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

[Thomeeque]

 Hi,

As title says EM3207 is a loose clone of the original 9V EHX Electric Mistress chorus/flanger adapted for MN3207 BBD chip.



( full gallery )

Additionally it features:

• Unity gain (no volume drop compared to true-bypass) without need of additional amplification,
• Input RF filter to avoid interferences between internal clock and AM radio rubbish picked from the air,
• Improved VCC filtering for LFO section to lower danger of LFO ticking leaking into the audio signal via supply tracks.

More that year ago I did announce this project in 9V Electric Mistress retrofit with MN3007 thread, but it was frozen for four months already at the time I did announce it (it needed some tweaking where I've got stuck and I had to switch myself to something more important for me at the time), but there were few requests recently in the retrofit thread and I had some time for it now, so I did defrost it and gave it try again. I have made some changes and I quite like the result now. Unfortunately I cannot say how close or far it is from the original EM (I don't own original EM nor have access to it), but it's a nice flanger with EM character definitely.


( don't print this schematic, following PDF contains high-quality print version )

EM3207_v1.1_Build_Instructions.pdf (complete build instructions, *DRAFT1* at this moment)

Hopefully I'll have a time to make some small audio demo over this weekend.

More notes may come later, enjoy, T.

[GodSaveMetal]

Thanks my Friend I have to make this project!!! it's a great pedal!!! I have the mistress with MN3007!!!! it sounds OK!!!

[quarara]

Genius.

[StephenGiles]

Excellent drawings, what is the advantage of having the additional two inverter buffers after the clock?

[Scruffie]

Cheers Thomeeque! Didn't think you'd go to this much effort, I just wondered if you had a layout

Now to get this Through Zero Flanging in a 1590BB... Muwahahahaha... ahem.

[StephenGiles]

Now Mike Irwin did get TZF with just one SAD1024 a few years back but the secret remained his.

[Fender3D]

Now Mike Irwin did get TZF with just one SAD1024 a few years back but the secret remained his.

It shouldn't be an huge secret since SAD1024 is (better was?), actually 2x512 stages, each block with separate clock pins...  

BTW
great job, Tomas 

[oldschoolanalog]

OK. Who's going to be the first (not named Tomas) to try & verify?
Sorry, not me this time.
Nice work as always T.

Now Mike Irwin did get TZF with just one SAD1024 a few years back but the secret remained his.

It shouldn't be an huge secret since SAD1024 is (better was?), actually 2x512 stages, each block with separate clock pins... 

Proximity of the clock lines to each other might lead to heterodyning issues when using an SAD1024 in such an arrangement. Somebody more knowledgeable might chime in here (hint; Stephen?).

@Luigi: Is everything OK on Sicily? With Mt. Etna erupting and all that...

[quarara]

@Luigi: Is everything OK on Sicily? With Mt. Etna erupting and all that...

Well, we're used to it!
At any rate, these days the volcano is not really erupting, there is just a little bit of smoke coming from the highest craters that doesn't worry us.

[oldschoolanalog]

@Tomas: How does this one compare to the (one of 3 in known existence ) EM1022 you designed a while back?
For those who are wondering what an EM1022 is:
http://thmq.mysteria.cz/em1022/EM1022_Build_Instructions.pdf
Thanks!

[StephenGiles]

@Tomas: How does this one compare to the (one of 3 in known existence ) EM1022 you designed a while back?
For those who are wondering what an EM1022 is:
http://thmq.mysteria.cz/em1022/EM1022_Build_Instructions.pdf
Thanks!

Well - almost 5 actually, I built a couple of EM 1022s with "bounce" about 10 years ago. They were both the 2 battery circuit with one half of the 4013 used in the LFO. I gave one to my nephew and mine should be  - yes it's on the shelf in front of me!

[Thomeeque]

 Thanks for all the compliments and interest, guys, I really appreciate that I'm short of time now, I'll add some comments later.. Cheers, T.

[azrael]

awesome work!

[soundclone]

i want to build this pedal,but i can find all tantalum cap in local store. can i substitute all tantalum cap with electrolyte cap?

[oldschoolanalog]

Yes.

[soundclone]

I'm sorry...i mean :

i want to build this pedal,but i CANT find all tantalum cap in local store. can i substitute all tantalum cap with electrolyte cap?

[oldschoolanalog]

Yes!

[kranja]

Great design, thank you very much. I will give it try even if  I'm quite a beginner. Could you give me some more details about the off board wiring of the toggle switches, what kind of toggle switches do I need, what are those caps on the photos (I'm not sure if I need only one DPDT switch as stated in the pdf or an additional spdt switch which I'm not sure where to connect)? Has somebody allready fitted this board in a 1590BB enclosure, will this kind of pots fit this box http://www.banzaimusic.com/Alpha-16-PC-ANG-10k-lin.html ?

[Thomeeque]

Great design, thank you very much. I will give it try even if  I'm quite a beginner. Could you give me some more details about the off board wiring of the toggle switches, what kind of toggle switches do I need, what are those caps on the photos (I'm not sure if I need only one DPDT switch as stated in the pdf or an additional spdt switch which I'm not sure where to connect)?

Hi, you're welcome Switch with caps you see on the photos is one of "ADVICED MODS" ("Play with C17 (clock cap)..") Just ignore it for this moment, build it and make it working without any mods first. There is only one switch in the basic version, mode switch (SW_MODE), it is DPDT switch and it's wiring is indicated on the schematic. OK, maybe this way it's more obvious:

Has somebody allready fitted this board in a 1590BB enclosure, will this kind of pots fit this box http://www.banzaimusic.com/Alpha-16-PC-ANG-10k-lin.html ?

Looks like this type. There's only 16-9.3-4.9=1.8mm space between PCB and back of pot. You need at least 8mm (height of the IC in the precise socket) space there. Either look for more suitable pot type* or you may try to straighten legs and bend them as close to pot body as possible like this:



This way you should theoretically gain 5.2mm, remaining 1mm you could gain by using shim (I'm not sure it's best word for what I mean, but it should be obvious from the picture) between PCB and the indention on pots leg (there should remain at least 1.5mm of the leg on soldering side of PCB for propper joint).

Good luck, T.

* Edit: Ask ~arph

[Mark Hammer]

First, for doing all the work to redesign the circuit and board to accommodate a 3207.  Very much appreciated.  Not just by me, but by many others, I'm sure.

Second, the layout is very compact.  Compact enough, that a person could consider shoving two of them in the same pedal.  This creates some interesting possibilities.

First, there is the obvious possibility of splitting a mono input signal and having two asynchronous flanger outputs.
Second, there is the possibility of having a mixer and combining the two flanger signals into a single more complex mono output.
Third, there is the possibility of lifting the dry signal from each flanger outputs, and running them "stereo-out" to separate amps or mixer channels.  At slow sweep speeds, this can produce both apparent movement as the phase relationship between left and right keeps changing.  It can also produce "flanging in-air" (though that likely requires standing in the sweet spot).  At faster sweep speeds, you get stereo vibrato, which can be interesting.
Fourth, with dry lift, and setting one of them to "filter matrix" (non-swept) mode, combining flanger A and B gets you variations of through-zero flanging.

Clearly, throwing a pair of these into a suitably-sized chassis, that can accommodate both boards, a splitter/mixer board, additional jacks and toggles, can yield something truly wonderful.