Beginner's Distortion Design

[mattthegamer463]

Thanks PRR, I was under the impression I could turn it into non-inverting by just feeding signal into the + side of the op amp.  Silly me, I should have known better.

New plan with experimental switchable 2nd gain stage (boost stage)



Does anybody think theres value to that or is it just another dimension of freedom easily met using other means?

[slotbot]

i think now you have a positive feedback connection in the first opamp stage... its not going to work to well like that.


are you trying to get an inverting or noninverting setup in the first stage?

edit:

also you need to properly bias the new stage you added. you could do this by running the side of the 1 meg pot that is now connected to ground to Vcc/2 and removing the 47 nf capacitor.

if you want some really good basic building block circuits look at this document on single supply op amp design by texas instruments. it is very simple and easy to use.

http://www.eng.yale.edu/ee-labs/morse/compo/sloa058.pdf

[mattthegamer463]

I think I hit all the nails on the heads this time.  I've got the inputs biased (Vcc/2) and set up negative feedback loops for all the op amps.

[slotbot]

i *think* you just accidentaly reposted the same schematic instead of your new one.

[Fender3D]

Sorry mate, but...
the junction R3-R7 should go to the U3A non inverting input (+), R6-C2 to the inverting input, you should do the same with U3B.
You should check the switch J4, it may provide some switching noise since you should have a DC voltage biasing U3B there.
Then you'd better set to ground the lower rail connecting R8-C4-R5 and so on, just for "understanding" sake

[mattthegamer463]

i *think* you just accidentaly reposted the same schematic instead of your new one.

Thanks, I fixed it.  I really need to start naming these better...

Heres my photoshop layout so far.  Its a little cluttered in the middle but a necessary evil to make everything fit and maintain symmetry.  Sized for a 1590BB enclosure.



For the boost/power footswitches, they are the outside dots, and the dots directly above the labels are LEDs.  I'm going to try my first ferric chloride etch on aluminium using PNP blue.  Does anyone think this font and the warping is asking too much out of the etch?  The layout is 4.5" by 3.5".

[mattthegamer463]

So, I've done tons of work and the circuit has gone through a dozen different changes, and has now been totally reworked like three times.  However, I have absolutely no confidence in the EQ circuit (which has not changed, since I still can't figure out how its negative feedback works) so I would like to steal a EQ circuit from another pedal.  I'm thinking the Dr. Boogey one would be pretty good?  Does anyone have one they might recommend?  Active or passive, really doesn't matter as long as I can use a TL071.

[mattthegamer463]

I've done tons more work and now finally I have this done:



The SB is the diode sub-board.

My other designs kept squealing, oscillating and doing all sorts of inexplicable things. This one works great, now I just need to sort out an EQ design and I'm golden.

[deadastronaut]

i think your etch will be ok...in negative though...so you burn the letters away...and not the whole facia..

anyway..looks like a cool project...like the idea of the rotary switch..nice...

not to sure on the boogey eq....everyone seems to mod it....

[mattthegamer463]

i think your etch will be ok...in negative though...so you burn the letters away...and not the whole facia..

anyway..looks like a cool project...like the idea of the rotary switch..nice...

not to sure on the boogey eq....everyone seems to mod it....

Yes of course, but showing an inverted and reversed ready-to-etch layout wouldn't be so nice for you folks to read now would it?

I'm still trying to get the original EQ working, I found a variation of it that uses the same parts but in a more sensible arrangement.

[mattthegamer463]

So I've finally got this circuit done and working great.  I cut out the EQ entirely and went with a simpler tonestack.

Heres some imagery:







Heres most of the schematic.  Its a little different and missing the tone control so I will update and computerize it soon.

[mattthegamer463]

Etched the enclosure today.  More painting tomorrow

[mattthegamer463]

Completed:

[deadastronaut]

looks great.....any soundclips?....

[arawn]

looks awesome definitely need some clips

[mattthegamer463]

I'm looking to buy a USB recording interface soon, I'll do some clips then.

[mattthegamer463]

I got my recording interface, and a condenser mic, and made a demo video.  Tell me what you think:

http://www.youtube.com/watch?v=XxdXAe769IU

I apologize for the playing.

[arawn]

sounds good!!

[mattthegamer463]

I want to make a very small run of four of these.  I would like to have a couple spoken for before I get to work building.  If anyone would like to buy one, please PM me.

Cost is $125 CAD ($120 USD) + shipping, which will be calculated later.

If you have any special requests we can discuss them via PM.

[mattthegamer463]

PCB's for the production: