# Germanium II



## K Pedals (Feb 10, 2020)

Just finished this one up


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## chongmagic (Feb 10, 2020)

Sweet I have one of these to build, how do you like it? Is that the new hammered Tayda enclosure?


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## K Pedals (Feb 10, 2020)

chongmagic said:


> Sweet I have one of these to build, how do you like it? Is that the new hammered Tayda enclosure?


I like it...
It a real quality standard distortion...
Yeah that’s the new Tayda box...


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## Chuck D. Bones (Feb 10, 2020)

Very nice!  Love that hammertone finish!  As soon as Tayda has another 15% off, sale, I'm ordering some.  How does the tone and sustain of the Ge clipping compare to other BMPs you've built?


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## cooder (Feb 10, 2020)

Sweet! I need me a G2 again as well since I let a friend try one I built yonks ago and he twisted it out of my hands...


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## K Pedals (Feb 10, 2020)

Chuck D. Bones said:


> Very nice!  Love that hammertone finish!  As soon as Tayda has another 15% off, sale, I'm ordering some.  How does the tone and sustain of the Ge clipping compare to other BMPs you've built?


A lot less gain...
A little darker...
Not as much of that static sound of a big muff... a little smoother...


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## Mourguitars (Feb 10, 2020)

Pretty work K Pedals !

Mike


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## Barry (Feb 10, 2020)

Nice!


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## chongmagic (Feb 10, 2020)

Did you use an A50k for Sustain?


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## K Pedals (Feb 10, 2020)

Yeah I found a 50k that measured 48k so I used that one...


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## chongmagic (Feb 10, 2020)

Could you do me a favor and take the voltages on your Q5? I am just getting unity gain and slight distortion. I don't think that should be the case.
I am getting around 3.8 on the emitter. The other are around 4.5 or 9v.


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## K Pedals (Feb 11, 2020)

I’m getting 3.9v on the collector 
The base is showing .62v and emitter is 35mv??
But that can’t be right can it???


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## chongmagic (Feb 11, 2020)

I meant the collector. The emitter is about the same for me.


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## chongmagic (Feb 11, 2020)

Compared it to my Aion G2 and they are pretty close in sound.


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## Chuck D. Bones (Feb 12, 2020)

K Pedals said:


> I’m getting 3.9v on the collector
> The base is showing .62v and emitter is 35mv??
> But that can’t be right can it???



Looks about right to me.


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## Chuck D. Bones (Feb 12, 2020)

Chong:
The amount of gain you get is going to be very dependent on the leakage in the Ge diodes.  They don't just leak DC current, they leak AC current too and that makes more negative feedback around Q4 & Q5, reducing gain.  Cornish probably hand-picks the diodes in his builds.


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## chongmagic (Feb 12, 2020)

Chuck D. Bones said:


> Chong:
> The amount of gain you get is going to be very dependent on the leakage in the Ge diodes.  They don't just leak DC current, they leak AC current too and that makes more negative feedback around Q4 & Q5, reducing gain.  Cornish probably hand-picks the diodes in his builds.



I used some D9V and only measured the forward voltage which was pretty much consistent for all four. I didn't measure the leakage though, probably should have.


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## Robert (Feb 12, 2020)

I've always preferred to use a pair of silicon diodes in the first clipping stage (D3/D4) on these, germanium in the second stage.


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## Bret608 (Feb 13, 2020)

I remember over at Madbean that jubal81 figured out something with reverse resistance and the role it plays in how much a diode will clip. You basically measure the resistance going through the diode in one direction, then the other. I don't remember which direction is which, but the higher of the two readings is usually the reverse resistance. Is this the same thing as figuring out the leakage? Anyway, I think you want higher numbers--500k would not distort much; 2m or above is better. The one wrinkle here is that your DMM needs to be able to read resistances of 2m or more. Mine does not so I haven't personally tried this out yet.


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## geekmacdaddy (Feb 13, 2020)

Very nice build.


