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30th January 2007, 01:46 PM
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#1 |
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diyAudio Member
Join Date: May 2005
Location: Roma
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Slone 11.4 questions...
hi everybody...
i want to build this amp from the Slone's book... now, i can't find the 2SD699 and the 2SB649. suggestions for equivalents??? MJE340/350??? BD139/140??? and... i have a pair of 47uF and a pair of 10uF MKT capacitors for audio applications... i want to use the 10uF caps as input decoupling caps, can i do this? I want also replace the 220uF electrolitic on the scematic to eliminate electrolitics from the signal road... dO you think that i can replace the 220uF with the 47uF without problems??? waiting for replyes... |
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30th January 2007, 08:18 PM
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#2 |
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diyAudio Member
Join Date: Jun 2004
Location: Warsaw
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Try 2sa1837/2sc4793 from toshiba.
Caps change is OK. |
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30th January 2007, 09:55 PM
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#3 |
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diyAudio Member
Join Date: May 2005
Location: Roma
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2SA1837/2SC4793 seems to be hard to find in my country... can you suggest me an european equivalent?
i think that the function of the 220uF cap is only a low pass filer... is this right??? what is the effect of my substitution?? thanks... |
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31st January 2007, 09:43 AM
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#4 |
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diyAudio Member
Join Date: Jul 2004
Location: Scottish Borders
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Hi,
the 649/669 is an excellent driver. There are few equivalents that can match it. The 1837 is 50% of the speed and 66% of the SOA @ 50Vce, not a good replacement. Try Dalbani for this transistor pair. For good bass response the 220uF in the NFB loop is already too small. 470uF would be better. If you replace it with a 47uF you will move the low frequency roll-off frequency up a full decade above optimum. The input filter is set to 110mS, this could be dropped to 80 to 90 mS if you want and you would be far better replacing the two 22uF electrolytics with one plastic film 10uF if you can find one to fit the space available. The NFB filter should be set to at least 1.4 times (half an octave) larger than the input filter so aim for 140mS (330r & 470uF=155mS). The output transistors are obsolete and their replacements 1943/5200 are faked by many sources. Take care to select from a reputable source.
__________________
regards Andrew T. |
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