EM3207 (v1.1) - MN3207 based EHX Electric Mistress (9V) clone

[DrAlx]

I'm working on a vero layout to try and fit a TZF flanger into a 1590BB (using the EM3207 as a starting point).  While going over my vero layout for the EM3207, I realized I got the values for RT2 and RT3 the wrong way around in my layout and build.  They can still be trimmed OK of course.  In any case, i have put a corrected layout (with switch wiring and alignment procedure) in a single image here...

http://www.imageshack.com/i/5njet6j

BTW, has anyone tried Thomas's TZF add-on for the EM3207, and if so were there any heterodyning issues ?

Yes, No (although that is not necessarily gunna be the same for each build) and it didn't work that well.

I think the EM is too 'light' on the flange for it, i'd go with an MXR-117 to try it.

Thanks for the info Scruffie. I am wondering what you mean my 'light'.  Are you talking about having a maximum delay time that is too small, or something else?
I was going to tweak quite a few other things (i.e. put identical LPFs in both delay paths).  I'm thinking the 2 paths ought to be as similar as possible apart from the different delays.
I am wondering if one path is heavily filtered (as in the separate TZF add-on) but the other one isn't (as in the regular EM) then phases at the zero point might not all cancel properly.
Maybe the effect is too small to make any difference.  If range of delays is a problem then I'll have to go back to the drawing board on this.

[Scruffie]

I'm working on a vero layout to try and fit a TZF flanger into a 1590BB (using the EM3207 as a starting point).  While going over my vero layout for the EM3207, I realized I got the values for RT2 and RT3 the wrong way around in my layout and build.  They can still be trimmed OK of course.  In any case, i have put a corrected layout (with switch wiring and alignment procedure) in a single image here...

http://www.imageshack.com/i/5njet6j

BTW, has anyone tried Thomas's TZF add-on for the EM3207, and if so were there any heterodyning issues ?

Yes, No (although that is not necessarily gunna be the same for each build) and it didn't work that well.

I think the EM is too 'light' on the flange for it, i'd go with an MXR-117 to try it.

Thanks for the info Scruffie. I am wondering what you mean my 'light'.  Are you talking about having a maximum delay time that is too small, or something else?
I was going to tweak quite a few other things (i.e. put identical LPFs in both delay paths).  I'm thinking the 2 paths ought to be as similar as possible apart from the different delays.
I am wondering if one path is heavily filtered (as in the separate TZF add-on) but the other one isn't (as in the regular EM) then phases at the zero point might not all cancel properly.
Maybe the effect is too small to make any difference.  If range of delays is a problem then I'll have to go back to the drawing board on this.

I mean in general sound, this isn't as 'Jetty' as some flangers, more musical chorusey. My opinion anyway and that such a flanger might help with the harmonics needed to get pleasing through zero flanging...

Putting the zero add on out of phase might help the sound a bit perhaps?

[Hemmel]

DrAlx's stripboard template asks for 27*23, however the only stripboards I found have 20 strips max. Does anyone know where I could get bigger stripboards ?

[DrAlx]

DrAlx's stripboard template asks for 27*23, however the only stripboards I found have 20 strips max. Does anyone know where I could get bigger stripboards ?

27 holes is 2.7 inches.   So search with inches in the size     i.e. use a search term like

    Stripboard 4''

You get lots of hits on amazon.  e.g.

http://www.amazon.com/Prototype-Stripboard-2400hole-Phenolic-Pitch/dp/B008CI1Z6U/ref=sr_1_10?ie=UTF8&qid=1377634912&sr=8-10&keywords=stripboard+4%27%27

and even eBay.  e.g. from Canada ...

http://www.ebay.co.uk/itm/Phenolic-Stripboard-4-x8-101-205-mm-3200Hole-Prototype-PCB-Veroboard-/151030620176?pt=LH_DefaultDomain_2&hash=item232a206010

[DrAlx]

I finally built my veroboard TZF.  It is based on Thomeeque's EM3207 and TZF mod with some differences.

1) The BBDs are biased locally (i.e. with separate bias to the audio op-amps).
2) A 2 pole active LPF before the BBDs.
3) 3 pole active LPFs after each BBD.  The filter characteristics are different to Thomeques.  I have ~15 kHz cutoff.
4) A DPDT switch to give the option of additive/subtractive flanging.
5) A DPDT centre-zero switch to give regular flanging / TZF flanging / or plain vibrato.
6) Regardless of flanging mode, the 2 signal paths always go through LPFs, so the 2 signal paths are balanced.

I don't have an oscilloscope and haven't checked for unity gain yet so I may tweak things further.
It should just about fit a 1590BB if I file down the input/output jack sockets a little bit.

