mj 15003/4 on musical fidelity a100-x

mosfet1 · 14th January 2007, 04:12 PM

hi there!
mj series sounds better than 2n3055 And complementary, in a musical fidelity a100? I mean : can I upgrade with these transistors? what's the difference in sonic performances?

thanks walter

AndrewT · 14th January 2007, 04:15 PM

Hi,
what DC voltage is on the supply rails of the MF a100?

jaycee · 14th January 2007, 08:30 PM

From reading Mark Hennessy's page, the MJ15003/4 will drop right in and be a hell of a lot more reliable than the remarked MJ2955/2N3055. I doubt it'll improve the sound any, though.

djk · 14th January 2007, 09:03 PM

"what DC voltage is on the supply rails of the MF a100?"

The MJ15003/04 are 140V vs the 3055/2955 being 60V, so it shouldn't be a problem.

"I doubt it'll improve the sound any, though."

The MJ15003/04 have higher Beta at higher collector currents, so the distortion will go down a bit (but even though it will measure better, there may be no big difference in the sound).

AndrewT · 15th January 2007, 08:23 AM

Hi,
the reason I asked at what voltage the MF run with, was to allow assessment on whether the 2955/3055 was a suitable transistor in the first place.

It the existing transistors are unsuitable then anything with sufficient SOA will be an improvement, even if only that it does not blow up and irrespective of sound quality.

What voltage does the MF run at?

sixtek · 15th January 2007, 09:16 AM

AndrewT, as I remember that runs at +/-25V idle rails (like MF A1).

AndrewT · 15th January 2007, 11:43 AM

Hi,
+-25Vdc should allow most lower voltage power transistors to work.
I guess that voltage would allow about 25W into 8r. Does that seem right?
Any of the beefier and/or more modern semis would make a good replacement.
Do you need To3 or To220 or To247 or some other package?

jaycee · 15th January 2007, 12:26 PM

They are TO-3 devices in the A1. They run at quite a high dissipation and it's been known that the 2955/3055's often give out under the thermal stress.

Be sure of which A1 you have. The Final edition is actually a rebadged B200 which is MOSFET outputs.

You really can't do better than Mark's page on this:

http://www.mhennessy1.f9.co.uk/mf_a1/index.htm

Everything you could want to know is there pretty much

AndrewT · 15th January 2007, 01:05 PM

Hi,
the MJ15003/4 can operate upto 250W, 200degC and will survive better than the lower specified 3055, even on the same heatsink.

14th January 2007, 04:12 PM	#1
mosfet1 diyAudio Member Join Date: Nov 2006	mj 15003/4 on musical fidelity a100-x hi there! mj series sounds better than 2n3055 And complementary, in a musical fidelity a100? I mean : can I upgrade with these transistors? what's the difference in sonic performances? thanks walter

14th January 2007, 04:15 PM	#2
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, what DC voltage is on the supply rails of the MF a100? __________________ regards Andrew T.

14th January 2007, 09:03 PM	#4
djk diyAudio Member Join Date: Feb 2001 Location: USA	"what DC voltage is on the supply rails of the MF a100?" The MJ15003/04 are 140V vs the 3055/2955 being 60V, so it shouldn't be a problem. "I doubt it'll improve the sound any, though." The MJ15003/04 have higher Beta at higher collector currents, so the distortion will go down a bit (but even though it will measure better, there may be no big difference in the sound). __________________ Candidates for the Darwin Award should not read this author.

15th January 2007, 08:23 AM	#5
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, the reason I asked at what voltage the MF run with, was to allow assessment on whether the 2955/3055 was a suitable transistor in the first place. It the existing transistors are unsuitable then anything with sufficient SOA will be an improvement, even if only that it does not blow up and irrespective of sound quality. What voltage does the MF run at? __________________ regards Andrew T.

15th January 2007, 11:43 AM	#7
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, +-25Vdc should allow most lower voltage power transistors to work. I guess that voltage would allow about 25W into 8r. Does that seem right? Any of the beefier and/or more modern semis would make a good replacement. Do you need To3 or To220 or To247 or some other package? __________________ regards Andrew T.


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14th January 2007, 08:30 PM	#3
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	From reading Mark Hennessy's page, the MJ15003/4 will drop right in and be a hell of a lot more reliable than the remarked MJ2955/2N3055. I doubt it'll improve the sound any, though.

15th January 2007, 09:16 AM	#6
sixtek diyAudio Member Join Date: Jan 2007	AndrewT, as I remember that runs at +/-25V idle rails (like MF A1).

15th January 2007, 12:26 PM	#8
jaycee diyAudio Member Join Date: Apr 2004 Location: Norwich, UK	They are TO-3 devices in the A1. They run at quite a high dissipation and it's been known that the 2955/3055's often give out under the thermal stress. Be sure of which A1 you have. The Final edition is actually a rebadged B200 which is MOSFET outputs. You really can't do better than Mark's page on this: http://www.mhennessy1.f9.co.uk/mf_a1/index.htm Everything you could want to know is there pretty much

15th January 2007, 01:05 PM	#9
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	Hi, the MJ15003/4 can operate upto 250W, 200degC and will survive better than the lower specified 3055, even on the same heatsink. __________________ regards Andrew T.

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