Green Ringer.....(whiskey tango foxtrot, over?)

[thermionix]

So I decided to breadboard a Green Ringer, because...why not?  I followed this GGG schematic:

http://www.generalguitargadgets.com/pdf/ggg_gro_sc.pdf

From the soundclips they provide, seems like it should be fairly clean with a clear octave effect.  But I'm getting a crappy fuzz with little or no octave effect.

Details.  For Q2 I used the only 2N3906 I have, hFE about 205.  They recommend low, I don't know if that's low enough.  Q1 and Q3 are 2N5088s, unmeasured.  They say those don't matter so much.  Resistors are all 1%, so I consider those "matched" where appropriate.

I'm trying two sets of diodes.

First set is Ge (1N34A), closest matching pair I have is about 10mV apart.  I guess that's not close enough, because I get virtually no octave, just crappy fuzz.

Second set is Si (1N4148), dead on matched.  I get some octave, but less than what I hear in the samples, and still crappy fuzz.

Both of these setups sound pretty cool in front of my FF, but no Band of Gypsies level goodness.

Just for shiggles I plugged the Ge setup into my Rat, and while I got no octave, it made one of the coolest distortion sounds I've ever heard from pedals.  Smooth as all get out, it took the raspy edge away from the Rat tone, and I guess lowered the overall distortion level just a bit.  Weird.

Still I'd like to know if there's something I should be doing to make the GR sound correct.

Any input is appreciated.

[EBK]

...but no Band of Gypsies level goodness.

The not sounding as good as Jimi problem is always caused by user error. 

[GibsonGM]

The sweet, sweet sound of a ring mod  (LOL)...

[duck_arse]

I can't help except to say - there has been a few threads over the last 12 months on getting more ring from a ringer. my search didn't find the one I was thinking of (Mark Hammer might be along soon), but here's 2 3 links anyway.

http://www.diystompboxes.com/smfforum/index.php?topic=112126.0
http://www.diystompboxes.com/smfforum/index.php?topic=110031.0

http://www.diystompboxes.com/smfforum/index.php?topic=113381.0

[anotherjim]

As clean guitar is very asymmetrical, it breaks down the logic of getting an octave up by rectifying. Carefully balancing the rectifier will not help.

As always, neck pickup, tone fully rolled off, then hunt for the sweetspot on the neck to give it as close to the fundamental notes as possible.

If it still don't sing like a choirboy, we have to suspect build error or try a different guitar. PAF class 'buckers seem the most likely to work for me.

[amptramp]

The Green Ringer is an attempt to get fullwave rectification of the input.  It works, but it is dependent on the characteristics of the diodes.  Ignore the power supplies as shown and look at the action of the circuit:



The explanation of how it works is shown on this site:

http://www.electroschematics.com/6761/precision-full-wave-rectifier-circuit/

Putting the rectifier diodes inside the feedback loop of an op amp gives you diodes with no more than a millivolt of drop because the gain of the op amp overcomes the drop.  You can use normal silicon diodes like a 1N4148 and the diode drop is negligible.  It minimizes the crossover distortion that occurs in the standard Green Ringer when the voltage is below the conduction voltage of both diodes.

[Plexi]

I would try to push it...with a LPB.

The sweet, sweet sound of a ring mod  (LOL)...

Smooth as cream (?)

I skip this one and goe for a Foxx Tone Machine...

[thermionix]

As always, neck pickup, tone fully rolled off, then hunt for the sweetspot on the neck to give it as close to the fundamental notes as possible.

If it still don't sing like a choirboy, we have to suspect build error or try a different guitar. PAF class 'buckers seem the most likely to work for me.

I quadruple-checked for errors before posting about it.  Guitar has P-90 in bridge and PAF in neck.  Will try again with the tone rolled off.

But is the GR supposed to be fuzzy?

[Mark Hammer]

1)  Yes, it is fuzzy.

2) Some sort of boost ahead of it helps.  A compressor would be optimal.

3) Use schottky diodes instead of germanium or silicon.  Matching helps.  Ideally, you want a pair with Vf below 200mv.

4)  A back-to-back silicon diode pair, in series with a 1-2k resistor, all going to ground from the output, helps by keeping the level fairly steady, so that you can hear the octave bloom as you hold a note.

[thermionix]

Thanks Dr. Hammer.  I actually did put my dynacomp in front for a bit, but I had fuzz on after so I guess I didn't really hear the change too clearly.  It was very late and I was trying to keep volumes way down too.  I'm about to go mess with it all again.  I don't have any Schottky diodes, guess I need to stock some.  I'll check out the mod you suggest too.

[anotherjim]

Funnily enough, although Ron has shown a proper precision full wave rectifier, I find that the worst sounding octave up scheme of them all. Very harsh fizz.
I think the zero crossing dead spot in the Ringer diode, does at least alleviate the narrow spike where the 2 half cycles join that you get with a precision rectifier.

