I'm just trying to help people build successfully! The amps are so good, they really are the pot of gold at the end of the rainbow.
It's a 2-part winning process, you learn something and have the wonderful experience of building the amp, and then you get to listen to it!
The Aleph J is, in my opinion, the crowning glory of NP's designs, and in his opinion, the best of the Aleph series.
It's a 2-part winning process, you learn something and have the wonderful experience of building the amp, and then you get to listen to it!
The Aleph J is, in my opinion, the crowning glory of NP's designs, and in his opinion, the best of the Aleph series.
My problem with to little bias on Aleph J fixed. But 68k i series with the 100k trimpot was way to much. A 10 k resistor instead of the jumper in R27 position was fine to get the a bias up to 400mV
Zen Mode wrote: "well , nothing wrong with extra options , I'm just witness that boyz are often confused".
Why cant important corrections like this be taken into the first post of this thread. I went through a lot of post to see if the "R27 problem" have been discussed. It ended up with a "unnesessary"question in this thread. Anyway, thanks for the help.
Eivind S
Zen Mode wrote: "well , nothing wrong with extra options , I'm just witness that boyz are often confused".
Why cant important corrections like this be taken into the first post of this thread. I went through a lot of post to see if the "R27 problem" have been discussed. It ended up with a "unnesessary"question in this thread. Anyway, thanks for the help.
Eivind S
Almost there
I completed the build of my Aleph J and the only missing part is a zener diode I will get tomorrow🙂
I plan to test the amp with a bench supply before hooking the amp up to the dedicated supply, but there is something that I don't understand..
In this post sound happy does so using a +25V/0V supply, while I would think the correct would be to use a bipolar +25V/0V/-25V supply.
What am I missing?
Also, I read somewhere that the AJ pulls much more current from the positive rail. Does anybody have some numbers on this? I'm just trying to understand what to expect so that I can set the current limiters on the bench supply in a meaningful way.
Thanks!
I completed the build of my Aleph J and the only missing part is a zener diode I will get tomorrow🙂
I plan to test the amp with a bench supply before hooking the amp up to the dedicated supply, but there is something that I don't understand..
In this post sound happy does so using a +25V/0V supply, while I would think the correct would be to use a bipolar +25V/0V/-25V supply.
What am I missing?
Also, I read somewhere that the AJ pulls much more current from the positive rail. Does anybody have some numbers on this? I'm just trying to understand what to expect so that I can set the current limiters on the bench supply in a meaningful way.
Thanks!
it is bipolar supply , meaning +25Vdc/GND/-25Vdc
in reality - with 2x18Vac xformer and usual cap. bank , you can expect more like 22V5 rails
we can freely say that current is equalized in rails
in reality - with 2x18Vac xformer and usual cap. bank , you can expect more like 22V5 rails
we can freely say that current is equalized in rails
Ok - thanks! I use a 2x21V 400VA toroid, so I will probably get 25-26V after CRC.
I was just wondering how soundhappy could do it with a +25V/gnd bench supply😕
I was just wondering how soundhappy could do it with a +25V/gnd bench supply😕
didn't checked what he was doing
most probably mistake in (his) explanation , simply because it'll not work properly without bipolar supply
most probably mistake in (his) explanation , simply because it'll not work properly without bipolar supply
well ......... there must be some sort of reference ...... or you'll have effect of speaker flappin' in da breeze ...... 
Hi,
Here's an Aleph-J in a store 4U chassis wired with XLR inputs. The jfets
are 2sj108V instead of the more customary 2sj74/lsj74. The IRFP240
mosfets were curve traced and matched at 850mA. PSU consists of
a 2x18VAC 300VA Plitron and 8x22000 uF caps in CRC (R~0.12 ohm)
Bias was set at ~1.7A (0.4V over 0.47R source resistor) after about 1
hour. It sounded fine with the test speakers.
I hope in the coming weeks to get some time to run it in,
recheck and adjust the bias and offsets, before trying it with
the main speakers.
Thanks to Papa for this wonderful design and Jim for the build guide.
Cheers,
Dennis
Here's an Aleph-J in a store 4U chassis wired with XLR inputs. The jfets
are 2sj108V instead of the more customary 2sj74/lsj74. The IRFP240
mosfets were curve traced and matched at 850mA. PSU consists of
a 2x18VAC 300VA Plitron and 8x22000 uF caps in CRC (R~0.12 ohm)
Bias was set at ~1.7A (0.4V over 0.47R source resistor) after about 1
hour. It sounded fine with the test speakers.
I hope in the coming weeks to get some time to run it in,
recheck and adjust the bias and offsets, before trying it with
the main speakers.
Thanks to Papa for this wonderful design and Jim for the build guide.
Cheers,
Dennis
Attachments
Nice build, great amp! The Aleph J is still my stationary centerpiece. "One day" I'll finish the VFet amp from the store. Life keeps happening though.
Enjoy your Aleph J !
Enjoy your Aleph J !
Thanks guys.
I have a soft spot for the Aleph, (my main amp for over 10 years was a DIY A30)
and I look forward to spending some quality time with the Aleph-J.
It's nice to be able to do some diy work again. Next up should be the vfet2 amp
and hopefully I can slowly work back up to an SMD project I had to abandon a
few months ago.
Cheers,
Dennis
I have a soft spot for the Aleph, (my main amp for over 10 years was a DIY A30)
and I look forward to spending some quality time with the Aleph-J.
It's nice to be able to do some diy work again. Next up should be the vfet2 amp
and hopefully I can slowly work back up to an SMD project I had to abandon a
few months ago.
Cheers,
Dennis
Congratulations - looks great!
I also finished mine a few days ago, but unfortunately I have some problems with oscillations and the bias (can't get it above 0.32-0.35V). The same circuit as the store boards, but using PCBs made by a friend. I'm trying different things but till now without success🙁
Any known causes (and remedies) for oscillations of the Aleph J?
Cheers,
Nic
I also finished mine a few days ago, but unfortunately I have some problems with oscillations and the bias (can't get it above 0.32-0.35V). The same circuit as the store boards, but using PCBs made by a friend. I'm trying different things but till now without success🙁
Any known causes (and remedies) for oscillations of the Aleph J?
Cheers,
Nic
Dennis, that's absolutely beautiful!! Well done. 😀
Is that the PSU board from Burning Amp Fest '15? Did any of the other parts make it in that amp?
Is that the PSU board from Burning Amp Fest '15? Did any of the other parts make it in that amp?
Hi Jim,
Yes, that's the PSU board from BA2015. Funny how much faster it was to
build a PSU with a PCB. 🙂 I picked up a softstart board also but have
not had the opportunity to use it yet. Thanks again Jim.
Cheers,
Dennis
Yes, that's the PSU board from BA2015. Funny how much faster it was to
build a PSU with a PCB. 🙂 I picked up a softstart board also but have
not had the opportunity to use it yet. Thanks again Jim.
Cheers,
Dennis
