9V ELECTRIC MISTRESS BUILD COMPLETED(with pictures)

[sta63bmx]

Finally, it is finished.  BTW, Photobucket is the shiznit.  A few months ago my cousin mentioned that he would like to have an Electric Mistress.  I thought about it, but didn't want to build him an 18V pedal.  So when I saw Markus' 9V layout, I took it for a sign.  I ordered all the parts from Small Bear and got this guy built, and I couldn't be happier with it.  Anyways, the thumbnails clicky pop a bigger version.

Top View



This was a top shot with some temporary marker labels so I wouldn't get mixed up.  The jacks are all on the top end of the pedal. 

Profile View



Here it is in profile, showing the jacks.  From right to left here it goes input, output, 9VDC, and the filter matrix switch.  I wanted a slide DPDT but I didn't have one.    I am leery about the durability of the toggle there, but sometimes you just gotta use what you got.

Final Guts Shot



This is what the guts look like.  I used ribbon cable throughout, real handy for packing it all in.  The board is on non-insulated standoffs.  They touch unconnected parts of the ground plane, I think.  The battery is to the left of the main board.  It barely clears the footswitch.  I have to move the battery up towards the jacks a little to make it fit.  The little daughter board there is for the LEDs.  I brought in 9V power directly from the jack to a "bus" on the top of that board.  From there we go through a pair of 5K resistors, one for the on/off LED and one for the rate LED.  The low side of the on/off resistor goes to the LED and then comes back and to the ground "bus" at the bottom of that little piece of perf.  The rate LED has a wire to it and back to the board, where it goes to the collector of a 2N5088.  The base of that transistor is driven by a wire from pin 7 of the LM324.  I used a 357k base resistor and then I have a 357k resistor in parallel with a 100k pot/100k resistor series combination.  This lets me control the "off" brightness of the rate LED.  I know it's kind of goofy-looking, but I couldn't decide if I wanted it FULLY off during the low parts or not.  It works.  That little board is on standoffs, too.

The "ground bus" on that little board goes to the footswitch, and it's connected to ground when the pedal is on, floating if the pedal is off.

Final Graphic



I could not get any etchant here in town, can you believe it?  The etch didn't work the first time because the aluminum top was clear anodized and I didn't know it.  I'm going to try and make a new top piece once I get some etchant, and etch this graphic like MarkM does with his boxes.  For now I'm using this graphic.  I printed with an inkjet on a self-adhesive laminating sheet, then covered that with another laminating sheet to keep the ink from being rubbed off.  That was my wife's idea.  It worked out ok, and the label looks alright.  Better than the marker, anyways.

Another Guts Shot



This one kind of shows how the enclosures work.  This is half of an old Ithaco module that went in a small rack.  The way the modules were made, each one would slide in a rack and plug into a common backplane.  The sides of this box are aluminum extrusion, and then the top and bottom just slide into slots in the extrusion.  Then they are held in place by the end panels.  Since I salvaged these, the end panels had to be taken off for plain panels cut from sheet aluminum.  It's a nice box though, about as big as the Sovtek ones at Small Bear.  It's about 6"x4.5"x2".  I'm glad it was deep, since the only standoffs I had were tall.  I have about 10-15 enclosures of this type, and I think I can cut most of them down like this.  I just have the machine shop cut it in half and I cut new end panels on their shear, drill them, and I'm done.  The sheet top and bottom are no longer supported in the middle, though, so I like having the stomp switch to the side.  I could turn the box the other way and then the flat panels would be the "sides" instead of the ends and I could center the footswitch.  Some of these are bigger, and I'm going to save at least one for a tube pedal.  The only downside is that clear anodizing, and it is a PITA to sand off.  But if you're not etching, no worries.

Artwork



I just made this in Powerpoint.  Cheesy, I know.  That's the Clockwork Orange font.  Came in handy.

LFO Signal



I don't know how the LFO works in this pedal, but this signal is present on pin 7 of the 324 and the CCW lug of the rate pot.  It goes from about 0.6V to 6V above the board ground plane and has a 50% duty cycle.  I use this signal to drive the base of an NPN transistor.  You have to fiddle with the pulldown and base resistor values, but it's easy now that I know where I was screwing up before (not having a base resistor, I am a moron).

Board Shot



I don't want to contemplate the current draw of this pedal with five chips. lol  Sounds nice, though.  I salvaged a nice little 9V power supply from something else in the lab and rigged it for this pedal.  I think it might be regulated, since the pedal is dead quiet.  Those are my dummy jacks.  I did NOT use true bypass switching at all.  It sounds fine to me in "bypass" more.