From the pics you'll see I used adhesive copper foil as a ground plane.  There is a clear layer of adhesive-backed plastic on top of it to provide electrical insulation from the bare wires on the top, and to prevent accidental connections to component legs..
I will post the whole project instructions and the procedure for making the ground plane at some point in a new thread.  In the mean time, here is a soundclip showing the subtractive and additive TZF.  There's just a fuzz box before the flanger.

soundcloud.com/alex-lawrow/my-through-zero-flanger

and some pics

http://imageshack.com/a/img801/2586/yjo4.jpg
http://imageshack.com/a/img855/9305/otz6.jpg
http://imageshack.com/a/img856/6966/3tni.jpg
http://imageshack.com/a/img203/6876/1pv5.jpg

[StephenGiles]

Great stuff!

[GodSaveMetal]

I finally built my veroboard TZF.  It is based on Thomeeque's EM3207 and TZF mod with some differences.

1) The BBDs are biased locally (i.e. with separate bias to the audio op-amps).
2) A 2 pole active LPF before the BBDs.
3) 3 pole active LPFs after each BBD.  The filter characteristics are different to Thomeques.  I have ~15 kHz cutoff.
4) A DPDT switch to give the option of additive/subtractive flanging.
5) A DPDT centre-zero switch to give regular flanging / TZF flanging / or plain vibrato.
6) Regardless of flanging mode, the 2 signal paths always go through LPFs, so the 2 signal paths are balanced.

I don't have an oscilloscope and haven't checked for unity gain yet so I may tweak things further.
It should just about fit a 1590BB if I file down the input/output jack sockets a little bit.

From the pics you'll see I used adhesive copper foil as a ground plane.  There is a clear layer of adhesive-backed plastic on top of it to provide electrical insulation from the bare wires on the top, and to prevent accidental connections to component legs..
I will post the whole project instructions and the procedure for making the ground plane at some point in a new thread.  In the mean time, here is a soundclip showing the subtractive and additive TZF.  There's just a fuzz box before the flanger.

soundcloud.com/alex-lawrow/my-through-zero-flanger

and some pics

http://imageshack.com/a/img801/2586/yjo4.jpg
http://imageshack.com/a/img855/9305/otz6.jpg
http://imageshack.com/a/img856/6966/3tni.jpg
http://imageshack.com/a/img203/6876/1pv5.jpg

PLEASE POST HERE MAN AN INSTRUTIVE HOW TO MAKE THAT!!!!!!!!!!!!

I STAY TUNED!!!!!!!!!!

[DrAlx]

I have just done an Instructable for my method of applying a ground plane to strip-board.
I'm quite new to this whole forum thing so I don't know the best place to share this info.
Here's the link.

http://www.instructables.com/id/Method-of-applying-a-copper-ground-plane-to-strip-/

[GodSaveMetal]

I have just done an Instructable for my method of applying a ground plane to strip-board.
I'm quite new to this whole forum thing so I don't know the best place to share this info.
Here's the link.

http://www.instructables.com/id/Method-of-applying-a-copper-ground-plane-to-strip-/

Excelent man; fine details and TIPS, and please the layout of that  you post here  please man your layout and all to make one! 

[DrAlx]

I have put a link to my veroboard TZF build instructions in a new thread.
Please use that thread for discussion and comments

http://www.diystompboxes.com/smfforum/index.php?topic=104694.0

[peterg]

Can someone post a verified schematic for the MN3207 based EHX Electric Mistress (9V) clone?

[Dave W]

Can someone post a verified schematic for the MN3207 based EHX Electric Mistress (9V) clone?

page 1, post 1 of this thread. its all there… 

[DrAlx]

Here is how you can improve the sweep ratio of the EM3207 Electric Mistress if it is poor (this is quite likely as I explain below !!!).

Note that changing the clock capacitor or adjusting the clock trim-pot cannot fix a poor sweep ratio.  You need to do what I describe here.
The following modification let me achieve a sweep ratio of about 20:1  (delay range of 0.66 ms to 13.3 ms) compared to the very poor 4:1 ratio I had before.
Note that you should not confuse the range in "filter-matrix" mode with the dynamic "sweep" range.  
They are not the same and in fact the following modification will not change the behavior of filter-matrix mode at all.

Here's the modification:   Replace R24 (30k) and R26 (10k) by a single 100k multi-turn (precision) trim-pot.
Pins 1 and 2 of the trim-pot should replace R24, and pins 2 and 3 should replace R26.
This effectively gives us the ability to trim the ratio of R24 to R26.
To maximize the sweep range, follow this procedure:

=======================================
First tune "filter-matrix" mode as follows:

In filter-matrix mode, put the "Rate" pot at minimum (to avoid LFO supply wobble) and put the "Range" pot at maximum.
Then adjust the clock-trim pot to give a BBD delay of 10 ms. (Each BBD clock line should have a period of about 19.5 ms).
The end result of this (for my build) was that filter matrix BBD delay can go from 1.3 ms to 10 ms.  (A ratio of 7.5 : 1).
Note that this ratio in filter-matrix mode will not change much with the clock trim, and should always be around the 7:1 area.
The main point of tuning filter-matrix mode first, is to make sure the clock is not set too fast.
We need to allow it to run slow to achieve a big range in sweep mode.

