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Old 24th April 2009, 08:03 AM   #41
massimo is offline massimo  Italy
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Quote:
Originally posted by Zen Mod



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
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.
The CCS might be another strory.
Thank you Choky anyway.
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Old 24th April 2009, 08:13 AM   #42
Variac is offline Variac  United States
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Quote:
isn't easier to make XCCSwhatevercascoded BOSOZ , with altered gain ? make it with altered positive PSU , and it will drive even bridgedbalancedparalleled F44 .......
Or maybe make that Pumpkin Preamp! Will it drive an F4?
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Old 24th April 2009, 09:06 AM   #43
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by massimo

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

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Old 24th April 2009, 09:07 AM   #44
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally posted by Variac


...... Will it drive an F4?

what's F4 ?

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Old 24th April 2009, 10:40 AM   #45
massimo is offline massimo  Italy
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Thanks again Choky, now is clear.
I'm not a tech guy and I dindn't consider what you pointed out.
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Old 1st May 2009, 08:25 PM   #46
Variac is offline Variac  United States
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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
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Old 1st May 2009, 08:42 PM   #47
amp_guy is offline amp_guy  United States
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Default my vote

BA1 universal board
outrageous is just adaquate
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Old 2nd May 2009, 02:06 AM   #48
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Quote:
Originally posted by Zen Mod
BA1 PS

Does this PS topology represent use of a center tapped and/or series wired transformer?
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Old 2nd May 2009, 01:37 PM   #49
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I'm interested on BA1

domo arigato
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Old 2nd May 2009, 06:55 PM   #50
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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.

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