Voltages



If you're building one, these are the voltages I got.  I used the 200 ohm resistor between PS ground and the other ground and it floated the power ground about 1.8V.  I measure 9V across the battery or DC adaptor, but then the board ground is floated.  So if the negative battery terminal is 0V, then the board ground is about 1.8V and the 9V power is only 7.2V above that.  It makes the voltages kinda weird.

Final Notes

I really like this pedal.  The bias is most critical, but then there are a lot of different sounds with the clock trim.  I almost made this a front panel control.  The pedal is noisier when the clock trim is centered.  The center of the range had more detuned sounds that I didn't like as much, so I kept it out of there.  I'll let my cousin decide later.  No pops or hisses.  I have it set so I can get a little oscillation with the color (feedback?) knob, but you can back it off.  The slow, subtle flanging I REALLY, really like.  It sounds freaking awesome.  It also nails the "Love Stinks" intro by Nazareth.  Man, I wanna build one for myself, but I can't afford the giant chip.    Well, once I have money I'll build it.

Thanks to Markus for making the layout.  I really like it.  I had to scrape some of the PNP blue before etching to make sure some of the pads weren't touching each other, but that's it. 

[mikey]

Very nice.  I've been thinking about trying this build for a while now but I felt like there wasnt enough feedback on the layout.  After seeing this thread though I might have to give it a shot.  Good stuff.

[sta63bmx]

I was the same way with the GGG layout, and I decided to try this one, since I liked the 9V version.  I had no problems with the layout and etch, but I did have to clean up some pads after ironing.  If you want to bring that pin 7 signal out to run a flashing light, you can just drill another hole in the pad for the CCW lug (Is it CCW? It's marked pin 1 in the layout pictures) of the rate pot, I think the leftmost one if you're looking at the top of the board with the pots soldered to the edge AWAY from you.  I used a 360k base resistor on the NPN transistor I used to switch the flashing LED and then a pulldown (50-500k) on the base to make sure the light would turn OFF.  Everything fit easily on the board, lots of space.

That 200 ohm resistor in the PS ground still confuses me, but the pedal works.  I really think the clock trim should be a front panel control.  It completely changes the nature of the effect.  If I build this again, I'll bring it out to the front panel.  I no longer have the pedal in my possession, but I can borrow it to measure any voltages or whatever if someone's looking for more info while building it.

My cousin was using it at practice tonight and I was jealous. lol

[rody82]

Finally, i've built it too! 
Not in the box yet, but it sounds awesome!
I have just a little problem with it.
With a strong input signal (bridge humbucker
on my guitar), it distorts a bit. No matter how i
set the bias trim.
Is it because of the less headroom (9V) ?
few notes: i've connected batt+ to PS+, cause it was
impossible to get it work because of that r23 (2k7 resistor
just after batt+, that gave me a few hours of unnecessary debugging  )
i've used a simple 4558 chip, but also tried JRC4558D, with the
same results.
any ideas?

thanks for the super layout!

[John Lyons]

WoW! now that's what I call a build report! If you had some sound clips in there I'd reccomend that the guys put up a pic of you for the home page.!!!

Looks nice and thanks for all the info and voltage etc etc etc.
John

[markusw]

Thanks for veryfying the layout and thanks to sta63bmx for posting the voltages and the cool pix

That 200 ohm resistor in the PS ground still confuses me, but the pedal works.

I used a jumper instead without any problems. Maybe give it a try to jumper it and see if noise increases.

Finally, i've built it too!
Not in the box yet, but it sounds awesome!
I have just a little problem with it.
With a strong input signal (bridge humbucker
on my guitar), it distorts a bit. No matter how i
set the bias trim.
Is it because of the less headroom (9V) ?
few notes: i've connected batt+ to PS+, cause it was
impossible to get it work because of that r23 (2k7 resistor
just after batt+, that gave me a few hours of unnecessary debugging )
i've used a simple 4558 chip, but also tried JRC4558D, with the
same results.
any ideas?

thanks for the super layout!

Interesting. I do not get a noticeable distortion even with my active bass guitar cranked up but I run it at about 12V w/o the 200R. Thus there should be around 4-5V more headroom. Don't know how the SAD's distortion correlates with supply voltage though.  I'm using a 15V Zener btw.
In my clone distortion clearly depends on the setting of the bias trim. At around 50% travel there is a hot spot with no distortion. Distortion clearly increases if I turn the trim up or down.

In order to check if the SAD really is the source of the distortion you might use an audio probe to follow the audio signal. Maybe it's just a "not perfect" solder joint. Maybe also try running it at 12V and see if you can get rid of the distortion.

