Adding waveshaper to ADA Flanger

[jmasciswannabe]

Decided I would document this attempt and open it up for advice. I was wanting to mod an ADA Flanger using this schematic I found searching the forum:

http://www.wizardinside.it/foto/schemi/HyperLFO.png

Fender3D was kind enough to respond to a PM and confirm that the switching section should go between range wiper and R65 in this schematic but also mentioned that "since this wave converter greatly attenuates the voltage at its input, you'll have to tweak some resistors (R53 or 54 or 52) to achieve a proper manual range."

Can I just measure voltage at R65 before the mod, then add the mod in and adjust R52 until it has the same voltage after I insert the mod?

He also said "to obtain a proper hyper-sinusoidal waveform, I avoided T3 and set a fixed ratio for LFO biasing (thus centering its waveform at 1/2V supply)" ... is there a way to measure this with a meter to properly set T3.

http://moosapotamus.net/images/FlangerClone_SCH_rev5_MN3007_jan2010.gif

[Fender3D]

Hi Ian,

you don't need measuring LFO output voltage, since you know VCO sweeps from 34.8 KHz to 1.3MHz (69.6KHz ~ 2.6MHz with MN3007)....

tweak IC3c's resistors to obtain those values at 4047 pin 13.

About T3:
according to ADA notes, you set VCO range referring P3's CW and CCW positions, then set T3 so that LFO sweeps from 69.6KHz to 2.6MHz.

Since the best hyper-sinusoidal waveform is obtained with LFO biased (almost near) 1/2 Vcc, you can set T3 for circa 1/2Vcc @ IC4's pin 2, then set T4 and T5 (P4 fully CW, rate at minimum) for desired sweep range (69.6KHz ~ 2.6MHz).
then tweak R52, R53 or R54 so that manual control sweeps the same...

Just a little more tricky...

[jmasciswannabe]

Cool. This helps a lot. Thanks!! I feel like I am trying to make words without knowing what the letters sound like!

[jmasciswannabe]

Can anybody make suggestions as to the modded values to R53 or 54 or 52 to make this work? I have hooked up the switch and it has shifted a lot lower, like 20-60 instead pf 69 to 2.6....i tried a 1m trimmer for r54 with no luck. I am assuming there is math calculation and formulas involved here of which I have no clue....

[Fender3D]

Did you swap R66 for a 160K?

Does it work (sweep) ok with LFO?

If it works ok with LFO sweeping, R52, 53 and 54 should be adjusted just to offset the different TR3 setting...

[jmasciswannabe]

I saw that note on your schem about the ada being 51k but didn't know to  change it. Will do that and give it another shot this afternoon. Also, you mentioned setting up t3 auto seep by getting 1/2vcc at pin2 on IC4. I am assuming this is 1/2 the chips supply voltage? If so, this is a much more effective way than setting it by ear!

[jmasciswannabe]

Well, replaced the resistor and still no go. It looks like the lfo voltage swing is getting decimated as it leaves the source of the jfet. On the drain it is identical to the pin 7 voltage on the lfo, but gets knocked down to about .8 - 1.2  volt when it comes out the source. I triple checked my parts and even replaced the 2n3819 but still the same.

[Fender3D]

I just quickly breadboarded it...
no 2N3819, so I used a BF245, changed some resistors with similar values, (lazy to search...)
15k and 16k for last op amp...

results:
LFO sweep: 11.53 to 4.30 V
waveshaper: 4.75 to 10.01 V (triangle output)

I think you have other issues, 'cause mine almost works ok

[jmasciswannabe]

Any reason a 2n3819 would not work but a j201 would? I've got it working and am taking a break to fine tune later.

[Scruffie]

Any reason a 2n3819 would not work but a j201 would? I've got it working and am taking a break to fine tune later.

The pin outs are different?

[jmasciswannabe]

Yeah, I knew about the pinout being different. Central n23819 is even different form the ON 2n3819. When going through this I got so frustrated and scrapped the first board and did another with a socket. Anyway, I've made progress....with the j201 i am getting proper LFO swing. Gonna get the switch going...just have it set to triangle for now....and then switch to sine and see if I can't get it calibrated. Using a flintlock board this time around, will post at MB with sound samples and link here for folks to hear once satisfied.

[12Bass]

Looking forward to hearing the results!

[jmasciswannabe]

Alright folks, getting closer. I've got the switch and can hear the waveforms. The problem now is that the manual sweep is greatly diminished. The widest I have been able to obtain is about 800KHz. I gather the solution is in adjusting the r52, r53 and r54 resistors, but I'd rather not go blindly about it. Can anyone suggest some values or give me an idea of the resistors interactions?
I guess I will install trims, if not and go from there...

[Fender3D]

You need higher voltage gain to offset the waveshaper's attenuation.

IC3d is an inverting op-amp:
Gain = R54/R53
R52 (and R51, but I wouldn't touch this...) set(s) reference voltage.

[jmasciswannabe]

FENDER3D, first and foremost, thanks for all your help and time with this. I felt bad that you had to breadboard due to me not trying different jfets. Anyway, I plan on using this tool when I get home as I do not have the voltages handy here:

http://www.daycounter.com/Calculators/Op-Amp/Op-Amp-Voltage-Calculator.phtml

I am going to adjust r54/53 to adjust the gain and then r52 to retain original output voltage. Will update after tinkering!

[Fender3D]

You're welcome Ian...
Good to know you didn't surrender

Let me know what you think about the mod