Green Ringer Alt?

[orangecountylumbertruck]

I've almost got enough spare parts for a Green Ringer:

http://www.beavisaudio.com/schematics/Images/Green-Ringer-Schematic.png

I don't have any 2N5088s, but I've seen people replace them with 2N2222s or 2N4401.  I've been using 1N4148s for D1 & D2, trouble is, I'm not really getting any octave / pitch shift.  I am using a 2N3906 for Q2, maybe it's an orientation issue, or perhaps it's my makeshift substitutions?  I seem like I'm getting a little dirt, just no octave boost.

[MaxPower]

The magic seems to happen where the 2n3906 and diodes are. Did you match the diodes? Also, make sure R8 and R9 are both 68K. All too easy to put a 680, 6.8K or something by mistake. If no one helps, try LTSpice or Tina-ti to see what kind of voltages you should be getting at various points in the circuit.

As far as transistor substitution goes, check the data sheets. They should have similar gains (beta, hfe, whatever).

[thehallofshields]

I seem like I'm getting a little dirt, just no octave boost.

Try boosting the front end and rolling off treble. In my several builds, the circuit just didn't have enough gain to drive the diodes consistently, but when I drove the Ringer with a compressed fuzz (instead of the Q1 stage) and the "Green Ringer Filter Mod" that you can search for, the octave just jumped out on every note and sounded great.

If it still doesn't work, check your resistor values around Q2 to make sure that your Phase-Splitting is balanced.

[orangecountylumbertruck]

I looked at the datasheet for the 2n5088 and its seems to be a much higher gain transistor than all the ones I have laying around, mostly 2n3904s and 2n2222s.  I imagine that's gotta be part of my problem.  Even when using the 2n3904s and some fuzz driving the ringer, I didn't get very good results.  I'll have to order a couple 2n5088s and give that a try.

Thanks for the help folks!

[thehallofshields]

You have a Silicon PNP in Q2 Correct? You haven't say, put a 2n3904 where a 2n3906 should be?

[orangecountylumbertruck]

Nope, I hade a 2n3906 @ Q2.

[orangecountylumbertruck]

I breadboarded this up again yesterday and I totally see what your saying about the treble and gain.  I was using 2n3904s at Q1 & Q3, and a 2n3906 at Q2.  If cut the treble I could hear the desired effect once I got above the 12th fret, anything under that was pretty unnoticeable.  I'm going to play around with a couple other schematics or maybe put in a small boost before the ringer.  Thanks so much for y'alls help!

[Mark Hammer]

The difficulty with octave-up fuzzes is that they double the frequency of everything.  If the guitar signal was a sine wave generator, that would be fine.  But it isn't.  The result is that the doubled fundamental gets lost amid all the additional harmonic content.

I'm not knowledgeable enough, but I am extremely curious about the role of the feedback network from Q2 to Q1 in the Foxx Tone Machine.  The Foxx has arguably one of the best, and most robust octave-ups among the many various units out there.  Others may sound pleasing, but the Foxx has an octave you can easily hear over a significant chunk of the fingerboard.  My sense is that the feedback network "prepares" the signal prior to doubling in a way that works in its favour.

[thehallofshields]

So... Q2 is a Phase-Splitter with the Diodes pointed in the opposite direction as the GR because.... the diodes are biased (Vs->100k->Diode->100k-Vg) to have a trickle current like the GR?

[thehallofshields]

I realized this morning that the Danelectro French Toast I've had in my closet for 10 years is a SMC Foxx Tone Clone. Mark is right, it does more or less break that 7th fret rule.

Looking at Feedback Network raises a few thoughts:

First, I'm surprised that it doesn't unbalance the Rectification. I guess the 4.7k -> Ground must really outweigh the >100k path to Q1's Base.

Second, I think this circuit could benefit from an LPF on the input side, could the 1nf Cap be filtering some highs?

Third, I recall someone somewhere calling this an implementation of the Fuzz Face's 'Negative Voltage Feedback'. I think that's a reasonable theory because you are basically getting Q2's Emitter tied to Q1's Base via 150k Resistor. Before trying to find the magic, we should first consider the possibility that Q1,Q2 are forming a clipping stage and creating compression for more robust Octaving.

[Mark Hammer]

It's the range of the "scoop" in the feedback, created by that two-cap/three-resistor network, that I am convinced is responsible for the robustness of the octave in the Foxx.

I guess the experiment to breadboard is to build everything up to, and including the Q2 phase-splitter section, and look at the output (emitter OR collector) with the 1nf cap, and/or the 100nf cap to ground, omitted.

[thehallofshields]

I'm sorry. What do you mean by 'scoop'?

[Mark Hammer]

Look at the midscoop network on the output of the Superfuzz, Shin-Ei FY-2, or any of a wide assortment of fuzzes that aim for a big bottom/searing top tone.  That's pretty much what you see in the feedback path from Q2 emitter to Q1 base.

[thehallofshields]

Thanks Mark. I would say that the Mid-Scoop to achieve a more consistent Octave effect goes against conventional wisdom, but I can't argue with results.

I've seen some complaints on other forums that the Tone Machine's Fuzz doesn't 'cut' as well as others, which most attribute to the Tonestack, but I noticed that it lacks the Mid Dumping Resistor -> Ground that the Muff has. The circuit now makes sense to me.

[snap]

isn`t midscoop in a feedbackloop a midbump overall?

[Mark Hammer]

Thant's my naïve understanding.  Which probably accounts for why the doubled fundamental sticks out so much on the FTM, as opposed to being buried underneath a pile of doubled harmonics on many other octave-up units.