Output impedance
Hello Henrik:
Yesterday I modified my X-BSOZ to more closely resemble yours.
I now use 10K R120/R121. The only difference to yours is the following:
Balanced attenuator places one resistor between the gates of Q101/Q102.
I am only using 10uF output caps instead of 33uF. I may change this next, but I want a high pass of 120 Hz for my ESL panels.
I get the low pass via an OPA132 opamp network off the output of the X-BSOZ.
Is the output impedance of your X-BSOZ really 20R balanced?
Is that measured or calculated?
With the 10uF cap, 10K amp and 20R preamp I should get a high pass with an Fc about 800 Hz. The audible Fc that I hear seems much lower around 200 Hz.
Thanks
Hello Henrik:
Yesterday I modified my X-BSOZ to more closely resemble yours.
I now use 10K R120/R121. The only difference to yours is the following:
Balanced attenuator places one resistor between the gates of Q101/Q102.
I am only using 10uF output caps instead of 33uF. I may change this next, but I want a high pass of 120 Hz for my ESL panels.
I get the low pass via an OPA132 opamp network off the output of the X-BSOZ.
Is the output impedance of your X-BSOZ really 20R balanced?
Is that measured or calculated?
With the 10uF cap, 10K amp and 20R preamp I should get a high pass with an Fc about 800 Hz. The audible Fc that I hear seems much lower around 200 Hz.
Thanks
Hi Ignatz
I suggests you make a filter othrerwise, but as I said before, I am not an expert in active filtering.
If you run the X-BSOZ with a load at 10K, then your outputcaps only need to be 1uF for a flat responce from 1Hz and up, the only reason for my higher value is becauce that my XSOZ has an extreme low inputimpedance at 120 Ohm.
I am not an expert in active crossovers, but I shoud more than think twice befor using an opamp for this purpose, cant you make it passive or something else?
It is simulated, but I can easiely drive my 30 Ohms Headphones. As an experiment, you can place a 20 ohm resister across the output, then the signal shoud be attenuated to half the value if the outputimpedance is 20 Ohm.
The outpucap is inside the feedbackloop, which lowers the low end roll off. That is why you only need 1uF at 10K load, while the BSOZ needs 10uF for the same load as I recall.
I suggests you make a filter othrerwise, but as I said before, I am not an expert in active filtering.
different type of feedback
In Henrik circuit, the capacitor is put in the feedback loop. In Pass Aleph P1.7, there are input capacitors as well as output capacitors located outside of the feedback loop. The circuit pattern is near the same. For the issue on the location of capacitor, what is the essential difference between them, based on the viewpoint of sound, electronics, and control? Thanks for your response.
In Henrik circuit, the capacitor is put in the feedback loop. In Pass Aleph P1.7, there are input capacitors as well as output capacitors located outside of the feedback loop. The circuit pattern is near the same. For the issue on the location of capacitor, what is the essential difference between them, based on the viewpoint of sound, electronics, and control? Thanks for your response.
I am rather buisy these days, so I will not be able to answer this question untill the weekend, I need some curves to illustrate what happens. It shure is an intersting question. I have never heard the difference between caps inside and outside the feedbackloop, so my answer will only be a tecknical one.
Different Type of feedback
About three years ago I built the BSOZ with the stock parts listed at the Pass web site. This preamp has no feed back and one output cap. It sounded very good but it seemed to attenuate the high frequency sound a bit.
I then dismantled the BSOZ and used most of the parts to build the P1.7. This has feed back and both input and 30 uF of output caps. Initially I thought this preamp sounded slightly better than the BSOZ, but after listening to it for about 8 months I wanted to upgrade the quality of the caps.
Because of the high cost of the numerous caps for the P1.7 I rebuilt the BSOZ using better caps and Kimber silver hook up wire.
I also modified the layout to obtain the minimum signal path. I attenuate this unit with a single resistor placed between the drains of the IRF610.
Until recently this was the best sounding preamp I have every built or heard.
Next I adjusted the BSOZ to an approximate version of the X-BSOZ; however, the best sounding configuration I have heard so far is Henrik's X-BSOZ "sort of" with a 180R gain resistor instead of a wire and no R120/121.
My X-BSOZ is slightly different than Henrik's layout because I have two outputs. One output cap configuration gives me a high pass first order Butterworth filter at 120 Hz. This is inside the feedback loop. The other output cap configuration provides all pass which runs to an opamp 2nd and 3rd order Butterworth low and high pass filter. This output cap configuration is outside the feedback loop.
About three years ago I built the BSOZ with the stock parts listed at the Pass web site. This preamp has no feed back and one output cap. It sounded very good but it seemed to attenuate the high frequency sound a bit.
I then dismantled the BSOZ and used most of the parts to build the P1.7. This has feed back and both input and 30 uF of output caps. Initially I thought this preamp sounded slightly better than the BSOZ, but after listening to it for about 8 months I wanted to upgrade the quality of the caps.
Because of the high cost of the numerous caps for the P1.7 I rebuilt the BSOZ using better caps and Kimber silver hook up wire.
