A note about P3 -
I do have a distortion analyzer and have made a few quick observations around the adjustment of P3.
The Jfets were reasonably matched Idss from N to P (Within 0.1mA) Mosfets were unmatched. Bias set to 1.0V across Mosfet source resistors and DC offset tuned to minimum before the output capacitor.
I set P3 to it's mid-point before installation, making it about even from pin 1-2, and from pin 2-3. (Roughly 50ohm each way.)
Long story made short - using the distortion meter to tune for minimum distortion made some difference, but not enough to worry about. From .025% L and 0.19%R with the pot just set, and I could tune it down to .015%LR with the distortion meter. Not a huge gain.
I have not done any listening tests past that. Just what's measured so far.
I do have a distortion analyzer and have made a few quick observations around the adjustment of P3.
The Jfets were reasonably matched Idss from N to P (Within 0.1mA) Mosfets were unmatched. Bias set to 1.0V across Mosfet source resistors and DC offset tuned to minimum before the output capacitor.
I set P3 to it's mid-point before installation, making it about even from pin 1-2, and from pin 2-3. (Roughly 50ohm each way.)
Long story made short - using the distortion meter to tune for minimum distortion made some difference, but not enough to worry about. From .025% L and 0.19%R with the pot just set, and I could tune it down to .015%LR with the distortion meter. Not a huge gain.
I have not done any listening tests past that. Just what's measured so far.
my favorite B1 version is the Nelson version with the Axon 10uF and the Vishay 1uF and the +18V rails only.
a bit dark, but I like it really.
I do not like in comparison the direct coupled versions, though they should sound better…..
my last try is the Hypnotize hot rodded I am just trying…..by friendliness of tea-bag!
for me Pumpkin(g) and BA-3 are the optimum also. (at the moment)
😀😀
I liked the B1, loved my hotrodded DCB1 but found it held no candle to the Aikido 12VAC with 12ua7 tubes (Mullard CV4003) - huge soundstage and full body. Yes there are somethings I miss about my DCB1 but the warmth and soft glow of tubes is attractive. Unfortunately even with the Aikido 8x gain (with 12au7) I still find it lacking in gain so I am going to re-introduce my BA3 with F4 but in its own chassis.
You can always use 6922/6922 or 12AX7/12AX7 in Aikido to get enough gain. Easy - just a couple of resistor swaps.
True, but my most prized tubes are 12au7 🙂 The pairs of CV4003 cost me an arm and a leg but well worth it.
I do have a box of 6922 and 12ax7 enough for several preamps so I might just order another kit from tubecad and try it. But those 12AX7 with 50 gain might be too much and those can get quite noisy.
I do have a box of 6922 and 12ax7 enough for several preamps so I might just order another kit from tubecad and try it. But those 12AX7 with 50 gain might be too much and those can get quite noisy.
please - do not mention 12AX7 in Pass Forum 
that's same as mentioning 2SK246Y , when needing 2SK369V
disclaimer - all 12AX7 based schematic I saw in last two decades were old school , without taking in account strengths of that tube , while multiplying weak points of it
6DJ8 is good , when used ......... good
edit: conclusion - 12AX7 is for sissies , except in case when sissy is having some brain
that's same as mentioning 2SK246Y , when needing 2SK369V
disclaimer - all 12AX7 based schematic I saw in last two decades were old school , without taking in account strengths of that tube , while multiplying weak points of it
6DJ8 is good , when used ......... good
edit: conclusion - 12AX7 is for sissies , except in case when sissy is having some brain
No argument that 12AX7 has lots of problems - but it is a known quantity in audio. (Not necessarily good, but known...)
Sorry for distraction of tubes :0 Back to BA3 and Pass 🙂
So if I was to go with pair F4 (50watts) what is minimum gain I need? Most seem to recommend 20x gain with stock/single F4. Maybe I should just wait until universal power suply and deluxe 4U chassis become available......decisions decisions....at least many choices 🙂
So if I was to go with pair F4 (50watts) what is minimum gain I need? Most seem to recommend 20x gain with stock/single F4. Maybe I should just wait until universal power suply and deluxe 4U chassis become available......decisions decisions....at least many choices 🙂
2Vrms , as standard these days , means 2V x 2 x 1.41 = 5V65Vpp
as F4 balanced is capable of , roughly , 40Vpp ..... calc is simple
40/5V56 = 7.07x = 17db
so , 20db of gain is safe bet
as F4 balanced is capable of , roughly , 40Vpp ..... calc is simple
40/5V56 = 7.07x = 17db
so , 20db of gain is safe bet
Thank you Mr Zen. I will finish up BA3 in separate chassis - it will provide flexibility in any new preamps I build or any other amps too.
if you make BA3 Bal , you'll not need any other preamp soon , except for simple pleasure of making new one
edit : Mr is your GrandMa , not Zen
edit : Mr is your GrandMa , not Zen
if you make BA3 Bal , you'll not need any other preamp soon , except for simple pleasure of making new one
edit : Mr is your GrandMa , not Zen
How would you compare Pumpkin to a BA-3?
Just did a Mouser order for all the parts for my Pumpkin - $$$ adds up, especially the Shunty parts!
if you make BA3 Bal , you'll not need any other preamp soon , except for simple pleasure of making new one
edit : Mr is your GrandMa , not Zen
Any advantage in building the ba 3 balanced as opposed to single ended if ones sources are all SE, when feeding a f4?