Question about Crescendo?

BD139/140

Hi!
i use those transistors and they deliver acceptable results, but preferrably use MJE340 and MJE350 or MJE15030 and MJE15031.
i guess that BD139/140 is what you have in your scrap-box, so try them first and if you are not pleased, just replace them... just make sure all four transistors is the same brand/make and from the same batch of production.
-good luck!
 
swede said:
I believe OnSemi/Motorola MJE15030 and MJE15031 are good replacements. You might have to recalculate a resistor or two, don't remember exactly why/which.

If you're going to bias them a lot, you need to put heatsinks on them.

//magnus

Thanks. Very quick reply.....

I ask this because local distributor don't have same manufacturer MJE340 and MJE350 transistors. ( MJE340 was manufactured by Motorola. MJE350 don´t have any other letters or identifiers besides MJE350.)
I have two MJE340 and MJE350. One of each per channel or so.
I have measured those transistors with multimeter and result is that both MJE340 hFE was about 42 and first MJE350 hFE was 50 and second MJE350 hFE was 64.

Is there still more important measuring "technology" exist?
Some WWW sites?




I hope You understand my english.
 
Thanks!

but damn... local distributor don't have those BF469-BF472 transistors.
There was only these BFxxx transistors:
BF 177, BF 180, BF 199, BF 200, BF 254, BF 259, BF 494, BF 858, BF 8712, BF 324, BF 509, BF 872, BF 914 & BF 968.

What I have to do now?

Can I use those MJE's even those MJE350's have so much bigger hFE

or anyhow does it make any problems?


I ask this because I don't wan't pay any postages.

If there is not any solutions for this, then I must order those transistors by mail...
 
Eccu,

You have listed BF871 (I guess incorrectly shown as BF8712) and BF872; go ahead and use these in place of BF471 and BF472. Yes the original circuit uses MJE340 and MJE350s and the sonic properties of these are supposedly superior to the BFs as pointed out in a related post in this site. I have built the Mini-Crescendo and Crescendo using BF 469, 470, 471 and 472s but was not too happy with the transparency and speed. The post I am referring to said that the MJEs corrected this aspect.

Perform a search!
 
Hi Eccu,

don´t use BF469/470 transistors in a crescendo! BD139/140 do sound a lot better and MJE340/350 give a small improvement over the latter.
Since these parts are not expensive and there´s little work involved you can try out for yourself.
I was amazed how much difference the step from BF to BD made.

(even Elektuur admits in their article on the milenium that the BF couldn´t deliver the current needed to drive the output stage.)

william
 
I agree with Samuel that BF-types are quite OK but not perfect. The are intended to use in video amp in TV-sets.

If you are looking for good driver transistors they should have:

Voltage rating 30-50 % more than the supply voltage or the voltage which can occur across collector-emitter.

Current gain at least 50, 100 or more is good

Linear current gain (no drop at high currents)

Enough power rating , more than 5 watts, 10-20 is good.

Speed, 100 MHz at least but not too much.

Not so much speed reduction at low currents.

BD139, 140 are good and cheap for +- 35 Volts power supply.
 
Samuel Jayaraj said:
Eccu,

You have listed BF871 (I guess incorrectly shown as BF8712) and BF872; go ahead and use these in place of BF471 and BF472. Yes the original circuit uses MJE340 and MJE350s and the sonic properties of these are supposedly superior to the BFs as pointed out in a related post in this site. I have built the Mini-Crescendo and Crescendo using BF 469, 470, 471 and 472s but was not too happy with the transparency and speed. The post I am referring to said that the MJEs corrected this aspect.

Perform a search!
[/QUOTE


Yes, my misspelling. BF8712 = BF871 & BF 872.

I have not found that thread yet. Maybe I have wrong keywords.
 
peranders said:


BD139, 140 are good and cheap for +- 35 Volts power supply.

Yes... You are right.

BD139/140 are rated 100V, so can I can use those because I have transfomer with two 38V (AC) outlet?
(38VAC is about 52-53VDC)


Swede mentioned that I can use MJE15030/15031. Those are rated 150V. So if I decide use these, is there some superior sonic results coming.


