Guys, planning building an f4 ( with either ba3 or juma lsk preamp, any idea on which will be more suitable?) later this year and taking care of planning and doubt clearing in the meantime.
Does the f4 design allow for higher power output using higher supply voltage and bias such as in the f5/f5t design? I would be aiming at 35-40w into 8ohm and maybe 50-60 into 4ohm.
Does the big 5u chassis allow for two channels per side, in a single chassis parallel mono configuration? This would be a bit cheaper than mono blocks and more important much smaller. What power output would I expect from such a configuration into 6-8ohm?
Does the f4 design allow for higher power output using higher supply voltage and bias such as in the f5/f5t design? I would be aiming at 35-40w into 8ohm and maybe 50-60 into 4ohm.
Does the big 5u chassis allow for two channels per side, in a single chassis parallel mono configuration? This would be a bit cheaper than mono blocks and more important much smaller. What power output would I expect from such a configuration into 6-8ohm?
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Yes, you can scale the F4 up to about 30-32V. Much past that and the Jfet J74 start to let the smoke out.
In theory that should be 50W into 8ohm. More into 6 or 4. But being a follower, your preamp needs to swing +/- 30V as well... So it will need higer voltage rails as well.
Yes, you could mount two rows of PCB to the 5U - on on the heatsink face with the transistors up, one on the chassis floor using the other row of the heatsink's transistor mounting points. It's going to be hot.
You may want to look at the BA-3 complimentary output stage, it has provisions to connect the PCB holding the output fets to make a bigger amp.
Are you planning on making the output stage single-ended or bridge balance?
In theory that should be 50W into 8ohm. More into 6 or 4. But being a follower, your preamp needs to swing +/- 30V as well... So it will need higer voltage rails as well.
Yes, you could mount two rows of PCB to the 5U - on on the heatsink face with the transistors up, one on the chassis floor using the other row of the heatsink's transistor mounting points. It's going to be hot.
You may want to look at the BA-3 complimentary output stage, it has provisions to connect the PCB holding the output fets to make a bigger amp.
Are you planning on making the output stage single-ended or bridge balance?
So my plan at the moment is the salas simplistic phono stage for vinyl rig which is single ended. I am also planning a digital front end (one box network player/dac combo) still haven't decided what, but most high end projects have balanced outputs.
I am planning on single ended pre and power amps to accommodate the vinyl rig which is my preference.
So it would actually be parallel mono operation to achieve higher output power. I've also considered building mono blocks with high performance 83mm heatsinks and 100mm height cases, which would allow for stacked dual mono f4's in the same space as big 5u case, but the cost increase more than doubles.
However, I might start with a single f4 in the 4u asmy current speakers, rega rs3 are 6 ohm 89db, so I should get about 30w, the minimum recommended by the manufacturer. And don't play loud very often, so it should be doable.
Next speakers will be around 94-95 efficiency, so 25w will be more than enough.
I am planning on single ended pre and power amps to accommodate the vinyl rig which is my preference.
So it would actually be parallel mono operation to achieve higher output power. I've also considered building mono blocks with high performance 83mm heatsinks and 100mm height cases, which would allow for stacked dual mono f4's in the same space as big 5u case, but the cost increase more than doubles.
However, I might start with a single f4 in the 4u asmy current speakers, rega rs3 are 6 ohm 89db, so I should get about 30w, the minimum recommended by the manufacturer. And don't play loud very often, so it should be doable.
Next speakers will be around 94-95 efficiency, so 25w will be more than enough.
I had already read about the crippled F4, what are the advantages? As I see it the output trannies on the BA3FE make the same duty as the buffer.
