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Old 28th February 2003, 08:39 PM   #1
red is offline red  Romania
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Default Questions about transistors

Hello all you diy lovers!!!
I have some things to ask you about transistors...I would like to build a 120watts amplifer on a 4 ohm load.I have a nice power supply of 2x30 V Ac>ihave a romanian cheap schematic that looks a lot like the esp 3A project.But the problem is the power transistors.In the schematic is mentioned the pair 2N3055/2N2955 that also made in Romania but they are kind of laisy.I mean that the low frequencies are kind of unpleaseant.I was thinking,after reading some othe articles, to use the 2Sc3281/2Sa1302 pair.A friend of mine told me that these are very hard to tune up in an amplifier and that they may work quite well for a while if and then burn both my loud speakers and themselfs if they aren't set up properly.
The last question would be what I need to know in order to tune up this amplifier???
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Old 28th February 2003, 10:48 PM   #2
halojoy is offline halojoy  Sweden
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Cool Re: Questions about transistors

Quote:
Originally posted by red
Hello all you diy lovers!!!
I have some things to ask you about transistors...I would like to build a 120watts amplifer on a 4 ohm load.I have a nice power supply of 2x30 V Ac>ihave a romanian cheap schematic that looks a lot like the esp 3A project.But the problem is the power transistors.In the schematic is mentioned the pair 2N3055/2N2955 that also made in Romania but they are kind of laisy.I mean that the low frequencies are kind of unpleaseant.I was thinking,after reading some othe articles, to use the 2Sc3281/2Sa1302 pair.A friend of mine told me that these are very hard to tune up in an amplifier and that they may work quite well for a while if and then burn both my loud speakers and themselfs if they aren't set up properly.
The last question would be what I need to know in order to tune up this amplifier???
Almost any TO3 tansistors are an upgrade from 3055/2955.
You will have a lot to chose from.
I like the MJ15024/25 (or MJ15022/23).

About "tune up" problem, I can not understand.
And if you get a pair of transistors to work,
they are the last thing that changes their operation with time.
At least they will not burn anything, after some time.

I guess your friend mean that using such fast transistors
can make the amplifier oscillate, and burn LOAD.
But that can be avoided with proper compensation capacitance.

I think that those transistors you think about,
are an overkill.
But if you can easy get them, so why not?
You can then tell us about your experiences with them.

/halo - thinks super-fast transistors are good for voltage amp stage
and possibly output transistor drivers
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