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Old 21st December 2001, 08:34 PM   #1
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Location: Riyadh, Saudi Arabia
Question Aleph 2 MPSA18

Hello to everyone. I'm a amplifier diy hobbyist from Riyadh, Saudi Arabia. The MPSA18 is not available in Riyadh, even in Farnell distributor. Would anyone recommend a replacement for MPSA18 in Aleph 2. If there is, does it needs a bias resistor changes?
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Old 21st December 2001, 08:47 PM   #2
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This is just a generic NPN transistor in a TO-92
case. Almost any decent such device will work
fine without modification. I also usually use
Zetex Z450's for this, but you should be able to
plug almost anything in.
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Old 23rd December 2001, 10:50 PM   #3
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Mr. Pass, sir thank you for your reply. I can't imagine "the legend" is replying to my queries.
I have one more question about R1 and R8 in the Aleph 30 and 60. What are their values and function? Other Aleph design does not have these resistors? Why in Aleph 30 and 60?
I'll appreciate your inputs. Thank you.
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Old 24th December 2001, 12:08 AM   #4
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Lightbulb R1 & 8

R1 is used to trim Power Supply Rejection
R8 is used to trim DC Offset

refer to thread for explanationhttp://www.diyaudio.com/forums/showthread.php?s=&threadid=1193
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Old 29th December 2001, 01:49 PM   #5
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Thank you cp642 for your enlightenment on the aleph60 R1 and R8.
I have one more question regarding the shorting plug. Since all of my equipments are single ended, I only need the positive input, what shall I do with the negative input? Should I connect it to ground? Do I need to modify the ckt?
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Old 29th December 2001, 05:43 PM   #6
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For single-ended use, the negative input goes to ground.

Grey
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Old 25th June 2002, 12:07 PM   #7
swede is offline swede  Switzerland
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So an MPSA06 with a current gain factor of 100 would do as well?

Sorry for being so junior...

//magnus
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Old 25th June 2002, 10:15 PM   #8
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gain of 100 or greater is preferred, but not really
essential.
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Old 27th June 2002, 08:02 AM   #9
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I have used as well as a lot of other people here in europe the BC550C transistor. It seems to work fine.
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