Introducing: The Hard Pusher!

[KerryF]

Hey guys.  Well heres one of my Booster designs from my booster research.  This is the second, less complex one that I was doing for the booster thread I had.  This isnt the main one.  I will get that schematic done and post that when its finished.  I also have a fuzz pedal design finished but still in the process of stuff with that, another booster, and this one.  I designed all 3 of those (fuzz, booster 1, and booster 2 [this one]) all in 4 days  .

So anyway... Introducing the Hard Pusher!!!  Heres some info on it:
*Input to a High Pass Filter (HPF)
*A silicon diode pushing the signal through a boosting JFET
*A Shaka Braddah style MOSfet diode to diode pushing the boosted signal
*A Low Pass Filter (LPF) through a Low Cut Filter creating a Band Pass Filter
*Volume/Boost control to output

Schematic:


Heres something from Markm with my little expaination for it:

Looks pretty cool Kerry!
Little bit of the "JFETvulcan" influence with the 1N914 there....nice though.

Thanks!  I got the idea for the diode before the JFET and then the mosfet diode and diode from the Clipboard from Dano12.  I built that and all it is, is a passive clipping pedal with DIP Switches for each diode.  When you turn on different combinations, it boosts and adds some nice tone.  So I decided to just use the diodes like in that circuit as boosting inside a booster.  This should add a harder "push" to the JFET boost and probably cause a nice sound (maybe something like a pushed tube breakup).

Please let me know what everyone thinks!  Tell me if theres any problems I need to fix or anything.  Hopefully this is a bit different than most people have seen before.

Kerry 

[Meanderthal]

 Just a suggestion- you may want to insert a recovery gain stage after the bandpass filter... they have a way of reducing gain...

[Dragonfly]

or...even better than a recovery stage...you might take a look at Mark Hammers "Stupidly Wonderful Tone Control"...seems like this would be a VERY appropriate usage for it....cool tone control, very little / no  signal loss...

still curious on the mosfet section though....

AC

[Dragonfly]

BTW...have you built this one yet, or is it a "design schematic" at this point ?

sound clips ?

AC

[KerryF]

Thanks for the suggestions.

The mosfet and diode are just used to push the signal.  Like in the Clipboard by Dano he has the different diodes on a DIP switch.  I built that and realized the tones all of the diodes add, and how the push the sound louder and make it sound better.  I decided to add these to push the sound inside the pedal.

I think a tone control would be a good idea for this.  Thanks.

This is just a design schematic.  Not tried it, but I plan on breadboarding it soon.  Just want to make sure no one finds any small problems before I test it.

[petemoore]

Just want to make sure no one finds any small problems before I test it.
  not sure you:
  won't be needing a gate bias resistor.
  that signal will pass the 1n34, or what it and the mosfet are intended to do...I don't know what exactly 'push' equates to, but the impedance of the input Mosfet is high...
  Will get much signal after the seriesed 1n34/mosfet.
  Whether/how much it matters which way the input diode faces.
 

[Mark Hammer]

or...even better than a recovery stage...you might take a look at Mark Hammers "Stupidly Wonderful Tone Control"...seems like this would be a VERY appropriate usage for it....cool tone control, very little / no  signal loss...

still curious on the mosfet section though....AC

Just a side note.  I was looking through a binder of schematics from Tim Escobedo's Circuit Snippets site (http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html) the other day and noticed that he had used the same tone control on his digital octaver (http://www.geocities.com/tpe123/folkurban/fuzz/dof.gif)  as early as January 2003, which beats my posting of it (mid 2005) by a long shot.  The idea popped into my own head quite independently after looking at something entirely different (I seem to recall it was an Aphex schematic), so there is no theft of IP.  All the same, Tim had this idea earlier so nods should go in his direction.  I may have popularized it and drawn attention to it as a potential add-on to circuits, but Tim had the good design sense to simply implement itlong before I did.  His insights into simple things that make big differences never ceases to amaze me.

Sorry for the interruption.  Carry on.

[KerryF]

Thanks for the info guys.

Like I was saying about the Diodes and MOSfets as diodes...  When I say "push" I am meaning that the sound will be mildly boosted through like when I tried the Clipboard/FlexiClip.  I decided these diodes would do a nice boost/push, then the JFET would boost this boosted/pushed signal louder, then the other diodes would push the boosted signal and maybe smooth it out.

[KerryF]

Updated schematic:

[KerryF]

Heres a little Breadboard layout without the Tone Control, just to an output capacitor and then out so we can test it.

[zyxwyvu]

On your updated schematic and layout, did you mean to remove the trimpot on the J201? Connected as it is, the 1N34 will only see +9v, no audio signal.

Edit: Also, you probably need a capacitor on the end to remove any DC voltage going out.

[KerryF]

Petemore said I didnt need the bias resistor.

I would be getting signal from the Transistor.

[zyxwyvu]

Petemore said I didnt need the bias resistor.

I would be getting signal from the Transistor.

I'm not quite sure if I misunderstood what he said, but if you connect any point directly to +9V, the battery will pull it up to that voltage. Without a resistor between +9v and the audio path, they cannot be at a (significantly) different voltage. I recommend breadboarding it anyways.

[KerryF]

Petemore... Can you please clear up what you said...  Thanks.

[petemoore]

  The source is 1k up from ground...so to speak, 'normal' value to see here.
  The gate on a Jfet gain stage must be exceeded by the source voltage, 'source higher than gate', I see no resistor pulling the gate toward...er...I see no gate resistor.
  Anything connected to 9v+ will be at 9V+, no wiggle room or room for the drain to swing, it's held at V+.
  A resistor there will bring it down,
  I would say use 50k+ as pot/pot resistor etc. to bias the drain, socket the transistor...get a transistor that'll bias with swing room on the D.
  To get the source above the gate I would use a big R to pull gate toward Gnd. See Fetzer Valve, Stratoblaster and those gain stages have these resistors.
  I think the mosfets super thin sheet of glass like conductance on it's input [Ie almost no conductance] will stop the signal path..

[Meanderthal]

 zyxwyvu certainly has a point about the missing output cap. You would have a very nasty DC offset without it. Like 9v or so. Among other things, this would make the pot crackle really bad...
Without any bias the FET won't do much of anything, not even fart. Not the same animal as BJT(which also would need proper biasing)
I'm afraid I don't understand the diode "push" concept at all... I understand clippers all right, but that aint what's happening here. Looks more like diode compression...

[KerryF]

Petemore- Guess I miss understood you.  I will:
*Put back that bias trimpot
*Make that pull down resistor larger (say 10k?)
*Take away that MOSfet so its only the diode.
*Add an output cap to the schematic

Meanderthal- I added an output cap on the Breadboard layout for prototype.  I forgot to add it to the main schematic though.  I will when I get home.

kerry

[KerryF]

Updated Schematic and Layout:





Petemore, or someone, can you check it out now and tell me if this looks better?  Thanks for the help!

[petemoore]

  Have you tried it?

[KerryF]

Planning on testing it today.  Just wanted to make sure the major visible problems and debugging in the Schematic was worked out.  Im hoping this works in the way I plan it to.  I am also planning on buying an Epiphone Valve Junior practice amp and hopefully the boost works especiallly good for tube amps.