The F4 is finally back home, a few adjustments, some soldering of components which were not correctly installed, bias adjusted and voltage stable at 200mV as per project, I will soon insert it into my chain past the Audio Research SP9 while the BA-3 preamp in the build as to have an extra voltage on the output to drive the F4 but I am starting to itch at what comes next, what about a big box with both preamp and power amp, kind of a Class A integrated amp with about 50W output?
As far as "what comes next?", I don't know. And "preamp and power amp in same box".... well it's important to understand that the original BA-3 was not just a preamp, but an entire amplifier consisting of both the front end AND output stage elements. With the claim to fame of excellent subjective and measured performance without the use of negative feedback loops anywhere. (I won't get into the arguments of ... this vs. that on the subject)
Burning Amp Number Three
It's also important to understand that the BA-3 front end (FE) was meant to be paired with the single ended follower output stage (BA-1), OR the push-pull follower output stage (BA-2). Remember that a "follower" stage provides current gain only, NOT voltage gain. Again, people can do their own research about the virtues, pros and cons, etc. of the different types of topologies here. The Firstwatt F4 was a commercial product where you don't know what a customer is going to be putting in front of it. So the JFET buffer stage that it has for the input stage (IPS) makes it very easy and friendly to drive no matter what. The F4 output stage is very, very, very similar to the BA-2 push-pull output stage (OS). The experienced savvy amp builders around here realize the JFET buffer is not always needed depending on what you're using ahead of it, so they just bypassed it in those situations. So, when you see the term "crippled F4", you now know what they mean.... no buffer.
I'm curious to hear about your impressions of a (now, hopefully) properly functioning F4 in your system, and how those two preamps will sound with it.
Burning Amp Number Three
It's also important to understand that the BA-3 front end (FE) was meant to be paired with the single ended follower output stage (BA-1), OR the push-pull follower output stage (BA-2). Remember that a "follower" stage provides current gain only, NOT voltage gain. Again, people can do their own research about the virtues, pros and cons, etc. of the different types of topologies here. The Firstwatt F4 was a commercial product where you don't know what a customer is going to be putting in front of it. So the JFET buffer stage that it has for the input stage (IPS) makes it very easy and friendly to drive no matter what. The F4 output stage is very, very, very similar to the BA-2 push-pull output stage (OS). The experienced savvy amp builders around here realize the JFET buffer is not always needed depending on what you're using ahead of it, so they just bypassed it in those situations. So, when you see the term "crippled F4", you now know what they mean.... no buffer.
I'm curious to hear about your impressions of a (now, hopefully) properly functioning F4 in your system, and how those two preamps will sound with it.