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Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 11 Mar 2012, 17:22
by gigelmargel
coldcraft wrote:how about a full-stereo Pareidolia with a Ramp Function?

I've got it on the drawing board. The idea is to have 2 pareidolias sync'd to the LFO but 180 out of phase (treble is up on the left while down on the Right).


Woow...it sounds very interresting :)

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 11 Mar 2012, 18:18
by coldcraft
i hope it comes together well. In stereo, it would sound as if the treble and bass are going left to right with a 180 degree lag between them. I'll add an input buffer and output buffer as well as configure it so it can be driven with a mono signal or an already stereo signal.

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 18 Apr 2012, 19:36
by soggybag
The stereo Pareidolia sounds like a great idea. Seems, to my amateur eye, that R6 and R12 mix the output of the two Mu Amp stages. I'm guessing you could just connect R12 to it's own output jack.

You may need to add a volume. Imagine the Volume pot as a dual pot with R6 connected to one pot and the R12 connected to the other pot. Using a switching jack you wire it to switch between mono and stereo.

Here's a couple questions.

Seems you could probably use any type of LFO. Is there something special that this circuit is getting from the XR2206?

I get that the LFO is fed out phase to Q3 and Q6. What I'm curious about here is what happens at C6 and C12. These are some how controlling the output of the two Mu Amps.

There seems to be a filter on each of the Mu Amp Stages. Is this happening through C5 and C11?

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 18 Apr 2012, 20:14
by Nocentelli
soggybag wrote:I get that the LFO is fed out phase to Q3 and Q6. What I'm curious about here is what happens at C6 and C12. These are some how controlling the output of the two Mu Amps.

There seems to be a filter on each of the Mu Amp Stages. Is this happening through C5 and C11?


The input caps (C3=270p and C9=100n with C10=5n to ground) probably also separate the input signal into high and low bands, not sure of the role of C6 and C12.

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 19 Apr 2012, 00:17
by coldcraft
soggybag wrote:The stereo Pareidolia sounds like a great idea. Seems, to my amateur eye, that R6 and R12 mix the output of the two Mu Amp stages. I'm guessing you could just connect R12 to it's own output jack.


I didn't mean stereo as in treble-left, bass-right. what I'm thinking of is basically 2 pareidolias that have LFOs that are out of phase. The treble will alternate Left to right while the bass runs Right to Left.

started on it here, viewtopic.php?f=72&t=16592

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 19 Apr 2012, 01:40
by roseblood11
1 + -1 = 0 :scratch:

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 19 Apr 2012, 13:24
by coldcraft
roseblood11 wrote:1 + -1 = 0 :scratch:



more like 1 + i,

or even better,
cos(t) + i*sin(t).

The LFO driving the Left Pareidolia is out of phase with the LFO driving the right channel. The actual audio is in phase and the outputs of the channels are sent to different amps. The result will be more like a panning/vibe than a tremolo/vibe.

i guess it will be easier to just build the damn thing and make a nice demo.

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 26 Apr 2012, 10:39
by audioguy
roseblood11 wrote:I use a little Fender amp, similar to the princeton in catalinbreads video. And the pedal simply doesn't work with that amp. The treble side of the sweep makes my ears hurt and the bass side distorts the amp even if it's set to a totally clean sound.

Did you use Pruttelherrie's layout?

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 26 Apr 2012, 11:41
by roseblood11
No, I used the vero layout.

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 26 Apr 2012, 13:31
by audioguy
roseblood11 wrote:No, I used the vero layout.

Does anyone know if the PCB has the same issues? I would imagine the values are the same, so probably so, huh?

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 26 Apr 2012, 17:27
by roseblood11
It's not even sure that we're talking about any issues. Maybe the original pedal sounds exactly the same...

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 26 Apr 2012, 17:55
by audioguy
roseblood11 wrote:It's not even sure that we're talking about any issues. Maybe the original pedal sounds exactly the same...

Good point!

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 08 Dec 2012, 15:07
by v0d00blues79
Hi, I just built this board using Haralds vero layout and I’m having a bugger of a time getting it going. I’ve probed the audio path and I have audio all the way up to the Drains on Q3 and Q6, but I’m not getting anything past that. I’ve tried a coulple pairs of 2N5457′s to no avail. Could I ask that anyone who has built this post up their voltages so I can double check mine? I’m getting around 1.3V at the Source pins and that seems really low to me. Any help anyone might be able to offer would be greatly appreciated!

