Cool Pedal Alert!

[Gary]

Tried Tim Escobedo's FET Driver last night.  I suggest you try it, too.

http://www.geocities.com/tpe123/folkurban/fuzz/snippets.htmlWow!%20%20I%20wish%20I%20hadn't%20taken%20so%20long%20to%20try%20it.%20%20It%20sounds%20pretty%20amazing.%20%20Nice%20response,%20small%20parts%20count,%20great%20high%20and%20low%20gain%20sounds.%20%20Highly%20recommended.%20%20It's%20astounding%20it's%20been%20sitting%20there%20unnoticed%20since%20March.Thanks%20again,%20Tim.%20%20Great%20work.

[Gary]

http://www.geocities.com/tpe123/folkurban/fuzz/snippets.html

I hate computers.

[Paul Marossy]

Hmm... I missed that one on Tim's site. Did you have much trouble tweaking the resistor values to get it sounding good and getting the right voltage on the drains of Q1 & Q2?
I myself would probably use trimpot for all of those...

[george]

yeah

[Gary]

The first resistor I had to change to 100k, the second drain setup was the stock two 47ks.  I had drain voltages of 4.8V.  It's definitely worth breadboarding to see if you like it.  I do, and will build it into a pedal with some minor tweaks on the caps to get my favorite voicing.  It's very close as is.

[WGTP]

How does it compare to Grace, SRPP and Meteor type circuits? You new this was coming.  :wink:

[Gary]

WGTP,

It compares nicely.  It isn't as high gain as Doug's Meteor.  It is about the same gain as the old Grace 2.  It has a nice "thump" to it that doesn't exist on designs I've seen so far.  Some may like that (like me) and some may not.  It is realtively high gain, but not overly so.  Think Marshall, not Mesa.

I tweaked the bypass and coupling caps to cutoff the sound below 100Hz.  It sounds really good.  I tried adding a simple LPF to the output, but that kills the low Z output.  The output power of this circuit is very high.  The LPF dopped the volume by half, but that's due to loading.  It sounds great either way.  If you set your amp a little dark, you don't need to filter out any highs in the circuit itself.  It is quite nice.  I have hardwired the gain control Tim shows and I use the guitar volume to roll the grit back.  It works very well that way.  It can go totally clean from the guitar volume.  It almost sounds like that project I was showing you awhile back, but didn't post.  If you remember.  I like Tim's deal better, because of the smaller part count.  You get atleast 9/10 of the sound of my last project.

[WGTP]

When I first saw the bootstrap circuits, I was wondering about building both the Jfet and the Bi and (you guessed it) running them together.  I guess you could use 2 of the Jfets and get additional gain.  Hmmmmm.

[Gary]

Or just use two of the bootstrapped sections into each other...  Double Hmmm...

[Paul Marossy]

I drew up a PCB layout this morning and will try to build it this weekend. If it works OK, I'll post it for anyone who is interested.

[Gary]

Paul,

Post your opinions on this circuit, if you will.  I'd like to hear from someone else to see if I'm insane.

Thanks!

[Paul Marossy]

OK, sure, I'll let y'all know what I think about it. I etched the board, populated it and soledered it all up last night. I'll be testing it sometime today.  

[Vasiliok]

Just breadboarded this circuit.
It gives very high gain.
I'd say too much gain for my taste... :shock:

Replaced first 330k pot with 33k pot. Still very high gain.

Added simple one knob tone control. It can shape the sound the way I like: more bass, less highs...

So... Very simple good sounding circuit.  :wink:
Try to add tone control!!!

[Paul Marossy]

Well, I fired it up last night and it has a lot of gain, but a lot of noise, too.
I looked at the schematic and it notes that the drain voltage on Q1 and Q2 should be 1/2V+...

I put a 100K trimpot in place of the drain resistor on Q1, and I measure 4.5V on the drain with 100K of resistance. I used the two 47K resistors as shown on the schematic on the drain of Q2, and that measures about 3.3V

I checked my layout against the schematic and my pinouts for the transistors, too. I can't find any obvious mistakes. Any ideas why my drain voltages would be that high? All J201s have the same pinouts, don't they?
I guess I'll have to check my layout again...

[Gary]

Paul,

You may have to twiddle those 47k resistors over the second jfet.  I had to change the first drain resistor to 100k also.  Try other j201s at the scond spot, or twiddle those resistors.  Be careful, this circuit has LOTS of output power.

[WGTP]

Is there any thing to be gained by controlling the amount of "feedback"?  

I assume that J202's will work in this?