Two Build reports

[jmusser]

I took a little time away from the XORUS research insanity, to build a couple pedals I'd had bagged up to build for awhile. First up, was the Neoctavia. Wow! That one there is a real screamer! It has several aspects of the Bobtavia, but it is its own beast. You don't have to wonder if it's an up octave box or not, because it will have blood running out your ears and down your neck if you play it more than 10 minutes! The up octave seems to be all over the finger board, but of course it's way more evident up above the 10th fret like they all are. The only real exception to this, is Tim's Octup Blender, which gives such a high amount of squarewave buzz with up octave products in it, that the transistion from the lower part of the neck to the upper part of the neck is virtually seamless. Anyway, the Neoctavia is a great up octave circuit. In the archives, there are several mods to try on this beast, but I don't think I'd try a session of mods with this thing without ear plugs. Next, I built Joe Davisson's Vulcan Overdrive, and like it a lot. I personally believe I like it better than his Blackfire. The Blackfire does better with my tube amp, where the Vulcan does better with the SS amp. I believe this is due to the diode copression between each stage, like he uses in the Antiquity Fuzz, that makes it sound more tube like in a SS amp. When you use either in the tube amp, I feel that you loose the versatility of that tone. Both the Blackfire and the Vulcan have very good sustain. The Blackfire has almost Big Muff sustain, which I am guessing is from the extra high gain stages. I still don't like either one quite as well as the 3 Legged Dog in my SS amp. It just happened to be the one those marriages made in heaven. This is only personal preference of course, and has to do more with my equipment probably than it does with the actual circuits. So far, I haven't built a Davisson circuit I haven't liked. I'll give one more plug for his Antiquity Fuzz. It does for the SS Amp, what the germanium Fuzz Face does for the tube amp. So far, it's been the closest thing to getting the Fuzz Face tone through a SS amp that I have seen, and if you've only played it through a tube amp, you'll never know. To me, it just doesn't have remotely the impact on your tone in a tube amp as it does in the SS amp. I don't know if this was intentional or not, but it sure seems to have turned out that way.

[tungngruv]

Hey JM, listen to my Neoctavia w/ a Joe gagan fuzz ahead of it. I have always thought this was one of the best D.I.Y. Octave up's.
http://www.tungngruv.com/sounds/Neoctavia.mp3

[RDV]

Hey JM, listen to my Neoctavia w/ a Joe gagan fuzz ahead of it. I have always thought this was one of the best D.I.Y. Octave up's.
http://www.tungngruv.com/sounds/Neoctavia.mp3

It helps to be able to play like that too.

Is that through an amp?

RDV

[MartyMart]

WOW  !!
I can play like that too ..... if I double the speed of the recording ! 

Great noise 

Marty.

[Caferacernoc]

How does the inline diode cause compression in the Vulcan Overdrive? I don't get that. My understanding of diodes tells me it would cause gating. Thanks.

[jmusser]

Nice sample. It is a wicked beast to be sure. As for the diode compression, that will have to be directed to Mr. Davisson. He says that's what it's there for, and I can varify that is the tone you get out of it, and that it does work. The "How" part of I'm not sure of.

[tungngruv]

 

Is that through an amp?

Yes, through a clean Marshall, only the gain from the fuzz part of the SkyRipper, then through a Shure 58 into a 4 track.  It gets the idea across. Really a great sounding upper octave when used with a fuzz, by itself it's not nearly as cool sounding.

[Joe]

The diode is biased to be only slightly on. In this state, small signals will pass through the diode unaffected, because the resistance of the diode is small when it conducts. But a large signal peak (from a previous transistor stage, for example) overcomes the slight biasing of the diode and causes it to become reverse-biased in proportion to the size of the peak. The resistance of the diode increases with the level of reverse-biasing.

