new overdrive part 2 live and learn

[jneely]

So I completed the new overdrive I put together and took it from the bread board to the box. It was then I noticed the unbelieveable amount of hiss coming out of my new jewel.

Luck would have it I have messed with BS170's quite a bit and realized the RC4558 was amplifing the hiss of the mosfet. So a snip and a tuck here and there and the 4558 was now first and the boost second.

NO NOISE FULL UP! It makes my daddy-o sound like something a rookie would have tossed together.'



I had to adjust some of the values in the feedback loop to lessen the drive a bit but it no sounds perfect.

I'd love to share it a hear suggestions for improvments.

Anyone willing to take a handdrawing a post it?

Jeff

[RDV]

There is a schematic template at http://www.generalguitargadgets.com/v2/index.php?option=html&file=instructions/jdstmplt.htm which is extremely easy to use with MS Paint. Then when you get it drawn up nice you can open a free //www.photobucket.com account and download them yourself. I convert mine to a jif first cause it takes less time to load.

Looking forward to seeing your handi-work!

RDV

[jneely]

Thanks for the info here's my first rev.


http://img78.photobucket.com/albums/v255/JNEELY/SWEETLAVA3.jpg



:lol:

[jneely]

Already correcting myself :roll:

[jneely]

Sorry some cap values out of place in the first one :!: .


http://img78.photobucket.com/albums/v255/JNEELY/sweetlava7.jpg

[jneely]

chip voltages & zener protection is assumed.

[Transmogrifox]

Looks good.  I like that 2-pot idea you have going on there.  I can see that being quite useful for messing with the gain at low levels.  That's a good way to drive a MOSFET, too.  I haven't found a MOSFET type yet that isn't guilty of excessive noise compared to low noise BJTs.  Maybe that's why JFETs show up more often in FET distortion circuits around here.

Nice work :wink:

[jneely]

http://img78.photobucket.com/albums/v255/JNEELY/sweetlavarev3.jpg

This is the magic right here. Wow this thing sounds good now. It sounded great before but what an improvment switching the tail of the feedback loop to VR insted of ground.

The 4001 diode really makes it sound sweet.

Thanks RG for the "Tech of " section on your page.

Jeff

[RDV]

I love it when a plan comes together!

RDV

[Lonestarjohnny]

I could'nt see it on the first one but I got it on the third,  :lol:
Looks like a nice build jneely,  
Thank's for the look,
JD

[petemoore]

Thank you for sharring, J. Neely !
 I whipped up 1 batch of Sweet Lava, [cool name], sounds great so far, after only initial testing.
 I hope J. that you don't mind it being compared to a TS or SD, because it IS comparable, but I think the Mosfet in there puts a Smooth on the Clip [just my impression], whatever it is...I like it.
 Sounds thick/full, tonal quality, loads of drive, it's a 'keeper' for sure.
 Like a 'less snorky' sounding TS. Very nice indeed.
 I'm guessing the 500k is a drive knob?
 And "Zener"?,,,I have a 2N7000, no protection on it...I was wondering about that as I build...should I put something in there for 'longevity's' sake? Perhaps [didn't I see used for Mos protection] an LED?
 TS Lovers: This is a good one to try.
 I sockettec the .1uf to ground under the controls, opting for smaller .01uf value there. Really nice sound, gainy-er than any TS's I've built.

[WGTP]

On Joe Davidson's Mosfet circuits he uses P channel Mosfets, BS250 and says that they are inherently quieter than the N channels.  The Obsidian with lots of gain is still quiet.  

[jneely]

Cool it's nice to hear someone else like the tones.

I find the 500k pot allows me to shape the tone and cuts a little gain .  One way it seems to have a thicker sound.

I use a 9v zener from the source to the gate to protect it from overvoltage.

The schem I posted does sound like a ts . I replaced that 5k resistor on the loop tail to a 15k . It sounds more like natural break up now. You sacrifice some of the gain but its still loud. This sounds like amp overdrive to me this way.  If your happy with the 5k I'd leave it. I'm thinking of putting them on a switch.

I thought about replacing the .1 cap but I just haven't done it yet.

Last night I tried a tl082 it sounded good but not what I'm after, it was a little noisy also.

Glad you like it.
Jeff