Introducing the citrus boost.

[nelson]

Based on the orange MKII "boost" section, using a mosfet gain stage for high input impedence. Sort of inspired by the "super hard on" by zvex too, using negative feedback.

I havent built it, no idea if it works. Just an idea.






Comments, suggestions etc more than welcome.

[spudulike]

Sort of inspired by the "super hard on" by zvex too, using negative feedback.

Erm ... ?

[nelson]

Yeah?

Erm?



maybe not.

[Paul Marossy]

Sort of inspired by the "super hard on" by zvex

Your circuit looks quite a bit different than the SHO...

I havent built it, no idea if it works.

Got breadboard?! 

[nelson]

Sort of inspired by the "super hard on" by zvex

Your circuit looks quite a bit different than the SHO...

I havent built it, no idea if it works.

Got breadboard?! 

I have never seen an SHO schematic..or peaked inside...so not really surprised...just going by description by zvex....

I think it should work fine.

I will breadboard it at some point.

[The Tone God]

I have never seen an SHO schematic..or peaked inside...so not really surprised...just going by description by zvex....

You envoked the "Z" word which of course as you know brings about a range of reactions and with the recent flame out thing might still be a bit raw. I'm sure some are just curious.

Back to the Citrus. Bread it up and let us know how it works.

Andrew

[Johan]

looks cool..I do think the feedback is positive thou...be carfull with that one, or it might squeel...

johan

[petemoore]

  I can't tell you if you'll have to dicaround with the bias or not, looks interesting enough, and the feedback like that has to do 'something' It looks to + Feedback so that'd...enhance the output...lol...'enhance'...such a lovely word...as in 'enhance level of output", ...enhance the squealing...who knows...
  Although I can't vouch for whether it'd work, it looks like you've chosen interesting looking enough bias arrangements and topology for the circuit, which is ok, that it looks different too.
  Could it use static protection diode on the Mosfet like Mosfet Boost or Blue Magic?

[Paul Marossy]

Well, it's one thing to have knowledge about something. Sharing it is another matter. 

Anyhow, I am interested to hear some more about this Citrus Boost. Mostly about how it works and sounds! 

[nelson]

  I can't tell you if you'll have to dicaround with the bias or not, looks interesting enough, and the feedback like that has to do 'something' It looks to + Feedback so that'd...enhance the output...lol...'enhance'...such a lovely word...as in 'enhance level of output", ...enhance the squealing...who knows...
  Although I can't vouch for whether it'd work, it looks like you've chosen interesting looking enough bias arrangements and topology for the circuit, which is ok, that it looks different too.
  Could it use static protection diode on the Mosfet like Mosfet Boost or Blue Magic?

Yes it could.

[puretube]

Z-TRUS ?

need a vexoboard-layout...   

[lovekraft0]

My first attempt at breadboarding this went rather pear-shaped, and I couldn't get anything to bias right, so I kinda modded it until I could get it to work for me. The results are below:

I used a 2N7000 and a 2N5457, with the bias adjusted to about 5.25 -5.5 volts (I've found that's about maximum clean headroom, at least in my experience). I was having trouble with the feedback loop screwing up the cathode current of the MOSFET, so I moved the loop inside the coupling cap - kinda counterintuitive, but it works much better. Changed the MOSFET cathode bypass cap to let some bass through ( you might prefer a 22uF, or even a 47UF if you want massive bottom). The 220K "grid stopper" on the JFET gate was just a happy accident (hmm..., was that supposed to be red, red, yellow or red, red, red?  ) - when I replaced it with the original value (2K2), I didn't like the sound near as much, so I went with the "mistake". You could probably get away with a 10K trimmer - mine biased out at about 5.1 volts at 3.3K. The 100K/82K divider biased the MOSFET at about 5.3 volts on the drain.
It sounds pretty nice - good clean fun at the low end, with some bass rolloff and sparkle as you turn it up, and some fairly smooth "toobey" clipping rolling in towards the top. Sorry, no clips, at least until I get my computer sorted out. I didn't try bypassing the cap on the JFET, so that's still open for exploration - I think I'm gonna box this one up!

[Paul Marossy]

Thanks for the taste test lk. 

EDIT: You know, this is very similar in concept to the Blue Magic - a MOSFET pushing an FET...

[nelson]

awesome!