Thanks,

Andy

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 12 Sep 2013, 22:26
by soggybag
I just built one of these from Sabrotones vero layout posted here. It passes a signal. Though it's a little distorted, sounds like the mu amps are working. But, there's no phasing or modulation. The LEDs are lit, but don't pulse. I'm guessing the XR2206 is not modulating.

Anyone got any suggestions on what to check with this chip?

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 13 Sep 2013, 01:17
by soggybag
Comparing the Schematic posted earlier the Sabrotone layout seems to switch the op-amp pins, IC1a and IC1b are swapped.

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 13 Sep 2013, 01:45
by soggybag
Measuring pin 2 of the XR2206, it seems to be cycling from about 3.5V to 4V. At pins 1 and 7 of the op-amp I see a constant 3.8V.

Question: Does the output of XR2206 seem about right? If so then there must be some problem in the connection between pin 2 of the XR2206 and the op-amp, would that seem a reasonable guess?

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 22 Sep 2013, 20:21
by Pruttelherrie
soggybag wrote:Measuring pin 2 of the XR2206, it seems to be cycling from about 3.5V to 4V. At pins 1 and 7 of the op-amp I see a constant 3.8V.

Question: Does the output of XR2206 seem about right? If so then there must be some problem in the connection between pin 2 of the XR2206 and the op-amp, would that seem a reasonable guess?

In mine, pin 2 of the XR2206 sweeps around the 3.9V, but the outputs of the opamps are not constant: they sweep/cycle as well. So I think your guess is right, look for problems around the opamps.

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 24 Oct 2014, 17:05
by dancloud69
Hi,

this is for all who think their build of the Pareidolia sounds trebly and thin:

A few weeks ago I built this effect using Harald Sabro's layout. I too found this effect to be really trebly and not very nice sounding. Still, as I had boxed it right away I didn't want to leave it at that.

Last weekend I therefore had another close look at the schematic, and I believe I have found (and fixed) the cause of the trebly sound:

The problem exists right at the input of the pedal. As was described before, the input signal is split into a high and a low signal path. The highs are sent through a high pass filter using R1/C3, the lows are sent through both a high pass filter (R7/C9) and a low pass filter (R8/C10). Applying the filter cutoff formula to both the R1/C3 and the R8/C10 filter shows a probable error in the trace:

The highs are cut below 589Hz, while with the 5nF/1MOhm the lows are cut above about 32Hz!
This results in a very wide notch in the signal, which as far as I can see fully explains the extremly trebly and hollow sound.

I changed to 5nF cap C10 to a 250pF (just had that value as a silver mica, also decided to use a socket), and viola... the pedal suddenly sounds really close to what I hear in the Youtube demos, and definitely not trebly and hollow any more. With the 250pF, the lows are filtered above 637Hz which gives a nice overlap of the two signal paths between 589 and 637Hz (or wider, as the filters are not very steep).

I'm not sure about the original value of C10, so I played around with several capacitor values between 470pF and 150pF, but currently like the 250pF best. It does give the characteristic phasing in the mids. If the phasing in the mids is felt to be too intense, a capacitor value of 270pF or even 330pF will reduce or almost eliminate it. Some more overlap can be created with e.g. a 220pF cap.

So if anyone has given up on this pedal but still has the build, I strongly suggest you try this fix.

Best,
Dan

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 24 Oct 2014, 20:08
by roseblood11
I always was sure that this pedal didn't sound right - and sold it. Maybe I have to build a new one now...

Re: Catalinbread Pareidolia Harmonic Mesmerizer

PostPosted: 05 Jan 2015, 00:30
by stringsthings
I changed to 5nF cap C10 to a 250pF (just had that value as a silver mica, also decided to use a socket), and viola... the pedal suddenly sounds really close to what I hear in the Youtube demos, and definitely not trebly and hollow any more. With the 250pF, the lows are filtered above 637Hz which gives a nice overlap of the two signal paths between 589 and 637Hz (or wider, as the filters are not very steep).

I'm not sure about the original value of C10, so I played around with several capacitor values between 470pF and 150pF, but currently like the 250pF best. It does give the characteristic phasing in the mids. If the phasing in the mids is felt to be too intense, a capacitor value of 270pF or even 330pF will reduce or almost eliminate it. Some more overlap can be created with e.g. a 220pF cap.


This fix worked very well! I used a 330pf in mine. Thanks dancloud9!