Andy Armstrong, Soft Fuzz, in: Hobby Electronics, July 1983 🇬🇧

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modman
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Post by modman »

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Hobby-Electronics-1983-07-S-OCR Soft Fuzz.pdf
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Hobby-Electronics-1983-07-S-OCR Soft Fuzz 2.jpg
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Manfred
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Post by Manfred »

SoftFuzzLayout.JPG
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Manfred
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Post by Manfred »

The value of R2 with 470 ohms was immediately suspicious to me, the circuit needed a high input level until the output signal began to clip, with 470 kiloohm then worked at lower levels.
Also, the frequency response showed that 470 Ohms must be the wrong value.
With 470 Kiloohms, the frequency response was then hi-fi and not suitable for guitar, there are still some things to improve.
R1 should have at least 560 kilohms I think that here also a digit "0" was forgotten in the value.
SoftFuzzFR.jpg

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Frank_NH
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Post by Frank_NH »

That seems right, Manfred. R2 is supplying the reference voltage for biasing IC1a, so 470K should be correct. The input resistor looks like an anti-pop resistor, so 1 meg would work there.

I'm curious to see what the soft clipping looks like. This is an unusual soft clipping feedback network which could potentially provide a more interesting distortion than the typical diode arrangement. I guess I should sim this in LTSpice too!

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Post by Manfred »

Frank_NH wrote: 31 May 2022, 16:17 That seems right, Manfred. R2 is supplying the reference voltage for biasing IC1a, so 470K should be correct. The input resistor looks like an anti-pop resistor, so 1 meg would work there.

I'm curious to see what the soft clipping looks like. This is an unusual soft clipping feedback network which could potentially provide a more interesting distortion than the typical diode arrangement. I guess I should sim this in LTSpice too!
SoftFuzzClippingCurves.jpg

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SoftFuzzClippingCurves2.jpg

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