Transistor gain comparison chart?

[moid]

Hello everyone

When playing with fuzz circuits it can be interesting to swap in different transistors to the original design to see whether the circuit sounds better/worse/weirder.  For those of us hampered by a lack of experience of knowing which transistors are high gain / low gain etc it occurred to me that it would be a really useful thing to have a chart showing which transistors get louder / are more gentle / do things you wouldn't expect to audio, but I can't find anything via google. I'm aware that hfe is the unit to look at and higher equals more gain, but something that showed some numbers for low / high and the transistor name would be really useful. I realise that the data sheets have some of this info, but I find them quite hard to understand in most cases and wondered if anyone had seen a simple chart with transistor names and their hfe next to them. Thanks!

[reddesert]

Beavis Audio had a great chart of common silicon transistors, pinouts, and gain ranges. It's still available on the internet archive but is now harder to find, so download it and save it:

https://web.archive.org/web/20150414091326/http://beavisaudio.com:80/techpages/Transistor-Pinouts/index.htm

[moid]

Brilliant, thanks very much!

Wow, some of these transistors have ridiculous amounts of gain - 2n5308 for example. Presumably the reason why I don't see these used in fuzz circuits is because with 9v of power that much gain will clip the audio beyond any comprehension so it becomes pure loud noise?

[idy]

2n5308 is a Darlington: two transistors in one package, multiplying their individual gains. The Ampeg Scrambler uses 2n5306 darlingtons...

[R.G.]

To a first approximation, if you have to know a transistor's gain any closer than low, medium, or high, you're doing it wrong.  Well, OK, not "wrong" as "wrong" is a politically incorrect term for anything, but um, lessee now, you have incompletely understood circuit design as of yet, and need to move to the next lesson and master it. There, that's better. 

The sound of a circuit is very much more about the circuit than the transistor in it. This is because transistor gain isn't a number, it's a suggestion. A transistor has a given gain in only one set of conditions. Good circuits recognize this, and use feedback to stabilize the circuit's performance so the actual gain may wander around as it wants to, and the overall performance will remain pretty much stable.

It is possible to design circuits where one specific transistor or one particular value of current gain will make it sound GREAT. The temptation is to replicate that. However, you usually find that the circuit is nearly irreproduceable because any other transistor of the SAME type number will not have the same characteristics, including gain, that the circuit depends on.

Also, know the differences in transistor types. Darlingtons are different, although related to normal bipolars.

So yes, worry about gain and other characteristics enough to be familiar with them. But you'll probably be disappointed if you depend on them.

[Guitar Poppa]

Hello Moid !
Your question opens a wide world !

If you are patient, you have to compile for years all the data shits that will pass within your reach, and all your experiments on the bench. It's heavy, but it's powerful. I did it for 10 years and now I have almost 100 pages of charters of European and Russian germanium transistors (I'm french)... It is ideal when you have calculated a circuit in a professional way, and have to choose precise components for small series...

In a majority of cases, you have not to work this way... You just have to know some types in a scale of classic gains :
For exemple, talking about a Fuzz Face : 80 to 110 for classic, 50 to 80 for smooth overdrive, 100 to 300 for modern buzz...

This gives a base, but as RG wisely says, the feedback control will impose a total gain, lower than the product of the two transistors gains ... In other words, the choice of the transistors is not absolute: it determines a range of possibilities, a tendency to a more or less sharp or grainy fuzz effect.
In facts, qualitative choices are as important: germanium or silicon, audio or high frequency transistors, preamplification or output stage transistors, second transistor gain higher or lower than that of the first ... The sonic color and texture will more depend of these choices than the absolute choice of an item in charts...

If you want to make a documentation, collect the transistors by family, it is quite enough:

-- Silicon transistors with gain about 125, 300, 500 ... (in Europe, the codes are clear: BC549B means B = silicon, C = audio, 549 = identity, B = gain about 300). BC173A would be about the same in another brand, with 'A' meaning 125 average gain...

-- Preamp germanium transistors : Gain about 60-120 -- the famous NKT275, the european AC125 family... AC126 family with more gain (100-250)
-- Output stage germanium transistors : Gain 50-120 -- the classic AC128, with a special liquid sound when well biased and all 1W 1A brothers...
-- Radio frequency germanium transistors : Gain 60-200 -- AFnnn series, especially AF124, known in historic treble boosters...

