Feedback Cap in Aleph and Aleph J

Fox · 12th November 2008, 06:15 AM

Folks,

Last night, I started comparing the schematic of the Aleph 5, which I made several years ago, and the Aleph J. Besides the obvious differences, I saw that the 220uF electrolytic cap in the feedback loop of the Aleph 5 was replaced bij a 1 uF film cap in the Aleph J. I have searched the forum but somehow failed to find an explanation why the cap is so big in the Aleph 5 and so small in the Aleph J. Perhaps you can offer me an explanation.

Regards,

Fox

wuffwaff · 12th November 2008, 11:05 AM

Hi,

the 220uF cap in the Aleph 2,3,4,5 is much bigger than needed for a flat frequency response. It was probably chosen to keep all three caps the same.
Another reason you can use a smaller value in the AlephJ is the higher values of the resistors and the lower input capacitance.

William

Fox · 12th November 2008, 03:23 PM

Hi William,

Thanks for the explanation. I also figured out that a 33 uF cap should me more than enough to go straight down to 10 Hz. At least, that's what my simulator showed me. It appears that Nelson has a lot of 220uF caps on stock

.

Greetz,

Fox

12th November 2008, 06:15 AM	#1
Fox diyAudio Member Join Date: Dec 2002 Location: The Netherlands	Feedback Cap in Aleph and Aleph J Folks, Last night, I started comparing the schematic of the Aleph 5, which I made several years ago, and the Aleph J. Besides the obvious differences, I saw that the 220uF electrolytic cap in the feedback loop of the Aleph 5 was replaced bij a 1 uF film cap in the Aleph J. I have searched the forum but somehow failed to find an explanation why the cap is so big in the Aleph 5 and so small in the Aleph J. Perhaps you can offer me an explanation. Regards, Fox

12th November 2008, 11:05 AM	#2
wuffwaff diyAudio Member Join Date: Aug 2001 Location: Ingolstadt Germany	Hi, the 220uF cap in the Aleph 2,3,4,5 is much bigger than needed for a flat frequency response. It was probably chosen to keep all three caps the same. Another reason you can use a smaller value in the AlephJ is the higher values of the resistors and the lower input capacitance. William __________________ een ooievaar is geen konijn want zijn oren zijn te klein!

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12th November 2008, 03:23 PM	#3
Fox diyAudio Member Join Date: Dec 2002 Location: The Netherlands	Hi William, Thanks for the explanation. I also figured out that a 33 uF cap should me more than enough to go straight down to 10 Hz. At least, that's what my simulator showed me. It appears that Nelson has a lot of 220uF caps on stock . Greetz, Fox

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