Jfet BOZ

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#101
Blues said:



Ok. On 2nd thought, if we can tune it to the load line without a cascode and we have enough voltage swing with a single jfet...let's keep it simple! ..........
Click to expand...

exactly............
me (humble,as always) thinks that Papa's intention was exactly that- answering on original question..........

there are more than few non-minimalistic preamps around .......
taking it in more complicated way- it will look as chopped xcccscdwhatever BOSOZ or The Pumpkin..........
and that's entire another story...... where to stop in adding parts and what is improvement,but real one.......



Battery PS would make it a killer...we won't worry on rectified PS noise.
Click to expand...

:devilr: next step is little preamp ditto in giant horn ..........hehe
 
#102
Re: Re: Re: Pass 2SK170 BOZ

Babowana said:




Yea . . . thanks for reminding me of it ^^

Oh, I forgot that Blues also got a special F4 front end from Papa ^^


:darkside:
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Babowana, where was that F4-frontend posted?

BTW, thats a nice and simple J-fet BoZ. Just read through the whole thread backwards, that was a bad idea😀 Better start from page 1.

Steen🙂
 
#105
On this pre - Do you guys think the attenuator (volume control) should go on the input or the output? I'm talking about a 'twisted' constant impedance relay setup - or similar.

Steen,
where ya been? I'm waiting for someone to comment on how this thing sounds. I'll give you an hour or two to get one together:clown:
 
#106
mpmarino said:
On this pre - Do you guys think the attenuator (volume control) should go on the input or the output? I'm talking about a 'twisted' constant impedance relay setup - or similar.

.............
Click to expand...


when you use that sort of three legged fuses,you always must use pot on input,just because any not-attenuated signal will drive little bstrd in saturation and output sig will be more than clipped.
just look at bias voltage present between g-s and compare it with blabla 2V from CD out..........
 
#109
Nelson Pass said:
Yes, the minute you are willing to bias the input at other than
ground you can make for great improvement.

As to the question about cascoding, yes you can, but you no
longer have the load-line cancellation discussed earlier, and
you will have to alter other parts of the circuit.

😎
Click to expand...

Thank you Mr. Pass,

Actually I've been playing with this jfet for few weeks when I got time before this thread started.
Still scratching my head how to improve it's sound. Cascoding with 2SK246 make the high freq. a little bit harsh and I have to bypass the drain resistor with 100pF.

The circuit was taken from www.tubecad.com, a variation of Aikido circuit. I have built the tube version and i'm very very pleased with it's sound.

The jfet version sounds better than few preamp already made but the tube version still better. I wonder if this circuit still have room for improvement.

This is the actual circuit.


rgds,
G33/33
 

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#111
FFT AC Analysis Phase nad THD distortion of my Jfet BOZ

lineup said:
I know I have 2SK170GR spice models. They are the ones easy-to-find.
And this is the variant of 2SK170 I can easily buy in my country.

I will also present a fourier analys:
- Level of 2nd 3rd 4th harmonics.

For one rudimentary No-feedback JFET circuit, like this one,
we can expect some 2nd harmonics
and considerably less 3rd harmonics

Regards
lineup 🙂
.
Click to expand...


I promised to present FFT Fourier analysis
of my version of Jfet BOZ 😉
I can report, that such analys has been done, today.


Diagram of 2nd, 3rd ....8th, 9th harmonies
confirm my earlier posted prediction, fully:
.
For one rudimentary
No-feedback JFET circuit,
like this one,
we can expect some 2nd harmonics
and considerably less 3rd harmonics
.
Click to expand...


If there are any much calls for it
- I publish/post my Analys Results***
If not, I keep it in my safe and for my own works.


2nd Harmonics regards lineup 🙂
Lineup Audio Lab Inc.

_______________________________
*** Note:
I have the following
- FFT at several frequencies, 9 harmonies
- AC Analys, deci-Bell, dB, scale = bandwidth
- Phase Analys, degrees
- THD % distortion, at several different:
..frequencies within audioband
..loads
..amplitudes
 
#112
Re: Re: Re: Re: Re: Re: Re: Pass 2SK170 BOZ

mpmarino said:
On this pre - Do you guys think the attenuator (volume control) should go on the input or the output? I'm talking about a 'twisted' constant impedance relay setup - or similar.

Steen,
where ya been? I'm waiting for someone to comment on how this thing sounds. I'll give you an hour or two to get one together:clown:
Click to expand...

Try to install the attenuator at the input, which is best in terms of output impedance of the preamp.
I am sure that with Manu and Twitchie handling the testing, its in the best of hands.


Blues said:



😀 The sound is :cloud9:. I love its sound more than the A3.

Now this Jfet pre-amp looks delicious...I'm thinking of using an sj74 instead to match my Zv4jC.
Click to expand...

Excactly🙂 The simplicity of the J-fet-BoZ is very appealing. Could be fun trying to use it with the F4. What was the gain, 24dB?
Could be just the thing for an ultrasimple preamp/amp combo.
Greedy boy, signing out.

Steen🙂
 
#114
jacco vermeulen said:

Vince,
a few years ago i bought a +10k package of metalfilms by the cheap, including values such as 1M.
Not that i was totally out of resistors, think the deal on Russian made resistors i couldn't resist was a couple of months before the big score.
Sooner or later, they always come to good use.
.
Click to expand...

yah, jacco
( sounds like a dead parrot's name, to me = john cleese, monty ptyhons 😀 )

I also buy large packages with resistors.
At least 10 resistors per value.
I prefer 0.6 Watt MetalFilm and I can get these here locally
in those big packages.


> Sooner or later, they (metallized resistors) always come to good use.

.. in your Jfet BOZ, imagine
.. how is your setup?
----->Nelson's original, 2nd harmonics distortion
----->Lineup's special circuit, for lower THD distortion


Regards lineup 🙂
 
#116
Actually, since it is a battery power, I was thinking to minimize the capacitance....just 10 uF electrolytic bypassed with 100 nF....

I see no reason to add 1000's of uF...please let me know if that is a bad idea...

By the way, after a bit of rechage, I measured 10.25 v on the battery (!). Seems like it contains 8 cells (1.2 volts nominal) so they are supposed to settle at around 9.6 V, giving me a 19.2 v for a preamp. Somewhat higher than 16 v as sugested by Nelson, but it should work...

Regards,

Vix
 
#117
Vix said:
Actually, since it is a battery power, I was thinking to minimize the capacitance....just 10 uF electrolytic bypassed with 100 nF....

I see no reason to add 1000's of uF...please let me know if that is a bad idea...

Regards,

Vix
Click to expand...

Just asking out of curiousity🙂 I dont know what is needed for a battery supply in terms of capacitance.

Steen🙂
 
#119
Getting the mains power out would be real nice (I am pretty sure I have DC on mains at home). I would like to have a charging circuit that goes 'auto on' when the pre is turned off.

Also, it would be super nice to have a simple phono pre in the same case off the same battery supply. How about another Jfet BOZ in series with a RIAA filter hanging off of it - somehow.
 
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