I tell you about european types, which I know and use everyday... It is easy to use them because their code is significient.
This is more confusing with the American 2Nnnnn codes, which doesn't signify the type of component ... It will be necessary to investigate and record, but these few families that I've told you gather enough specific models to start a good documentation.

Hope it will help you and everyone on this site !
Guitar Poppa — guitarpoppa.com

[moid]

To a first approximation, if you have to know a transistor's gain any closer than low, medium, or high, you're doing it wrong.  Well, OK, not "wrong" as "wrong" is a politically incorrect term for anything, but um, lessee now, you have incompletely understood circuit design as of yet, and need to move to the next lesson and master it. There, that's better. 

Thanks I think that's the most polite way you could put that! Have you ever considered a career in PR?

The sound of a circuit is very much more about the circuit than the transistor in it. This is because transistor gain isn't a number, it's a suggestion. A transistor has a given gain in only one set of conditions. Good circuits recognize this, and use feedback to stabilize the circuit's performance so the actual gain may wander around as it wants to, and the overall performance will remain pretty much stable.

It is possible to design circuits where one specific transistor or one particular value of current gain will make it sound GREAT. The temptation is to replicate that. However, you usually find that the circuit is nearly irreproduceable because any other transistor of the SAME type number will not have the same characteristics, including gain, that the circuit depends on.

Also, know the differences in transistor types. Darlingtons are different, although related to normal bipolars.

So yes, worry about gain and other characteristics enough to be familiar with them. But you'll probably be disappointed if you depend on them.

That's very useful, I assumed (erroneously) that the amplification of the sound and then clipping it was the major determinate to a fuzz, but every time I think I'm beginning to understand something it becomes more complex...

[moid]

Hello Moid !
Your question opens a wide world !

If you are patient, you have to compile for years all the data shits that will pass within your reach, and all your experiments on the bench. It's heavy, but it's powerful. I did it for 10 years and now I have almost 100 pages of charters of European and Russian germanium transistors (I'm french)... It is ideal when you have calculated a circuit in a professional way, and have to choose precise components for small series...

In a majority of cases, you have not to work this way... You just have to know some types in a scale of classic gains :
For exemple, talking about a Fuzz Face : 80 to 110 for classic, 50 to 80 for smooth overdrive, 100 to 300 for modern buzz...

This gives a base, but as RG wisely says, the feedback control will impose a total gain, lower than the product of the two transistors gains ... In other words, the choice of the transistors is not absolute: it determines a range of possibilities, a tendency to a more or less sharp or grainy fuzz effect.
In facts, qualitative choices are as important: germanium or silicon, audio or high frequency transistors, preamplification or output stage transistors, second transistor gain higher or lower than that of the first ... The sonic color and texture will more depend of these choices than the absolute choice of an item in charts...

If you want to make a documentation, collect the transistors by family, it is quite enough:

-- Silicon transistors with gain about 125, 300, 500 ... (in Europe, the codes are clear: BC549B means B = silicon, C = audio, 549 = identity, B = gain about 300). BC173A would be about the same in another brand, with 'A' meaning 125 average gain...

-- Preamp germanium transistors : Gain about 60-120 -- the famous NKT275, the european AC125 family... AC126 family with more gain (100-250)
-- Output stage germanium transistors : Gain 50-120 -- the classic AC128, with a special liquid sound when well biased and all 1W 1A brothers...
-- Radio frequency germanium transistors : Gain 60-200 -- AFnnn series, especially AF124, known in historic treble boosters...

I tell you about european types, which I know and use everyday... It is easy to use them because their code is significient.
This is more confusing with the American 2Nnnnn codes, which doesn't signify the type of component ... It will be necessary to investigate and record, but these few families that I've told you gather enough specific models to start a good documentation.

Hope it will help you and everyone on this site !
Guitar Poppa — guitarpoppa.com

Thanks very much Guitar Poppa, I didn't realise the codes actually meant something (I assumed they were just product codes). I've learned some new facts. I'm going to read through your website now, there's a lot of interesting looking pages to consider.