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Old 14th July 2010, 11:04 AM   #1
Skorpio is offline Skorpio  Denmark
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Default BoZ versus BosoZ

According to most responses the BosoZ outperforms the BoZ. According to Mr. Pass, this is due to the distorsion type (2. or 3. harmonic structure) and that most people perfers 3. harmonic to 2.

I will only need single ended in and out and I am therefore thinking about why the BosoZ should be better?

The main differences as I see it is that BoZ has a relative high Source resistor (100R), give some amount of local feedback. And that the bias is somewhat assymetrical (20V accross MOSFET and 40V accross Resistor), perhaps giving the sonic signature?

My purpose is to drive an F4 and to get a sound close to a vacuum tube preamp. Therefore I am leaning towards the BoZ circuit...but BosoZ is more flexible...
Why is Boz biased at 20V at output instead of half-supply (30V)? Would changing this alter performance towards BosoZ?

The major question is, is the sonic difference more a matter of personal taste (like tubes versus transistors) or is the a major step up in quality from BoZ to BosoZ?
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Old 14th July 2010, 08:36 PM   #2
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Check this out BF862 Preamp
You will need to adjust the gain for F4

I am not sure if you can run the BOSOZ single ended in and single ended out.
If you can, I wonder if all the positive comments still apply.

Last edited by Melon Head; 14th July 2010 at 08:48 PM.
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Old 14th July 2010, 08:59 PM   #3
Zen Mod is offline Zen Mod  Serbia
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Juma's BF862 pre isn't intended for driving buffer amp .

Juma can make preamp which will make your speakers bleed ........ but this one isn't of that sort

Skorpio - there is ( somewhere ) thread named BOSOZ for F4 or something like that

if I remember well - result is jfet based cascoded differential stage ........ that thread later results in funny development
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Last edited by Zen Mod; 14th July 2010 at 09:02 PM.
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Old 14th July 2010, 09:09 PM   #4
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Also check out this Pearl Two
I am pretty sure the gain is easily adjustable.

EDIT: Thanks for the info Modstar

Last edited by Melon Head; 14th July 2010 at 09:11 PM.
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Old 14th July 2010, 09:52 PM   #5
Zen Mod is offline Zen Mod  Serbia
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Quote:
Originally Posted by thanh1973 View Post
Also check out this Pearl Two
.....
last time I looked - Pearl was phono dedicated stage .....
I'm not telling that you can't make line stage of it , but I have some doubts that OP is willing/able to do that ......

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Old 14th July 2010, 10:37 PM   #6
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What if you removed the input stage (ie parralleled jfet stage) of the pearl 2?
So you end up with differential input with buffer output.
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Old 15th July 2010, 04:40 AM   #7
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Sorry for taking this thread completely off topic.
I am double-plus ungood.
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Old 15th July 2010, 08:20 AM   #8
Skorpio is offline Skorpio  Denmark
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Thanks for the response...

I have tried some experiments with BoZ. Drain resistor is changed to 470R and source resistor is 47R. Gain approx. 20dB. Supply 60V regulated with improved Bosoz regulators. Drain current is close to 70mA and drain at half supply, so 2W power heats up the MOSFET...

Sound is very promising...I think this close to what I need
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Old 15th July 2010, 08:59 AM   #9
mjf is offline mjf  Austria
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QUOTE Drain current is close to 70mA and drain at half supply, so 2W power heats up the MOSFET...

......yes,you need a bigger heatsink on (all) the mosfets.power dissipation in the original boz is only around 20v x 40ma = 0,8w on the preamp mosfet.
i used irf510n in my boz and use it mostly with my tube poweramp.
greets
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Old 15th July 2010, 09:02 AM   #10
Vix is offline Vix  Yugoslavia
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Skorpio,

BoZ is a good preamp, but it's mostly a first step, not last . So, once you fiddled with it, forgetaboutit
Try this instead (see pic-Zen Mod copyleft)

Alternatively, you may wish to try this one:

The SSTART Preamplifier Why on earth would anyone do such a thing? Article By Grey Rollins
Attached Images
File Type: jpg Jfet-Bosoz.jpg (24.9 KB, 409 views)
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