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Old 27th January 2009, 05:11 PM   #1
neazoi is offline neazoi  Greece
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Default MJ15003 or MJ15022 ?

Hello, I have a nice class-A hybrid amplifier which uses tubes for preamplifier and BJTs for final.

The final is a classic design similar to some I have found on the internet (2 transistors per channel, 10W output in class-A, no output cap) and uses MJ15022.

1. I have some matched MJ15003 in stock and I would like to know if I can direct replace them. The total quescent current is 1A per channel.

2. I need some reviews about MJ15003 and MJ15022. Which of the two types is better in terms of sound quality?

3. Both of these transistors seem to be better than the 2N3055, right?


Thank you very much.
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Old 27th January 2009, 05:21 PM   #2
lineup is offline lineup  Sweden
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They are very similar TO-3 devices.
Both can dissipate same amount of heat, power.
And yes!! .... they should be to prefer over 2N3055.

My choice would be MJ15022/23 (or the same MJ15024/25).
MJ15022 is a slightly bit faster than MJ15003.

Which can be seen by these data:
Quote:
MJ15003, fT=2 MHz, cob=1000 pF (Output capacitance)
MJ15022, fT=4 MHz, cob= 500 pF
Datasheets from http://www.datasheetarchive.com/
MJ15022 data
MJ15003 data
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Old 27th January 2009, 05:33 PM   #3
pooge is offline pooge  United States
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I would opt more for the MJ21113/4 pair.

Datasheet MJ21113/4

same higher ft as MJ15024, but less beta droop and higher minimum hfe to put less strain on unknown drivers.
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Old 27th January 2009, 05:39 PM   #4
lineup is offline lineup  Sweden
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pooge
I agree, MJL21193 would be a real upgrade.
Same package would fit = TO-3
They have good performance at considerably higher gain, hFE,
which means they are an easier load for driver stage transistors.
This is a very good quality
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Old 27th January 2009, 05:56 PM   #5
wg_ski is offline wg_ski  United States
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At that low power and current level, you would be hard pressed to tell the difference between one type of epi-base transistor and another. If you actually were stressing their capabilities, maybe, but at 10W and 2A of peak current swing no way. The proper transistor to use is whichever one you have in your hand. Save ordering the 21193s until you really need them.
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Old 27th January 2009, 08:39 PM   #6
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Quote:
Originally posted by lineup
pooge
I agree, MJL21193 would be a real upgrade.
Same package would fit = TO-3
They have good performance at considerably higher gain, hFE,
which means they are an easier load for driver stage transistors.
This is a very good quality

Line-up, I would agree with wg_ski that the differences become negligible at low power, but I would prefer the sound of the MJE15003 for this power and if I can drive it with BD139/140 the combination makes very good sound.

Nico
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Old 27th January 2009, 08:46 PM   #7
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Slew rate of 1V/week is almost too good already.

From my experience, which is less than line-up, because he is older, is that an amp using very fast transistors seem to be pronounced in mid/high and highs at moderate volume setting and a get better or smoother balance ant higher volume settings. I stand to be corrected as my judgment is subjective.

Nico
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Old 28th January 2009, 06:49 AM   #8
neazoi is offline neazoi  Greece
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Ok, as a conclusion, it seems then that the choise of MJ15022 is not a bad one, though there are better transistors to use, like MJL21193, but at such low power the differences are not too noticeable.

I appreciate for your comments
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Old 28th January 2009, 07:54 AM   #9
lineup is offline lineup  Sweden
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Quote:
Originally posted by Nico Ras
Line-up, I would agree with wg_ski that the differences become negligible at low power, but I would prefer the sound of the MJE15003 for this power and if I can drive it with BD139/140 the combination makes very good sound.
Of course depends on the actual amplifier application.
I have only been talking in general terms, as I have no idea about this amp.

There can be at least 2 reasons to use MJ15003 and not experimenting with 'faster' devices:

1. The circuit was trimmed to be optimally working using MJ15003 or MJ15022

2. MJ15003 has got lower saturation voltage at HIGH current, than JM15022.
So, means that it could deliver more current before get's strangled
at low voltage supply margin.


Finally, I will agree with others here, who has an idea about your amplfier:
Whether you use MJ15003 or MJ15022, in this case
does not really matter.
The are practically identical. And the difference fT 2 to 4 MHz
would not matter for output stage followers.


Bottomline:
Use MJ15003 if you have such.
Or MJ15022 if you have such.
You will not gain anything by buying new Transistors..


Regards
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