Germanium darlingtons?

[Peter Snowberg]

I'm just wondering if anybody has tried to make a fuzz using Ge darlington pairs?

Lower gain Si units sound great in fuzzface circuits, but I'm wondering how a couple stages of really high gain Ge might sound in a non-feedback circuit? All this Si piggybacking has me thinking about other non-conventional setups.

Thanks,
-Peter

[Johan]

ther three knob tonebender has two Ge's set up as a darlington....sound great...

Johan

[bobbletrox]

What's the advantage of darlingtons anyway?  I've seen a 2n5088 substituted with a MPSA13 (as in the Bass Fuss)...is it just for more gain?

[Peter Snowberg]

What's the advantage of darlingtons anyway?

The current gain (aka Beta) of a Darlington pair is equal to the product of the current gain of the two transistors used. At least that's it in a nutshell.

Thanks Johan!

Take care,
-Peter

[brett]

With all of thet gain, what is the frequency response like?  

Many fuzzfaces have a seriously limited ability to reproduce highs because of the limits of Ge trannies (parasitic capacitances, etc)

I've given up using AC127s because although they have more gain, and leak much less than AC128s ( ), they mostly cut so much treble ( :cry: ) that they are useless.  Hence I can't imagine that the frequency response of Darlington AC127s would go much past a couple of kHZ.

[toneman]

Stompboxers,
Here, we're talking audio response.
Even, limited audio at that, not 20-20K response.
AC127/128s have F/t of 1Mhz.
see data sheet here:
http://www.dialelec.com/d.asp?x1=QSJXAKOUWSWPNSVWSD&X2=107&X3=83.4KB
enter password with CAPs exactly as shown.

Who would/could sell a transistor that *only* worked on audio?

As a note, 2N3904/3906 have Beta that range from slightly less
than 70 to slightly  over 200.  I believe the 2N5088 average more the 400.
A darlington will be usually over 800!   My DMM tranny tester can't measure them.
The clipping of a transistor is determined by how it is biased in the circuit.
This determines when, at what input amplitude, it clips.  
Also, biasing can determine if it clips on positive or negative transitions,
or both.
Google for how to figure load lines for transistor biasing.  Using a curve
tracer really simplifies, AWA using a transistor Beta checker that's built
in to many cheap DMMs.
Google on "darlington" also.
AFN
tone

[brett]

Even, limited audio at that, not 20-20K response.
AC127/128s have F/t of 1Mhz.

That F/t of 1MHz is at unity gain, n'est pas?  If it's like the bandwidth product of op-amps (which I suppose it isn't really), an AC127 with hFE=160 would get to 6kHz then dud out.  That's about what I hear with my AC127s in a fuzzface.  No highs (even to my 43 year old ears).  My AC127 fuzzface won't even reproduce the top string on my guitar above about the 7th fret!!

[Nasse]

:shock: Should the best use of darlington Ge´s be in some other fuzzes than Fuzzface? Ones that work better with high gainers? :shock:

[toneman]

Hey Brett,
i shall have to give a FF a try when my germaniums arrive.
(AC188s)

an AC127 with hFE=160 would get to 6kHz then dud out. That's about what I hear with my AC127s in a fuzzface. No highs (even to my 43 year old ears). My AC127 fuzzface won't even reproduce the top string on my guitar above about the 7th fret!!

what version R U using?
the one @ your URL?   All caps as marked?

what about "pre-emphasis" ?
And. of course, EQ?

Have these other weird(marked) GE germaniums i discovered last week.
Will give them a go 2. :?

[brett]

I've used the standard NPN ff circuit (ie caps=2.2uF in, 0.1uF out, I think), with a trimpot for the resistor on the collector of Q2.  Different bias settings made little difference to the amount of treble I was getting, and I figured that the AC127s that I was using simply didn't extend up to the top of the audio range at the gain levels used.  

Interestingly, an NPN Easyface that I've built with AC127s AND a small emitter resistor on Q1 (reducing its gain) DOESN'T have the same problem.  So I suspect that the problem lies with the very high gain (ie limited only by hFE) of Q1 in the standard NPN fuzzface.

[Paul Perry (Frostwave)]

Who would/could sell a transistor that *only* worked on audio?
tone

well...... the guy who sold me some OC71s in 1963 for a start  

[Gearbuilder]

Hi Brett,


I've done many FF and each one has got a different bandwidth.Even on   the same circuit ,i've try several Trannys on sockets before i'd like the sound .
I'm not sure but it seems in first that the transistor's fabrication and the brand are very important even if you've choose  the right  gain .The second point is that Germs haven't got a good frequency linearity at different  gain,in a fuzz circuit ,gain are so important that you're in non linearity place and this give some surprises.Sometimes goods,sometimes bads .The amount of third and second harmonics are very important (this give ''color :wink: of the sound''
It's like tubes in the amps the harmonics  are reproduced in different way at different levels.
Bruno