Now go to "sweep" mode and tune it as follows:

1) Put the "Rate" pot at minimum (i.e. slowest sweep).  This is important because you need to minimize the effect of C15 (which decreases the triangle wave amplitude for fast sweeps).
2) Put the "Range" pot at maximum.
3) Trim the newly added pot so that the sweep goes as high as possible without breaking up or "popping" at the top.
4) Put the "Range" pot at minimum and confirm the sweep still does not break up or pop at the top.  If it does, then trim further.
(The whole point is that there should be no popping, regardless of how the "Range" pot is set).
5) That's it.
=======================================

Explanation:

The LFO design of the EM3207 has a sweep ratio that is VERY sensitive to component tolerances (even using 1% resistors) and supply voltage.  I found this out first hand after building two of them and noticing one had poorer sweep ratio than the other, and that it could not be fixed by the clock trim.

I did a Monte Carlo analysis of the original EM3207 (without my trim-pot mod) using a 9V LFO supply voltage, and random +/- 1% errors on the 7 fixed LFO resistors.  I found significant variation in the maximum sweep ratio.  Things are worse if you run the LFO off a 10V supply rather than 9V (which is what the resistor values were designed for), and the analysis shows it is then possible to have an unlucky combination of resistor errors that cause the sweep to "pop" at the top, and it will not be possible to trim this out with the clock trimmer.  This happened in 10% of cases when running at 10V.  (You will be able to trim it out using the mod described here of course).

[DrAlx]

My Monte Carlo analysis and thinking was badly flawed .
The modification works but the explanation is complete rubbish.  I was wrong about the effect of tolerances being as extreme as I first thought, and the "popping" on 10V supply.  
I failed to account for the range pot and how it is wired up and that was a mistake.
I have reworked things and finally managed to get an analysis that matches what I observed in practice
Here's an editable spread sheet with correct results.  You need to scroll to the very top.
Basically I calculate the ratio of max and min control voltages applied to the comparator.

http://1drv.ms/1fbfI0h

Edit the resistor values in red, and Excel will generate 999 other random variations and look at the distribution of sweep ratios.
The results are in green.

It seems that the sweep ratio for the 9V Electric Mistress is actually quite small by design (in the range of 3:1 to 4:1).
It is nothing to do with a BBD limitation, it is just the nature of the LFO.  So there was nothing wrong with my builds afterall.
I can't comment on the really old 18V versions of the EM, as that had different LFO.

For some reason I was expecting the range to be more like the 7:1 range in filter matrix mode, or even larger. When I saw one build had sweep ratio of 3:1 rather than 4:1 (which I still think is a big difference) I tried to see if I could fix it.
In any case, it shows that with a slight tweak, you can take the LFO for the EM and use it to produce pretty large flanger sweeps.

[kowe90]

Hi
i finished the electric mistress based on mn3007 v1.1 layout, the pedal "work" i get dry signal but i don't have any effect, any pot affect the signal.
I use a 15v 5w zener, i have checked all the components and solder but i can't found the error.
i don't know how to make it work properly, i need help!!!!
thanks

[Govmnt_Lacky]

Hi
i finished the electric mistress based on mn3007 v1.1 layout, the pedal "work" i get dry signal but i don't have any effect, any pot affect the signal.
I use a 15v 5w zener, i have checked all the components and solder but i can't found the error.
i don't know how to make it work properly, i need help!!!!
thanks

Go here and repost:

http://www.diystompboxes.com/smfforum/index.php?topic=29816.0

[Dave W]

help is here but we need a lot more info. for now, get your schematic and check all the Vs. the correct Vs are posted somewhere here (do a search). then get an audio probe, signal source (a guitar will do but a signal generator is preferred) & an amp and go to it. also…. remember this has to be biased properly.
no effect at all is usually an easy fix. its the intermittent problems that are a PITA.
there are a bunch of us who have developed and successfully built this and it is one of the easier flangers to build and "get right". read the 3007 retrofit thread. any info you need is probably all in there.
    

[DrAlx]

Hi
i finished the electric mistress based on mn3007 v1.1 layout, the pedal "work" i get dry signal but i don't have any effect, any pot affect the signal.
I use a 15v 5w zener, i have checked all the components and solder but i can't found the error.
i don't know how to make it work properly, i need help!!!!
thanks

I haven't found an "MN3007 v1.1" layout, only the "MN3207 v.1.1" layout.
I'm sorry if this is  a stupid question, but did you rework Thomeeque's MN3207 layout for the MN3007,
or did you simply try and substitute the MN3007 for the MN3207 and increase the supply voltage to 15V?

[Dave W]

here ya' go….
http://www.diystompboxes.com/smfforum/index.php?topic=91981.msg798618#msg798618
reply #81

[kowe90]

hi
it works right now, i need to adjust it but it works
the best sound at 15v, at 9v it is a little bit noisy.
Thank for your support