Some NPN transistors below, which I have a possibility to get (without postage):

MJ 1000 60V/8A/da/di/90W/23a 4.20€
MJ 10007 400V/10A/da/di/150W/23a 15.95€
MJ 10016 500V/50A/da/di/250W/23a 17.90€
MJ 15003 140V/20A/250W/23a 5.35€
MJ 15022 200V/16A/250W/23a 7.55€
MJ 15024 250V/16A/250W/23a 10.10€
MJ 16014 450V/20A/250W/23a 10.95€
MJ 16018 1500V/10A/175W/23a 12.60€
MJ 3001 80V/10A/da/di/150W/23a 3.30€
MJ 410 200V/5A/100W/23a 2.50€
MJ 802 100V/30A/200W/23a 5.85€
MJE 1100 60V/5A/da/70W/16h 3.35€
MJE 13005 700V/4A/75W/17j 2.50€
MJE 15030 150V/8A/17j 5.05€
MJE 200 40V/5A/15W/14h 2.50€
MJE 3055T 70V/10A/90W/17j 1.65€
MJE 340 300V/0.5A/20W/14h 1.65€
MJW 16212 650V/10A/150W/16j 14.30€
TIP 33C 110V/10A/80W/18j 2.50€
TIP 35C 100V/25A/125W/18j 3.35€
TIP 50 400V/1A/40W/17j 1.65€
TIP 642 100V/10A/da/di/175W/23a 4.20€
TIPL 762A 800V/6A/120W/18j 5.90€
TP 3008 <1GHz/4W/26V 4.00€
TP 3022B <1GHz/15W/26V 6.00€
TPS 1001 10.10€
2 SC 1505 300V/0.2A/15W/17j 2.00€
2 SC 3259 800V/3A/40W/da/17j 5.85€
2 SC 3271 300V/1A/5W/14b 1.65€
TIP 141>>>TIP142 3.35€
TIP 142 100V/10A/da/di/18j 3.35€
TIP 3055 70V/10A/17j 2.50€
TIP 31C =BD 241C 115V/3A/40W/17j 1.50€
TIP 33C 110V/10A/80W/18j 2.50€
TIP 35C 100V/25A/125W/18j 3.35€
TIP 50 400V/1A/40W/17j 1.65€
TIP 642 100V/10A/da/di/175W/23a 4.20€
TIPL 762A 800V/6A/120W/18j 5.90€
2 N1308 Ge/25V/0.3A/2a 0.80€
2 N1613=BC140 75V/0.5A/0.8W/2a 0.60€
2 N1711 75V/0.5A/0.8W/2a 0.80€
2 N1893 120V/0.5A/0.8W/2a 0.80€
2 N2218 75V/0.8A/0.8W/2a 0.80€
2 N2219 75V/0.8A/0.8W/2a 0.80€
2 N2222A 75V/0.8A/TO-18/2a 0.80€
2 N2222A 40V/0.5A/TO-92 plastic 0.50€
2 N2369 40V/0.2A/2a 0.65€
2 N3014 40V/0.2A/2a 0.80€
2 N3054 90V/4A/75W/22a 4.20€
2 SC 3858 200V/17A/200W/20j 8.50€
2 SC 3953 120V/0.2A/8W/14b 2.00€
2 SC 3996 1500V/15A/180W/77j 18.00€
2 SC 3998 1500V/25A/250W/ 22.00€
2 SC 4123 1500V/7A/60W/di/18c 5.85€
2 SC 4236 1200V/6A/100W/16j 4.50€
2 SC 4382 200V/2A/25W/17j 3.00€
2 SC 4484 30V/2.5A/1W/ 1.65€
2 SC 4793 230V/1A/20W/17j 2.55€
2 SC 5171 180V/2A/20W/17c 2.55€
2 SC 458 30V/0.1A/9b/7c 0.70€
BD 137 60V/1.5A/12.5W/14h, kts.2N4923
BD 139 100V/1.5A/12.5W/14h 0.85€
BD 159 375V/0.5A/14h 2.50€
BD 237 100V/2A/25W/14h 1.30€
BD 241C =TIP31C 115V/3A/40W/17j 1.50€
BD 243C 115V/6A/65W/17j 2.00€
BD 245C 110V/10A/80W/18j 2.50€
BD 249C = TIP35C 115V/25A/125W/18j 3.35€
BD 649 = BD 901
BD 681 100V/4A/da/di/40W/14h 1.35€
BD 901 100V/8A/da/di/70W/17j 1.65€
BD 911 100V/15A/90W/17j 2.50€
 