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## K Pedals (Feb 13, 2020)

geekmacdaddy said:


> Very nice build.


Thanks man!!!


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## Chuck D. Bones (Feb 13, 2020)

Bret608 said:


> I remember over at Madbean that jubal81 figured out something with reverse resistance and the role it plays in how much a diode will clip. You basically measure the resistance going through the diode in one direction, then the other. I don't remember which direction is which, but the higher of the two readings is usually the reverse resistance. Is this the same thing as figuring out the leakage? Anyway, I think you want higher numbers--500k would not distort much; 2m or above is better. The one wrinkle here is that your DMM needs to be able to read resistances of 2m or more. Mine does not so I haven't personally tried this out yet.



The other wrinkle is that the resistance reading depends on how much voltage your DMM applies to the diode when it makes the measurement.  There is no standard.  For comparison purposes, it's a good way to go as long as you always use the same DMM.  The Cheap Chinese Transistor Testers measure reverse current, but they do not reveal the applied reverse voltage used.  It's probably close to 5V because that is the internally regulated voltage.  In the case of back-to-back diodes, the reverse voltage one diode sees is the forward voltage of the other diode.


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## jubal81 (Feb 14, 2020)

What Bret & Chuck said.
Germanium diodes vary widely in leakage, even among the same batch of the same part number. Using them as feedback clippers isn't a good idea, but in a case like this, they MUST be selected for low leakage. That means picking ones with the highest reverse resistance. I've found some that are 6M or more on my Fluke 83V, which the company says tests at below .6V.

The closest through-hole Si alternative I've found for a low-leakage Ge diode is the Bat46. It tests out around 10M reverse resistance. I think it'd make a great alternative for the G2, especially for use in the first clipping stage if you can only scrape together 2 low-leakage Ge diodes for the second stage.

The Klon gets away with wide variances because the Ge diodes are hard clippers following a low-impedance output from an opamp.

Conan, what is the riddle of Germanium?
FV isn't strong, boy, leakage is stronger.


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## chongmagic (Feb 14, 2020)

jubal81 said:


> What Bret & Chuck said.
> Germanium diodes vary widely in leakage, even among the same batch of the same part number. Using them as feedback clippers isn't a good idea, but in a case like this, they MUST be selected for low leakage. That means picking ones with the highest reverse resistance. I've found some that are 6M or more on my Fluke 83V, which the company says tests at below .6V.
> 
> The closest through-hole Si alternative I've found for a low-leakage Ge diode is the Bat46. It tests out around 10M reverse resistance. I think it'd make a great alternative for the G2, especially for use in the first clipping stage if you can only scrape together 2 low-leakage Ge diodes for the second stage.
> ...



I may replace mine with BAT46 diodes. And to be honest, I have never been fond of Ge clipping, I know this circuit is a little different, but I have never preferred it when it was an option.


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## chongmagic (Feb 14, 2020)

I built one of these from GuitarPCB and they use 1n914s, and it sound pretty fantastic.


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## Robert (Feb 14, 2020)

chongmagic said:


> I may replace mine with BAT46 diodes.



If you do decide to swap them, try it after replacing the pair in the first stage (leaving Ge in the second stage).


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## jubal81 (Feb 14, 2020)

chongmagic said:


> I built one of these from GuitarPCB and they use 1n914s, and it sound pretty fantastic.



Never occurred to me before, but an On-On DPDT to switch between Si/Ge would be a fun mod for this circuit.

I messed with this one quite a bit about 5 years ago and found that once you get the diodes selected, it's a pretty good fuzz-flavored overdrive and not nearly as dark as it is with leaky Ge diodes. I think a lot of the magic comes from running it into a tube amp that's already breaking up.

I've found I prefer the Skreddy designs for this territory - more versatility and less temperamental.


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## Chuck D. Bones (Feb 14, 2020)

Or even on-off-on switch for some asymmetric transistor clipping like the Flugelhorn, Acid Rain, etc.


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