Could you guys do me a huge favor?

[ExpAnonColin]

I've just finished my FIRST PCB design, and I'm about to order quite a few of them, but I want to check check check it first.  I might try printing it onto perf and building one, but I think it would be easier if you guys just all let me know that it was A-OK.  It's for the parallel universe.  Here's the PCB:

I did a good job packing it in there, eh?  Maybe too good of a job?  Here's an enlarged version with parts:

Note that I added a .1uf capacitor to the input and output along with a 1meg to ground, which aren't on the schematic.  Also, the 47k resistor is not 100k on purpose.  Here's the schematic:


Thank you all SO much.  If anyone is willing to make a .pcb or gerber file for me of this, I'll pay you $2 via paypal.  The PCBs should be available for about $2-3 very soon, if all goes well

P.S.-Mention you helped me when buying one and I'll send it to you for $1 off.

-Colin

[Peter Snowberg]

That looks nice.

I'll trace it out after diner, but I would suggest one change before you commit to a PCB. I would add a coupling cap in series with that 100K. This will stop DC from appearing at the output and causing a pop when switched in. I would use anything larger than 0.1uF, but experiment a little.

If somebody doesn't beat me to it, I'll also draw up a .pcb (PCB Express) if that's the type of .pcb file you need. Gerber is quite standard, but pcb is not.

As a general note, you'll probably want the holes for the wires to be a little larger. I use 0.035" for components and 0.046" for wires.

Take care,
-Peter

[ExpAnonColin]

Peter-thanks for the suggestion.  By the 100k do you mean the 47k?  If you look on the design, I actually already added one (if that's what you were talking about).  Just didn't put it on the schematic.  If you could do the pcb or gerber, whichever, I'd greatly appreciate it.  And if you could make the hole sizes a bit bigger, that'd be good too

-Colin

[Peter Snowberg]

:oops: You're right. I was looking at the schematic.

I'll be happy to do a PCBExpress .pcb file, but I'll leave the Gerber for somebody who uses something like Eagle. I have the Demo copy of Eagle, but I havn't fired it up more than twice since I installed it.

-Peter

[ExpAnonColin]

:oops: You're right. I was looking at the schematic.

I'll be happy to do a PCBExpress .pcb file, but I'll leave the Gerber for somebody who uses something like Eagle. I have the Demo copy of Eagle, but I havn't fired it up more than twice since I installed it.

-Peter

Well, as I said, either works!  Just let me know if the PCB looks OK and all.

-Colin

[Transmogrifox]

...so this thing is basically doing AM on guitar???  Oscillator modulates the clipping rail == square-law modulator.  


This is a kind of a distorted ring-mod variation, eh?

[ExpAnonColin]

...so this thing is basically doing AM on guitar???  Oscillator modulates the clipping rail == square-law modulator.  


This is a kind of a distorted ring-mod variation, eh?

Yeah, you got the general idea.  Here are some soundclips:
http://experimentalistsanonymous.com/puplus/soundclips/

-Colin

[Transmogrifox]

oh....and a buffer on the input is always a good idea when you're looking at the LM386 50k max input impedance.

If you are building this to sell it, put some form of a signal limiting device on the input because the maximum ac rating on the 386 is +/- 400mV if I remember correctly.

A distortion pedal can maintain anywhere from 0 to 2 or3 V amplitude on a 50k load.

Just a thought...

[Transmogrifox]

thanks for the sound clips,

very cool idea

[ExpAnonColin]

oh....and a buffer on the input is always a good idea when you're looking at the LM386 50k max input impedance.

If you are building this to sell it, put some form of a signal limiting device on the input because the maximum ac rating on the 386 is +/- 400mV if I remember correctly.

A distortion pedal can maintain anywhere from 0 to 2 or3 V amplitude on a 50k load.

Just a thought...

I was thinking about buffers, but after using this thing extensively, I think it's doing OK without them (although sellingpeople pedals as such isn't the nicest thing to do, but I'm sure they'll run a pedal with a buffer somewhere after it).

-Colin

[ExpAnonColin]

oh....and a buffer on the input is always a good idea when you're looking at the LM386 50k max input impedance.

If you are building this to sell it, put some form of a signal limiting device on the input because the maximum ac rating on the 386 is +/- 400mV if I remember correctly.

A distortion pedal can maintain anywhere from 0 to 2 or3 V amplitude on a 50k load.

Just a thought...

