i'm not the expert (not at all)🙏
but so far i read from passdiy, with common source mode we can get both voltage and current gain and also can handle more at lower impedance.
maybe it's easier to match with any preamp and speakers? IDK.
but at least to my ear, F5 sound very good on the bottom, and i love bass.🙏😁
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Preamp matching will not be altered at all by the output stage config.
Perhaps I am oversimplyfing things, if you want F5, build the F5, and if the BA-3, build the BA-3.
What I can say is that the BA-3 allready is a bass machine. But the bass is probably more rounded and voluptious than that of the F5, I would think.
For speakers with 4-8 ohms benign impedance, meaning preferably devoured of nasty impedance dips, the BA-3 is perfect. For nastynezzez needing extreme current, F5 or F5T are the go to’s. Or do the XA252. Easy.
Perhaps I am oversimplyfing things, if you want F5, build the F5, and if the BA-3, build the BA-3.
What I can say is that the BA-3 allready is a bass machine. But the bass is probably more rounded and voluptious than that of the F5, I would think.
For speakers with 4-8 ohms benign impedance, meaning preferably devoured of nasty impedance dips, the BA-3 is perfect. For nastynezzez needing extreme current, F5 or F5T are the go to’s. Or do the XA252. Easy.
point is - taking DF as observed factor - one must observe entire amplifier as a whole
for my peanut brain in state of juststartedfirstmorningcoffee, common source OS is having greater Rout than common drain OS
resulting that CS OS is having smaller DF than CD OS
now, what's happening with each one if and when NFB loop is closed around, that's another bag of bones
for my peanut brain in state of juststartedfirstmorningcoffee, common source OS is having greater Rout than common drain OS
resulting that CS OS is having smaller DF than CD OS
now, what's happening with each one if and when NFB loop is closed around, that's another bag of bones
isn't that df f5(cs) is bigger than df f4(cd)?
what about BA3FE ??
that is complementary common source (drain as output) with no feedback loop
can it scaled up into an amplifier? maybe with increasing the bias and paralleled the devices?
F5 is having NFB loop closed all around
F4 is having no NFB
BA3 as complete amp - so FE + OS, no NFB
again - compare complete amps , thinking what every sub-circuit is doing
I'm still sure that CD OS is having more Cojones than CS OS, when observed separately - out of broader context
and you took them out of context, presuming completely opposite characteristics of stages, when Rout is in question.
F4 is having no NFB
BA3 as complete amp - so FE + OS, no NFB
again - compare complete amps , thinking what every sub-circuit is doing
I'm still sure that CD OS is having more Cojones than CS OS, when observed separately - out of broader context
and you took them out of context, presuming completely opposite characteristics of stages, when Rout is in question.
The BA-1 / BA-2 / BA-3 thing is maybe a little confusing. With the Burning Amp series, you basically had two front end options, a "typical" LTP w/FB, and one without FB. Then you have two back end options, i.e. output stages. One is single-ended, one is push-pull. The idea was to be able to mix and match the FE and OS options as you see fit. Read the articles for clarity. The First Watt F4 is basically the push-pull OS with a buffer stuck on the front of it, that makes it easy to drive with about anything (buffer has high input impedance). But the "front end" of an F4 is whatever you put in front of it, and you make sure that it (preamp whatever) has enough gain and voltage swing to meet your needs.
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ok, but what is this accomplishing? What's the final goal? This specific design or certain performance numbers?
I am still waiting for those proto PCBs from SR. Let a sissy enjoy his amp 
Hey guys, I plan on building the BA-3 as gain stage for the F4. The stores specs the jfets as
"BA3 Gain Stage: 6-8 mA (2SJ74 operated at 5 mA) / 8-11 mA (2SK170 at 10 mA)"
The P and N need different idss???
"BA3 Gain Stage: 6-8 mA (2SJ74 operated at 5 mA) / 8-11 mA (2SK170 at 10 mA)"
The P and N need different idss???
Papa sez 10 mA in the BA3 article.
"These JFETs were chosen at Idss
figures of 10 mA (Idss is the current that flows when the Gate and Source are at the same
voltage). If you get lower values, you may want to consider higher values for P1 and P2, say
1 Kohm. They are best matched, but P3 can be adjusted to compensate for some mismatch."
I went with these and I am happy.
"These JFETs were chosen at Idss
figures of 10 mA (Idss is the current that flows when the Gate and Source are at the same
voltage). If you get lower values, you may want to consider higher values for P1 and P2, say
1 Kohm. They are best matched, but P3 can be adjusted to compensate for some mismatch."
I went with these and I am happy.
