Tonepad's flanger301. any way to turn it into chorus/like?

[jrc4558]

subj.
I read Mark Hammers writings on the clocking speed, but this being my first project that involves MN3101. I'm not all that familiar with this chip. Hence I have a chance to screw up unless the wise of this forum wont guide me. hehe. Isn't that what I say all the time? Anywhoo...
Is this a 180pF cap between pins 5 and 7 on the MN3101? Will making the value larger make it sound more like a chorus?
Need your advice, ladies and gentlemen!

[Bill Bergman]

Plug it in to 9vdc instead of 18vdc and you get some strange effects...

[jrc4558]

Well, I thought of that, but that will change the LFO rates as well, wouldn't it?

[Bill Bergman]

It's really not too useable but it sounds cool. Sorry this was just an obsevation not really intended for an answer to your original question.

[Mark Hammer]

There are a few systematic differences between flangers and choruses:

1) Choruses never have regeneration.  Just a straight wet/dry combination.  Some choruses allow the user to reduce wet-level.

2) The delay range is proportionately smaller for choruses (e.g., 5-15msec or  3:1) compared to flangers (e.g., 500usec to 10msec or 20:1), and is generally longer.

3) The LFO sweep range is usually broader on a flanger since the more obvious comb-filtering action on a flanger can still be noticeable even when the LFO sweeps at very slow rates (e.g., 0.2hz or slower).  Once a chorus starts to sweep slower than maybe 0.5hz, it gets hard to detect, unless the sweep width is so wide that the pitch change is made obvious.

4) Flangers are generally more tolerant of wide sweep because of the diminished pitch distortion and concentration on comb-filtering.  As always in modulation pedals, slower sweep requires greater sweep width to yield effects that are noticeable, and conversely faster LFO rates demand lower sweep widths to be pleasing.

5) Since there are big steps between BBD chip capacities, the use of slower clock frequencies to achieve longer delay times in BBDs of identical capacity means that flangers need less lowpass filtering than choruses.

With those differences in mind, conversion of the FL301 into a chorus might involve:

a) A regen cancel switch (DPST) that lifts the input and wiper leads from the regen pot so you can leave the regen where it suited the flanging, rather than turning it all the way down and having to readjust.  

b) A cap bump from 180p to maybe 220p or 270p to shift the delay range.  If you put a 270p and 510p in series, and used a SPST to shunt the 510p cap, you'd have effective values of 270p and 176p, which is a reasonable approximation.  Alternatively, 240p and 560p in series gets you 168p and shunting the 560p gets you back to 240p, which may be a more reasonable spread.

c) I don't know how fast the LFO bubbles on the FL301 since I didn't finish mine.  If it bubbles fast enough for chorus purposes, then you don't have to change the back-to-back 10uf caps to shift the range.  On the other hand, if the LFO covers too wide a range and you find yourself unable to dial in small differences in bubbliness, consider switching in a 330k fixed resistor across the leads for the Speed pot so that its fastest range is distributed across more of the pot's rotation (permitting more dialability).

d) If the sweep range is so broad that dialing in subtlety is tricky, you can simply tack a 15k-22k fixed resistor in series with the input lug on the Depth pot.

e) The filtering on the FL301 seems to me to be steep enough to tolerate somewhat slower clock rates.  If not, we can tackle that beast when we get to it.

There, is that a concrete enough depiction of what you can do?

[jrc4558]

God yes! Thank you Mark! Thank you Bill!
Now I need to get it working right. So far I have only clean sound going through it, which means that the delay line is not working right. Give me time.

[Metallor]

so where is the schematic for the tonepad flanger301?

thanks

[Bill Bergman]

http://www.tonepad.com/projects.asp?projectType=fx