.org thread with the KoT analysis. Go thru the posts until you find where someone measures the forward voltage of the exact diodes used in the KoT.

Now - the BB V1 uses a pair of TWO diodes in series. The 1N4148 diode that it uses will obviously have a different forward voltage.

Take the forward voltage figure of the KoT diode, and double it. Next, measure the forward voltage of the 1N4148, and maybe a few other common diodes. You need a meter that measures diodes to do this - it's really simple. Use the money you save from not ordering the rare diodes to fund your meter purchase instead, IMO.

Finally - you need a ____ diode to go in series with the 1N4148 that will give you a combined forward voltage that equals TWO of the strange KoT ones.

Say that the BB measures 550mV for a single 1N4148 - that makes 1100mV forward voltage for a pair.

Say that the KoT forward voltage for a pair of its diodes is 900mV (that's just a guess). Now use a 1N4148 and a germanium diode or Schottky diode with a forward voltage of around 350mV. You will end up with the same forward voltage for the series pair.

There is really nothing magical about any type of diode for clipping purposes, per se (there are exceptions, but they are rare). The only important facet in the case of tweaking a BB to get it to KoT clipping is matching the forward voltage of the diode series pair. All that means is that the individual diode forward voltages must "add up to the same amount."

You can think of the diode forward voltage like a different mathematical constant, for the sake of this addition. Each one has a fixed value. So with the KoT, x = A + A. With a cheaper/practical workaround, it means that x = B + C. So (A + A) = (B + C).

A good case in point with this is the Zendrive. Hermida seems to have purposefully chosen very common and affordable diodes and put them in series to get specific forward voltages. He could have searched high and low for some unusual type that would have allowed him to not need to "mix and match." If you like the Zendrive, then you can understand that Hermida was pretty slick to do that.

[smoss469]

I'd just like to be able to recreate the Prince of Tone's Boost setting, that thing is glorious!

[cousinpaul]

Originally Posted by smoss469

I'd just like to be able to recreate the Prince of Tone's Boost setting, that thing is glorious!

I've heard the YouTube clips. Kind of surprised nobody here has jumped on that one. Lots of love for the PoT over on The Gear Page.

[smoss469]

Originally Posted by cousinpaul

I've heard the YouTube clips. Kind of surprised nobody here has jumped on that one. Lots of love for the PoT over on The Gear Page.

I've got 1

[11 Gauge]

Originally Posted by smoss469

I'd just like to be able to recreate the Prince of Tone's Boost setting, that thing is glorious!

It should be the same as the dipswitch in the KoT:

OD - quad of clipping diodes in feedback loop

dist - pair of clipping diodes shunted to ground

boost - no diodes at all (some folks set up both sides of the KoT this way)

There's typically always the two variations with those toggles in the vast majority of drive boxes, with the other being to simply sub two different types of diodes, and have one setting simply be "no diodes."

Since the Bluesbreaker never had a lot of clipping for an OD, the first op amp stage driving the second in a "boost configuration" would sound desirable to lots of folks. You could almost think of it like a Micro Amp Deluxe.

Many other drive pedals with a diode lift toggle tend to get a little buzzy on the decay because they can be driven a lot harder than with the BB circuit - the standard "diode lift" candidates like a Rat with a 3-way toggle.

I've often told folks that if they like the KoT with the dipswitch set to lift the diodes to try building a BB V1 from a kit, and that no diodes makes a simple build even more simple! Just socket the op amp so you can stick different ones in there, and give the 4580 in the K/PoT (and a zillion other newer pedals) a try.

[smoss469]

The GGG Board has a spot for 5 diodes, would you just jumper all 5 then to get the boost mode?

[11 Gauge]

Originally Posted by smoss469

The GGG Board has a spot for 5 diodes, would you just jumper all 5 then to get the boost mode?

No - one of the 5 is for polarity protection with your 9VDC in, so that one must be in there. The 4 clipping diodes are all in a row in the lower RH corner of the board.

You can't jumper the diodes - you have to leave them out.

Actually, if you intend to use the diodes, there is a 6.8K resistor in series with them (R11 in the pic of the GGG board above, IIRC). You could put a switch in place of that resistor (with the resistor in series - you could put it in-line with one of the two switch wires and heat shrink it). If the resistor is removed/disconnected (left open), the diodes are out of the circuit.

ACTUALLY - that 6.8K series resistor is part of what makes the V1 Bluesbreaker so daggone good. You could just replace that resistor with a pot. 10K would obviously give you the stock clipping effect when set near max. BUT - if you used a larger pot, more resistance would have the effect of lessening what the diodes do, and making it "gradually more boost-like." Just a guess, but a 25K to 50K pot would probably work well.

[cousinpaul]

Originally Posted by smoss469

I've got 1

What's up with the "low mid lift" swich? Does it tighten up the lows like a Tube Screamer?

