I prefer without the buffer if your source can drive a few
hundred ohms without distortion, but often they can't,
and this often makes the buffered piece sound better.
hundred ohms without distortion, but often they can't,
and this often makes the buffered piece sound better.
Thinkin' at the I/V converter (balanced) that I 've build (with reference D 1 schematics) out of the dacs , probably if I need that lower output impedances is better put a follower at the output of the preamp(!?) or paralleling devices and circuits...
Nelson
I beleve You.
The only problem with the X-SOZ (without buffer) is the limited high roll off at inputimpedances > 200-300 Ohm.
In my listening test, the unbuffered X-SOZ with an inputimpedance at 1K showed some really nice manners, execpt for the highest frequences.
But BOSOZ needs outputcaps at 100uF to keep a deasent low frequence roll off when driving an impedance at 200 Ohm, and it seems to loose haf the gain when it does, so therefore I went for the buffer.
Do You think BOSOZ with output caps at around 100uF will do a good job as source for an unbuffered X-SOZ with an inputimpedance at say 220 Ohm?
By the way, the buffered X-SOZ still sounds verry nice.
I beleve You.
The only problem with the X-SOZ (without buffer) is the limited high roll off at inputimpedances > 200-300 Ohm.
In my listening test, the unbuffered X-SOZ with an inputimpedance at 1K showed some really nice manners, execpt for the highest frequences.
But BOSOZ needs outputcaps at 100uF to keep a deasent low frequence roll off when driving an impedance at 200 Ohm, and it seems to loose haf the gain when it does, so therefore I went for the buffer.
Do You think BOSOZ with output caps at around 100uF will do a good job as source for an unbuffered X-SOZ with an inputimpedance at say 220 Ohm?
By the way, the buffered X-SOZ still sounds verry nice.
Peter
I have some figurs to You, which illustrates the tendencies from one of my earlier posts:
With R13=10k and R14=1k High roll off is 45kHz (-3db.
With R13=100k and R14=10k High roll off is 6kHz (-3db).
With R13=1k and R14=100E High roll off is 200kHz (-3db).
You asked me in an earlier post:
So in your opinion buffered X-SOZ sounds better than just X-SOZ?
And I answerd: Far better!!!!
Nelson just pointed out, that if You have a source that can drive 200 Ohm load, this might not be the case.
Nelson keeps us on the track, realy nice.
I have some figurs to You, which illustrates the tendencies from one of my earlier posts:
With R13=10k and R14=1k High roll off is 45kHz (-3db.
With R13=100k and R14=10k High roll off is 6kHz (-3db).
With R13=1k and R14=100E High roll off is 200kHz (-3db).
You asked me in an earlier post:
So in your opinion buffered X-SOZ sounds better than just X-SOZ?
And I answerd: Far better!!!!
Nelson just pointed out, that if You have a source that can drive 200 Ohm load, this might not be the case.
Nelson keeps us on the track, realy nice.
Peter
In other words:
100 Ohm impedance High roll off is 200kHz (-3db).
1k impedance High roll off is 45kHz (-3db.
10k impedance High roll off is 6kHz (-3db).
This is du to the input capacitance of the mosfet, say 1700pF.
In other words:
100 Ohm impedance High roll off is 200kHz (-3db).
1k impedance High roll off is 45kHz (-3db.
10k impedance High roll off is 6kHz (-3db).
This is du to the input capacitance of the mosfet, say 1700pF.
Should I alter my perception...?
Perception so far:
The input buffer is “mainly” to improve the distortion and corresponding sound.
Perception in the future:
The input buffer is “mainly” to raise the critical highest frequency.
Should I...?
Perception so far:
The input buffer is “mainly” to improve the distortion and corresponding sound.
Perception in the future:
The input buffer is “mainly” to raise the critical highest frequency.
Should I...?
