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

[Mark Hammer]

The second timer has a very high sampling frequency. The high sampling rate timer just increments a counter. The LFO-function calculates the actual duration of the pulse and the according number of high sampling rate events.

The A/D is not a problem, the ATMEGA has built-in 10-bit converter: 1024 steps are enough. The problem remains the "very high sampling frequency", as you can see from my post, a 16MHz crystal is not enough to reach that frequency values. The problem here is not that we cannot produce such signal, but that the uC is too slow to produce a "continous" sweep between 60k and 2M...

For a great result we should have something like a 100MHz or 1GHz oscillator!! 

But one of these devices would still be perfect for generating an "optimized" LFO output that adjusted waveform and amplitude with speed.  Imagine an LFO that got more hypertriangular and had greater sweep width the slower the speed: a 2-knob flanger (speed and regeneration).

[Thomeeque]

The circuit of your proposal is very small!! I made the Jorge's pedals and is enormous; please man how I adaptate the MN3007 for the PCB of yours? the 3207 are fails and only the 3007 are goods in PERÚ please I want to do that!!!

 EM3007 (v1.1)

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

 EM3007_v1.1_schema_1200DPI.png
 EM3007_v1.1_PCB_1200DPI.png
 EM3007_v1.1_PCB_mirror_1200DPI.png
 EM3007_v1.1_jumpers_1200DPI.png
 EM3007_v1.1_names_1200DPI.png
 EM3007_v1.1_values_1200DPI.png

 Build instructions (including shopping list* and wirepad positions) remain same.

 * Two exceptions:
 1x MN3207 MN3007 (IC2)
 1x Zenner 10V 15V/5W (D3)

 T.

[sugonidamaso]

Hi T! How does it differ from the 3207?Thanks!

[Thomeeque]

Hi T! How does it differ from the 3207?Thanks!

 It is EM3207 v1.1 adopted for use of MN3007 BBD chip, all diffs are listed in the small table at top of the schematic, there are no any other changes. T.

[GodSaveMetal]

The circuit of your proposal is very small!! I made the Jorge's pedals and is enormous; please man how I adaptate the MN3007 for the PCB of yours? the 3207 are fails and only the 3007 are goods in PERÚ please I want to do that!!!

 EM3007 (v1.1)

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

 EM3007_v1.1_schema_1200DPI.png
 EM3007_v1.1_PCB_1200DPI.png
 EM3007_v1.1_PCB_mirror_1200DPI.png
 EM3007_v1.1_jumpers_1200DPI.png
 EM3007_v1.1_names_1200DPI.png
 EM3007_v1.1_values_1200DPI.png

 Build instructions (including shopping list* and wirepad positions) remain same.

 * Two exceptions:
 1x MN3207 MN3007 (IC2)
 1x Zenner 10V 15V/5W (D3)

 T.

Mr.Thomeeque your amazing!!! you are great!!! thank THANKS for your work!!!!!!!!!! muchísimas gracias!!!

[Thomeeque]

 You are welcome, Roberto Good luck with your build! T.

[12Bass]

Thanks Thomeeque!  May have to build one of these with the MN3007s I have.  Ever built up an A/DA clone?

[mth5044]

Now do a polychorus 

Great work! I hope one day to build this! Thanks!

[Thomeeque]

Thanks Thomeeque!  May have to build one of these with the MN3007s I have.

 Good luck to you too then

 It's interesting, I have choosen MN3207 as the shortest BBD still in production (?), but it looks like there's still enough MN3007s

Ever built up an A/DA clone?

 Nope, with EM it was love at first sight and I don't want any other!! But I may try it's LFO/VCO, could be interesting..

Now do a polychorus 

 Sure, sure..

Great work! I hope one day to build this! Thanks!

 Me too

 Cheers, T.

[head_spaz]

Are pcbs still available for this project?

[12Bass]

It's interesting, I have choosen MN3207 as the shortest BBD still in production (?), but it looks like there's still enough MN3007s

I've found lack of headroom to be a bit of an issue with my SAD1024 A/DA clone, so that is a big factor in wanting to use the higher voltage MN3007 instead of the MN3207.  Usually I play bass, so that application might require a little more headroom than guitar.  Didn't have too much trouble sourcing MN3007s.  Plus, I've already got an 18 V supply for my A/DA.  

Nope, with EM it was love at first sight and I don't want any other!! But I may try it's LFO/VCO, could be interesting.

Please let us know if you do.  I'm curious to know how it might impact the sound of the flanger.  The different LFO is one reason why I'm curious to build an EM, that and because the signal path is somewhat more straightforward.

[oldschoolanalog]

Nope, with EM it was love at first sight and I don't want any other!! ...

In the realm of flanger "relationships"; infidelity is not only a good thing; but an absolute necessity!
Speaking on a (slightly) unrelated note...
Tomas; is that totally cool singer in your band single? (Say yes and I'm on my way to Prague!)
The Dark Side?, Cookies? I'll bring the beverages!

[Thomeeque]

Are pcbs still available for this project?

 I'm sorry, but they never were you have to etch yours or order it from some PCB pro (others may give you hint, where are you from?)

