Is there a simple octave up and octave down in one pedal?

[Ben Lyman]

Make the two diodes in the Green Ringer half both Schottky types and you'll be happier.  Trust me, it makes a positive difference.

Cool, thanks Mark! I got a pile of 1n5817, those might do the trick, eh?
Did you notice I put a 10k pot with a bypass cap on the emitter of the Green Ringer first transistor? Whoa mama!

[Mark Hammer]

Yep.  A bit of additional gain, via the pot, and a bit more sensitivity, via the diode swap-out, and the octave becomes more reliable and achievable below the 7th fret.

5817s are what I used.

[Ben Lyman]

I was looking at the EQD Tentacle and it looks identical to a Green Ringer except maybe this 100pF from input to ground pictured below.
Makes sense I guess to shave off some highs to get the best results from the GR so I tried it on the breadboard.
It didn't make much difference if any at all so I thought maybe I could try to simulate the same low pass that my guitar tone knob gives when turned all the way down.
I put a 22nF and it seemed to kill the whole signal, I guess it just sends everything to ground?
How can I simulate the same tone as my Tele or Strat tone knob rolled all the way down?
I have  250K pots with a 22nF cap in one guitar and 33nF in the other.

[robthequiet]

Probly make a traditional low pass, put a resistor inline in front of cap, maybe 10K and go from there. In addition to your tone pot.


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[amptramp]

That 100 pF on the EQD tentacle is there to avoid radio signal interference.  The base-emitter diode of Q1 forms a rectifying junction that can demodulate AM radio.  The 100 pF to ground swamps these signals (which are in the 530 to 1710 KHz range).  It may have a slight effect on the audio but that is not what it is there for.

[sergiomr706]

Maybe I didnt understand the meaning of this mod, but, its not supposed to remove high frequencies from the signal so the green ringer can do his work much better?

http://www.diystompboxes.com/smfforum/index.php?topic=32326.0

Kind of neck pu plus tone control rolled down?

By the way ben, i heard your modified gr with ge / si and really liked, sounded like sitarish to me, so cool, didnt you first tried that octave up for your actual octave up/down research? I have a lowrider tycho octavia clone foxtone and superfuzz but im tempted to build your ge/si. Good luck with your breadboarding

[Ben Lyman]

Rob- I tried a few takes on that idea and I think the resistor is lowering the guitar signal too much or something, I just couldn't get a good sound. I can't understand how a guitar with a 22nF tone cap can be working and passing a good strong signal but putting a 22nF cap in the pedal kills the signal completely. I still have much to learn 

Ron- Thanks again, that makes perfect sense. I did have that radio problem with my first build but including the input buffer seems to have solved it.

sergiomr706- Thanks, I have seen that filter mod before but never tried it because it has 6 extra parts but maybe I will have to give it a shot. My GR Fuzz project is a good one but I decided not to add any more fuzz to this one, it sounds really good with a Tone Bender or Fuzz Face but I don't want to add that in yet without an extra footswitch to toggle it on and off. In Fact the thing I have going now sounds really good with or without any fuzz so I'll probably leave the extra parts out and just use it with a separate fuzz pedal.

[Ben Lyman]

I don't know what happened before but obviously I did something wrong or bumped something loose when I tried the 22n to ground at the input. This time I tried the 3-pole filter from the Green Ringer mod and just put it right on the input. I took a couple parts off and settled on just the 220r and 22n. I want it at the input because the Shocktave benefits from it just as does the GR. I also remember something about a cap right here is "loading down" the guitar signal so is that bad? Should I move the filter somewhere else?

At Duck Arse's suggestion, I added a Bazz Fuss to the output and it really fits well with the theme. It needs a little attenuation so I squeezed a 100k fuzz pot in between.

Overall, sounds very good now, lots of different sounds available from all the controls too. I still wonder if the LPF at the input is a bad idea though.

[anotherjim]

The input cap will load down the guitar, but mostly only causing high cut - which is what you want. A big problem with old simple bypass switching that leaves the circuit input connected. Problem solved with true bypass.

Filtering like that means the 220R isn't really setting the filter frequency, the guitars own source impedance will be more significant. Not actually a problem if the input always is direct guitar of similar character. Any buffer pedal in between means the 220R then becomes the significant R in the RC formula.

[Ben Lyman]

Thanks Jim, I thought about putting it right on the buffer emitter (my Q8 above) then connecting the two signals to that but I haven't gotten that far yet. Seems like a weird idea and probably won't work anyway, I don't know.

