I often get asked about different transistors. People often want to know which ones may be 'best' for their rig or to add to their collection.
Every transistor will impart its own character on the circuit, but it's also important that a circuit be optimized for a particular transistor. It's a bit of a back and forth game that has to be played. Even similar model numbers produced by different manufacturers can sound/behave very differently so its imporant to be specific about which ones you are talking about.
Below I've compiled some general notes about the characteristics of transistors that are, or have previously been offered in Dominion Electric products. This list is by no means exclusive and the traits described are based on my personal experience. I hope you find some of these notes useful in your search for tone!
Some would argue these are the 'holy grail' of germanium transistors. Most famously used in the original 60's Fuzz Faces, they are THE sound of early-era Hendrix.
These are extremely rare to find these days and notoriously temperamental, however, when you catch them on a good day there is nothing better for THAT Sound.
Bombastic fuzz and woody rolled-off cleans.
The big brother to the NKT275 - these are the same transistor just sorted for higher gain. Not often will you find two that pair up nicely for an all-germanium face-style fuzz but they work excellent as the germanium transistor in hybrid fuzzes where you are looking for some of that vintage germanium character.
Old Newmarket CV7005s have a very similar spec to an NKT275 but are often on the lower gain side. If you want a low-gain fuzz with great clarity these might be up your alley.
These old Texas Instruments military CV7003s (military-spec OC44s) are hands-down one of my favourite transistors available. Personally these should be as highly regarded as any old NKT275, if not more. Unfortunately these are EXTREMELY rare and for good reason.
Some of the BEST temperature stability of ANY germanium transistor and an amazing tonal character that has a 'smoky' lower mid character but a clear top end. Try to grab a pedal with these if you can, you won't regret it.
These military-spec RCA transistors are VERY temperature stable for germanium, making them more idea for people who want to play them in different environments.
They have a clarity and enhanced high end that is especially good for darker sounding amps or humbucker guitars. Some of the best cleanup of any germanium I've tried.
Mullard AC 128
I'm a huge fan of good old AC128s. When you find a good pair they have a 'smoky' quality to them that is reminiscent of early-era Hendrix tones. Not quite as clear or defined as some other germanium variants but tons of mojo.
Famously used in the germanium versions of the Cesar Diaz Texas Squareface. The NTE103 has great warmth and provides huge, saturated fuzz tones. It's most famously known for its glassy cleanup characteristics but to me it's a bit more organic and woody than it's silicon counterpart, the NTE123AP.
TI BC 183
As used in the vintage Fuzz Face, the Texas Instruments BC183 is one of my favourite transistors. It really splits the difference between germanium and silicon to my ears and is a perfect choice for people looking for a great 'all around transistor'.
As it's a silicon transistor it is temperature stable and won't drift in/out of spec from your basement to a hot stage. It has some of the warmth of old germaniums but also some of the aggressive attack of other higher gain silicon. Cleanup is clear and organic.
TFK BC 108
As used in the vintage fuzz faces of the late 60's and 70's the Telefunken BC108 is a great transistor if you are looking for those late-era Hendrix tones.
They tend to have more gain and aggressive treble content compared to say a 183. This means they will have a bit more 'cut' but the rolled off clean tones are some of the glassiest. They LOVE Marshall amps.
TFK BC 109
Telefunken BC109 is very much the big brother to the BC108. They way I describe them is that they just have more of everything. If you're after the classic Pink Floyd 'Time' solo this is what you're after!
These are a very interesting transistor that shows up in some old 70s Fuzz Faces. It has a much darker/grittier quality that some of the other 'standard' silicon types. These often work really well into brighter sounding amps and are killer for that broken speaker type sound.
One of the rarest silicons in old Fuzz Faces, the BC130 sounds like a more aggressive BC108 to me.
Famously used in the silicon versions of the Cesar Diaz Texas Squareface, the NTE123AP is very bombastic in nature. Huge, saturated fuzz tones. These days it's most famously known for its very glassy cleanup characteristics.