In your version Vce is at about 10V and in MC version at 5-6V so that base is covered for all those BJTs discussed since the signal is miniscule in that stage. From the easier available ones, the 2SC2240BL and BC337/338-40 combine desirable traits of high hfe, high impedance Ic/Vce characteristics and low internal resistance. Not champion low, but low. Both will be nice to pitch against BC550C which is largely adequate in that position and see if you can actually feel any change. Kean is welcome to comment further.
The BC337-25 are better than the BC550 at the qualities I mentioned. I know this because my Kmultiplier requires very good Vcesat characteristics. One much overlooked issue with BJTs is that a changing Vce not only causes base leakage, but it also causes changes in Vbe. This was the problem with my Kmultipliers; base leakage was not a problem because source impedance was low; but that didn't matter because when the BJT enters the quasi-saturation region, Vbe starts to wander much with Vce.
This perspective might not matter so much for BJTs with 5V Vce, although it still applies. It may be that the C2240 beats all these categories, but I don't think so because it is a high-voltage transistor and my experience is that low-voltage transistors have the best collector impedance.
Salas has more practical experience so I would go with his advice. The one thing I stress is that any time there is base leakage, Vbe also wanders, so Vcesat be more important than you think.
An excellent low-voltage transistor with good Hfe characteristics is the PEMZ7 from NXP, and it's family. That negative collector impedance region could be dangerous though...
This perspective might not matter so much for BJTs with 5V Vce, although it still applies. It may be that the C2240 beats all these categories, but I don't think so because it is a high-voltage transistor and my experience is that low-voltage transistors have the best collector impedance.
Salas has more practical experience so I would go with his advice. The one thing I stress is that any time there is base leakage, Vbe also wanders, so Vcesat be more important than you think.
An excellent low-voltage transistor with good Hfe characteristics is the PEMZ7 from NXP, and it's family. That negative collector impedance region could be dangerous though...
I checked around a little and the BC338-40 has even lover voltage 30V vs. BC337 that has 50V, and the 40 indicates higher hfe and that should be good?
I will in the end try both some off the high voltage versions of the Q5 transistor in question and some off the lower ones, and see if I can hear any difference with the Stax lamda pro earphones toghether with the driver SRM-717. I will both try out some of the 2sc's and the BC's.
All off this will take it's time off course, because I will do a good Hfe matching, and of cource getting a hold of them at a reasonable price. The results I find will be posted.
With kind regards
Martin
I will in the end try both some off the high voltage versions of the Q5 transistor in question and some off the lower ones, and see if I can hear any difference with the Stax lamda pro earphones toghether with the driver SRM-717. I will both try out some of the 2sc's and the BC's.
All off this will take it's time off course, because I will do a good Hfe matching, and of cource getting a hold of them at a reasonable price. The results I find will be posted.
With kind regards
Martin
Niko kalispera
Could you please have a look at the IDSS values below?
Can any of those be used on the pre-pre stepup? (7ma IDSS required per the pdf)
Thanks in advance
Could you please have a look at the IDSS values below?
Can any of those be used on the pre-pre stepup? (7ma IDSS required per the pdf)
Thanks in advance
You can certainly make two channels by using this group in first+last pair, middles pair.
8,47
8,76
8,95
9,01
Add 3R3 source pin resistor to each one before it meets the common ground.
Got a 1000 BC337-40 fresh from Fairchild
how many do you need?
how well matched?
Some how my Simplistic second build gone in back burner....
And got BC337 for other project now on back burner as well
If it were me, I'd choose the lowest Hfe grade I could get away with, as Vcesat characteristics get worse with higher Hfe. From the datasheet curves it seems that different voltage parts of the same family, like the BC546 and BC550, have the same Vcesat characteristics, so I do not worry about voltage grades as much as I do about Hfe grades within a family of BJTs. But I don't know for sure. It will be interesting if there are audible differences.
I have finally started to build the RIAA circuit with shunt supply.
I am getting a strange phenomenon at the moment with the shunt. It's fed 38.7V from via a LM317 pre regulator. The first time I switched on the supply I could only get 38.33V out however I adjust the 5k pot. The LEDs light up OK. So I disconnected and double checked the shunt circuit with the schematic. There seemed to be no error so I wondered whether the I had connected the sense wires properly to the dummy load (it's all lashed up temporarily). So I powered up again and bingo I was able to adjust the voltage across the dummy load to 28V. It seemed steady for a few minutes so I checked the temperatures of the IRFP9140s - cool, no problem there. The LM317 was hot though - it's getting 50V in and dropping to 38.7V (30V ac secondary on the trafo). I then blew gently on the components and suddenly the voltage shot up to 38.3v across the load again. It was as if someone had flicked a switch.
I'm wondering whether it's the LM317 that's struggling or possibly a dry solder joint.
I am getting a strange phenomenon at the moment with the shunt. It's fed 38.7V from via a LM317 pre regulator. The first time I switched on the supply I could only get 38.33V out however I adjust the 5k pot. The LEDs light up OK. So I disconnected and double checked the shunt circuit with the schematic. There seemed to be no error so I wondered whether the I had connected the sense wires properly to the dummy load (it's all lashed up temporarily). So I powered up again and bingo I was able to adjust the voltage across the dummy load to 28V. It seemed steady for a few minutes so I checked the temperatures of the IRFP9140s - cool, no problem there. The LM317 was hot though - it's getting 50V in and dropping to 38.7V (30V ac secondary on the trafo). I then blew gently on the components and suddenly the voltage shot up to 38.3v across the load again. It was as if someone had flicked a switch.
I'm wondering whether it's the LM317 that's struggling or possibly a dry solder joint.
Have you used small caps (0.1µF)? Try soldering them directly at the pins of the LM317. This should avoud oscillating.
The 317 is a series regulator. The power dissipated in the series regulator is Vdrop times average output current.
If you hang a shunt regulator on the output of the series regulator then the total and substantially constant current of the shunt regulator becomes the average current being supplied by the series regulator.
Equals very hot series regulator. Possibly hotter than either of the CCS or the Shunt mosFETs. Compare the sinking and size of those three semiconductors to see your problem.
If you hang a shunt regulator on the output of the series regulator then the total and substantially constant current of the shunt regulator becomes the average current being supplied by the series regulator.
Equals very hot series regulator. Possibly hotter than either of the CCS or the Shunt mosFETs. Compare the sinking and size of those three semiconductors to see your problem.