One Q (I already asked ): what is that 2k7 resistor supposed to do?? BTW, rody82 there is a note on the schem that the 2k7 is shorted by the ps jack

Markus

[Doug_H]

Nice!

Wow, what a challenging project!

Doug

[rody82]

Still  have that distortion. Only when i use a loud humbucker
and pick the strings hard, but its there, audible and annoying...
The less the power supply voltage is, the more it distorts, so
i guess if i'd give it 12V it'd be okay. I used fresh batteries so far,
i'll try a 9V wall wart, then i'll try a 12V supply. (I just dont have a 15V
Zener... What if i leave it out?)

by the way i had a little bit higher voltages than sta63bmx. For example
3,8-4V where he had 3-3,6...  7,2V instead of 6,5-6,8...
could this be a problem?
I've tested the bypass output, and it was distortion free, so i guess its
not the opamp.

[rody82]

Some additional notes, maybe this will explain some things...
there were some pretty "exotic" resistor values, so i used the closest
available
R25 : 12k instead of 13k (in the send-return feedback path)
R37:  68k instead of 62k (near that Q1 transistor)
R32:  27k instead of 30k (near the rate pot)
R30:  22k instead of 24k
oh and i used 4,7uF elko because 5uF doesnt exist

[markusw]

Re distortion: AFAIK you do not need the Zener as long as supply isn't more than 15V (17V seem to be the absolute max for the SAD1024).
I would jumper that 200R and go with the 12V supply (plus a 12-15V Zener if you have one).

Could you post voltages of battery and V+ (after the 10R) ? Maybe your circuit draws less current than sta63bmx's. This might explain the slightly different voltages you get.
Edit:  suppose the slightly different part values might a good reason too.

Markus

[rody82]

Its 7,8 - 8,1V after the 10R.
Tried with 12V but it wasnt perfect, the distortion
was still there.. it was a bitt better though.

[rody82]

Got a bit closer...
It already distorts at the output of the second 4558 (IC2B), and
at the input of the SAD1024 (pin2)...

[markusw]

Its 7,8 - 8,1V after the 10R.
Tried with 12V but it wasnt perfect, the distortion
was still there.. it was a bitt better though.

Assuming your battery is around 9V your circuit seems to draw a bit less current than sta63bmx's.

Had a look at the simulation of the audio path and IMO the distortion at the second opamp's out may be caused by the treble preemphasis. Your guitar signal most likely will be higher in this freq range than my bass. So you really might give it a try with 15V.
Alternatively, you might change R7 and R8 both to 130k like in the original schem. This should reduce the overall signal level by about 50% (also in bypass). The values indicated in my schem are derived from Bernard's modded unit.

Markus

[A.S.P.]

Lost Info Society...

[rody82]

I'll go mad...   
Tried 130k for R7 and R8, even tried 100k and 150k
Tried removing the feedback loop (removing R25)
But at the end, i always have some distortion when picked hard...
Is it normal, that V+ varies over time? (7,8 - 8,1V) Is it because
of the clock noise? (Its not really audible and not disturbing)
I also noticed, that the distortion is audible only at some parts
of the sweep and mostly at deeper frequencies... (low E and A strings mostly)
Maybe this is because of the V+ changing?
If i  lower the gain of the second opamp will it help? (IC2B)
How can i do that?

[markusw]

Does turning the bias trim change anything?

Might be that the clock runs at too low frequencies somehow interefering with the audio signal. This would explain why you get the distortion only at some parts of the LFo sweep. On the other hand you already get the distortion before the SAD and the opamp run at 12V should be able to deal with a guitar signal.  Did you check the solder joints in this area?

Will have to check if V+ varies with the LFO on my unit.

I'm pretty clueless because I didn't experience this issue.

[sta63bmx]

I am pretty sure I noticed distortion when I was running out of the correct bias region.  That's all I remember on that.  Did I actually build this pedal?  I have already forgotten about it since I've been doing other stuff. lol  I just wanna say that the layout was pure dynamite and a joy to build.  My ONLY issue was making sure to scrape before etching.

I can probably get some sound clips.  I will try to do that, since everything is miked at band practices.  The "filter matrix" setting is my favorite thing about the pedal.  With a footcontroller, that would completely rule.

[rody82]

I'm using 12V now.
Changing R13 (just after IC2A) to 6K solves the problem,
but then, the signal gets too much quieter, so this is not a real solution.
Resoldered the joints around the IC, no improvement..

By the way, yes, the bias trim does change things,
but as i've said, the distortion is before the SAD, so even at the best
position it can be heard.

[rody82]

Maybe i was wrong. If i take out the SAD, the distortion stops...
But no flanging then 

[A.S.P.]

Lost Info Society...