Germanium transistors for Fuzz - 4

Switching transistors
ex : 2N404 (the american classic)

The first transistorized circuits for automation and computing required specific components that were straightforward in their response but without extreme bandwidth. Rather close to radio frequency transistors, they are distinguished by their reliability and deliberately moderate maximum frequency. Some models may produce a vintage sound grain, suitable for Fuzz Face. They could make as much reference as the ubiquitous small power audio transistors : American do-it-yourselfers have not been mistaken, and have since a long time embraced the classic 2N404 …

Average characteristics of the 2N404 family

Collector-emitter voltage: 20 to 40 V (more than in other families).
Dissipable power: 50 to 150 mW, sometimes more in some items.
Maximum collector current: 50 to 150mA, sometimes up to 500mA.
Hfe gain: 100 typical; 200 or more not rare in some models …
Maximum frequency: 1 to 20 MHz (above, we enter the family of Radio transistors).

The transistors in these ranges of characteristic will work well in Fuzz, where they will bring reliability, easy biasing, and a very homogeneous granularity — sometimes even almost too wise. Models with maximum frequency < 3MHz will sound softer. Models with maximum frequency > 6MHz will sound sharper.

OC43, OC140* Black Glass ; SFT308 (Eastern Europe) ; 2N711 and 2N404 (USA).

Panorama

European models :

The very first switching transistors were black glass, Their gain and maximum frequency were average . Their good reliability, little leakage current and a homogeneous round tone should nowadays be still welcome by the designer.

OC43 … One of the first switching transistor.
Very reliable … It gives stable fuzz with an homogeneous sound, rounder than more modern models. Very rare todays, so do not miss !

OC45 … Little brother of the OC44 (a classic radio frequency item).
Gain and especially maximum frequency are lower. Typically good.

OC139 *, 140 *, 141 *; CV7112 * (= military OC140 *) … They are npn, which is uncommon in this family. Perfect to realize Fuzz boxes with negative ground.
Broadband sound, always well defined, both in clean overdrive or fuzz.

Industrial transistors have developed this dimension of reliability without temerity…
In Europe, one recognize them by their specific three-letter prefix: ASXnn ASYnn, ADYnnn …

ASY25, 32, 37, 48, 70, 76, 77 …
Models for slow switching. Produce a rather rounded sound.
ASX12, ASY26, 27, 31, 32, ASY70 …
Models for medium frequency switching. More nervous in the treble.
ASY28 *, 29 *, 73 *, 74 * …
Npn, in the same middle frequency range.

ADY11, 13, 20 … Small power transistors, for slow switching,.
Rather warm tone due to their limited maximum frequency, sometimess combined with a rugged saturation grind.

Some general purpose transistors can be successfully tested :

SFT107, 108, 128 … In the core of the characteristics.
SFT306, 307, 308 … The first has a little limited gain ; the third is perfect.

Americans models

My list is far from exhaustive, because I already had a lot to do with European transistors from the west and east … I give some recognized models, and that I could experiment.
The reader should consult websites dedicated to transistors and presenting reliable equivalences: Alltransistors.com for example …

2N388 *, 396, 428 … Industrial models to (re) discover …
2N711 … Very common and used at the end of the 60s.
The exact type of industrial transistor that can be used in any sauce.

2N404, 2N404A … Very popular in the USA …
Generous gain, powerful saturation, never dark. Perfect for a ripping fuzz !

2N1305, 1307, 1309 … Good vintage industrial items.
Their gains increase following the numbering of the codes.
2N1304 *, 1306 *, 1308 * … Npn version of the previous ones.
For negative ground Fuzz boxes.
These 2N130x models can have a leakage current which is not so harmless…
This may be good for the sound grain, but does not facilitate the bias adjustment.

2N1603, 1605 * …
2N5088, 5089 …
To discover, like many others, in the same way as the European ASYnn …

Soviet models

At present, I have not been able to recognize Russian models that were specifically presented for computing. Such models should be found in the GTnnn series already presented on the 3rd page as radiofrequency models.
If we focus on the band of 2 to 20 MHz, we would find:

Two models whith moderate gain and frequency, for vintage and not too hairy fuzz :

ГT109Г, E, Ж …
Good vintage sound. Models with other suffixes have too lo gain.
ГT2307 …
Has nothing to do with ГT307, an radiofrequency model.
It is the Russian military version of the european SFT307, and works well with a mid gain.

Medium gain models (80-120) typical of the Fuzz Face, with a well balanced sound :

ГT2308 …
Has nothing to do with AT308, a radiofreaquency model …
It is the Russian military version of the european SFT308.
Right well in the expected features : gives beautiful homogeneous Fuzz …
Very good behavior in treble booster : clear, with flexible dynamics.

ГT1323 …
Has nothing to do with ГT323, a radiofrequancy model) …
This is the Russian military version of the european SFT323.
Too good for fuzz ! Better exploite it in preamps or boosters.

П30 … MП30 …
A medium frequency transistor rare in the Пnn series, usually confined to the low frequency domain.