blue box question

[makkimo]

hi
i'm building a mxr Blue Box from Tonepad but now i'm looking for some suggestions about building the version including all component in the layout or the one in the NOTES (1977) leaving out some components?
what's the difference between the 2 in terms of sound?
thanks guys

[makkimo]

really no one?!!!!!!!!!!!!!
   :cry:  :cry:

[Torchy]

crp

[downweverything]

ive been wanting to build this one.  never noticed somebody had a layout.  thanks.

[downweverything]

the extra parts just look like power supply filter caps and a pulldown resistor etc.  R25 should eliminate switch popping, the other parts should clean up a noisy supply by making a low pass filter.  id leave them in.

[makkimo]

i've just finished mine leaving all components as in tonepad layout and it seems to work but...: is it normal a strong drop in volume sensation???
is it caused by the octave down or this could be a real building problem(i'm using a hcf4013be cip)
what about the mod switching between the first end the third pin of the 4013??? mine just does nothing

[vfr800fiman]

I just finished building a "Deluxe" Blue box last month using all of the mods on the schematic. I even did the 1 to 2 octave switch design and a switch for the capacitor value change on both the fuzz and the square wave channel. This gives me more tone control over the 2 sounds.
I love it!
http://webpages.charter.net/porkchop/effects/bluebox1.JPG
http://webpages.charter.net/porkchop/effects/bluebox2.JPG

[vfr800fiman]

OOPS!
I forgot to mention that Mark Hammer suggested all of these mods to me in this post.
Thanks Mark!

It is hard to imagine ANY analog octave box that will work flawlessly with every playing style and instrument without any modification.  Tracking optimization is the heart and soul of all such boxes.

I should be working, but here is a brief rundown of things you can change to alter the way the unit behaves.  I am using Francisco Pena's redraw and part numbering as the reference:

1) IC1A is the input and initial gain stage.  It provides enough gain to feed/drive the envelope follower formed by C7/8, D2/3, and R15.  The gain of IC1A is set for about 471, with a high end rolloff of just under 1130hz, and low end rolloff of about 16hz.  Making C7 or C8 smaller will raise either rolloff point, and making them bigger in value will lower it.  C4 also rolls off high end, but I couldn't tell you where.

2) The time constant of the envelope follower (i.e., how quickly it reacts) is set by R15/C8.  Increasing R15 will lengthen the time the gate is on, as will increasing C8.  Increasing C8 will slightly increase attack/onset time and lengthen decay time.  Sticking a small value (<1k) resistor between D2 and R15/C8 will also increase onset time, yielding a softer less sputtery attack.  (NOTE: This will make the follower a bit less sensitive so gain from IC1A may need to be increased to offset that)  The envelope follower serves to "gate" Q2 and Q3 such that sounds/notes which are not really sufficiently consistent to trigger octaves from IC2 tend to be squelched.  In such instances, the envelope signal would be too small to turn Q2/3 on and pass signal to the output.  Though R13/14 are equal values, making both fuzz and octave turn on simultaneously, I'm wondering if tinkering with the value of R13 might not be useful in permitting *some* fuzz to come through even when octaves don't (or vice versa).  C7 limits the low end sensitivity of the envelope follower.  Make it smaller and bass notes won't turn the gate on quite so easily.

3) IC1B forms another gain stage of around 101 (due to R6/R23 ratio) though the R7/R9 network attenuates that output considerably, presumably because Q1 needs them to be there.  Note that a gain of 471 times a gain of 101 is, well, a LOT of gain to be squeezed out of a puny 4558 and a 9v battery.  Naturally, the signal is very heavily clipped.  A cap across R6 would do wonders to help smooth out the resulting distortion.  For instance, a 47pf cap would roll off high end starting around just under 3.4khz, eliminating the buzziness.

4) The collector output of Q1 goes to flip-flop IC2B, which divides the signal it sees by 2, producing an octave down.  The output of IC2B goes to the other half, IC2A, and gets divided down by 2 again, yielding divide by 4 overall, and a note 2 octaves down.  As has been mentioned by others, there is no reaon why a person could not insert a switch to direct R11 to *either* pin 13 or pin 1 of IC2, to select between one or two octaves down.  I would imagine the biasing of Q1 is important here since the flip-flop does not divide everything it receives, just the content above a certain threshold.  I don't know how to do it, but it stands to reason that one could conceivably bias Q1 in a manner that results in triggering IC2 *without* requiring a fuzzy input signal from IC1B.

5) Q2/3 provide both buffering and gating of the fuzz and octave signals.  Their collector outputs feed the panning/blend control formed by R20 and R16/17.  Think of R16 and one leg of the pot as forming an attenuator, and R17 and the other leg of the pot as forming another.  As you attenuate one signal more, you attenuate the other one less.  The output of this attenuator/blend network is mixed passively via R18/19 and fed to the output pot.

6) There is NO tone control on this unit, other than what the blend pot achieves.  The flip-flop puts out a square wave which is not rounded off by much of anything except C9, which also rounds off the fuzz signal as well (global roundoff).  One of the things that people often complain about (and which they like about the PAiA Rocktave) is that you can't independantly vary the tone of the octave down.  Often, muter sounding octaves are a more pleasing and palatable addition to one's sound.  How could one achieve this in the BB?  Simple.  Take C9 out and move it so that it goes to ground from the junction of R17/R19.  If you want to get deluxe, get yourself a 3-way toggle (SPDT, centre-off), and have it select between .0068 (buzzy) and an additional .01 or .022uf cap in parallel for considerably "warmer" sounding octaves.  If you feel like it, you can do the same for the fuzz channel too atthe junction of R16/R18.  Being able to separately vary the tone of each channel AND their level balance will provide a great deal more flexibility in the unit, and likely a lot more pleasure and reduced frustration as a player.

All of this being said, it IS a monophonic unit and can only produce octaves of a note at a time.  Chords will confuse it.