K Pedals
Well-known member
Thanks man!!!
Germanium II
- Thread starter K Pedals
- Start date
Chuck D. Bones
Circuit Wizard
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.
jubal81
Well-known member
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.
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.
chongmagic
Well-known member
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.
chongmagic
Well-known member
I built one of these from GuitarPCB and they use 1n914s, and it sound pretty fantastic.
Robert
Reverse Engineer
If you do decide to swap them, try it after replacing the pair in the first stage (leaving Ge in the second stage).
jubal81
Well-known member
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.
Chuck D. Bones
Circuit Wizard
Or even on-off-on switch for some asymmetric transistor clipping like the Flugelhorn, Acid Rain, etc.
