Analogman - King of Tone  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
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Boba7
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Post by Boba7 »

So someone on the pedalpcb forums just posted a few pics of two different KOT (one low and high gain, one double high gain) and C4 and C22 (the caps in the feedback loops) are both 100pf on both builds
See here: https://forum.pedalpcb.com/threads/prin ... 02&slide=0

So the only difference between low gain and high gain is the 1k/100k resistor, no difference in the feedback loop capacitor!

The 750p value posted by sprentis is still quite a mystery... to me it’s probably Analogman playing with us pedal nerds like he did with the painted resistors

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rtcustom
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Post by rtcustom »

Boba7 wrote: 07 Aug 2020, 20:21 The 750p value posted by sprentis is still quite a mystery... to me it’s probably Analogman playing with us pedal nerds like he did with the painted resistors
Why do you think that?
Honestly, the pedal (clone !) has noticeable noise for an overdrive with 100p when both channels are ON! Even with shielded in/out wiring.
Didn't you think that maybe he wanted to reduce the noise of the pedal with that 750p op-amp feedback capacitor?!?

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Boba7
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Post by Boba7 »

rtcustom wrote: 13 Aug 2020, 12:15
Boba7 wrote: 07 Aug 2020, 20:21 The 750p value posted by sprentis is still quite a mystery... to me it’s probably Analogman playing with us pedal nerds like he did with the painted resistors
Why do you think that?
Honestly, the pedal (clone !) has noticeable noise for an overdrive with 100p when both channels are ON! Even with shielded in/out wiring.
Didn't you think that maybe he wanted to reduce the noise of the pedal with that 750p op-amp feedback capacitor?!?
Could be. But the 100p value has been documented several times for both channels, low and high gain, whereas the 750p cap is an exception, and there is an exemple in this thread of a painted resistor in a KOT. So I wouldn’t be surprised, that’s all.
Ill keep the 100p value in my builds, feel free to experiment with other values!

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rtcustom
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Post by rtcustom »

Boba7 wrote: 13 Aug 2020, 22:35 Ill keep the 100p value in my builds, feel free to experiment with other values!
In my latest build, i was thinking of inserting 680p considering it is hard to get 750p .. but .. perhaps the best test is to place the sockets and thus determine the differences in noise and tone between 100p & 680/820p ...
I'll try and report the results ;)

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turbofeedus
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Post by turbofeedus »

Who would have thought there's be a necro post in the infamous KoT thread :o
Anywho, I did some more plots on KoT diodes, expanding specifically the 1S1588.
I had three different "styles" of (allegedly) 1S1588 in my collection, which I will refer to as "big", "mid", and "skinny" from top to bottom.

Image

- "big" has a wide blue band that wraps around the cathode edge of the glass package
- "mid" has a medium width blue band, and the orange color inside the diode is a bit darker
- "skinny" has a narrow blue band

However, as far as Vf curves are concerned, they are effectively identical.
That is to say, the variation between the three styles is no greater than the variation between any two of the same style. (Is there a statistics term for this?)
Measured with a DCA75, note the zoomed in x-axis.

Image

Oh! Also wanted to add, I did some I/V traces for the BAS33 vs MA858 (with a couple others):
Contrary to an earlier claim, the BAS33 had slightly lower Vf than the MA858, but the curves are quite similar as Frank_NH predicted.
I haven't tried any listening tests, don't have a KoT build on hand.
Also fun fact, the BAS33 was End-of-Life'd last week, so now might be the time to grab some.

Image

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Blues1911
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Post by Blues1911 »

UPDATE: I have just verified that, in the february 2024 batch, C4 and C22 (the caps in the feedback loops) are 0.20 uf ceramic (BC 204).
Respect to my self built clone (with 100pf feedback loop cap), the original specimen that I have just bought seems to have more presence and compression, and a sensibly better cleanup with guitar volume (more chime), but I'm still not sure if that depends from this single cap, or what.
More to follow, as soon as I can upgrade the cap on my clone.

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