hi

go for the bf 870 s and bf 871 i have used them in crescendos - they are a very good choice , if you could get hold of a transistor data equavalent it would help - from what i remember there is very little difference betwn bf 470 & 870 , 471 & 871 ull find the prices more or less same too

suranjan
 
BF420 & BF471 & BF871 are NPN 300V 50mA sharing the same die buf in different packages

BF421 & BF472 & BF872 are PNP 300V 50mA sharing also the same die in different packages

BF42x are TO-92
BF47x are TO-126
BF87x are in a propietary Philips package similar to TO-220 but with some built-in heat-sinking

These are really small signal devices since Hfe and Ft starts to drop above 10mA

BD139& BD140 [when not fakes] are old but still cool and very useful devices. They are fast and usable up to 100V at low currents <50mA. I like them for VAS or predrivers. I've succesfully used them in pulsed operation sustaining 24V and 1,2A at the same time during 1uS at 70Khz repetition rate [provided adequate heat-sinking]. In that application [same base drive currents] they proved to switch much faster than other BD2xx/BD4xx/BD7xx/BD9xx, TIPxx and MJE150xx transistors I've also tested [being MJE150xx the next better choice]. It's a pity I forgot to test MJE340/MJE350
 

Bonsai

Member
Paid Member
2003-07-25 10:44 pm
Europe
www.hifisonix.com
BF vs MJE vs BD

I'm really surprised at the comments about the BF4xx (and by implication the BF8xx) devices in terms of sonic performance.

These are fast video amplifier transistors in both NPN and PNP versions and make great VAS transistors and output stage buffers. They may not have enough power handling capability to be used to directly drive the output stage on larger amplifiers, but you would normally go for a triple in this situation anyway in order to not load the VAS.

In the VAS, my experience is that they are very superior to the MJE340/50 devices which suffer from base storage effects (as much as 1uS). The BF4xx devices have none of these problems and you canas a result do away with Baker clamps and all the other things needed to get around these problems.

I've done a lot of modelling using both the MJE's and the BF's (and built some amps using these devices) and my vote would always be for the BF4xx types.

If there appears to be a sonic difference between the devices, its probably arising from some other mechanism at work in the amp - is the compensation ok? Is the VAS being loaded excessively or less? etc etc.


On the Crescendo amp by the way, be carefull about using transistors in the VAS stage that are a lot different from the original BF4xx types specified. THey used the input capacitance of the output mosfets as part of the compensation scheme and relying on global feedback around the whole amp to keep it stable. I would think an MJE type used here for example that was overdriven as happens would lead to all sorts of nasty problems.
 
Bipolar transistors in a VAS behave like a MOSFET placed here, ie: The lowest the impedance that drives the base, the fastest the device responds

Higher current or voltage bipolars tend to be slower due to bigger charge storage. A MJE340/350 or MJE150xx stores far more charge than a BF871/872
 

Jay

Banned
2003-02-11 9:02 am
Jakarta
Okay, I'm not thinking it through, so be patient if this sounds stupid.

In the driver stage, do the standard mini-crescendo amplifies in full wave? I guess it is very probably that till this stage the transistors are running in class A.

The background of the question is that I feel that the bad sound quality of this amp is due to the insufficient amplification stage. So adding another stage could be a solution.

So why not using a darlington in the driver stage? Not common but why can-not? This could be a very good idea, if it is not a very bad one. At least I'm bringing this thread up :D