Rangemaster transistor bias vs. leakage

[percyhornickel]

I´ve build a NPN Ge with the AC127 and just put a lineal 100K instead 68k resistor, works fantastic so you can set the bias to your taste (standar bias collector 7V is very good) and even I put an input cap selector.

Sorry for the late reply, Gmail has, for some reason, marked reply notifications as spam and I wasn't getting them in my inbox. Yes, I've done all the legwork for biasing, and I've been able to get around 7V, the problem is this (quoting RG Keen's article):

If Rb1 is below 27K or above 82K, or if Re is below 2.7K or above 5.1K, your transistor either has the wrong gain or is too leaky to use, you'll have to use another one.

If you're needing to go above 82K for the 68K resistor you're in the same boat as me.

No I don´t need to go above 82K, even with 68k sounds great. I just wanted to have a wider bias to choose.

[zbt]

Most Iain say here, is true.

I like BD139, wish has Brian May signature on it, but it would be mojo hard to find.



if dont mind be proegnimatic read this

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjc_8u_kdX6AhWCS2wGHXG_AOoQFnoECAwQAQ&url=http%3A%2F%2Fwww.aesmelbourne.org.au%2Fwp-content%2Fmedia%2FTHE%2520AKSA%2520STORY.pdf&usg=AOvVaw3O3u7AxxbMUoF64muplXUE

dont worry you just have to feel it.

Try replace RC with CCS, and make it look like a capacitor, it would be fun.

This thing for me still egnimatic, cause I cant smell it

quote from R.G. Keen

but germanium has more oompf.

the only thing remain is leakage, remove frying oil hiss,
that crackle eggs probably the thing, add bacon and cheese would be more tasty.
but don't be too much, add just a little bit, again this selection of mojo
because so little, I feel, only trained ear can hear it.

I want to believe germanium has bacon, egg, and cheese,
so I have to proof it I am right. ha ha ha.

cheers, thanks to Iain

[Steben]

I could be wrong, but most power transistors have rather low cut off voltages at low signal currents. These currents are not the working zone they were designed for. Do not look for the classic 0.7V, but rather 0.4V to 0.5V. This makes the B-E transient more round in that classic range master asymmetrical compression at least in theory. Power transistors found their way in many Fuzz Face experiments years ago. And of course they tend to have overall less current gain than small signal transistors.

[zbt]

some textbook using
0.7 (Si) and 0.3 (Ge)
0.6 (Si) and 0.2 (Ge)

BD140

VCC -9.110
VC  -7.820
VB  -0.963
VE  -0.452
VEB  0.508

You are right, is around 0.5

[Steben]

some textbook using
0.7 (Si) and 0.3 (Ge)
0.6 (Si) and 0.2 (Ge)

BD140

VCC -9.110
VC  -7.820
VB  -0.963
VE  -0.452
VEB  0.508

You are right, is around 0.5

The amount of idle (collector) current flowing is proportionate to the VBE (or VEB )
here it is << 1mA. A current completely off power output applications.

[mac]

Beware of fake ACs, try japs

Matsushita 2SB172-5-6, 2SA101-2, 2SD352 (npn)
Toshiba 2SA52-53, 2SA49, 2SB54-6
Hitachi 2SA77
Sanyo 2SD72 (npn)

or NPN silicon 2N2369, TIPs, mpsa42-92, 2sc1213... tons of 60 < hfe < 150 silicons out there.

It's all about the input cap + low input impedance, and the right gain.
The Big Muff input stage without emitter resistor, B to C cap and input 33k resistor, and a 4n7 to 6n8 input cap will do it with a low or high gain Si.

mac

[zbt]

For Si replace 68K to 82K or 3K9 to 2K7
leakage solve by bias
Using CCS does not reduce noise, if it noisy it still noisy,
so natural selection still remain.

for Ge probably a smoother asymetric clip



https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=2ahUKEwjA7uiR3dz6AhXu-jgGHSZaA4IQFnoECA4QAQ&url=https%3A%2F%2Ffrank.pocnet.net%2Fother%2FMullard%2FMullard_Volume4PartIII_transistors_1968-11.pdf&usg=AOvVaw1KxS_RbFrjF_FVcKz9gGYL


Temperature, heat from tubes, transformers ?
The hotter electron will go wild free, (Come on Si, Rock On!)
moving Q point toward 4.5V ?
Still guessing...

For Si I would go for BMTB, Ge prefer RM

Fairchild S9016G smooth

[zbt]

After trying it, I feel like silicon is like the sound of a half-filled biscuit tin, while germanium feels like a tin filled with a little bit of biscuit crumbs 



this is an experiment with RC bias

[Steben]

After trying it, I feel like silicon is like the sound of a half-filled biscuit tin, while germanium feels like a tin filled with a little bit of biscuit crumbs 



this is an experiment with RC bias

hahaha




sounds about right if not fed into an already driven amp or pedal.

Salt is no food unless on a steak

[zbt]

  cant find that juicy fat yet, going to use 1% resistor for more accurate measurement.

less salt more fat