aleph j build question

audionut · 22nd April 2011, 01:14 PM

I have Brian's Aleph J boards, and all the pieces parts to build a few Aleph J channels...

The boards give you the option to have two or three output devices. Nelson's Aleph J design is of course 2 output devices. But the Aleph 30 with 3 output devices has been prefered over the Aleph 3 with 2 output devices. (I have built both)

Should I use two or three output devices in the Aleph J. The front end will be 2SJ74BL...are they sufficient to drive three output devices??

Bill Fuss · 22nd April 2011, 09:20 PM

I've built versions with two and three fets. I chose to use parallel jfets in the three fet version to eliminate the possibility that one was not enough, but I've really never seen anything concrete to justify it. Getting 4 well matched jfets can be a problem but it can be done.

audionut · 25th April 2011, 02:33 PM

Was there a preference for one version over the other??

I note that you cannot drive less than 8 ohm loads to the full 25 watts...sometimes I parrallel drivers in the Bi-amped system I have.

Bill Fuss · 25th April 2011, 03:25 PM

My main spkrs are 4 ohm Seas MTMs so I was looking for more current capability. I built monoblocks and run about 3.5A bias.
The spkrs are relatively efficient (88db)so the power output isn't really a concern, and I also raised the AC current gain to about 50% so they really aren't Aleph Js per se. They work great for me, YMMV. As soon as I find the $$$ I will sub the SemiSouth jfets for the signal 240s.

Best, Bill

22nd April 2011, 01:14 PM	#1
audionut diyAudio Member Join Date: Jan 2002 Location: Cleveland ohio	aleph j build question I have Brian's Aleph J boards, and all the pieces parts to build a few Aleph J channels... The boards give you the option to have two or three output devices. Nelson's Aleph J design is of course 2 output devices. But the Aleph 30 with 3 output devices has been prefered over the Aleph 3 with 2 output devices. (I have built both) Should I use two or three output devices in the Aleph J. The front end will be 2SJ74BL...are they sufficient to drive three output devices??

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22nd April 2011, 09:20 PM	#2
Bill Fuss RIP Join Date: Oct 2005 Location: Central Florida	I've built versions with two and three fets. I chose to use parallel jfets in the three fet version to eliminate the possibility that one was not enough, but I've really never seen anything concrete to justify it. Getting 4 well matched jfets can be a problem but it can be done.

25th April 2011, 02:33 PM	#3
audionut diyAudio Member Join Date: Jan 2002 Location: Cleveland ohio	Was there a preference for one version over the other?? I note that you cannot drive less than 8 ohm loads to the full 25 watts...sometimes I parrallel drivers in the Bi-amped system I have.

25th April 2011, 03:25 PM	#4
Bill Fuss RIP Join Date: Oct 2005 Location: Central Florida	My main spkrs are 4 ohm Seas MTMs so I was looking for more current capability. I built monoblocks and run about 3.5A bias. The spkrs are relatively efficient (88db)so the power output isn't really a concern, and I also raised the AC current gain to about 50% so they really aren't Aleph Js per se. They work great for me, YMMV. As soon as I find the $$$ I will sub the SemiSouth jfets for the signal 240s. Best, Bill

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