[Cozybuilder]

Ben-
I'd remove the LPF at the input to the buffer. Doesn't the 2K7 and 22n from the buffer out (emitter) form a LPF with a knee of about 2681 Hz for the GR? Why not do the same concept for the Shocktave input? 100n then 2K7 and 47nF for a knee at 1255 Hz. The 100nF passes the full signal, not used in the LPF calculation. You could play with the R and C values (use the LP filter calculator for guidance):

http://www.learningaboutelectronics.com/Articles/Low-pass-filter-calculator.php#answer1

[duck_arse]

I have questions - how come the buffer emitter resistor is 220k in the shocktave, why so large?
- is you using a darlington in yer bazz?
- fuzz level instead of mix pot?
- are you any happier with the tracking now?

[Ben Lyman]

Ben-
I'd remove the LPF at the input to the buffer. Doesn't the 2K7 and 22n from the buffer out (emitter) form a LPF with a knee of about 2681 Hz for the GR? Why not do the same concept for the Shocktave input? 100n then 2K7 and 47nF for a knee at 1255 Hz. The 100nF passes the full signal, not used in the LPF calculation. You could play with the R and C values (use the LP filter calculator for guidance):

http://www.learningaboutelectronics.com/Articles/Low-pass-filter-calculator.php#answer1

Good idea Russ, thanks. I actually removed the LPF that was in the GR part when I added the LPF to the input. So maybe two separate LPFs coming off the buffer would be better I guess. I wonder if I could just have one single LPF coming off the buffer and connect the two signal paths to that LPF?

I have questions - how come the buffer emitter resistor is 220k in the shocktave, why so large?
- is you using a darlington in yer bazz?
- fuzz level instead of mix pot?
- are you any happier with the tracking now?

Duck- I used a Bazz Fuss schematic that I found on the web that has a 2n5088 and it works great. I think the only difference is the collector resistor.
No mix pot (yet?) just a gain pot on the high octave and another gain pot on the low octave for mixing, then the "Fuzz" pot to set the level into the Bazz.
Very happy with the tracking now after reading through the thread that I linked us to on the last page. Joe talked about it a little, so I had a trim pot on the collector, got 4v5 and found I needed a 12k resistor for best performance. It's not like a digital POG or Whammy pedal but I never expected it to be. It's very organic and sweet, even with the occasional jumping up from the lowest guitar notes.

[duck_arse]

[which collector has the trimmer? 12k not shown on yr dia.]

[Ben Lyman]

[which collector has the trimmer? 12k not shown on yr dia.]

That would be my Q4. Try a trimmer and maybe even start auditioning different diodes while adjusting the trimmer for about 4v5.

Joe refers to it as Q2 in the thread I linked us to on the last page. He says:
    It wouldn't be uncommon for the collector resistor to be 15k, 18k, or even 22k, whatever gets it in the ballpark of 4.5v
   The collector resistor acts like the top half of a voltage divider, with the transistor and emitter resistor making up the bottom half.

And Duck, I don't know why the Shocktave buffer has a 220k emitter resistor, I only copied it from the way it was drawn but I could try a 10k and see what happens.

[duck_arse]

well, I don't want to sound like an arse, but ..... your Q4 is in the ringer. and now I read that other thread, I wonder if the cut-down front-end, without centred bias, was the cause of the hopping and mistracking I was having on the bb. (we'll never know now.)

[Ben Lyman]

Sorry, my bad. I meant R4 on my Q1.
Here's an updated schematic before I go and try out Russ' idea of moving the LPF

[anotherjim]

If you don't want the uncertainty of the LP filter at the immediate input, I think it can be introduced inside existing circuit but would have to be in two places.
Shocktave cap to ground after R2 (10k)
GR insert 10k before C2 and add cap to ground. Adding the 10k shouldn't reduce wanted signal level into the GR by much.
Then it don't matter what's driving this confection, LP filter should do the same job. Each LP can be optimised a bit to suit.

[Ben Lyman]

Thanks Jim. Do you think it would've been optimal to have that extra 10k from buffer emitter to Green Ringer? Upper octave seems better with no resistor. I like this so far:


The separate filters are working pretty nice. The low octave always sounds best with a lot of filtering, so it gets the 10k and the 10n. It's a pretty good balance to allow some guitar tone knob control in either direction.
The high octave works best with only a little filter (470p) to allow for traditional Green Ringer sounds by turning off the low octave and turning the fuzz down to a minimum.

[duck_arse]

hey ben! I'm back at this, as the uboat, erm, sank. and I am surprised by how well the shocktave tracks, now the gain is more righter. one thing I've noticed about the flip/flop section is that the transistors produce quite a few small spikes as they do or don't switch on, which sounds as (relative) fizz in the low octave output. and, seeing as you have R21 there, if you wanted a cleaner low, you could split R21 into a pair of 47k in series, with 6n8 (to taste) from the mid point to ground to filter the spikes some.