swapping 2955/3055's for new on semi mjl4281A/mjl4202A ? - diyAudio
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Old 30th January 2004, 04:03 PM   #1
Tensop is offline Tensop  Lebanon
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Default swapping 2955/3055's for new on semi mjl4281A/mjl4202A ?

Hi guys, im in the middle of building an sc480 silicon chip amp, and was wondering if theres are directly replacable?


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Old 30th January 2004, 04:39 PM   #2
azira is offline azira  United States
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Just passing through the 'duh' test but uh... My 3055's are TO-220 and the 4281's are much bigger (TO-264)...
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Old 30th January 2004, 06:23 PM   #3
sam9 is offline sam9  United States
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Might be do-able. The packages are differennt but the pin spacing and pin-outs are the same or nearly so. Note, for example that the ESP P3A pcb can take either. The question of physical space remains. If all else fails a bit of air wiring might make is work.

I have no opinion whether you will actually hear a difference as other factors are involved as well.
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Old 30th January 2004, 06:28 PM   #4
Did it Himself
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There's a few variations of 3055s and 2955s. TIP3055 are in large package so MJ4281 will drop straight in. MJE3055 (or it may be MJL3055, I forget) are TO220 so it may be difficult.
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Old 31st January 2004, 09:32 AM   #5
Tensop is offline Tensop  Lebanon
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thanks for the tips guys. Physical spacing wont be a problem. i was just wondering if there was any electrical difference(for example the gain between the 2955 and its equivilent would be different). I'm planning to use other transistors as the power rating of these isnt as great as others that are easily availble


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Old 16th February 2006, 01:55 AM   #6
DilbyŠ is offline DilbyŠ  Australia
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Is there a conclusion to this idea? I'm considering doing the same thing with mine..
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Old 16th February 2006, 03:28 AM   #7
CBS240 is offline CBS240  United States
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Generally, variables like Hfe, Vce, Ic, SOA, speed, and thermal resistance to case may be a factor here. Just compare the datasheets.
All the trouble I've ever been in started out as fun......
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Old 16th February 2006, 07:21 AM   #8
AndrewT is online now AndrewT  Scotland
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which way are you swapping?

Are you planning to use the To220 3055s? instead of the To264 4302s?
regards Andrew T.
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Old 16th February 2006, 09:25 AM   #9
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Hi AndrewT,

The original SC480 kit has 2 versions, one uses 2 x TIP3055/2 x TIP2955 and the other 2 x 2N3055/2 x 2MJ2955 for output devices.


Looking at the schematic, I would "guess" substituting higher speed more linear output devices should be OK. I would suggest trying it for one channel and post the results. Its an EF output stage which I believe are less prone to oscillations.

Greg Erskine
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