I've found lack of headroom to be a bit of an issue with my SAD1024 A/DA clone, so that is a big factor in wanting to use the higher voltage MN3007 instead of the MN3207.  Usually I play bass, so that application might require a little more headroom than guitar.  Didn't have too much trouble sourcing MN3007s.  Plus, I've already got an 18 V supply for my A/DA.  

 I see..

Nope, with EM it was love at first sight and I don't want any other!! But I may try it's LFO/VCO, could be interesting.

Please let us know if you do.  I'm curious to know how it might impact the sound of the flanger.  The different LFO is one reason why I'm curious to build an EM, that and because the signal path is somewhat more straightforward.

 Yep, signal path in A/AD flanger is a tough puzzle

Nope, with EM it was love at first sight and I don't want any other!! ...

In the realm of flanger "relationships"; infidelity is not only a good thing; but an absolute necessity!
Speaking on a (slightly) unrelated note...
Tomas; is that totally cool singer in your band single? (Say yes and I'm on my way to Prague!)

 She was.. until the first night of our first road trip with her on-board .. then our totally cool bass player took his chance and scored

 But you can come to Prague to see me

The Dark Side?, Cookies? I'll bring the beverages!

 Yep, beverages were involved, lot of them

 T.

[Eduard_Solderingironhands]

Hello Thomas,

today I talked to colleague of mine who is expert for high frequency and asked him for some hints why the VCO doesn't operate up to 2.5 MHz. He asked me to build it in hardware and offered to make some measurements. The parts are ordered.
Until then he suggested (shot from the hip) to try a LM6511 or LM319 instead of the LM311 or to put a buffer between the LM311 and the 4013.

Best wishes

Ralf

[Thomeeque]

Hello Thomas,

today I talked to colleague of mine who is expert for high frequency and asked him for some hints why the VCO doesn't operate up to 2.5 MHz. He asked me to build it in hardware and offered to make some measurements. The parts are ordered.
Until then he suggested (shot from the hip) to try a LM6511 or LM319 instead of the LM311 or to put a buffer between the LM311 and the 4013.

Best wishes

Ralf

 Hello Ralf,

 that's cool, thanks! Sorry for the late answer, I have too much other duties lately. Just please note that it's not only about getting higher frequency, it's about clarity of V/f characteristics too. Clarity is actually more important - once sweep looses it's fluency, it's unpleasantly audible and therefor worthless (it's then better to stay at lower frequencies in the fluent area). Just to remind, goal is simple - VCO must follow this characteristic:

 

 with frequency doubled.

 Using common LM311N and after some tweaking* I have got this characteristic (measured on my "clock replica" for three different clock capacitor values):

 
 (click the pic for hi-res)

 As you can see, use of smaller clock capacitor moves highest frequency just by little (at the low end it's perfectly proportional), there is some sort of ceiling around 2MHz (actually, when you completely remove clock capacitor, it still ticks and maximum is IIRC 2.2MHz). Plus with small value the characteristic gets (audibly) "slowed-down" and crippled (you can see that "bump" around 1500kHz on the red curve)**. Twiddling with other parts has similar effect, EM clock using common LM311N seems to have this limit.

 If your friend would find the way how to move this ceiling to at least 2.5MHz either by modifying current circuit around LM311N or by using other commonly available comparator, it could be definitely interesting.

 On the other hand, 12BASS is right, for "normal" flange use we don't need it that much. It was more challenge for me than the real need

 Cheers, T.

* To extend clock's range it is necessary to make LM311's output stronger, unmodified it is not able to drive 4013's input properly above 1300kHz. Trick is to make R34 smaller, LM311's output is open collector (minimal value seems to be 1k, below this value it starts to fail again for some other reason - R34 = 1k was used for the characteristic above).

** So actually to get the biggest possible range and the most pleasing sweep it's best to stay with 47pF and move V_CTRL sweep range ("stock" range starts at 1.15V), which is relatively simple.

[Thomeeque]

 I have got few questions via PM (some of them already second time), I answer them here:

Do you know where, in Europe, I could get the 10V/5W Zener diode [D3] or can it be exchanged for something else? I haven't seen it anywhere...

 D3 is there for the overvoltage (10V is maximal V_CC for MN3207) and polarity protection. It is not necessary for function of the effect, you don't need to have it there at all, but I don't recommend to go without D3. If you cannot get 10V/5W Zener, try to get 1W or use at least normal rectifier diode (e.g. 1N4007) there for the polarity protection (if you use only 9V PSU for all your stompboxes, you should not overvoltage it). But 10V/5W zener diode should be pretty common part, shops around me sell e.g. 1N5347B.

I also have a question about the [100nF DC blocking] caps that go underneath the IC's, which pins are you talking about (V+)?

 I'm talking about supply pins - GND and V_CC (V_DD):

 IC1 (4558) - pins 4 and 8
 IC2 (MN3207) - pins 1 and 5
 IC3 (LM324) - pins 11 and 4
 IC4 (LM311) - pins 4 and 8
 IC5 (4013) - pins 7 and 14
 IC6 (4049) - pins 8 and 1

 Solder as close to the pins as possible. It is an optional step, which should help with potential noise issues. Do it as the last step, when circuit is perfectly working.

