ESP Project 23

tiroth · 30th January 2002, 09:10 PM

For ESP Project 23 would MJE2955/3055 be appropriate input devices? I happen to have a lot of these lying around.

Thanks.

paulb · 30th January 2002, 09:24 PM

I think they would if the voltage ratings are okay (I haven't looked). I don't think you need much gain, which is good because the 2955/3055 don't have much.
If you really want to be sure, you can email Rod - he's pretty good at answering inquiries.

lohk · 30th January 2002, 10:27 PM

No, I think this is no good choice.
Power transistors rarely are good input transistors.

Why don't you make lots of good sounding amplifiers with this devices?

Klaus

tiroth · 31st January 2002, 04:28 PM

Quote:

Originally posted by lohk
No, I think this is no good choice.

Really? This is not a circuit in the signal path, so "quality" is not really an issue as long as the circuit is still operational. Do you think it would not work correctly?

I should have mentioned that my rails are 42, so the max "normal" voltage the transistors should see is 39v, with a worst case (output shorted to unloaded rail) of 50v. I believe this is well within the 60v safe region. [output shorted to rail means I have bigger fish to fry, but I'd like to avoid secondary explosions in a fault state]

I would email Rod, but because he is so helpful to so many people I like to avoid bothering him where possible.

Thanks for your responses.

lohk · 31st January 2002, 09:52 PM

No, it is not a question of "quality".
MJE3055/2955s are designated output high current transistors, they need to be driven properly to function in an apropriate way. You can use them for input devices in sensing circuits for example, when high currents have to pass through. They have only low gain, and are quite non-linear at low currents, which can also be a problem here. And they are much bigger and more difficult to implement, and...
I think that they will not work the way you want. But if you insist, you can try it nevertheless ! It is up to you.
You can use - as Rod suggests - any transistor which meets the voltage specs. Current will be low, so possibly BC546/BC556 will work as an alternative. Boy, I have lots of these lying around ! (A zip-loc bag full of them actually...)

best wishes
Klaus

tiroth · 1st February 2002, 01:22 PM

Thanks for the suggestion lohk. I think I'll pick up some BC546/BC556 on my next order to be safe. :)

30th January 2002, 09:10 PM	#1
tiroth diyAudio Member Join Date: Dec 2001 Location: Pittsburgh, PA, USA	ESP Project 23 For ESP Project 23 would MJE2955/3055 be appropriate input devices? I happen to have a lot of these lying around. Thanks.

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30th January 2002, 09:24 PM	#2
paulb diyAudio Member Join Date: Jun 2001 Location: Calgary	I think they would if the voltage ratings are okay (I haven't looked). I don't think you need much gain, which is good because the 2955/3055 don't have much. If you really want to be sure, you can email Rod - he's pretty good at answering inquiries.

30th January 2002, 10:27 PM	#3
lohk diyAudio Member Join Date: Apr 2001 Location: Northern Noricum, near the Limes	No, I think this is no good choice. Power transistors rarely are good input transistors. Why don't you make lots of good sounding amplifiers with this devices? Klaus

31st January 2002, 09:52 PM	#5
lohk diyAudio Member Join Date: Apr 2001 Location: Northern Noricum, near the Limes	No, it is not a question of "quality". MJE3055/2955s are designated output high current transistors, they need to be driven properly to function in an apropriate way. You can use them for input devices in sensing circuits for example, when high currents have to pass through. They have only low gain, and are quite non-linear at low currents, which can also be a problem here. And they are much bigger and more difficult to implement, and... I think that they will not work the way you want. But if you insist, you can try it nevertheless ! It is up to you. You can use - as Rod suggests - any transistor which meets the voltage specs. Current will be low, so possibly BC546/BC556 will work as an alternative. Boy, I have lots of these lying around ! (A zip-loc bag full of them actually...) best wishes Klaus

1st February 2002, 01:22 PM	#6
tiroth diyAudio Member Join Date: Dec 2001 Location: Pittsburgh, PA, USA	Thanks for the suggestion lohk. I think I'll pick up some BC546/BC556 on my next order to be safe. :)