build report: 9v electric mistress

[gaussmarkov]

this is a follow-up to my post about trying a fab house to make a pcb.  i sent olimex a board that i designed from markusw's project for the 9v electric mistress (thank you markus!)  you can see a pic of it in the earlier post.

the basic design strategy was pretty simple:  i moved the positive power supplies to the component side of a 2-sided board and then filled in the rest with ground pour.  i tried to be careful about keeping the LFO away from the signal.  i also took out a few features of the original that markus had also removed from his build.  the result was a smaller layout than the original.  here's a pic of the guts of the assembled mistress inside a BB-sized box:



it fired up first time, though it took a little fiddling with the trimmers to get it right.  my experience was just as described in previous build reports.  the place to start is with biasing the SAD1024.  the current draw is only about 8mA.

after i got it in the enclosure, i was pleased to find everything nice and quiet.  this is what has been reported for markus' version, which reproduces the original EH layout.  i was going to experiment with smaller decoupling caps, but once everything was assembled and working that became less interesting.

here's a very short clip of two samples.  both have feedback and depth/range at max.  the first is at the highest rate then the rest is at the slowest rate.  this gives an idea of how clean the effect is.

the bottom line for fabbed boards is that it worked out very well.  and i'm very happy with my mistress as well.  markus did a great job.

[paperhouse]

clean build and great clip! fewer parts than i expected too. does it cut volume slightly when engaged like the originals?

[John Lyons]

"867-5309! ....for a good time call..."

Sounds good, looks good.
A bigger Box would be good for better jack and switch placement but very nice nice work guys.
Maybe now I can use some of that double sided board I have.

John

[gaussmarkov]

clean build and great clip! fewer parts than i expected too. does it cut volume slightly when engaged like the originals?

yes it does cut the volume slightly.  i plan to put in a little boost between the two switches.  does anyone know whether there is a recommended amount to boost?

"867-5309! ....for a good time call..."

Sounds good, looks good.
A bigger Box would be good for better jack and switch placement but very nice nice work guys.
Maybe now I can use some of that double sided board I have.

i would always get the numbers in the wrong order when we sang that one. 

it would be cool to actually make the double-sided board from scratch.  john, have you tried the method we were discussing some time back?

[John Lyons]

I haven't done any double sided boards yet. I think the idea about resgistering the two side with a pin at each corner or maybe even a pad hole at opposite corners should do it. Is the layout up at gausmarkov.net now?

I haven't looked at the schematic but can't you just squeeze a little more level out of the last op amp?
If not then a simple transistor recovery stage like in the big muff should do it.

John

[Michael Allen]

Can you post your layout? It looks great man, and i want to build this pedal. I etched the GGG layout but it's a mother....

[gaussmarkov]

I haven't done any double sided boards yet. I think the idea about resgistering the two side with a pin at each corner or maybe even a pad hole at opposite corners should do it. Is the layout up at gausmarkov.net now?

I haven't looked at the schematic but can't you just squeeze a little more level out of the last op amp?
If not then a simple transistor recovery stage like in the big muff should do it.

John

no, i haven't put the project files together yet.  but i will since there's interest.  and i will include the files i sent to olimex so that anyone who wants to can do the same as i did.

there's no amplifier after the SAD1024.  so i was planning to do a FET recovery stage on a daughter board.  it should really go on a redesigned board.    markus pointed it out to me -- but it was too late.  i'd already sent in my files

Can you post your layout? It looks great man, and i want to build this pedal. I etched the GGG layout but it's a mother....

fo - sho. 

[d@vide]

Hi Gaussmarkov
have you a spare pcb to sell me??

[gaussmarkov]

Hi Gaussmarkov
have you a spare pcb to sell me??

i wish i did, but i gave the other two PCBs away some time ago.    i bet that it won't be hard to find two others who would go in on a one-panel three-board purchase from olimex.  but perhaps i should design in a recovery stage before sending off for additional boards?

[bluesdevil]

Thanks Gaussmarkov!! Great timing, I was thinking of finally building up the 9v Mistress and decided to check back in to this forum for any updated info. Would be very cool to have the new reduced board with the gain stage built in, if possible. I like the idea of having it in a BB size box.
   Depending on cost I'd be willing to buy a board if someone wants to make a run with Olimex. PM me with details if it gets off the ground. Thanks Gaussmarkov!!
         

[gaussmarkov]

I have been thinking about the recovery stage to get the effect and by-passed signals to the same level.  Trying for low parts and easy to insert on the board that I have already designed.  And then it occurred to me that it would be far simpler just to attenuate the dry signal in by-pass.  A simple voltage divider will do the trick.  And easy to implement off the board.  One could just solder the pair of resistors right to the lugs of the by-pass switch.

Thoughts? 

[bluesdevil]

Personally, I would not want to pad down my bypassed signal. Maybe better to just build a LPB or Strat-o-blaster type circuit on a daughterboard at the output for a volume boost. Seems like it should be able to fit in that enclosure somewhere. Hell, I was just going to do away with the battery and use a power jack anyway, so lots of room for me.
   

[Uma Floresta]

fo - sho. 

I'd love to get a layout for this!   

[stobiepole]

Paul and I have been thinking about putting together a group buy thing for Electric Mistress boards. It's just a matter or getting my arse into gear and sorting out the details of taking orders and payments etc.

I should get onto it next week. Email me at stobiepole@gmail.com to hassle me if I haven't made an announcement by then.

Chris

[Uma Floresta]

Paul and I have been thinking about putting together a group buy thing for Electric Mistress boards. It's just a matter or getting my arse into gear and sorting out the details of taking orders and payments etc.

I should get onto it next week. Email me at stobiepole@gmail.com to hassle me if I haven't made an announcement by then.

Chris

I'd be interested! 

[soggybag]

I'd be interested. I have SAD1024 in he parts bin.

[Solidhex]

Yo

  Count me in too! I got the parts sitting in a bag...

---Brad

[bent]

just want to know...

instead of 2 X lm358 have you try using 1 X lm324...?

bent

[nbabmf]

I'd be in on this too.

[gaussmarkov]

just want to know...

instead of 2 X lm358 have you try using 1 X lm324...?

bent

markus did in his original layout.  i did not try it and i don't think it makes much difference.
dual op-amps seem easier to layout when trying to keep things small.