half wave rectification and Ge diodes

RnFR · Post by **RnFR** » 12 Jun 2009, 03:44

i just came up with a sick new fuzz. the only thing is, the output is dictated by the forward voltage of the Ge diode. i need the largest FV i can get in a Ge. above .5 would be ideal. anybody have any leads?

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i found one is a clear glass package with 2 black stripes that was pretty high, but no number. anyone know this diode?

IggY · Post by **IggY** » 12 Jun 2009, 04:54

can`t you series stack 2 germaniums? Double voltage but same soft knee?

RnFR · Post by **RnFR** » 12 Jun 2009, 09:18

nope. different kind of circuit.

UZILSD · Post by **UZILSD** » 12 Jun 2009, 09:46

Have a look here:
https://www.freestompboxes.org/viewtopic ... gain+trick
it's a trick I discovered that let you create a new single transistor with two. Among the other things it'll have a doubled FW breakup voltage, so if the single Ge trannies have 0,3V this arranging will yeld 0,6V (the sum of the values).

hope this help!

P.S. Maybe you could just put a Ge diode attached to the collector... and see the whole thing as a transistor wich has a V-fw equal to the transistor itself plus the diode. The diode free leg would become the new collector terminal.

rrhoads33 · Post by **rrhoads33** » 12 Jun 2009, 10:19

If we got just a little more info on what your circuit looks like, we could help you easier.

Cheers

RnFR · Post by **RnFR** » 12 Jun 2009, 20:29

UZILSD wrote:Have a look here:
https://www.freestompboxes.org/viewtopic ... gain+trick
it's a trick I discovered that let you create a new single transistor with two. Among the other things it'll have a doubled FW breakup voltage, so if the single Ge trannies have 0,3V this arranging will yeld 0,6V (the sum of the values).

hope this help!

P.S. Maybe you could just put a Ge diode attached to the collector... and see the whole thing as a transistor wich has a V-fw equal to the transistor itself plus the diode. The diode free leg would become the new collector terminal.

that's a really cool idea! i'll give it a try and let you know how it goes.

rrhoads33 wrote:If we got just a little more info on what your circuit looks like, we could help you easier.

Cheers

when i'm ready, i'll probably post it in the ready to build section. but for now, i'm just trying to source some parts! suffice to say it involves what i have come to understand us half-wave rectification.

so anyone know of a specific Ge diode that has a higher forward voltage drop than most?

UZILSD · Post by **UZILSD** » 12 Jun 2009, 21:51

RnFR wrote: so anyone know of a specific Ge diode that has a higher forward voltage drop than most?

Mmmm I've tested all models I've got (small signal PNPs) and are all the same... around 0.2 - 0.25V. Hardly 0.3V.

I think the only kind of Ge trannies with more Vbe are Ge power transistors.

For example this model
http://www.datasheetcatalog.org/datashe ... NTE105.pdf

the datasheet claims they have a Vbe of 0.65V. I don't have Ge Power trannies around so I can't test it personally.
They seem to be quite expensive anyway...

P.S. another way would be to use another transistor wired as a diode to increase V between the base and the new "emitter" (in the previous post I said collector but I meant emitter

). You could stack 2 trannies as diodes and easily achieve more than 0.6 V. Or use 2 Ge diodes directly. You could use even a silicon diode, but it could bring in the silicon tone. I think it should work if you consider the transistor-diodes arrangement as a whole.

culturejam · Post by **culturejam** » 13 Jun 2009, 00:20

I've got some that measure at 0.45V on my DMM. They are 1N34A.

The funny thing is that if I measure the same ones on my Atlas, they come up as 0.8V?? WTF?

