9V Electric Mistress retrofit with MN3007

[jorge r]

Having fun? I lost 4 hours and my board is still a mess and with a lot of work to do! And I'm doing it with Eagle... Updating the schematic was OK but populating the board is a nightmare!

I spent a week (6 afternoons) just to reorder those two boards. To redraw it all...           ...maybe after Christmas !!!!

[JRM]

I understand you perfectly: I've given up and I'll just not install the boost section. The intention was to shorten the board a little bit but it doesn't pay the effort.

[bazant17]

Today I've finished assembling. I made the pcb a bit more compact and managed to fit it into Hammond 1590BB enclosure. I used the version for MN3207 and it seems to work very well! Nevertheless, I've only adjusted the trimpots by ear, but as soon as I get an access to the scope I will carry out a proper alignment procedure. As far as I know, the MN3207 version should work better with low voltages (look at the THD figures in datasheets).

I've also changed the booster stage to lower the gain (now it's set to about 3).

Thanks for the layout!

A photo:


Greetings from Poland,
Mat

[oldschoolanalog]

Nice work/first post .
...and welcome aboard!

[Cerberus]

Build this flanger from the pdf file of jorge_r some pages back, it works in the sence that it get dry signal but no effect what so ever, not even a tick.

Compared voltages with the list from Just1More and its about equal with the exeption of 8.4v on pin 5 and 6 on the 3007.

Swapped the 3007 with my diy small clone and it works in there so its not the chip.

So i'm kinda lost in where to begin debugging, maybe some1 has some pointers for me?

[Cerberus]

Ignore post above, forgot to solder pin 8 of the 3007 socket  .... flanging now

[JRM]

Hi guys I'm going to pick up my pcb today. During the weekend I've taken a final look at the schematics and I've found something odd: if one takes the original EM9V schem (by Markus W.) and the retrofit board (by Thomeeque) and compare it with Tomeeque's 3207 schem, there are this differences (appart from other that are mods by Thomeque: unity gain, additional supply filtering for LFO and BBD bias cover):

1- There's a 100R resistance between VCC and pin 5 of MN3207 in the retrofit board that disapears on Tom's 3207 schem;
2- There's a 47uF cap between pin 5 of MN3207 and ground in the retrofit board that disapears on Tom's 3207 schem;
3- There's a 10R resistance between VCC and pin 1 of CD4049 in the retrofit board that disapears on Tom's 3207 schem.

Of course one can replace all this with jumpers but the important question is why were that components there and why were they removed?

[Thomeeque]

Of course one can replace all this with jumpers but the important question is why were that components there and why were they removed?

 Hi JRM!

 These parts form supply voltage filters for different sections (on the retrofit there is one for the BBD and one for the clock buffer).

 This improves supply voltage filtering of each section and prevents ripple & peaks generated by one section to get into supply rails of other sections.

 In the retrofit I've wanted to be save, because I don't know nothing about EMs (or other BBD circuits eventually) people are going to put it in (and this can be very topology and even PCB layout dependant) - this way should be the risk of the host circuit being negatively influenced by the retrofit (or vice versa) minimal.

 In the case of my EM3207 project I'm there from the beginning and completely so I have more control and therefor I may try to go more risky way (with the advantage of the lower part count leading to simpler and smaller PCB etc.).

 T.

[JRM]

Thanks a lot for your answer Tom. As I'm using jorge r's pcb layout which is mainly a retrofit embedded on the original board, I'll keep those 3 parts. As soon as I finish construction I'll post my results.

[Scruffie]

After forgetting the Zener for my Order to finally finish this thing, while searching to see how vital it was I found this old post by Markusw-

4) Will work. However, I recommend you to use a 15V Zener and run the thing with 12V (or even 15V) supply. Really sounds better!  Wink

http://www.diystompboxes.com/smfforum/index.php?topic=57937.20

Might be worth a shot for anyone interested in improving the sound.

[jorge r]

Several handmakers, including me, have used 12v supply (but with 12v zenner) and the result is much better. But please, don't do it with MN3207 version.

[azrael]

I etched one of jorge's boards. It looks great!