If building f4 crippled or BA3 OS, is it still ok to build it as pre/power amps, in different cases with different power supplies? I was thinking of having the FE powered by a regulated psu such as the one by Salas and tea bag.
crippled F4 is F4 sans input buffer ....... practically same stage as BA3 OS , if same number of outputs is used
idea was (someone's , don't remember) to remove buffer from F4 , when used with proper (driving capability , coyones,whatever) preceding stage ..... but as must with non-critical interconnects (low C)
so , I think I answered to both questions
regarding FE dedicated reg ...... well , you know what I'm thinking of them (usage and type) , taking in account that I'm always considering Shunty as integral part of
idea was (someone's , don't remember) to remove buffer from F4 , when used with proper (driving capability , coyones,whatever) preceding stage ..... but as must with non-critical interconnects (low C)
so , I think I answered to both questions
regarding FE dedicated reg ...... well , you know what I'm thinking of them (usage and type) , taking in account that I'm always considering Shunty as integral part of
How much more current? None.
You would need to reduce the bias amount (the measured voltage across the source resistors) to keep a constant bias.
Remember the limits on bias amount -
No more than 55C heatsinks and 65C devices
No more total bias (in W) than half your transformer VA
No more than 1/3 the mosfet rated maximum dissipation.
So a lower voltage drop (I.E., less current) will give same bias (in W) because you have more voltage.
That said, bias until you get 55C heatsink.
You would need to reduce the bias amount (the measured voltage across the source resistors) to keep a constant bias.
Remember the limits on bias amount -
No more than 55C heatsinks and 65C devices
No more total bias (in W) than half your transformer VA
No more than 1/3 the mosfet rated maximum dissipation.
So a lower voltage drop (I.E., less current) will give same bias (in W) because you have more voltage.
That said, bias until you get 55C heatsink.
New born F4 , healthy and strong. Crying loud at 350mV bias.
Special thanks to 6L6 for this guide and support. And also, though he did not address me directly, to ZenMod for his continued presence and overall guidance in these firums, funny guy, indeed mighty one.
Cheers
Special thanks to 6L6 for this guide and support. And also, though he did not address me directly, to ZenMod for his continued presence and overall guidance in these firums, funny guy, indeed mighty one.
Cheers
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
naah ...... I'm just playin' one in public
you are short few sides for Fugly , bu tin meantime you can give us few details - attached one and two smaller ones - central down and central up
Attachments
Well mighty Zen, good koan you gave me, good eye you have too.
The big F4 is seen in the previous picture being fed by the tubey Bottlehead S.E.X. Amp. It shares the company of kin, an ancient GFA 535 and a modern Sit2. They were waiting for this family member to come and join the crowd.
I will keep with the right effort, brothers, the alternative is too boring to either consider.
Another pic showing bias before it was turned to 350.
The big F4 is seen in the previous picture being fed by the tubey Bottlehead S.E.X. Amp. It shares the company of kin, an ancient GFA 535 and a modern Sit2. They were waiting for this family member to come and join the crowd.
I will keep with the right effort, brothers, the alternative is too boring to either consider.
Another pic showing bias before it was turned to 350.
An externally hosted image should be here but it was not working when we last tested it.
naah ...... I'm just playin' one in public
you are short few sides for Fugly , bu tin meantime you can give us few details - attached one and two smaller ones - central down and central up
Got you now Zen,
top is the very first unknown, the most arcane af all. Down, goes the fool, no numbers can help him count. That's how I got to do it, without knowing that I already know.
And this one to find the way:
An externally hosted image should be here but it was not working when we last tested it.
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it wasn't that hard , ne pas ?
me likee fact that you SIT-paid for Kudos (I was too , sort of , going to SF pilgrimage , few years ago ....... though I paid more sittin' in air stagecoach with semi-bad back than with gifted money) ........
however , if you are able to try - try some line stage with iron ..... and iron attenuator
I know that milky can sometimes became syrupy ........ but no when executed properly
absolutely nothing can't compare with vividness I had with my first WOT preamp .... or it just hit right buttons , dunno ......
indulge me , please ....... what proper** spks you have ?
** driven with SIT 2 ?