If the diode were heavily biased, it would take a much larger signal peak to cause reverse-biasing. The values were chosen to improve the sound without sacrificing too much gain. Bipolar transistors like the 2N5089 have a huge amount of gain available, so you can pretty much program it how you want. JFETs also work, but they have very low gain, which is why the JFET Vulcan has large drain/source resistors. That compensates for the gain loss, otherwise you'd need 5 stages (which is ok, but more complicated.)

[jmusser]

Thanks for the "How" part Joe on the diode compression. Do you find what I'm saying to be true about the compression diode circuits sounding better with SS Amps? It's not that they don't sound good with the tube amp, it's just that tubey tone really shows through in the SS. To me anyway.

[JimRayden]

I still don't actually get the compressing effect of the diode... I've always thought that series diodes cause crossover distortion....

-----------
Jimbo

[Joe]

Don't think of it as a diode, it acts like a resistance which increases with the input voltage. As long as the stages are set up in a sensible way (similar to a typical tube preamp) the transistors can't really hard-saturate.

I agree about the SS amp, most of the pedals were designed using one. The character of tube amps vary widely, but I think typical SS amps just duplicate the signal without much sugar-coating.

[WGTP]

Joe may not appove, but I like to mix his different gain stages, Jfet Vulcan, Vulcan, Blackfire, Obsidian, with others like the Mu-amp, BMP, diodes to ground, etc.  There is that modular approach again.  Great stuff.   

How about a Vulcan stage into the Antiquity Fuzz for a diode compression Tone Bender???   

[Aharon]

Is that through an amp?

Yes, through a clean Marshall, only the gain from the fuzz part of the SkyRipper, then through a Shure 58 into a 4 track.  It gets the idea across. Really a great sounding upper octave when used with a fuzz, by itself it's not nearly as cool sounding.

Yeah,it was kind of thought of like that,to go with another pedal,to add octave to your favourite pedal really.
Aharon

[Aharon]

I took a little time away from the XORUS research insanity, to build a couple pedals I'd had bagged up to build for awhile. First up, was the Neoctavia. Wow! That one there is a real screamer! It has several aspects of the Bobtavia, but it is its own beast. You don't have to wonder if it's an up octave box or not, because it will have blood running out your ears and down your neck if you play it more than 10 minutes! The up octave seems to be all over the finger board, but of course it's way more evident up above the 10th fret like they all are. The only real exception to this, is Tim's Octup Blender, which gives such a high amount of squarewave buzz with up octave products in it, that the transistion from the lower part of the neck to the upper part of the neck is virtually seamless. Anyway, the Neoctavia is a great up octave circuit. In the archives, there are several mods to try on this beast, but I don't think I'd try a session of mods with this thing without ear plugs. Next, I built Joe Davisson's Vulcan Overdrive, and like it a lot. I personally believe I like it better than his Blackfire. The Blackfire does better with my tube amp, where the Vulcan does better with the SS amp. I believe this is due to the diode copression between each stage, like he uses in the Antiquity Fuzz, that makes it sound more tube like in a SS amp. When you use either in the tube amp, I feel that you loose the versatility of that tone. Both the Blackfire and the Vulcan have very good sustain. The Blackfire has almost Big Muff sustain, which I am guessing is from the extra high gain stages. I still don't like either one quite as well as the 3 Legged Dog in my SS amp. It just happened to be the one those marriages made in heaven. This is only personal preference of course, and has to do more with my equipment probably than it does with the actual circuits. So far, I haven't built a Davisson circuit I haven't liked. I'll give one more plug for his Antiquity Fuzz. It does for the SS Amp, what the germanium Fuzz Face does for the tube amp. So far, it's been the closest thing to getting the Fuzz Face tone through a SS amp that I have seen, and if you've only played it through a tube amp, you'll never know. To me, it just doesn't have remotely the impact on your tone in a tube amp as it does in the SS amp. I don't know if this was intentional or not, but it sure seems to have turned out that way.

Thanks for the reports and glad you liked the NeOctavia.
Aharon