 Does it matter if it's the buffered or unbuffered cd4049?

 I'd say it could matter - since 4049 is here used as a clock signals buffer, buffered version makes more sence to me and I always used buffered version. But there may be other opinion, I have not done any deeper research about this matter yet.

 Good luck, T.

[asatbluesboy]

1) We seriously need a "thanks" button.
2) Love the heart tupperware thing.

[Thomeeque]

1) We seriously need a "thanks" button.

 Never mind, there's no "you're welcome" button either

2) Love the heart tupperware thing.

 He he, thanks I love it too, it's very useful for bare PCB circuits testing and tuning - shape is not ideal (walls are nowhere totally straight), but I needed it a lot and it was first metal can with acceptable dimensions available.

 Cheers, T.

[Eduard_Solderingironhands]

Hello Thomas,

unfortunately my colleague is quite busy at the moment, but I did some testing by my own. I built your 3207 version 1.1 and a VCO testbench similar to yours. What I found out up to now:

1. I got a genuine EH Deluxe Electric Mistress "Reissue" with the RD5106. The RD5106 would require double clock frequency similar to the MN3207, but EH kept the SDA clock frequency. The sound of the Reissue is similar to your 3207 version 1.1 except for longer delay and is definetly not worth the money.

2. The EH LFO goes from  1.26 V to 10.31 V @ 16 V for the vintage EM, which equals 8 % to 64 % Vs. The Resissue is 1.4 V to 8.0 V @ 12 V, which equals 12 % to 67 %.
My 3207 version 1.1 goes from 1.1 V to 3.95 V @ 9V which equals 12 % to 44 %. (At least that's what I measured from mine - Can you please confirm these values). In case these values are right you should extend the sweep range by adjusting R21, R22 and R27.

3. The LM311 has a responce time of 200 ns according to the datasheet. I dont`t think you can achieve 2.5 MHz with the LM311. This is my measurement of the LM311 @ 1 MHz:


4. I tried the LM319. This thing really speeds things up. You can easily let the VCO oscillate faster than 10 MHz. With the LM319 I found out that the maximum frequency of the CD4013s I have is 2.2 MHz. If the frequcency out of the VCO is faster, the CD4013 will get unstable.

5. Unfortunately I could not achieve the desired 2.56 MHz to 58 kHz with the LM319. As the LM319 has a faster responce, we must either increase the capacitor or reduce the charge current to the capacitor by the trimpot. If the capacitor is increased, the responce characteristic will change significantly. If the charging current is reduced the LM319 gets some strange oscillation at cetrtain frequencies. I am not sure yet what causes these oscillation. Here are some pictures.
LM319 @ 1MHz


LM319 with lower charging current and oscillation:


The slowest delays I could achieve without oscillation (Vs = 9V):
[Edit]new diagramm - now no nonsense[/Edit]



I would like to try the LM6511 next which is faster than the LM311 and slower than the LM319, but the shops I normally buy from don't have this one in stock.

Best wishes

Ralf

[Thomeeque]

 Wow, amazing work! Thank you, Ralf!

I built your 3207 version 1.1

 Nice, you are probably first one, how do you like it?

1. I got a genuine EH Deluxe Electric Mistress "Reissue" with the RD5106. The RD5106 would require double clock frequency similar to the MN3207, but EH kept the SDA clock frequency. The sound of the Reissue is similar to your 3207 version 1.1 except for longer delay and is definetly not worth the money.

 I wonder if they tried do double frequency as we are trying now

2. The EH LFO goes from  1.26 V to 10.31 V @ 16 V for the vintage EM, which equals 8 % to 64 % Vs.

 1.26 V to 10.31 V @ 15 V for the vintage EM, which equals 8.4 % to 68.7 % Vs.

 Huge range, I know

The Resissue is 1.4 V to 8.0 V @ 12 V, which equals 12 % to 67 %.

 Did you measure it in FLANGE or FILTER-MATRIX mode? F-M mode has extended range over FLANGE mode in the EC1000 reissue (different wiring of MODE switch) - FLANGE mode circuitry is 100% equal with EM3207.

My 3207 version 1.1 goes from 1.1 V to 3.95 V @ 9V which equals 12 % to 44 %. (At least that's what I measured from mine - Can you please confirm these values).

 Mine from 1.13 to 4.35V @ 10V which equals 11.3% to 43.5%, so I can confirm your values.

In case these values are right you should extend the sweep range by adjusting R21, R22 and R27.

 I've been playing with these values This is definitely possible way, but you have to be careful to not detune FLANGE vs. F-M ranges. I have found maybe easier (less invasive if you will) way:

 replacing RANGE pot by 250k (it extends top limit of range to almost 90%) and adding properly calculated resistor over C16 forming voltage divider with R30.

 It has it's drawbecks too (divider moves both limits down), but it allows IMO easier tuning of the clock (if you use pot over C16, you can move fluently minimal limit, which is the more interesting limit when hunting for highest possible clock).

 I'll answer to the rest later (now I'm going to lunch and for few LM319s ), cheers, T.