MN3007 ADA Flanger Clone Questions

[Valoosj]

At the moment I am working on my layout, and I have some questions. Is it ok to make IC2a, IC2d, IC3d and IC3c into one TL074? Changing the pins numbers on IC3d to 5,6 and 7. The V+ going to pin 4 would be the same as with IC3c then, and I would leave out C4, 22uF as I am using C26 which is 33uF . Is this ok, or should I use two TL072s instead?

The Vb generator, which parts are they exactly? I keep looking for a pair of resistors with one going to GND and one going to V+ but I can't find them.

[12Bass]

Vb comes from IC2d (pin 14).  The voltage divider is R7 and R8. 

From the look of things, I think it would work to combine IC2a, IC2d, IC3c and IC3d.  There's no mixing of audio and clock taking place, just Vb and CV.

[Valoosj]

Ah thanks for clearing that up. I was looking for the Vb signal right after the resistors, without an IC in between 

Just one more thing, if I don't want the expression pedal, I should connect R53 with the wiper on the manual pot, but what about R50?
I haven't the foggiest on how the switching goes when reading and re-reading the notes in the pdf. It never mentions R50.

[12Bass]

I'm not using the jack input either.  One mine, there's a jumper from S to SW on the PCB.  This connects R53 to the wiper of the Manual potentiometer.

[Valoosj]

I know, but what about R50, is it just left floating?

[oldschoolanalog]

If you're not using the exp. pedal jack just leave out R50.

[Valoosj]

Ok thanks for the help. The lfo part is done. I had to make some changes with the TL074 as mentioned above. Mostly just connecting some parts of the opamp to other 47ohm resistors and the adjacent elco. Next up is the audio part.

[mean_dorris]

Glad this topic is still up and running

This is so close to being done I can smell it.. I just can't seem to get the freq's right. 70ish khz is no problem but nothing I do will get them to go up past 150 or so khz, and I understand I need 20 times that?
Otherwise it sounds like a flange that isn't quite up to snuff. Voltages seem good. Replaced a few fried chips. Is it something obvious?

Thanks!

[oldschoolanalog]

Check your values for R68, R69 & C29.

[12Bass]

Can anyone explain why the diode limiter (D1 through D4) was moved out of the feedback loop of IC1b (as in the original A/DA design) and put in front of the op amp? 

I thought that part of the purpose of the limiter was to limit the sum of the input signal plus regeneration so that the BBD would be protected from overload.  However, as it stands, the diode limiter limits the input, but doesn't impact any level which might be added from regeneration, allowing for a BBD overload condition when regeneration is added.  From my own build, this sounds like what is happening.

[Valoosj]

I think I just found a mistake in the schematic. When I compare it with the layout (and some common sense, as far as I can say I understand it all) something is wrong.

The positive sides of D5 and D6 are connected with R31 and the output of IC3b. This is wrong, no?

[oldschoolanalog]

Good eye. That is wrong.
Don't know what happened but this is the proper schematic where that FWR section is concerned. That connection you mentioned does not belong.
I wonder if this is the reason some folks can't get the gate to work.

[mean_dorris]

Ah, I'm glad my post made sense. My brain doesn't seem to work as well this time of night :S
R68, R69 and C29 seem to check out. C29 measures around 45pf though, is that too high?
Thanks again

In regards to that last issue, after much flipping of the pcb it appears that the positives of D5 and D6 don't connect with R31 etc, at least on my board. I've got rev5.

[Valoosj]

Good eye. That is wrong.
Don't know what happened but this is the proper schematic where that FWR section is concerned. That connection you mentioned does not belong.
I wonder if this is the reason some folks can't get the gate to work.

The wrong schematic is from the pdf with rev.5. I'll check solderman's work, see if he has that trace, he couldn't get the gate to work either.

[12Bass]

BTW, Valoosj, if you are concerned about space, it might be worth leaving out the threshold pot and associated circuitry.  It serves as a noise gate which mutes the delay signal when the input level is low.  However, there's not much noise, so I never use it on mine; the pot remains at 100 % all of the time.

Just made a few adjustments tonight to the LPF before the SAD1024A (older version) and the clock range.  It's pretty easy to get the high end of the sweep so high that it affects mostly cymbals.  I tried to find a balance where the top of the sweep wouldn't completely lose the harmonics of a guitar/bass signal.  Because I don't have an oscilliscope, I used my DD-20 as a reference for the lowest delay time of 14 mS.  Basically, I set both the A/DA clone and DD-20 with high feedback, fed them both white noise, then adjusted until the frequency of resonance was the same (~ C#).

[Valoosj]

Oh I'm not concerned about space though It will all fit nicely with two separate PCBs.
Just need to finish the second TL074 (IC1 on the schematic), adjust some traces to make is a bit neater when I have space left and then check it with the schematic.

The lfo section is done, all of the resistors but one are lying flat. So space is not much of a concern.

Setting it up might be a bit of a problem, I don't have that many tools but a DMM. So I'll have to do it by ear.

[12Bass]

Setting it up might be a bit of a problem, I don't have that many tools but a DMM. So I'll have to do it by ear.

It's possible to get it tuned by ear.  Above I gave a method to set the lower clock frequency.  The highest clock (range) I set to taste. 

One of the tricky settings is the BBD bias.  After getting the bias in the ballpark, what I did was send the flanger a sine wave, say 200 Hz, from my sound card, and brought up the level gradually until the BBD output was clipping.  Then I made fine adjustments until clipping went away.  Then repeat with increased signal each pass until you've reached the limit of clean output and you've got optimal bias.

[oldschoolanalog]

C29 measures around 45pf though, is that too high?

Shouldn't be. Where are you taking your clock f readings from?
What is your supply V at IC's 5&6?
And, which rev. board are you using? There are 2 spots designated C29 on the Moose PCB. Mare sure you have the cap in the correct one (the spot "in between" the ICs, next to R68).
Picture?

[solderman]

Good eye. That is wrong.
Don't know what happened but this is the proper schematic where that FWR section is concerned. That connection you mentioned does not belong.
I wonder if this is the reason some folks can't get the gate to work.

The wrong schematic is from the pdf with rev.5. I'll check solderman's work, see if he has that trace, he couldn't get the gate to work either.

I wish I was so, but I found that Schem error as well and moosapotamus helped me to clear that issue. its's in this treqad some where

[solderman]

BTW, Valoosj, if you are concerned about space, it might be worth leaving out the threshold pot and associated circuitry.  It serves as a noise gate which mutes the delay signal when the input level is low.  However, there's not much noise, so I never use it on mine; the pot remains at 100 % all of the time.

I thought that the idea was that you could control the amount of flange with your attack on the strings, say you pic gently and you get a clean tone strum the strings and you have flanging. sort of the thing one can do with a fuzz or or tube amp to controll dist. That was a brilliant idea I thought but if it doesent change that much It won't be worth the trouble. Since I never got mine to work I didn't have the opportunity to judge.