Mxr - Blue Box

JiM · Post by **JiM** » 14 Sep 2009, 23:08

charlietheunicorn wrote:can i mod it with a few steps from a octave below to a octave above?

You just need a couple of XOR gates, like this : http://www.geocities.com/tpe123/folkurban/fuzz/dof.gif

Duckman · Post by **Duckman** » 14 Sep 2009, 23:16

Pin 3 and 13 are already shorted...what's the difference between short pin 1 with 3 or 13???

mictester · Post by **mictester** » 15 Sep 2009, 07:47

Duckman wrote:Pin 3 and 13 are already shorted...what's the difference between short pin 1 with 3 or 13???

Don't mess around with shorting chip pins - you'll end up with a 14-pin fuse! If you want to select one or two octaves down, you need to add a switch that connects the octave down feed to either pin 13 or pin 1.

C.

charlietheunicorn · Post by **charlietheunicorn** » 15 Sep 2009, 15:21

thanks jim, i will test it when i have some XOR's at home and a little bit more time than now

Duckman · Post by **Duckman** » 15 Sep 2009, 17:36

mictester wrote:
Duckman wrote:Pin 3 and 13 are already shorted...what's the difference between short pin 1 with 3 or 13???
Don't mess around with shorting chip pins - you'll end up with a 14-pin fuse! If you want to select one or two octaves down, you need to add a switch that connects the octave down feed to either pin 13 or pin 1.

C.

Tkx!

Swervedriver · Post by **Swervedriver** » 06 Jan 2010, 18:49

According to tonepad Transistors: 2N3904, 2SC1849, MPSA18, or 2N5088 can be used to make the Blue Box. I oredered the 2N3904 but I'm wondering if there is a difference between all of these any of you could share with me. Is it just the amount of gain? I assume they are all silicon.

Kregg · Post by **Kregg** » 28 Feb 2010, 03:18

I cannot imagine there being that much of a difference, I'm building one with the 3904's too.

For those who have used Tonepad PCB's ... has anyone had problems with there pads burning up?
I wonder if it has anything to do with the white coating material?
I've solder plenty of boards in my day and this is the second Tonepad board that I experience the same problem.

Kregg · Post by **Kregg** » 28 Feb 2010, 13:23

P.S. Oops ... should read "their pads burning up"

phibes · Post by **phibes** » 01 Mar 2010, 16:31

How hot does your iron get?

Kregg · Post by **Kregg** » 01 Mar 2010, 17:38

phibes wrote:How hot does your iron get?

Never took it's temp, it's rated 25W.

phibes · Post by **phibes** » 02 Mar 2010, 04:55

Do they use a thinner kind of material? I had that problem a year ago before I bought a temperature controlled iron.

mictester · Post by **mictester** » 02 Mar 2010, 07:22

Kregg wrote:
phibes wrote:How hot does your iron get?
Never took it's temp, it's rated 25W.

You should consider getting (or building) a temperature controlled iron.

I use a 12V or 24V 50 Watt iron with electronic control. The control circuit is really simple - it provides switched low voltage AC to the element. If any one is interested, it's a commercial circuit I designed in the late 70s, and I can post it here. It works by (effectively) measuring the resistance of the element (which varies with temperature, of course), and switching the supply on and off at varying intervals using a triac. It uses an LM311 comparator, a couple of transistors, a pot (for setting) a couple of presets (for calibration and a triac. There is a bicolour LED that shows red when heating and green when cooling, and flashes alternately when it's at temperature.

If anyone's interested, I'll scan the schematic and post it here.

himister · Post by **himister** » 02 Mar 2010, 14:30

Hello guys. While on the subject of Blue Box, I'd like to ask some of you if could help with one ''small'' problem. I'm building a Blue Box clone for a friend and I've done some mods to it. Following the mictesters advice I made a switchable octa mod and that works just fine. Also I made mod by disconnecting the C9 cap close to level pot to increase the highs in the tone, that one works well too but....
Since I made the board and done some testing there's an odd behavior in the octave part of the circuit... when blend pot is turned more on the octave side I get very odd intermittent octave sound, something like octave part is switching between 1st and 2nd octave without control and in very odd timing intervals...more like a ''broken robot'' sound.

I used a tonepads layout without R24 (330Ohm) resistor and instead of 0.05uF caps I put 0.047uF.
One more odd thing is that amount of distortion in the fuzz section is really heavy and good but sustain is short...something like when you pick on the riff and it chokes it self after few seconds. I tried to change some electro caps suspecting that maybe some of them are faulty but nothing helped so far....
Any advice would be very appreciated!

