Finding Low-Leakage Diodes?

Bricksnbeatles

Bricksnbeatles

Member known well
How do y’all do it? I know low leakage germs are like hens’ teeth these days, but gotta be somewhere to find em, right? I’ve been keeping an eye out for lots of diodes to bid on, but there hasn’t been anything good in ages; SBP and the other reputable sellers are a bit rich for my blood at $2-3 per diode.
Anyone know of what kind stuff to keep an eye out for on eBay/Craigslist that might have tons of diodes in it to salvage?

Tested the leakage recently on the Soviet diodes I got a while back, and not surprisingly they’re incredibly leaky. I have a few projects where I want to stick with actual low-leakage Ge diodes instead of silicon subs since I already have the other special mojo bits.
 
In my experience, the only way to find low leakage Ge diodes is to buy the cheap ones in bulk and test them. After all, all Germanium diodes have higher reverse leakage current and that increases with temperature. Another drawback of germanium diode is low reverse blocking voltage that limits its operation to low voltage rectification only.
 
Edit: I just woke up and my reading comprehension is still coming online. I talk mostly about transistors, but also mention diodes, which I also buy in bulk from Ukraine.

NOS from Ukraine, in bulk.

They won't all be winners, but at least the losers will be diodes.

I was looking at sets of three matches resistor SB a while back and they were like $15. If that's the rate people are willing to pay I've technically got a little gold mine in my garage, and have given away and used enough to probably get close to even (at least that's what I tell myself before I go to bed at night).

I've paid between $20 and $80 for various lots of transistors over a few years and have a few hundred still in my stock. I just keep an eye out and buy larger lots of at least 20 and up to 100.

I also do this with GE diodes. I got 200 D9V's for like $30 and Pedal Hacker is selling them for like $8 for a 10 pack.

If you have the cash and the space and don't mine being a crazy hoarder there's always a way.
 
peccary said:
NOS from Ukraine, in bulk.

They won't all be winners, but at least the losers will be diodes.
Click to expand...
Especially true of diodes 😉

peccary said:
I also do this with GE diodes. I got 200 D9V's for like $30 and Pedal Hacker is selling them for like $8 for a 10 pack.
Click to expand...
Yeah, I have 200 D9V and 100 D9K. They’re just incredibly leaky. Using the resistance reading method that Chuck has outlined in the past, I’ve tested around 20 of each, and the D9Ks Rd0 averaged 35k Ω while the D9Vs were averaging 78k Ω. Haven’t tested the actual Is of them but I will go thru them at some point and measure all ~295 of those diodes in hopes of finding a few at least that are low enough leakage for my purposes.

peccary said:
If you have the cash and the space and don't mine being a crazy hoarder there's always a way.
Click to expand...
I don’t have either, but I still dont mind being a crazy hoarder 😂
 
SillyOctpuss said:
This might be a dumb question but how does leakage affect a diode being used for clipping?
Click to expand...
IMO, diode leakage affects the clipping action (Fvd) very little. Diode leakage is about the backwards current aspect of the measured specification. What seems to affected by diode leakage in clipping elements is the trace curve derived from that backward for of current; so it's like to only affect the dynamics of attack transients during the clipping times.
 
SillyOctpuss said:
This might be a dumb question but how does leakage affect a diode being used for clipping?
Click to expand...
It doesn’t much for hard clipping.
For soft clipping it can be an issue, and it’s also an issue for stuff like a fox tone machine, green ringer, or other diode-based octave circuits where a high leakage can cause clean bleed— of course, silicon can make a good sub for those, but…
 
Cybercow said:
IMO, diode leakage affects the clipping action (Fvd) very little. Diode leakage is about the backwards current aspect of the measured specification. What seems to affected by diode leakage in clipping elements is the trace curve derived from that backward for of current; so it's like to only affect the dynamics of attack transients during the clipping times.
Click to expand...

Leakage is, in fact, the biggest factor and it's not close. Here's a link to s thread where it's explained.
 
I'd love to have an answer to this, too. So far I've tried the following models, all of which were too leaky:
  • D9D/E/K/L/V - Using the Chuck Bones method, equivalent resistance ranged from 9kΩ to 20kΩ. Too leaky.
  • D18 - Equivalent resistance ranged from 35kΩ to 91kΩ.
  • D310 - Equivalent resistance ranged from 12kΩ to 25kΩ.
  • D312A - Equivalent resistance ranged from 12kΩ to 25kΩ.
  • The worst offenders were so-called "Low Leakage" 1N34A from Amplified Parts, which had equivalent resistance that ranged from 1.2kΩ(!) to 12kΩ.
I've now have an excessively large stockpile of germanium diodes, which is nice, but all of them are way too leaky for use for clipping in a feedback loop.
 
Wild idea, but what if the G-2 doesn't use germanium diodes after all? I went back and looked at the original tracing thread for the Cornish G-2, and now I'm wondering if the original G-2 actually used germanium diodes rather than a glass package Schottky diode like the HP2835. The tracers were not able to determine what model of diode was used, but they saw a glass package like a germanium diode and measured a forward voltage of ~.22 volts using a multimeter. A Vf of .22 volts is on the low side for a germanium diode, but it's well in spec for a Schottky diode. Using a Schottky would also eliminate the leakage issue that seemingly every germanium diode has. Although Cornish has described the pedal as having "warm Germanium qualities," he also has a track record of exaggerating and making misleading statements about what is inside of his pedals.
 
Is there any chance some of the military spec diodes (e.g. the CV-types you can find floating around) are also sorted for low leakage like the mil-spec Ge transistors are supposed to be?
 
You must log in or register to reply here.
Back
Top