To keep a reasonable high frequence roll off, the X-SOZ needs a very low inputimpedance around 200 Ohm. To raise the inputimpedance to a more normal level say more than 10K, You need the buffer.
Thanks Henrik
So, the input buffer works for three:
(a) It increases the input impedance.
(b) Accordingly it improves the high frequency distortion.
(c) And it raises the upper critical frequency (-3dB).
One more question, please.
Could I expect the sonic improvement mainly from (b)
or mainly from (c)
or equally from (b) and (c)?
JH
So, the input buffer works for three:
(a) It increases the input impedance.
(b) Accordingly it improves the high frequency distortion.
(c) And it raises the upper critical frequency (-3dB).
One more question, please.
Could I expect the sonic improvement mainly from (b)
or mainly from (c)
or equally from (b) and (c)?
JH
may this depend on the characteristics of your source? if the preamp isn´t able to handle a low impedance as a load sonical improvements result out of a). THD of preamp will be lower.
jh6you
As Nelson pointed out, the buffer itself dosn´t improove the sound, on the contrary, but it helps the less ideal source to drive the input load. The ideal source is not at all affected by the character of the load.
a) Therefore, impedance itself has very little to do with soundquality, it depends on the environment.
b) Distortion (high or low frequency) is mainly produced in the mosfets, the buffer can´t remoove that, acctually it adds some.
The X-feedback lower the distortion both in buffer (if it is inside the loop) and output stage.
c) The buffers higher input impedance helps the X-SOZ keeping the high and low frequency roll off at a more reasonable level when the source is not ideal.
To me this is much more a question of compromises.
This is my understanding, I am relatively new in this, so I coud be wrong or not too precise.
As Nelson pointed out, the buffer itself dosn´t improove the sound, on the contrary, but it helps the less ideal source to drive the input load. The ideal source is not at all affected by the character of the load.
a) Therefore, impedance itself has very little to do with soundquality, it depends on the environment.
b) Distortion (high or low frequency) is mainly produced in the mosfets, the buffer can´t remoove that, acctually it adds some.
The X-feedback lower the distortion both in buffer (if it is inside the loop) and output stage.
c) The buffers higher input impedance helps the X-SOZ keeping the high and low frequency roll off at a more reasonable level when the source is not ideal.
To me this is much more a question of compromises.
This is my understanding, I am relatively new in this, so I coud be wrong or not too precise.
Thanks 
, 
, or whatever Nelson, nice to know.
jh6you
Selv tak.
In Korea they obvious also speaks Danish.
Mange tak means: Thank you very much.
Selv tak means: You are welcome or don´t mention it.
, , or whatever Nelson, nice to know.jh6you
Selv tak.In Korea they obvious also speaks Danish.
Mange tak means: Thank you very much.
Selv tak means: You are welcome or don´t mention it.
So Nelson, I'll bet a large percentage of the x zens are used with the Balanced line stage, BOSOZ. Do you feel that the X SOZ used with the BOSOZ benefits from the buffer or not? Are there suggestions you would make to mod the BOSOZ to make the fit the best?
This thread is an example of the best of DIY Audio. Lots of brainpower, thoughtfulness, great consideration for the feelings of others and communicating well even in a language not totally familiar to all (which has worked because of hte previouly mentioned attributes)
Stegano's cry in the wilderness about the possibilities of the XSOZ and sticking with the designing and real life making. Ian's great inputs, Henrics also and his beautiful test schematic and more beautiful real life tests! Of course The One and Only! and lots of contributions by others!
WoW 😉
This thread is an example of the best of DIY Audio. Lots of brainpower, thoughtfulness, great consideration for the feelings of others and communicating well even in a language not totally familiar to all (which has worked because of hte previouly mentioned attributes)
Stegano's cry in the wilderness about the possibilities of the XSOZ and sticking with the designing and real life making. Ian's great inputs, Henrics also and his beautiful test schematic and more beautiful real life tests! Of course The One and Only! and lots of contributions by others!
