freestompboxes.org

On reflection it seemed a bit daft to keep the 2 x 10K resistors so here's the version as per the schematic

[removed - schematic updated]

Hi guys I had some time and revisited the schematic and values. There was one mistake, not so big but still. I also looked at the pictures again and updated values. Now it looks much more sensible. It would be great if someone could look at it and confirm if it looks like it should. I marked where I took values from so now it is much more understandable I think.
Legend:
*- value from the pictures of the light drive
MXR- values from the distortion+
G-2- values from the Pete Cornish G-2
Not marked- values that would work fine I think.

Ok I looked again on the G-2 schematic and updated the value of the capacitor before the tonestack. Here is the schematic.

very strange biasing and values - also Ivark's vero surely won't work - the 9v dc input goes to a 10k resistor which then goes nowhere
AND the re is a 10k resistor after the tone control which goes nowhere as well.

I will have a look at some simulations.
cheers
bajaman

rollogreb wrote:Wow! Looking forward to seeing where this one goes. I've been wanting to try a soft sustain forever! Thanks guys!

That's not what this will give you. It's a "to ground" clipper, softened a bit by the resistor from the output of the first op-amp to the top of the diodes. The tone control is fairly crude and is not going to have much range. It's actually a fairly basic circuit, without anything much to recommend it.

bajaman wrote:very strange biasing and values - also Ivark's vero surely won't work - the 9v dc input goes to a 10k resistor which then goes nowhere
AND the re is a 10k resistor after the tone control which goes nowhere as well.

I will have a look at some simulations.
cheers
bajaman

It's because IvIark have based his layout on one of earilier versions of the schematic that I drawn. As you can see I have updated the values and corrected the mistake which was on the input of the +9V, I thought that there was two resistors in series which doesn't make much sense, while there was 4k7 resistor to LED from +9V and one resistor 91ohm which is distributing the +9V to the whole circuit.

bajaman wrote:also Ivark's vero surely won't work - the 9v dc input goes to a 10k resistor which then goes nowhere
AND the re is a 10k resistor after the tone control which goes nowhere as well.

The 10K from the supply went to another 10K to pin 8 (via a small link) with the diode in between, the 10K from the tone control (the one after the 220n at tone 2?) went to the non inverting input, both as in the original schematic. MWichni - is this good to go then now if I update? Cheers

You have to update the resistor connections from +9V as I had a mistake there which is corrected in the newest schematic. Other changes that I made is only value changes. The schematic looks fine now, at least for me. If you have some time you can correct your layout and try it out and report back. I'm also creating a pcb layout for it. I will post it when I verify it. Cheers and thanks to all of you who put some effort on this.

Slightly rejigged things as well:

PCB updated to include the fix/LED pads. Still matches the schem numbering.

Schem: http://dl.dropbox.com/u/8021347/Light%20Drive.sch
Board: http://dl.dropbox.com/u/8021347/Light%20Drive.brd

IvIark wrote:Oh and here's the Cornish buffer

Has anyone tried this "Cornish Buffer" ?
Is it verified ? .... very curious about this magical thing ...

There's nothing special about it. It's just an ordinary buffer in boot-strap circuit.

Has anyone else built this? Someone on my blog built it up and he said there is no bottom end and it sounds brittle.

IvIark wrote:Has anyone else built this? Someone on my blog built it up and he said there is no bottom end and it sounds brittle.

Which values this person used?

Exactly as per the last schematic you posted. I did have one value wrong but he swapped it and it sounded the same

Going to try this today using this layout. I have a love affair with 741 chips.

Ok i have it up and running but no glory. The damn thing oscillated like crazy. So i suspected R14 which i used a 68k. So out with the resistor wheel and i found that anything over 1k in that position started it oscillating. Also just to test things i disconnected C8 and tested the distortion plus part of the circuit and it worked well. Then i input guitar signal into C8 and tested the gain recovery stage. Which also worked well until i started adding more resistance at R14 and the recovery stage started to distort. So I think that R14 is perhaps 680r? The only problem is that with 680r there isnt much volume on tap. Have to wait for some more people to post some build reports. There maybe a mistake on my layout or i messed something up during the build. I had to sub a couple of parts, R12 i had to build a 990k resistor cause i ran out of 1M. And R13 the nearest value i had was 120r instead of 130r. Maybe the problem.
P.S clipping diodes in my build are OA90 Ge
Regards Johno

Hi, I think that in the recovery stage 6.8k and 120R should be just fine to determine the gain. Also 990k instead of 1M resistors shouldn't be any problem. Check again if everything is connected as it should be. I'm also not sure some of the values so you can experiment. Thanks for veryfing. I hope that today I'll try my build. Cheers.

I think you should breadboard it before you build one. I wish i did. Seems like there is a bias issue with the second op amp. I'm not smart enough to figure it out but hopefully someone can. There are good sounds there, like the ones i hear on gearmandudes you tube video but they are a bit farty and the squealing is unbearable. If you guys can figure this out it will be a kick arse circuit regardless of what Mictester says about it.
Johno

JOHNO wrote:I think you should breadboard it before you build one. I wish i did. Seems like there is a bias issue with the second op amp. I'm not smart enough to figure it out but hopefully someone can. There are good sounds there, like the ones i hear on gearmandudes you tube video but they are a bit farty and the squealing is unbearable. If you guys can figure this out it will be a kick arse circuit regardless of what Mictester says about it.
Johno

So which layout you used to build one and what values exactly you have used around second op-amp?