by dancloud69 » 24 Oct 2014, 17:05
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
- For this message the author dancloud69 has received thanks: 10
- aishabag23 (28 Feb 2017, 06:40), floris (12 Aug 2017, 21:53), G.G. (24 Oct 2014, 18:27), Intripped (25 Oct 2014, 14:20), joe_pineapple (25 Oct 2014, 09:10), lars-musik (24 Oct 2014, 21:04), Nocentelli (24 Oct 2014, 20:22), Pruttelherrie (26 Oct 2014, 19:02), stringsthings (05 Jan 2015, 00:27), tp801 (25 Oct 2014, 12:10)