Now, I'm a bit confused here. I would like to add TZF, but I'm not sure how to go about doing it. Can someone explain it to me?
I need to etch one of Thomeque's daughterboards, and thus need a second 3007, right?
Then I need to connect the daughter board's in/out to the send/return points on the Mistress, right?

Any help would be great.

[azrael]

anyone?

[Thomeeque]

I etched one of jorge's boards. It looks great!
Now, I'm a bit confused here. I would like to add TZF, but I'm not sure how to go about doing it. Can someone explain it to me?
I need to etch one of Thomeque's daughterboards, and thus need a second 3007, right?

 To achieve real-time TZF effect you need to delay "dry" signal before it's mixed with "wet" signal by few milliseconds, so the sweeped delay of "wet" signal can swing around it in both directions (so delta of these delays goes from negative value thru zero to positive and back).

 One of possibilities how to delay "dry" signal is to use one of my daughterboards (TZF3007 or TZF3207) - I'd advice you to use the variant using same BBD as the host circuit, if you have a choice. Unfortunately none of these modules was fully verified yet (AFAIK).

Then I need to connect the daughter board's in/out to the send/return points on the Mistress, right?

 Yes, that's the interrupted path where "dry" signal goes to mix with "wet" signal, TZF3007 and TZF3207 are designed to fit there, read the notes in TZF3x07 thread for more details.

 My advice would be to have bypass toggle switch for the TZF module, most time you won't probably use it (if you are building flanger pedal for guitar).

 T.

[juancra]

Hi all

After a long time I decided to build an Electric Mistress using a MN3007. After all the soldering and since it's a big PCB,   I checked all vias and pads and spotted a few mistakes, that were corrected. Then I plugged the EM to my amp. There's when the problems came in: I started tweaking the Bias preset until I had flanged effects and oscillations of all sorts, but I couldn't hear the guitar .The only things I get are those oscillations and weird sounds. Using an audio probe and a audio signal generator I traced sound from the input and until the second 5k6 resistor (the one that goes to pin 3 of the 4558), but I checked the resistor and it's solderings and are fine. I've tested pin 7 of the 4558 and I've got a powerful oscillation such as those I've got on the output jack. I've switched the op amp to a tlc2272 I had on my bench and got no results. Any clues on what could be wrong?

Regards!
Sebastian

[juancra]

As a possibly useful note, I've removed the Mn3007 and I've got no dry signal out from the EM.

regards!

[Thomeeque]

 Give us DC voltages at all 4558 pins (relative to ground).. T.

 Edit: By audio probe check if the signal gets to pin 1 of 4558.

[12Bass]

As a possibly useful note, I've removed the Mn3007 and I've got no dry signal out from the EM.

If you've heard some BBD-type sounds with the MN3007 in place, then it appears that there is signal coming out of the BBD line.  Is the guitar signal getting into the BBD, or are you just hearing random BBD noises which are unrelated to the input?

Perhaps there is a break in the dry signal path.  The question is to find the open point.  If there's no signal getting into both the BBD and dry path, then the break should be before the BBD, which implies somewhere surrounding IC1A.  If the delay line is getting guitar signal, then you know that the circuit is okay up to that point, which would imply that the break is further on.

[juancra]

Perhaps there is a break in the dry signal path. 

Indeed it was! I found a horrible solder point just before the first 5k6 resistor. Now I've got the effect running, but I presume it's still not working correctly.  I can get a lot of vibrato and chorus sounds, but no tipical 'Flanging' effects. I assume it needs more work on the trimpots, right?

[12Bass]

Indeed it was! I found a horrible solder point just before the first 5k6 resistor. Now I've got the effect running, but I presume it's still not working correctly.  I can get a lot of vibrato and chorus sounds, but no tipical 'Flanging' effects. I assume it needs more work on the trimpots, right?

Vibrato is what you should hear if only listening to the BBD output.  Are you hearing a modulated signal along with a dry signal?  VR1 will have a narrow "sweet spot" where the BBD signal is clean - it may take a bit of tweaking to get the bias set correctly.  From the sound of it, the clock speed may be set too low for flanging.  Try adjusting VR4 (clock trim) to raise the clock speed and see if that causes a flanging sound.