Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund)  [traced]

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

Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby silverface » 04 Jul 2012, 10:26

Can someone please explain the function of C3, the 1nF capacitor in the input buffer? And would lowering it to 100pF make it brighter?
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby sinner » 04 Jul 2012, 10:36

silverface wrote:Can someone please explain the function of C3, the 1nF capacitor in the input buffer? And would lowering it to 100pF make it brighter?



Yeah, it's low pass filter after all :thumbsup
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby sinner » 04 Jul 2012, 10:38

Look at this, can give you even more ideas

http://www.kitrae.net/music/BIG%20MUFF% ... 0GUIDE.jpg
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby fakcior » 04 Jul 2012, 11:10

Sinner, you're saying DH's trace is wrong? Like couple of mistaken values?
Can anyone check combination of 2x1n4148 at first stage and 2xoa47 at second?
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby sinner » 04 Jul 2012, 11:18

Never said that, perhaps Cornish did what we see on Dirks schematic, but we also hear a lot of opinions that the circuit is to dull for there likening. If it's really, then you have THE ears - now just half of brain and start twicking - BMP is not an rocket ship
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby sinner » 04 Jul 2012, 11:28

sinner wrote:
silverface wrote:Can someone please explain the function of C3, the 1nF capacitor in the input buffer? And would lowering it to 100pF make it brighter?



Yeah, it's low pass filter after all :thumbsup



My bad, I have just looked at Dirk's schematic. C3 is not an low pass filter, C9 is. And this is where I would start. Cornish said his buffers are unity gain, and add no coloration to the sound AFAIR, so BMP circuit it self is where the "problem" can be unsolved
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby Dirk_Hendrik » 04 Jul 2012, 11:36

All values in the schem are wrong. I did that on purpose. Before I posted photo's of the boards I painted new resistor color codes on the resistors. Then I replaced all UO-diodes with Ge and SI diodes......

gawd :roll:
That circuit was examined by hundreds. Don't you think that real errors would have shown by now? No. Decreasing that cap's value will not make it brighter.
Sorry. Plain out of planes.

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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby sinner » 04 Jul 2012, 11:43

Dirk_Hendrik wrote:All values in the schem are wrong. I did that on purpose. Before I posted photo's of the boards I painted new resistor color codes on the resistors. Then I replaced all UO-diodes with Ge and SI diodes......

gawd :roll:
That circuit was examined by hundreds. Don't you think that real errors would have shown by now? No. Decreasing that cap's value will not make it brighter.



I don't know to who you addressing your answer to, but if it's me then, then chill. As I said, I never was thinking you fuck it up, and definitely never said that.

The problem is me - I still believe FSB is about learning. Twicking is a part of it - matching to your likening. This tread shows that I'm in fact an lunatic

Good day
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby fakcior » 04 Jul 2012, 11:52

Sorry, Dirk
I didn't mean to offend you. I don't know how the process of tracing was leaded, because I haven't been here then.
But now PCB pictures don't work.
So I can assume it's all about diodes?
Again try 2x 1n4148 + 2x OA47.
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby MWichni » 04 Jul 2012, 12:03

All four diodes in the clipping section was germanium. Unfortunately Dirk was unable to determine the brand/model of the diodes because of the paint...
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby fakcior » 04 Jul 2012, 12:10

But in TopTone DG-2 is combination of Si/Ge and sounds pretty the same.

OA47s could do the job since they have lowest Vf of germanium diodes:
http://baec.tripod.com/articles/crystal.htm
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby silverface » 04 Jul 2012, 12:34

Btw I was not implying the trace is wrong, just that guitar->amp sounds 'different´ than with the buffer inbetween. Without the buffer circuit I feel it sounds a tad fuller or snappier for lack of better words. Though one might suspect just the opposite. In AG's trace of the Guild Brian May booster (http://analogguru.an.ohost.de/193/schematics/Guild_BrianMayBox.gif), which is basically a Cornish derivative, the cap between the transistor's B and E is 100pF. I'm only searching for clues :)

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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby MWichni » 04 Jul 2012, 13:23

fakcior wrote:But in TopTone DG-2 is combination of Si/Ge and sounds pretty the same.

OA47s could do the job since they have lowest Vf of germanium diodes:
http://baec.tripod.com/articles/crystal.htm


Yes, but they probably use 2xBAT48 and 2xGermaniums.
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby silverface » 05 Jul 2012, 08:41

I tried some different values for the 1nF cap, and it does make a noticable difference. A higher value mostly smoothes out the highs, and lessens the overall volume.

100pF : brighter, snappier, somewhat less full sounding, and more output volume.
470pF: a good inbetween value.
1nF (stock) : actually quite good, a well chosen value, though maybe a little too warm.

I'm going to do some testing at high volume soon to decide what value is best.
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby HydrozeenElectronics » 10 Jul 2012, 11:43

Can some on help me figure out why R11, R12 and R13 are connected to positive voltage and not just ground? I can see that they are part of some sort of boot strapping configuration to boost impedance I'm guessing but why the DC positive wouldn't the AC input just float right over the top of it to ground? I've really been trying to wrap my mind around this for a while now and any help would be appreciated.

Thanks
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby Dirk_Hendrik » 10 Jul 2012, 12:06

HydrozeenElectronics wrote:Can some on help me figure out why R11, R12 and R13 are connected to positive voltage and not just ground? I can see that they are part of some sort of boot strapping configuration to boost impedance I'm guessing but why the DC positive wouldn't the AC input just float right over the top of it to ground? I've really been trying to wrap my mind around this for a while now and any help would be appreciated.

Thanks


Which schematic are you referring to when you mention these resistors?
Sorry. Plain out of planes.

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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby HydrozeenElectronics » 11 Jul 2012, 01:50

Dirk_Hendrik wrote:
HydrozeenElectronics wrote:Can some on help me figure out why R11, R12 and R13 are connected to positive voltage and not just ground? I can see that they are part of some sort of boot strapping configuration to boost impedance I'm guessing but why the DC positive wouldn't the AC input just float right over the top of it to ground? I've really been trying to wrap my mind around this for a while now and any help would be appreciated.

Thanks


Which schematic are you referring to when you mention these resistors?


It's the buffer stage of the G2 pedal that is in the downloadable pdf at the beginning of the thread.
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby BaldPaul » 19 Jul 2012, 21:19

File unavailable. What gives?
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby Dr Tony Balls » 18 Sep 2012, 15:27

Does anyone have this schematic still? I have a printout hat I can either scan or just redraw if needed.
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Re: Cornish G2 - Guts, Schematic, Layout (from Tracer's Fund

Postby Intripped » 18 Sep 2012, 23:42

i have this - should be correct
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