Nobody replied on the other thread....Zen Mod said:
re-read answers in AJ thread
both biasing and modulation of output mosfets ,via input LTP , is referenced to neg supply ;
you can't alter any voltage level there without too much fuss .
improving CCS for input LTP is another issue - do what you think is best
look at Babelfish J schematic ;everything is boiled water ......
http://tiny.pl/zfgp
I cannot uderstand why replacing a fixed R with a pot or add an RC filter will alter bias and modulation.
The CCS might be another strory.
Thank you Choky anyway.
massimo said:
Nobody replied on the other thread....
I cannot uderstand why replacing a fixed R with a pot or add an RC filter will alter bias and modulation.
......
you can replace fixed R in input Jfet source with pot , but you can't include RC in neg PSU leg , between Jfet and output mosfet , because they MUST be on same fixed voltage level ;
even if input LTP is fed with CCS , any un-needed variation in input Jfet current consumption will transfer directly on output mosfet's modulation .......
imagine that you're on escalator stairs in shopping ;
imagine that you're standing on one leg , having just one hand on hand rest ;
that's fine .......
now imagine that someone put that sole leg of yours on bicycle pedals , an that you must rotate them ...... while your sole hand is still on that hand rest ..... that's same distraction
So, the BA1 is going to be directly useful to those
-that want to make something from scratch that is a little more outrageous than the typical First Watt offering. These amps are too big, too hot and too expensive to be a First Watt design.
-with a Burning amp chassis with single ended outputs (all the same kind of MOSFET).
-who want to change their Burning amp chassis to all one kind of MOSFET
-that like a more "Aleph like " sound (correct me if I'm wrong here Nelson)
One thing that PapaNelson has mentioned is that the front end on at least the first few Burning Amps will be the same. It is mostly the biasing part that will vary. SO, we need to know how much interest there is in a BA1 only board. IF not so much we could make a "universal board" for the front end with small "bias boards" to make it work with the various models.
SO PLEASE post here if you are interested in a BA1, whether a single board or a front-end board with small separate bias boards..
We'll determine that after we get an idea of interest..
Thank You
Mark
-that want to make something from scratch that is a little more outrageous than the typical First Watt offering. These amps are too big, too hot and too expensive to be a First Watt design.
-with a Burning amp chassis with single ended outputs (all the same kind of MOSFET).
-who want to change their Burning amp chassis to all one kind of MOSFET
-that like a more "Aleph like " sound (correct me if I'm wrong here Nelson)
One thing that PapaNelson has mentioned is that the front end on at least the first few Burning Amps will be the same. It is mostly the biasing part that will vary. SO, we need to know how much interest there is in a BA1 only board. IF not so much we could make a "universal board" for the front end with small "bias boards" to make it work with the various models.
SO PLEASE post here if you are interested in a BA1, whether a single board or a front-end board with small separate bias boards..
We'll determine that after we get an idea of interest..
Thank You
Mark
The initial Burning Amp versions will be for followers, and so it would
be quite easy to build the power supply and output stage up as a
power follower and then drive it with an outboard voltage gain stage.
The advantages of this approach are several fold:
Lower noise
Convenience of replacing or modifying the front end
More room for the front end
Easy option of separate power supply, greater voltage, regulation
However, down the road I anticipate a couple of versions where the
output stage is not a follower.
be quite easy to build the power supply and output stage up as a
power follower and then drive it with an outboard voltage gain stage.
The advantages of this approach are several fold:
Lower noise
Convenience of replacing or modifying the front end
More room for the front end
Easy option of separate power supply, greater voltage, regulation
However, down the road I anticipate a couple of versions where the
output stage is not a follower.
With the background sound of wheels running on the rail way, listening MP3 adjusted at the low volume to vaguely hear bass, I have just read through Papa's Burning Amp BA1 . . . Dammit . . . 24 output mosfets, 12 per each channel, 6 of the paralleled to be matched for the same Vgs . . .
God creates all, but never equally . . . even in small things . . .
What is the acceptable +/- tolerance in Vgs-matching of the six?
God creates all, but never equally . . . even in small things . . .
What is the acceptable +/- tolerance in Vgs-matching of the six?
0.1 volts will be adequate.
On another note, you will recall that BA1 was to originally coincide with the
new web software here at diyAudio. Now BA2 is being prepped for the
re-scheduled launch of the new software, as it was decided to release BA1
anyway to deflect the disappointment of the proletariat.
Those of you with the push-pull output stages can perk up.
On another note, you will recall that BA1 was to originally coincide with the
new web software here at diyAudio. Now BA2 is being prepped for the
re-scheduled launch of the new software, as it was decided to release BA1
anyway to deflect the disappointment of the proletariat.
Those of you with the push-pull output stages can perk up.
amp-guy said:
You're right about that - the F4 schematics had the same error, so the usual Pass Labs crowd has most likely stopped to notice...
Regarding the board layout, the question whether to include bias circuit or not has kinda postponed the updates. If the BA2 is essentially the same, but with a different bias arrangement it would be possible to make a "board sandwich" where the bias circuitry is a daughter-board on the general BA board.
cviller said:
You're right about that - the F4 schematics had the same error, so the usual Pass Labs crowd has most likely stopped to notice...
Regarding the board layout, the question whether to include bias circuit or not has kinda postponed the updates. If the BA2 is essentially the same, but with a different bias arrangement it would be possible to make a "board sandwich" where the bias circuitry is a daughter-board on the general BA board.
so the f4 zener diode should be 1n4736 not 2n4736?
is 1n4736 6.8v zener?
thanks
bakpaosiomay said:
I don't believe there is anything called 2n4736, and yes 1n4736 is a 6.8V zener - the correct device for the BA1.
http://pdf1.alldatasheet.com/datasheet-pdf/view/61854/GE/1N4736.html