Some questions about Joe Davisson's Shocktave

[Ben N]

For your reference: http://www.diystompboxes.com/analogalchemy/sch/shocktave.html

Having just re-read the Anderton Rocktave article for the twentieth time, and thinking abou the suposed benefits of compression and low pass filtering for any octave, up or down, it occurs to me to ask:

(a) What is the purpose of the emitter follower input stage on the Shocktave?
(b) Has anyone ever tried   Vulcanizing the Shocktave by adding a diode to the base of Q2, and if so, what happens to the 10k resistor?
(c) How about the GFR/Processaurus LPF mod for the Green Ringer (http://www.diystompboxes.com/smfforum/index.php?topic=32326.0)--would that work well in the Shocktave?
(d) And the all of the above question: What do you think about a Vulcan/GR/Shocktave combination: Vulcan input stage with emitter-bypass gain control, then a follower driving the LPF and splitting off into the GR rectifier and the Shocktave freq2voltage converter, with some kind of simple 3-way mixer at the end.

Thanks,
Ben

[Jered]

  Throw it on the breadboard and give it a try! Experimentation is my favorite part of DIY. It's also a great way to learn. Hands on, you can't beat it.
  Good luck and have fun.
  Jered

[Ben N]

Fair enough. I still would like to get anyone else's experience or theoretical perspective before I start, just for guidance.

In particular, I am puzzled by that e-follower input stage, and what to do about it.

[Ben N]

bump--anyone on the Shocktave input stage?

[ambulancevoice]

the shocktave input stage is just a high gain pre-amp to drive the octave stage
you could put diodes after the .1uf (the one under the .47uf cap that leads into the octave stage) in clipping configuration and make this thing a distortion with an semi clean lower octave to mix with it

[Ben N]

Thanks for the reply, AV.

I think maybe I wasn't clear--I understand that the two first trannies together are a preamp. But that first tranny is configured as an emitter follower (see, e.g., http://www.dself.dsl.pipex.com/ampins/discrete/ef.htm), so unless I am mistaken, its voltage gain is slightly less than unity. And while that would make a great current driver in front of a low impedance load, I don't get what the point is ahead of a common source amplifier. I'm sure Joe knew what he was doing--I'd just like someone to 'splain it to me before I go tinkering with it.

Also, as for the diodes, I'm not looking for clipping, but for compression, a la the Vulcan series diodes. Just trying to figure out the best way to accomplish that.

Anyone? (Is it just me?)

[ambulancevoice]

Thanks for the reply, AV.

I think maybe I wasn't clear--I understand that the two first trannies together are a preamp. But that first tranny is configured as an emitter follower (see, e.g., http://www.dself.dsl.pipex.com/ampins/discrete/ef.htm), so unless I am mistaken, its voltage gain is slightly less than unity. And while that would make a great current driver in front of a low impedance load, I don't get what the point is ahead of a common source amplifier. I'm sure Joe knew what he was doing--I'd just like someone to 'splain it to me before I go tinkering with it.

Also, as for the diodes, I'm not looking for clipping, but for compression, a la the Vulcan series diodes. Just trying to figure out the best way to accomplish that.

Anyone? (Is it just me?)

yeah i know you weren't looking for clipping, i just thought id give you some ideas
id say, just build and enjoy!