[amptramp]

If you don't like the precision rectifier, you could add a resistor from the base of Q3 to ground to keep the diodes both slightly forward biased so you could get the sound of a rectifier with maybe a 0.1 volt drop so you could make any diode work.  Perhaps instead of going to ground, it could go to a voltage above ground but below the anode voltage.  You could make R10 a pot acting as a diode bias control going to the bottom of the resistor that goes to the Q3 base.  There must be a sweet spot in there somewhere!

[thermionix]

Ah, the plot thickens...

So I went and hooked this back up, still had the Ge diodes in there.  Still no noticeable octave, but now it is clean, not fuzzy.  I mean very clean.  Somethings going on...

So I had recently mounted my little breadboard on an unused black shelf board that I jigsawed in half.  Did the aluminum angle strips to mount pots and jacks, plan was to buy at least 3 more little breadboards and snap them together.

Well, turns out the black surface of the shelf is conductive.  I put my meter probes on any two places and I get about 175K.  I guess it contains carbon to make it black.  My BB was stuck on with the double-sided tape that came on it, and I guess I had some component leads poking through that and screwing up the circuit.

So I went to peel it off, stuck pretty good.  Pried it off with a knife.  Double-sided tape stuff tore and pulled the connector strips out of the BB.  Ugh!  I can rebuild the BB, but for now I just put it aside.  I'll probably keep the shelf, but add a layer of plastic to keep leads from poking through.

[anotherjim]

Ouch!

[amptramp]

Ah, the plot thickens...

So I went and hooked this back up, still had the Ge diodes in there.  Still no noticeable octave, but now it is clean, not fuzzy.  I mean very clean.  Somethings going on...

So I had recently mounted my little breadboard on an unused black shelf board that I jigsawed in half.  Did the aluminum angle strips to mount pots and jacks, plan was to buy at least 3 more little breadboards and snap them together.

Well, turns out the black surface of the shelf is conductive.  I put my meter probes on any two places and I get about 175K.  I guess it contains carbon to make it black.  My BB was stuck on with the double-sided tape that came on it, and I guess I had some component leads poking through that and screwing up the circuit.

So I went to peel it off, stuck pretty good.  Pried it off with a knife.  Double-sided tape stuff tore and pulled the connector strips out of the BB.  Ugh!  I can rebuild the BB, but for now I just put it aside.  I'll probably keep the shelf, but add a layer of plastic to keep leads from poking through.

The black mat is designed to be conductive for ESD (electrostatic discharge) prevention.  Definitely you should keep it and just insulate the back of the breadboard.

[EBK]

I'm reminded of the time in college when I was having a lot of trouble debugging a breadboarded circuit.  Everytime I would start measuring things, I would get only erratic, intermittent results.  When I stopped trying to measure, it apparently worked fine.  Turns out the breadboard power supply terminals (those familiar screw-down banana jacks) were shorting on the stainless steel workbench whenever I was pressing down to take my measurements. 

Luckily, my copy of Electric Circuits, 5th edition, by Nillson and Riedel, had the answer*, and the problem was solved.

*Once the breadboard was placed on top of that book, it couldn't reach the workbench to short out.   

[thermionix]

The black mat is designed to be conductive for ESD (electrostatic discharge) prevention.  Definitely you should keep it and just insulate the back of the breadboard.

Well it's not a black mat, but a leftover shelf from some old flat-pack furniture.  I doubt it was intended to be conductive, but I can see the benefit in this case.  Weird thing about the breadboard, it came with a copper (brass?) plate to stick on the bottom, which I didn't use.  Seems for people who do stick the plate on, the component-lead-poke issue would be a problem for them too.

Edit:  Having one of those "derp" moments.  The connectors inside the breadboard are solid on the bottom, shouldn't be any component leads poking through.  Back to not knowing why I had crappy fuzz one day, clean the next.  Got the BB put back together and gonna rebuild the Green Ringer, will see what happens this time...

[thermionix]

Well I suppose it's working correctly now.  Don't know what's different, but I'm getting plenty of octave effect, using the same Ge diodes that were giving me none yesterday.  Actually all the same components, but some surely traded places.

On its own, pretty horrible sounding pedal.  Crappy, gatey fuzz with octaves.  Going into my FF it sounds great!  Band of Gypsies out the wazoo (Eric!).  No longer sounds good in front of the Rat.  Awful, really.

I'm curious what was going on yesterday when I got a sterling clean sound out of it.  I guess there's no way to know, but it sounded like a perfectly healthy preamp or buffer, not a malfunction.

[thermionix]

Just bringing this back up to make a correction.

I was transferring this from the breadboard to vero (my first vero!) and I noticed I had made an error on the BB.  I had Q2 backwards, with the emitter going to ground like usual.  That was the case when I was getting no octave and when it seemed to be working later.

Now that it's really correct, it sounds about the same, but I think a little more octave.  Still awful sounding on its own, but great through the FF.  Seems the circuit works with Q2 oriented either way.  Just maybe a little better when it matches the schematic.

[PRR]

No voltage measurements?