WoW 😉
I was considering this issue the other night, since it is
my observation that a properly set up BSOZ or even
BOZ can be perfectly happy driving the virtual ground
of the Zen amps and their variations. Their output is
simply a current source from the Drain of the Mosfet,
and their output impedance is whatever you load the
Drain with.
Actually, they are even happier driving a short with current,
as the Miller effect and the distortion associated with varying
voltage across the Mosfet disappear.
If I had been designing these preamps for Zens only, I
would have used this approach.
It's a simple matter to optimize either preamp circuit
for this, and short the input resistor of the Zen amps, and
I'll see what I can work up in the next few days, unless one
of you guys would care to beat me to it.
my observation that a properly set up BSOZ or even
BOZ can be perfectly happy driving the virtual ground
of the Zen amps and their variations. Their output is
simply a current source from the Drain of the Mosfet,
and their output impedance is whatever you load the
Drain with.
Actually, they are even happier driving a short with current,
as the Miller effect and the distortion associated with varying
voltage across the Mosfet disappear.
If I had been designing these preamps for Zens only, I
would have used this approach.
It's a simple matter to optimize either preamp circuit
for this, and short the input resistor of the Zen amps, and
I'll see what I can work up in the next few days, unless one
of you guys would care to beat me to it.
Integrated BSOZ and X-SOZ
Variac
Glad you like this thread, me too.
It has ben extremly educational to me, allmost everything i know about electronics i have learnd on this forum.
And thanks for asking Zenmaster Pass about the BSOZ and X-SOZ.
Nelson
Thanks a lot for your answer.
I believe i got your point.
Quote: "Their output is simply a current source from the Drain of the Mosfet, and their output impedance is whatever you load the
Drain with. "
Ok, I have scaled the load (R29/30) to 200 Ohm.
Quote: "It's a simple matter to optimize either preamp circuit for this, and short the input resistor of the Zen amps"
Ok, I have short (remooved) the inpuresistor at the X-SOZ. If I have understood You correct, the loadresistors R29 and R30 has replaced the former input resistors at the X-SOZ. The outputimpedance (R29/30) of the BSOZ forms the gainratio with R13/36 in the X-SOZ.
I have made this experiment as an integrated amp. in order to get down to basics, when this works we can separate them afterwards.
If my suggestions is correct, it is almost too simple, and it seems to work perfectly well, the only thing is the high value for C1 and C2. I have attached the file "Integrated BSOZ and X-SOZ.pdf" and a graph showing the frequensy responce. All made in my simulator.
Any comments on this one?
Variac
Glad you like this thread, me too.
It has ben extremly educational to me, allmost everything i know about electronics i have learnd on this forum.
And thanks for asking Zenmaster Pass about the BSOZ and X-SOZ.
Nelson
Thanks a lot for your answer.
I believe i got your point.
Quote: "Their output is simply a current source from the Drain of the Mosfet, and their output impedance is whatever you load the
Drain with. "
Ok, I have scaled the load (R29/30) to 200 Ohm.
Quote: "It's a simple matter to optimize either preamp circuit for this, and short the input resistor of the Zen amps"
Ok, I have short (remooved) the inpuresistor at the X-SOZ. If I have understood You correct, the loadresistors R29 and R30 has replaced the former input resistors at the X-SOZ. The outputimpedance (R29/30) of the BSOZ forms the gainratio with R13/36 in the X-SOZ.
I have made this experiment as an integrated amp. in order to get down to basics, when this works we can separate them afterwards.
If my suggestions is correct, it is almost too simple, and it seems to work perfectly well, the only thing is the high value for C1 and C2. I have attached the file "Integrated BSOZ and X-SOZ.pdf" and a graph showing the frequensy responce. All made in my simulator.
Any comments on this one?
Some resistor values shoud be finetuned, but i will wait until i have got some feedback on the more fundamental questions of this design.