[smoss469]

It says: "The tone from your lower strings will be enhanced a little".

I don't think it sounds like a TS though. It really adds some nice chunk to the sound without getting muddy or dark.

[cousinpaul]

I finally played mine out and wasn't crazy about it, though I can understand how it might work better than the stock BB with some amps. I changed it back to original '92 specs (R2-27k, R3-33k, C4-10pf) but kept the 10k gain-stopper resistor. I also raised the threshold of the HP filter to 234hz, which seems to make the pedal a little more "vocal" sounding to me.

[11 Gauge]

Originally Posted by cousinpaul

I changed it back to original '92 specs (R2-27k, R3-33k, C4-10pf)...

So few folks have played an actual early V1, and it's got to be in a gig setting to really understand why the pedal absolutely shines for that. And it's why the small minority who had one and let it go wished that they could bet it back.

It's not the most flexible OD, and it's just not a bedroom pedal, at all. But use a '92-spec V1 on a gig, and you might just appreciate it.

Damn JM for finding out about them.

The good news is once someone knows about the original recipe and gets one built up like that, they might just think they've died and gone to heaven.

There are so few "older generation" OD's that I think are absolutely perfect off-the-shelf stock, and the early V1 BB is one of those pedals.

[chrisgblues]

I never owned a V1 BB so I don't know what it sounds like in person, but I picked up the copy made by Mooer and it sounds great! I love the harmonic content, and it beefs up single coils just the right amount while leaving room for dynamics in your playing style. Just what I've been looking for to go into my Fender concert amp! I would be interested to see an actual comparison with a V1 BB, but that's not likely to happen any time soon.

Mooer Blues Crab (BB V1 Clone)

For the pure sonic quality I highly recommend it. However, the tiny little knobs are not user-friendly so be warned of that. The bonus is that it takes up about half a pedal space on your board. So far, it seems quite durable.

JMHO.

[cousinpaul]

The Blues Crab looks cool. Bet it sounds great into a Concert.

[aunchaki]

Originally Posted by rpjones

http://revolutiondeux.blogspot.com/2...overdrive.html
Just click on the circuit diagram and it will open in a much larger window.
I built it as per the suggestions but didn't add the presence trimmer as I read that it didn't do that much. I sourced all the KOT correct diodes as well as the IC, which wasn't easy to find. If I did it over I probably wouldn't add the switch for the clean boost (removes diodes from the circuit) and probably would leave out the IS1588 diodes for the distortion, it sounds nice but I find myself just using the overdrive most of the time.

OK, I'm finally trying to get my project going. I've read the zillion-entry forum posts on different boards, etc... Now I have just a few stupid questions and I'll be ready to source parts. Hopefully gurus rpjones, cousinpaul, and 11 Gauge will be able to guide me [crosses fingers].

I've read the great conversion diagram on revolutiondeux (link above). As I understand the instructions, they add two switches. DIP 1 is a treble boost, while DIP 2 seems to engage a pair of 1S1588 diodes for heavy distortion (rpjones makes reference to these in the quoted post above). They also seem to add a trimpot for treble boost.

I don't need treble boost and I don't want a distortion pedal--I want an overdrive pedal, that's all. So, could I just NOT do those additions (i.e. don't add the two switches and 1S1588 diodes, and the 50K treble boost trimpot)?

If that's so, It looks like I'll need to:

CHANGES TO EXISTING PARTS
R2: 4k7 to 27K
R3 3k3 to 33K
R7: jumper
C5 47uF to 100uF electrolytic
C6: jumper
C7: .22uF to 100nF film

NEW PARTS
add a 10K resistor (cutting trace)
add a 1uF cap

So far, it seems pretty easy. Looking at the reveolutiondeux diagram, I don't think the image of the PCB is the same as the current GGG PCB (look at the front & back pic I posted near the top of the thread). Before I start cutting traces, I want to make 100% sure of where the new components go. Can anyone offer some pointers? (NOTE: taking a closer look, the revodeux PCB image seems to be just a REVERSED image of the GGG PCB, can anyone else confirm this?)

If this is the case, it looks like the new 1uF cap uses the same holes as C10 and goes in parallel with it. Looking more closely, I don't see this on the revodeux diagram... It might be that the part names (e.g. R3, C4) might not be the same between the two diagrams. Ug...

The 10K resistor appears to be soldered directly to a trace on the back. What's the best way to do this, do I carefully try to scrape some of the covering to expose metal on the trace (sounds scary)?

Cousinpaul (above) suggests that just changing the values of R2 & R3 might get me most of the there. Still, if it's just a matter of simple part replacement, I don't mind doing it all (even adding the new parts and cutting two traces). Anyone have ideas/advice about how far I should go with the mods?

I know this is a rambling post, but I need to clear my head from circuit diagrams, so I'm just going to post it! Thanks!!