FirstWatt J2

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#2,125
EUVL said:
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
Click to expand...
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.

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.
 
#2,130
TI NexFETs are also very nice but no package larger than TO220. The csd18537nkcs RθJC is 1.6 K/W should be great for mini J2/F8 but needs extra care in heatsinking or cascoding for full size. Seems also great for 8W Mofo @12V to challenge your buddy's 300B. 🙂
 
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#2,133
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?
 
#2,136
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 🤔
 
#2,138
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
 
#2,139
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
 
#2,140
Perhaps stupid question...can cny17 be substituted with 4n35 without any need for bias tweeking?
 

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