I was thinking about buffers, but after using this thing extensively, I think it does a bit better in terms of self oscillation and whatnot without the bufer before the thing.  I was thinking out putting an OUTPUT buffer just because none of the botique guys do it and they probably should, but I figure they will probably run a pedal with a buffer after the thing.

-Colin

[Transmogrifox]

I was thinking INPUT buffer.  The 386 has plenty of kick to drive the output on it's own, so an output buffer would only be a plus if you were having trouble with picking up AM Radio when using this effect.


Input buffer makes the pedal respond more consistently to different guitars.  If you have a weak single coil pickup loaded down, it will sound differently than a humbucker would.  A high impedance input just doesn't load the output...but who knows, the loaded pickups may be some of the beauty of the effect like in the FF

[ExpAnonColin]

the loaded pickups may be some of the beauty of the effect like in the FF

That's the idea:)

-Colin

[Ansil]

really  you dont' need an input or output cap.  i mean if you use something in front of it. i tusualy has a cap on the outptu.  and if you use something behind it it usually has and input.   also most amps have an input cap..  so i figure it should be ok. i mean i dont' condone it but there are a few pedals i can think of that don't have input or output caps.



the lowball isone  in case anyone is going to ask me which ones

[ExpAnonColin]

Ansil-it's just good practice, you know?  I have plenty of .1uf caps, so hey.

-Colin

[petemoore]

say you have a 1uf output cap running into a 1uf input [one efkt to the next] that would be literally running two 1 uf caps in seties ...  would that not look like 2uf or something? Should I be trying to eliminate some in/outcpas where I can, and see if that retains bass rolloff at points closer to what I've chosen for each single ckt?

[Peter Snowberg]

Coupling caps are a very necessary thing. Don't try to eliminate them when they couple different DC potentials. You can "get away" with running an engine at redline, but don't expect a full life from it.

Colin,
I took the liberty of three small tweaks. The changes are in a second .pcb file here. Tweak 1 is that I added .1 to the spacing of the 0.1uF cap on the tone control to match film caps, tweak 2 was to add a diode to the 386 V+. You could always just bridge the position, but I would recommend using a schottky diode like the 1N5818 to protect the chip from polarity errors. I had a 386 amp for a while that was based on an old PCI modem but I fried it when I accidentally reversed the battery while plugging it in. Tweak 3 is the rotation of one resistor (1M to ground on the input) so that all resistors on the board can be done with 1/8 watt units lying flat.

http://127.0.0.1/_myfilearea/Parallel_Universe/pu10.gif">

Download the files here:
Layout 1.0
Layout 1.1 (with diode)
Layout 1.1a (one resistor orientation shifted by 90 degrees)

Double check it.

BTW: If you get 50 boards from ExpressPCB, it comes to $181, or $3.60 per board for "standard" service. For "production" service 50 boards comes to $287 or $5.74 each. 100 standard service boards is about the same cost, $286. For 100 production service boadrs, it comes to $342 or $3.42 per board.

Take care,
-Peter

[ExpAnonColin]

THanks Pete.  I'll be getting it through Futurlec.  Is the board on the same size?  I'm sort of blind here because I can't view pcb files.  Did you just rearrange pads, and is it still .9" by 1.1"?

-Colin

[Peter Snowberg]

Can Futurlec use files from ExpressPCB?  :shock: Gerber is an industry standard, but ".pcb" is proprietary from a number of programs. These files may be useless to you.  

That's a direct copy of the 0.1 grid with the art centered and a .1" boarder so yes, it's still .9" x 1.1".

Version 1.0 is exactly your layout with 0.035 holes for components and 0.046" holes for wires,
Version 1.1 just changes the spacing of the cap at the very top of the board and adds the 0.046 holes for a protection diode with a
Version 1.1a just swaps the size of two holes by pin 4 to allow all resistors to be mounted the same way.

Good luck with it. I can make any other changes you want (or don't ) to it.

Take care,
-Peter

[ExpAnonColin]

Thanks a TON peter!  Email me at colin@experimentalistsanonymous.com and I'll paypal you immediatemente.  Futurlec asks for PCB or gerber files, but it seems as though they even PREFER PCB because they only do PCB files for prototype boards.  Are you pretty sure the circuit will work as posted (with your corrections, too)?  I just checked it for the 3rd time and it looks OK.  I could use a 1n4001 without any rubble, right?

-Colin