Thanks in advance.
Cheers

bjk5959 · Post by **bjk5959** » 06 Apr 2010, 18:57

mictester wrote:
Duckman wrote:Pin 3 and 13 are already shorted...what's the difference between short pin 1 with 3 or 13???
Don't mess around with shorting chip pins - you'll end up with a 14-pin fuse! If you want to select one or two octaves down, you need to add a switch that connects the octave down feed to either pin 13 or pin 1.

C.

Does this mean using an SPST to switch between pin 3 connecting to either pin 13 or 1?

Also, does anyone have a vero layout for this? I saw a post on DIY for a vero, but the link was old. I don't want to pay $20 for a pcb from tonepad.

bjk5959 · Post by **bjk5959** » 07 Apr 2010, 08:09

Ah, nevermind on the wiring. I found everything I was questioning here:

https://www.diystompboxes.com/smfforum/ ... ic=79181.0

Still would love to see a vero layout.

Brainbender · Post by **Brainbender** » 18 Nov 2010, 11:26

mictester wrote:
charlietheunicorn wrote:another noob question, this pedal is really nice but can i mod it with a few steps from a octave below to a octave above? i think this would be sound great, too ..
Unfortunately, divider ICs are more readily available than multipliers! All that the Blue box does is use a pair of bistables (in the 4013) to generate a signal two octaves below the input, with a fairly crude attempt at an envelope follower to try to make the output follow the envelope of the guitar. However, there is a fairly simple way to get twice the input frequency using a logic IC or two - I'll draw it up and post it here. I've also got one box with a choice of various octave and fifth outputs, any or all of which can be mixed in any proportion.

To get other intervals requires slightly more complex electronics - I used a PLL (phase-locked loop) and some divider logic to select various intervals, but it's not a trivial mod. I'll draw it up if anyone's interested.

The easiest way to get just one octave down is to take the output from pin 13 of the IC instead of pin 1 - my box has a switch to choose between the two options.

The lack of output level can be addressed by adding an extra transistor stage to the output, after the output pot. I used a 470k resistor from the base to the mid-rail, a 10k from emitter to ground, and 56k from collector to +9V. The wiper of the volume pot feeds the base of the additional transistor through a 47n capacitor, and the collector of the transistor feeds the bypass switch through a 10 uF capacitor (it can be much smaller, but I've got a box load of them!). The positive end of the 10 uF to the collector of the transistor, and the -ve end is connected to ground through another 2M2 resistor (to prevent the dreaded switching "pop").

I'll draw up the mods and post them here if anyone wants them.

I'd really appreciate that!

EDIT: One more thing... Is worth to try to (instead of 50k log pot) replace it with some smaller value? 25k or less?

himister wrote:that one works well too but....
Since I made the board and done some testing there's an odd behavior in the octave part of the circuit... when blend pot is turned more on the octave side I get very odd intermittent octave sound, something like octave part is switching between 1st and 2nd octave without control and in very odd timing intervals...more like a ''broken robot'' sound.
I used a tonepads layout without R24 (330Ohm) resistor and instead of 0.05uF caps I put 0.047uF.
One more odd thing is that amount of distortion in the fuzz section is really heavy and good but sustain is short...something like when you pick on the riff and it chokes it self after few seconds. I tried to change some electro caps suspecting that maybe some of them are faulty but nothing helped so far....
Any advice would be very appreciated!

Thanks in advance.
Cheers

Well, welcome to the Blue Box world!

Everything you mentioned is normal. that's the pedal's behavior!

rvargas · Post by **rvargas** » 22 Nov 2010, 16:25

Hi all,

It's interesting to read all your posts.. In fact I've wanted to build a blue box since some time ago - it has fascinated me the concept of using digital logic chips to produce a fuzz and frequency divide. My question before building it:

Is there any known mod to "soften" the fuxx distortion given by the octave? Given that the D flip flops will give a squared out waveform, I understand why it gives such a computer-y sound sometimes, especially when the blend is up. I have though of putting some sort of lowpass filter before Q3 base (tonepad schematic), but do you think this would be effective? Any other suggestions?

Not that I want a clean octave down, but, as clean as possible would be nice..

Thanks!

hewie · Post by **hewie** » 07 Apr 2011, 18:23

Worked up this vero layout a few months ago, figured someone else might want to use it. Verified by me.

joeboo88 · Post by **joeboo88** » 07 Apr 2011, 18:37

Thanks a bunch Hewie, if your so inclined making up all these veros, make a pinnacle for me I hate perf board .

hewie · Post by **hewie** » 07 Apr 2011, 18:50

joeboo88 wrote:Thanks a bunch Hewie, if your so inclined making up all these veros, make a pinnacle for me I hate perf board .

Link me to the schematic and I'll see what I can do