RnFR · Post by **RnFR** » 13 Jun 2009, 01:50

yeah, i've got a few that read around .45, and i found one that measures .52. basically, the signal is going to go through the diode at the end of the circuit, they aren't going to be used as normal clippers, so the output of the fuzz is going to depend on having a larger FV drop. the one with a .52 drop still allowed for a decent sized volume boost, so i'd like to find some around there. i'm hoping that the diodes from the Harmonic Percolator might have a larger drop, we'll see when doug gets them measured. if so, is anyone interested in going in on an order from a parts sourcing place? i think that diodes of this sort could come in handy and do interesting things in many different circuits.

culturejam · Post by **culturejam** » 13 Jun 2009, 03:48

RnFR wrote: the one with a .52 drop still allowed for a decent sized volume boost, so i'd like to find some around there. i'm hoping that the diodes from the Harmonic Percolator might have a larger drop, we'll see when doug gets them measured. if so, is anyone interested in going in on an order from a parts sourcing place? i think that diodes of this sort could come in handy and do interesting things in many different circuits.

Sure, I'm in. But I guess I'm ignorant as to why you'd want a germanium diode to have a really high forward voltage drop.

UZILSD · Post by **UZILSD** » 13 Jun 2009, 08:01

RnFR wrote:yeah, i've got a few that read around .45, and i found one that measures .52. basically, the signal is going to go through the diode at the end of the circuit, they aren't going to be used as normal clippers, so the output of the fuzz is going to depend on having a larger FV drop. the one with a .52 drop still allowed for a decent sized volume boost, so i'd like to find some around there. i'm hoping that the diodes from the Harmonic Percolator might have a larger drop, we'll see when doug gets them measured. if so, is anyone interested in going in on an order from a parts sourcing place? i think that diodes of this sort could come in handy and do interesting things in many different circuits.

You asked 'bout diodes, and I replied 'bout trannies...
Sorry, it's a period that I'm drunk nearly all the time.

Regarding diodes, couldn't you just stack 'em in series to achieve the desired drop? I don't figure a circuit design in which you can't do that...

or just add an amplifier stage at the end of the circuit.

soulsonic · Post by **soulsonic** » 13 Jun 2009, 09:33

You could use a silicon diode?
Actually, the way you're using it, you may get the same result using a BAT41. I'll try it with a variety of different things and see what sounds like what.

RnFR · Post by **RnFR** » 14 Jun 2009, 04:30

well here's the circuit. it's basically a tweaked bosstone. as you can see it's not using normal diode clamps. i tried zeners and silicons and they sound like ass. i guess i might have to add another stage if i don't feel like picking through diodes. the smaller parts count turns me on though. oh, and no, i don't think you can't stack them like this.

IggY · Post by **IggY** » 14 Jun 2009, 05:00

RnFR wrote:nope. different kind of circuit.

two series diodes still don`t make a circuit, but can serve a purpose.
Are you sure you need a higher drop? How does it sound with a Si one?

RnFR · Post by **RnFR** » 14 Jun 2009, 05:09

IggY wrote:
RnFR wrote:nope. different kind of circuit.
two series diodes still don`t make a circuit, but can serve a purpose.

uh, okay.

IggY wrote: Are you sure you need a higher drop? How does it sound with a Si one?

as i said in the post above yours- it sounds like ASS.

IggY · Post by **IggY** » 14 Jun 2009, 05:27

RnFR wrote:
IggY wrote:
RnFR wrote:nope. different kind of circuit.
two series diodes still don`t make a circuit, but can serve a purpose.
uh, okay.
IggY wrote: Are you sure you need a higher drop? How does it sound with a Si one?
as i said in the post above yours- it sounds like ASS.

You mean: spluttery? or gated? that`s why I asked!

RnFR · Post by **RnFR** » 14 Jun 2009, 05:29

yes. sputtery and gated. of course depending on the diode.

IggY · Post by **IggY** » 14 Jun 2009, 05:40

RnFR wrote:yes. sputtery and gated. of course depending on the diode.

Ok, than back to this question:

Are you sure you need a higher drop?

RnFR · Post by **RnFR** » 14 Jun 2009, 06:49

do i really need to explain this again?

UZILSD · Post by **UZILSD** » 14 Jun 2009, 11:23

Try stacking 2 or 3 Ge diodes in series, it should increase V drop without altering tonal response, since all diodes are Ge. Give it a chance.
If it doesn't satisfies you, just add another stage and forget messing with diodes/trannies. I know that low parts count is appealing, but at this point if you got a sound you like and you only want more volume add an amplifier stage.