MXR Flanger clone

[Spencerleehorton]

ive given up with R7 and R8 as i think this is bias for tone, leave them how they are 100k and 10k.
Ive tweaked R5 down to 75k and R9 to 39k and sounds much better, still tweaking though!!!

 

[JohnRoberts]

ive given up with R7 and R8 as i think this is bias for tone, leave them how they are 100k and 10k.

They appear to be some kind of de-emphasis (HF roll-off) in concert with C3 (?) I think I can't read that schematic very well..

Ive tweaked R5 down to 75k and R9 to 39k and sounds much better, still tweaking though!!!

If those are what I think they are (unsure which is R9 probably the 82k), you are scaling the dry and wet gain up, relative to the BBD path, so that will degrade S/N in the  BBD roughly 6dB.

Have you tried just hitting it with a hotter input signal?

JR

 

[Spencerleehorton]

i've re-soldered everything and put pins in to solder too, to save the pcb, everything is sounding much better now!! must have been a bad contact, will put back to stock and see how it sounds!!!
One other note, one or all of the pots must have been shorting out to the case or something cause at one point it turned into a really cool delay pedal!!!
Might investigate this further and if possible put some switches in to get this effect, or possible a external volume pedal which could adjust speed!!

 

[Spencerleehorton]

Hi still playing with this flanger, I have too much bass when effect enabled could I change the 3.3nf cap  C3 to 4.7nf to cut more bottom end?
I have taken  R5 to 75K and R9 to  41K to get better mix of  dry wet level.

 

[JohnRoberts]

Hi still playing with this flanger, I have too much bass when effect enabled could I change the 3.3nf cap  C3 to 4.7nf to cut more bottom end?
I have taken  R5 to 75K and R9 to  41K to get better mix of  dry wet level.

After several months I don't remember what we were talking about.

Looking at a schematic I found from back then.  R5 looks like it will affect the dry signal contribution... changing from 150k to 75k will bump the dry signal +6dB

changing r9 from 82k to 41k will bump the wet signal +6dB

Output will be 6 dB hotter but mix will be the same.

JR

 

[Spencerleehorton]

Yes mix sounds more even between effect on and off but too much bottom end!
What can I try to cut bass?

 

[Spencerleehorton]

well i've put it all back to stock and the bottom end is too much, i need to find out why i've got so much bottom end when the effect is engaged?

does anyone know where in the circuit this could be happening please?

 

[JohnRoberts]

well i've put it all back to stock and the bottom end is too much, i need to find out why i've got so much bottom end when the effect is engaged?

does anyone know where in the circuit this could be happening please?

It might be instructive to plot out the response of all the filter poles/networks in the audio path.

From a quick glance the feedback network across IC1A looks like a de-emphasis network (that will attenuate HF content )

I don't trust reading the values off the low resolution schematic to calculate myself...

A de-emphasis in the summed output path suggests there is a pre-emphasis somewhere in the front end (maybe IC1B?).

De-emphasis without symmetrical pre-emphasis can sound boomy.

Caveat... this is speculation since I cannot accurately read the cap values.

JR

 

[Spencerleehorton]

How about this?

Or here’s the url link

http://www.madbeanpedals.com/projects/Collosalus/Collosalus2015.pdf

 

[Spencerleehorton]

It is quite strange as there is a little drop in level between effect on and off and when the effect is on it sounds boomy bass heavy how ever you want to say it, but if there was more top end it would probably sound about right level wise.
If you see what I mean .
I’m going to check all resistors, or at least try!!

 

[JohnRoberts]

OK I can read the values from that link... but i do not have time right now.

FWIW at a fixed delay you will get a comb filter transfer function so bumps and dips.

JR

 

[Spencerleehorton]

i've just checked all resistors and R7 and R8 were not correct, must have changed them at some point and not changed them back!!
Now i get nothing, don't have time now to fault find so im going to dig out the electric mistress and use that for the gig tonight.
A couple of traces have obviously come off as i could hear the effect but very low level, will trace with scope and see where it all gets too!!
learning a lot about reading the resistors codes!!!

 

[JohnRoberts]

OK I'm back from my doctor's appointment and it looks like I may live,  ;D  so here's some more quick observations.

The de-emphasis pole formed by R8 and C3 in the feedback looks like -3dB @ 5.3khz falling -6dB oct for maybe a decade .

The pre-emphasis pole formed by R4 and C2 starts increasing gain at 4.8kHz, so close enough for government work, at least in the audio bandpass.

If you are getting too much bass (not enough highs) perhaps check the values and connections for R4 and C2. 

JR

 

[Spencerleehorton]

The output is definitely down when effect is in, could do with boosting it up a few dB, will look at R4.

 

[Spencerleehorton]

Where should I go with R4, C2?
Lower or higher values?
Ideally I want this pedal to be at unity gain when effect is on, but I may want to be able to adjust it a little hotter.
The top end is definitely dampened.
I’ve heard a lot of people say the output is down -3db approx on this pedal.
You can hear it on some of the YouTube videos of the collosalus mad-bean clone.

 

[JohnRoberts]

Where should I go with R4, C2?

confirm that the values are what they should be.

Lower or higher values?

neither

Ideally I want this pedal to be at unity gain when effect is on, but I may want to be able to adjust it a little hotter.
The top end is definitely dampened.
I’ve heard a lot of people say the output is down -3db approx on this pedal.
You can hear it on some of the YouTube videos of the collosalus mad-bean clone.

I am not inclined to redesign somebody else's design.  Can't we ASSume it worked as designed?

JR

 

[Spencerleehorton]

as i have said, everyone who has talked about this version of the effect has complained about the low output when the effect is on.
I will double check i have R4 = 1k and C2 = 33nf and will change the 5532 just ot make sure.

 

[Spencerleehorton]

R4 is definitely 1k but need to take out c2 it says 332 on it so it could be 330nf but I think it is 33nf.
Have checked connections and is fine.

 

[Spencerleehorton]

This post details some evidence.

http://www.madbeanpedals.com/forum/index.php?topic=9101.0

 

[Spencerleehorton]

Digging through a couple more threads about this same issue I have found this:

when you up the gain by increasing the R7 (100K) it will get more bassy sounding. The fix is to increase R8 as well (try 33K) and C3 (try .001uf) and see how it sounds.

I had R8 = 33k and R7=220k but I didn’t change C3 from 3.3nf

Could anyone verify that this would work?