Best BJT's in the world.

[Asbjorn]

I'm not going to contradict you as I have tried several transistor types in headphone amps and found audible differences, but they also had different characteristics.

For instance I tried BF469 and BD139 as a VAS-Buffer in an amp and prefered BD139, although the difference was small. But in this case, their Beta is quite different, which should probably explain is (ie. in this position, a transistor with a higher Beta would work better)...

Can you sate more precisely which types you compared and in which position ? Did they have differing characteristics or not ? And most important, what did you hear ?

I believe everything is important, from the well documented data (Beta, Ft...) to the obscure ones (like chip size, thermal characteristics, variation of Cbc and Cbe with Voltages...)

Mind sharing your results ?
Thanks...

I have for instance compared several types a single ended output buffer (preamp).

In the output buffer I've tried these npn's: BC846, BC850, BC639, BC337/(40,27,16), MPSA06, MPS8098, BCX19, BC847BW and CW, BSR41, BC817, BCX70J, BCP56, BC107B (metal house), BC182L and more.

I've not compared the datasheets with what I've heard yet, but those with low hfe or higher voltage rating seem to have a more dynamic bass reproduction, they are more "full bodied", while the other sounds more thin. Those in metal house also generally sound more "clear" or "open" than those in plastic actually. Another result is that the BC337/40 sounds more dynamic than BC337/16 and 27.
Generally the bc3xx, bc6xx and bc8xx sounded the best, good dynamics, deeb bass, fine details without being "detail focused" and a natural coherent sound.

 

[millwood]

I have for instance compared several types a single ended output buffer (preamp).

I was curious if your impression would be different if you didn't what transistors you are listening to.

 

[peufeu]

Transistors

You say transistors with lower Hfe sound better, then that the BC337/40 (which has higher Hfe) sounds better than its lower Hfe brothers... interesting isn't it ?

Here's an interpretation :

Maybe transistors with higher current capability sound better in your application. These generally also have low Beta, except BC337/40 which has high beta/high current, hence your conclusions.

1. Transistors with a low Hfe sounding better would be strange : the more Hfe, the more "ideal" a transitor becomes...

2. But it is also logical that transistors with higher current output sound better (less Beta variations with current, less thermal effects due tu larger chip, etc).

So if the effect of 2) is larger than the effect of 1) we have a rational explaination for what you think.

Thus we must seek signal transistors like BC337/40 designed for high gain at high current (high current for a signal transistor, we are not talking apmeres here).

Looking at the Hfe / Ic curves, we see the BC547 says "ouch" above 10mA (Hfe=500 at 10mA, 250 at 100mA) whereas with BC337 this only starts at 100mA. If you bias your transistor with 10mA, a BC547 would be right in the wrong spot whereas a BC327 would still have a 10x margin before having nonlinear Hfe...

What do you think ?

Anybody wanna put BC337/40 in the input pair ?

 

[Asbjorn]

Re: Transistors

The small signal transistors used in ZAPfilter Mk 2 are:

PNP : 2SA1774
NPN : 2SC4617

Both from ROHM

I've just tried these and liked the sound. Very tight and dynamic sound.
Anyone who can think of other transistors with very linear hfe but with higher current output? Would be very interesting!

You say transistors with lower Hfe sound better, then that the BC337/40 (which has higher Hfe) sounds better than its lower Hfe brothers... interesting isn't it ?

Hmm, yes!

Here's an interpretation :

Maybe transistors with higher current capability sound better in your application. These generally also have low Beta, except BC337/40 which has high beta/high current, hence your conclusions.

1. Transistors with a low Hfe sounding better would be strange : the more Hfe, the more "ideal" a transitor becomes...

2. But it is also logical that transistors with higher current output sound better (less Beta variations with current, less thermal effects due tu larger chip, etc).

So if the effect of 2) is larger than the effect of 1) we have a rational explaination for what you think.

Thus we must seek signal transistors like BC337/40 designed for high gain at high current (high current for a signal transistor, we are not talking apmeres here).

Looking at the Hfe / Ic curves, we see the BC547 says "ouch" above 10mA (Hfe=500 at 10mA, 250 at 100mA) whereas with BC337 this only starts at 100mA. If you bias your transistor with 10mA, a BC547 would be right in the wrong spot whereas a BC327 would still have a 10x margin before having nonlinear Hfe...

What do you think ?

Anybody wanna put BC337/40 in the input pair ? [/B]

Well, I have played a little more with the bc337/40. It has at very dynamic and deeb bass, but it's a little loose you know - cannot shut up! Also the upper frequencies tend to be a little muddy. In this area the rohms are better, but I miss the dynamic bass from bc337 somewhat - maybe that's because the output current of the rohms are smaller?