"Star-Fire" pseudo Two stage booster (new schematic)

[kvb]

Simple explanation:LPB>BMP tone>Jfet output - all sections modified

     Here is a booster idea that I have completed (boxed up). It is done, done. Not halfway done like too many others.
I got it working on the breadboard and decided that I would take it to completion without hesitation or endless tweeking.
Of course there was a little tweeking/testing to be done.  And even though I tried to have a "just get it done" attitude I spent a great deal of time figuring out how I was going to get everything into the regular (B size?) enclosure. I won't go into too much detail until I can post a pic. But lets just say that when the case is open you could barely squeeze a toothpick in there.

The effect uses two push-pull pots. These were actually the basis for the whole effect. Everything was built around them.
The effect also uses two stomp switches. One is On/Bypass, and the other is for added boost/gain.
I tried switching bypass caps on a 2n5089 (popped) and the a j201 (no pop).

This was actually the second try of a two stage booster with tone control. Well now that I think about it, there was much playing around between the 2X Si and this Si to Fet version. I tried using diodes for an overdrive sound but was continually annoyed by the Si's terrible crackle when the strings were hit hard.

The values on the fet come from a web page. This is the first time I've heard a fet (in a circuit I built) sound good. I've stayed away because three separate attempts on three different circuits (all with different biasing values) did not sound good and left me confused.

The effect works as intended. A fairly clean boost that adds dirt to notes that are hit hard. Then one can switch to a louder, dirtier sound with a stomp.

There is a tone control. Turn it to the treble side and there is almost too much. (I guess I wanted to see what a treble booster was supposed to do, or sound like.) In the middle the tone is mid scooped. On the bass side it is thick.
Pull the tone pot and the scoop turns to a hump = decent mid boost sound (in this mode the Star-Fire sounds very similar to the AMZ mosfet boost).  Pull the volume pot and the tone control is bypassed for a balls to the wall fet blaster.


I've also been dismayed by my inability to post pictures of schematics without having to hassle others borrowing cameras and computers, so I just sat here at the library with my "I'm posting a dang schematic TODAY! Arrrgh!" attitude and here you go . . .

I just hope there's not already an effect called "Star-Fire"

Turn it on and your guitar will have the sparkle of a super-Star. Hit the second stomp and you'll be on Fire!



http://www.aronnelson.com/gallery/main.php/v/kvb/Star-Fire+schematic.gif.html

Please excuse any drawing wackiness - I was hauling 'you know what' trying not to get kicked off this computer.
If anyone could tell me how to get this image bigger I'd appreciate it. There's the link to the big pic in my gallery.

Go ahead and pick it apart.

[petemoore]

  Very cool low parts count variable application circuit !
  nice work !

[Gus]

  First stage

What is your input resistance?  I can work it out but you should do the math.

What is the bias stability of the first stage?( hint, hfe and emitter Rs and the 100K)

Fet

what is your output resistance?

[Renegadrian]

Some Q's...
Is it possible to use normal pots and DPDT switches? Is it possible to do it on VERO/PERF board?! Have you got a layout for us to see??
Wait to see some pics!!! 

[Dragonfly]

Simple explanation:LPB>BMP tone>Jfet output - all sections modified

Nice work...

But I do have a suggestion....

it seems to me that a better order would be ...

JFET----->BMP Tone----->LPB

The reason being hi input impedance with a low output impedance....for most people (and their guitars) , a more desirable setup.

[kvb]

*In my haste to post the schematic I forgot to thank those who have done far more of this than I have. Besides the LPB and "The Fet Amplifier" By Graham Knott, my sources for this project were Joe Davissons overdrives (470k in-between stages) and a comment by Zaphod Phil (18 watt - one year ago) about a Fender Champ mod involving a switchable cap at the power tube for boost.

Thanks everyone for trying to teach me right. The advice I've been following is "use yer breadboard!"

Everything I've been doing for the last six months has been on the breadboard with my guitar plugged in the whole time. I've been working on the two stage tone tweeker idea for just the last two. All of my decisions have been made based on other people's schematics, a minimal understanding of the components involved, and by listening to the changes produced as I switch pieces around.

  nice work !

Thanks

you should do the math.

Sir, maybe I would feel a little better if the math made sense to me. I hope that does not sound disrespectful. The problem is that all of the reading I have done (not enough, I suppose) has not brought me any closer to understanding what the numbers mean. I think I will be lost until I have someone walk me through it - in person - not on screen.
So, I appologize for not knowing how.

Are you hinting that there is a problem? If so, I'm open to suggestions.  I'm pretty good at desoldering, too.


Renegadrian, you can always use any type of switch. They take up space, though. Effects with many switches need bigger enclosures.
I'll try to post pics and sound clips, but don't expect a layout. Even I will not be trying what I had to do to get this thing done, again anytime soon.
I'm also anti-layout. The first (and last) one I ever used had an error. Finding the error taught me how to read a schematic.

it seems to me that a better order would be ...

JFET----->BMP Tone----->LPB

Thanks, and I understand but . .

I'm pushing the tone section with a low impedance source (?) and I'm distorting the signal at the fet with the frequencies determined by the tone control.
Nobody ever told the guys at ROG that there is something wrong with using a fet for output a la Fetzer.
I'm making up for the LPB's low input impedance by adding the small bypass cap for some treble emphasis.
The LPB is also set at moderately low gain. It's near 1k instead of the 380 ohms. It also has the input resistor and both are meant to keep the LPB from distorting.

It sounds good.

The breadboard version is still up and running. If there are any suggestions I can easily try them out.


And lastly, I'm happy to have a design for others to discuss. Thanks for taking the time

[Dragonfly]

it seems to me that a better order would be ...

JFET----->BMP Tone----->LPB

Thanks, and I understand but . .

I'm pushing the tone section with a low impedance source (?) and I'm distorting the signal at the fet with the frequencies determined by the tone control.
Nobody ever told the guys at ROG that there is something wrong with using a fet for output a la Fetzer.
I'm making up for the LPB's low input impedance by adding the small bypass cap for some treble emphasis.
The LPB is also set at moderately low gain. It's near 1k instead of the 380 ohms. It also has the input resistor and both are meant to keep the LPB from distorting.

Ive designed single stage jfet boosters as well, and they can sound great...search "sparkle boost", for instance....it was simply a suggestion to try...something that ive had good results with over the years.

It sounds good.

Thats what matters in the long run.

[kvb]

Last night, I tested this up against the AMZ mosfet boost. There are similarities in terms of sparkle and drive at various tone settings on the StarFire compared to the mosfet.

With the tone control engaged, the StarFire is a little quieter than the mosfet. The StarFire with the tone bypassed and in 'Fire' mode is just as loud as the mosfet boost, but it has more distortion.

What the StarFire does with single coils is something very different than what the mosfet does. I can only describe it by saying the tone of the strings comes through almost blaringly. The treble is almost too much.  The string tone is crystal clear and the clipping is soft and warm. The jump from low gain to high gain also seems to work just right with the single coils.


As far as a layout is concerned, I didn't mean to sound unfriendly (unforumly?).  I could probably get a layout posted before I could get pics and sound clips up. So, I'll see what I can do.