Pete Cornish - G2 Guts, Schematic, Layout (from Tracer's Fund) [traced]
- silverface
- Solder Soldier
Can someone please explain the function of C3, the 1nF capacitor in the input buffer? And would lowering it to 100pF make it brighter?
- sinner
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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
- sinner
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- sinner
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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
- sinner
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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
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
- Dirk_Hendrik
- Old Solderhand
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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
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.
gawd
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.
- sinner
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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
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
- fakcior
- Breadboard Brother
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.
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.
- MWichni
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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...
- fakcior
- Breadboard Brother
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
OA47s could do the job since they have lowest Vf of germanium diodes:
http://baec.tripod.com/articles/crystal.htm
- silverface
- Solder Soldier
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/schem ... MayBox.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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Yes, but they probably use 2xBAT48 and 2xGermaniums.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
- silverface
- Solder Soldier
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.
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.
- HydrozeenElectronics
- Resistor Ronker
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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
Thanks
- Dirk_Hendrik
- Old Solderhand
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Which schematic are you referring to when you mention these resistors?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
- HydrozeenElectronics
- Resistor Ronker
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It's the buffer stage of the G2 pedal that is in the downloadable pdf at the beginning of the thread.Dirk_Hendrik wrote:Which schematic are you referring to when you mention these resistors?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
- Dr Tony Balls
- Diode Debunker
Does anyone have this schematic still? I have a printout hat I can either scan or just redraw if needed.