Germanium transistors

Most of the pedals I build use germanium components, either transistors or diodes. I get asked a lot of what the differences between the models are used and what transistors work best in certain fuzz circuits. These are my preferences and opinions, please read them as such.

Tungsram

Hungary has a rich history in producing quality semiconductor components. The availability of NOS germanium components locally is one of the reasons I am able to keep costs relatively low.

Some general abbreviations found on Tungsram transistors:

  • HM - stands for Honvédelmi Minisztérium and is the abbreviation for military spec.
  • F - low noise preamplifier. AC125F
  • K - kapcsoló notes a transistor used for switching. Examples: OC44K, AC125K.
  • U - high voltage applications. AC125U

OC44K/OC1044/OC1045

These are the classic transistors used in treble boosters. These models have very low leakage which makes them ideal for this circuit. The HFE best range for a treble booster is about 55-90 but some people prefer higher gains. The key is to keep the noise low.

  • OC44K: has an HFE of 30...150.
  • OC1044 has a slightly higher 45...225.
  • OC1045: with specs similar to the OC1044 in theory (HFE 30...150). However, the ones I found so far were all low gain. I use these in Tone Bender MKIII or treble booster circuits.

OC1071/OC1072/OC1074/OC1075/OC1076/OC1077/OC1079

These transistors are the equivalent of the OC7x series. These are transistors for fuzz circuits:

  • OC1071: relatively low gain (HFE 30...75) but also low leakage. I use these in Tone Bender MKIII or treble booster circuits.
  • OC1072: higher gain than the OC1071 (HFE 45...120), however I only came across lower gain ones so far. I use these in Tone Bender MKIII or treble booster circuits
  • OC1074: rare to find and all over the place in terms of gain. I have used them in fuzz circuits where I would normally use an OC1075.
  • OC1075: one of the holy grails of fuzz circuits (HFE 60...130). This one is an ideal choice for Tone Bender MK1.5 and Tone Bender MKII circuits. I especially like them in the Tone Bender MK1.5 because I find this circuit to be bass heavy and the slight loss of bass compensates that in my opinion.
  • OC1076: rare to find and generally same spec as OC1077.  I only ever used one in a Tone Bender V828.
  • OC1077: this one is close to my heart, because I started out making fuzzes with a whole bunch of OC1077s. Gain is all over the place (HFE 45 and up). These are great in Tone Bender V828s and Tone Bender MKIIs. Occasionally, I used them in treble boosters also.
  • OC1079: low gain transistor. I only ever used one in a Tone Bender MKIII.

AC125/AC128/GC301TD

These transistors are more modern than the OC107x series.

  • AC125: probably my favourite transistor to use. I like them most in the Tone Bender MKII but I also used them in the Vox V828 fuzz as well as in Tone Bender MKIs and Tortenmann TA-100s. It's the Swiss knife of transistors.
  • AC128: harder to find well spec'd examples, these are my favourite transistors for the germanium Fuzz Face circuit
  • GC301TD: a transistor that was produced in the 1980s that has similar characteristics to the AC128. I use them in the germanium Fuzz Face circuit.

Tesla

The GC50x and GC51x series Czech made Tesla transistors are highly underrated in my opinion. I use these in Tone Bender MKIIs and MKIIIs.

  • GC508: considered equivalent to the OC72, OC76 and OC77 with an HFE of 65...220.
  • GC517: considered equivalent to the OC71 and OC75 with an HFE of 50...100.
  • GC518: considered equivalent to the OC71 and OC75 with an HFE of 75...150.
  • GC519: considered equivalent to the OC71 and OC75 with an HFE of 125...250.

Mistral

The Italian made SFT337s are the best transistors for Q1 in a Vox V828 fuzz. Low leakage and ideal HFE for this position.

The SFT353s are a suitable replacement for the SFT363Es that were in the original Vox V828s in Q2. Similar in characteristics to an AC128.

These come with a premium price because they are more expensive to obtain than the Tungsram transistors.

Mullard and Newmarket

The best makers of transistors from the United Kingdom. I only get these kind of transistors from time to time, so if you see an option with these grab them while you can! These come with a premium price because they are more expensive to obtain than the Tungsram equivalents.

I have used the following models so far:

  • Mullard OC76: Great for Tone Bender MK1.5s and MKIIs. Used as a Q3.
  • Mullard OC78: Great for Tone Bender MKIIs, mostly Q1 and Q2.
  • Mullard OC83: Great for Tone Bender MKIIs, all positions.
  • Newmarket OC75N: what can I say, it's an OC75. Great for Tone Bender MK1.5s and MKIIs.
  • Newmarket OC81: Great for Tone Bender MKIIs.

Others: Valvo, Toshiba etc.

I do get random other transistors as well from time to time. Please check the options for the product you are interested in!

If you have further questions about germanium transistor choices for each circuit, do not hesitate to contact me! I can always try to source transistors of your choosing as long as they are available.