I see EUVL advicing against the J2 for noobs. Oh, well. Maybe an F2J…
This is for noobs :
https://diyaudiostore.com/collections/aca-mini
It is not about the soldering, but the debugging in case of trouble.
Build something easy first, save your Semisouths for later projects.
My 2 cents,
Patrick
Anyone looked into these?
https://au.mouser.com/ProductDetail/UnitedSiC/UJ4C075044K3S?qs=e8oIoAS2J1RyyWdi8IF4XQ==
https://au.mouser.com/ProductDetail/UnitedSiC/UJ4C075044K3S?qs=e8oIoAS2J1RyyWdi8IF4XQ==
I have to correct myself, it was of course CodyT and Steve Jones that gave away the semisouths.I got the semisouth as a gift from Papa in a lottery. Does anybody know where I can find the J2 PCB? I have been searching on the forum but can’t find any active group buys. Preferrably not from China.
I regard myself as the biggest noob on DIYaudio, even if I already completed ACA F5, B1, B1 Triode, and almost there with F6, V-FET N-channel, and ACN. But I can’t keep completing ACAs over and over again.This is for noobs :
https://diyaudiostore.com/collections/aca-mini
It is not about the soldering, but the debugging in case of trouble.
Build something easy first, save your Semisouths for later projects.
My 2 cents,
Patrick
So you are saying I should save my pair of semisouths for an F8? I must say, I am having impure thoughts about the F8 now that it is no longer in production.
Rewind- sounds like you should go ahead and build the J2. You have the skills to build and you can ask for help here with trouble shooting if needed.
But the F8 is much newer, and for the original version of the J2 I can only make a mono amp with the parts I have. If only the schematic of the F8 would be released… pretty please?
https://www.diyaudio.com/community/threads/firstwatt-j2.151909/post-5892472
https://www.diyaudio.com/community/threads/firstwatt-j2.151909/post-5916241
2SK3497 eats up less voltage headroom (lower Vgs) and nearly same Yfs as SJEP.
Patrick
https://www.diyaudio.com/community/threads/firstwatt-j2.151909/post-5916241
2SK3497 eats up less voltage headroom (lower Vgs) and nearly same Yfs as SJEP.
Patrick
https://www.diyaudio.com/community/threads/first-watt-f8.358672/post-6654823
https://www.diyaudio.com/community/threads/first-watt-website-update.358313/post-6299428
No Gerbers, no support. At your own risk.
Patrick
https://www.diyaudio.com/community/threads/first-watt-website-update.358313/post-6299428
No Gerbers, no support. At your own risk.
Patrick
Just curious…I often have my head in the sand (so to speak).
I noticed that Reno HiFi mentioned on their webpage that the J2 is discontinued (I was looking at prices on some items being sold off before they close down for good).
I confirmed the available new column on First Watt page says “N”.
I wondered if there was an official announcement I missed?
I also wondered if Papa was going to release any official circuit into the wild?
I noticed that Reno HiFi mentioned on their webpage that the J2 is discontinued (I was looking at prices on some items being sold off before they close down for good).
I confirmed the available new column on First Watt page says “N”.
I wondered if there was an official announcement I missed?
I also wondered if Papa was going to release any official circuit into the wild?
Over the long haul you will see official schematics, but there will likely also be some diy versions of several pieces in the store.


As tempting as the J2 is it requires a lot of parts that is hard to source. Where as the Aleph-J is somewhat easier although still requires some p-channels. This has made me pondering about an Aleph-J with F8 style input stage. Nelson, have you tried something like that? Perhaps named Aleph-J.5 🤔
https://www.diyaudio.com/community/threads/udness-or-you-dont-need-semisouths.343164/
https://www.diyaudio.com/community/threads/udness-or-you-dont-need-semisouths.343164/post-6304339
Everything in stock at Mouser, still.
Patrick
https://www.diyaudio.com/community/threads/udness-or-you-dont-need-semisouths.343164/post-6304339
Everything in stock at Mouser, still.
Patrick
Hi Patrick,
I'm familiar with your efforts. I have bought the parts to try it out. However, my thought about the Aleph-J with F8-styile input stage was response to Nelsons comment about bringing something like the J2 to the Diyaudio store. Thinking that such a circuit perhaps would be easier to build. But, perhaps there might not be enough advantages in such a circuit, apart from using only 1 p-channel, compared to the standard Aleph-J. The p-channel can be had for reasonably price through the shop.
Mogens
I'm familiar with your efforts. I have bought the parts to try it out. However, my thought about the Aleph-J with F8-styile input stage was response to Nelsons comment about bringing something like the J2 to the Diyaudio store. Thinking that such a circuit perhaps would be easier to build. But, perhaps there might not be enough advantages in such a circuit, apart from using only 1 p-channel, compared to the standard Aleph-J. The p-channel can be had for reasonably price through the shop.
Mogens
Aleph-J is different from the J2 in the way the current source is modulated.
The J2 (and F8) modulated current source using the optocoupler is a simpler circuit and has less stability issues.
Putting J2 in the store means putting Semisouth's also in the store.
Unless you use MOSFETs in its place, but it is not a J2 anymore.
And you still need 2SJ74's, which is not an active part.
My 2 cents,
Patrick
The J2 (and F8) modulated current source using the optocoupler is a simpler circuit and has less stability issues.
Putting J2 in the store means putting Semisouth's also in the store.
Unless you use MOSFETs in its place, but it is not a J2 anymore.
And you still need 2SJ74's, which is not an active part.
My 2 cents,
Patrick
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