I also modified the layout to obtain the minimum signal path. I attenuate this unit with a single resistor placed between the drains of the IRF610.
Until recently this was the best sounding preamp I have every built or heard.
Next I adjusted the BSOZ to an approximate version of the X-BSOZ; however, the best sounding configuration I have heard so far is Henrik's X-BSOZ "sort of" with a 180R gain resistor instead of a wire and no R120/121.
My X-BSOZ is slightly different than Henrik's layout because I have two outputs. One output cap configuration gives me a high pass first order Butterworth filter at 120 Hz. This is inside the feedback loop. The other output cap configuration provides all pass which runs to an opamp 2nd and 3rd order Butterworth low and high pass filter. This output cap configuration is outside the feedback loop.
In Henrik's PDF the R103-106 are rated at 1W each. Nelson use two 750? 3W on each side. But I've bought 1k5 2W, will it be enough to have a singel resistor at each side or do I have to use four of them?
I've finished the PSU yesterday, but not tested it yet. I suspect that the recifters going to get very very hot, but haven't got any heatsinks for them.
Then I must figure out how to fit four enourmus 33uF on the veroboard 🙂
Yesterday I replaced my old NAD 3020 (used as preamp) with a 10k ALPS pot = HUGE difference. Now I'm playing my Rega Planet>>SOZ>>Proteus with a big smile.
//vit
I've finished the PSU yesterday, but not tested it yet. I suspect that the recifters going to get very very hot, but haven't got any heatsinks for them.
Then I must figure out how to fit four enourmus 33uF on the veroboard 🙂
Yesterday I replaced my old NAD 3020 (used as preamp) with a 10k ALPS pot = HUGE difference. Now I'm playing my Rega Planet>>SOZ>>Proteus with a big smile.
//vit
Resistor wattages
My 3 watt resistors run quite hot using +/- 60 volt rails.
The current through a 1K5 resistor will be approximately 60/1500= 0.04 amps
The heat given off by one 1K5 resistor will be about 60 x .04 = 2.4 watts.
If you keep all sides of your 2w resistors clear of any obstructions and possibly slightly wrap them with a little bit of thick copper wire with the ends sticking out an inch or two to act as a heat sink you will probably be O.K. but the resistors will likely be very hot and may slightly change in value as a result of the higher heat.
If your rail voltages are +/- 55 volts or less your 1K5 resistor should be putting out about 2 watts.
My 3 watt resistors run quite hot using +/- 60 volt rails.
The current through a 1K5 resistor will be approximately 60/1500= 0.04 amps
The heat given off by one 1K5 resistor will be about 60 x .04 = 2.4 watts.
If you keep all sides of your 2w resistors clear of any obstructions and possibly slightly wrap them with a little bit of thick copper wire with the ends sticking out an inch or two to act as a heat sink you will probably be O.K. but the resistors will likely be very hot and may slightly change in value as a result of the higher heat.
If your rail voltages are +/- 55 volts or less your 1K5 resistor should be putting out about 2 watts.
Hi Vit
The R103-106 is actually dissipating 1W each with 60V rails.
I always like to be on the safe side, so in real life they shoud be rated higer. As Ignatz said, 6W as total for all resistors R103-106 will give you some real hot resistors, I would go for more, like 8-10W or so, and give them some good space on the board, and let them "fly" a couple of milimeters above the board.
The high value for the outputcaps at 33uF is becauce of the very low inputimpedance at my X-SOZ which is 120 Ohm. For normal loads / impedances at 10K they only need to be 1uF and then you will get a -3dB lowend rolloff at only 0.3Hz.
The R103-106 is actually dissipating 1W each with 60V rails.
I always like to be on the safe side, so in real life they shoud be rated higer. As Ignatz said, 6W as total for all resistors R103-106 will give you some real hot resistors, I would go for more, like 8-10W or so, and give them some good space on the board, and let them "fly" a couple of milimeters above the board.
The high value for the outputcaps at 33uF is becauce of the very low inputimpedance at my X-SOZ which is 120 Ohm. For normal loads / impedances at 10K they only need to be 1uF and then you will get a -3dB lowend rolloff at only 0.3Hz.
Gain resistor of 10R
Henrik:
I must compliment you again on the sound quality of your modification.
I have been auditioning your “X” modification to the bosoz for a few weeks now.
A few days ago, I changed back to my version of the original bosoz and after listening to it for about 10 minutes I immediately changed back to your X-bosoz configuration. The difference was so large that I do not have to make this test again. I will stay with the x-bosoz version.
I am still finding it difficult to describe in words the very noticeable difference in sound other than very crisply focussed and very fast with no edge. The resolution and presentation of fine detail is also much more pronounced.
My x-bosoz set up is slightly different than yours, because I have two-output sets of caps; however, I am now down to a 10R gain resistor instead of a 0R.
Can you direct me to a link where you obtained your simulation software for this circuit?
I would like to simulate my exact configuration to optimize my trial and error experiments.
Thanks
Henrik:
I must compliment you again on the sound quality of your modification.
I have been auditioning your “X” modification to the bosoz for a few weeks now.
A few days ago, I changed back to my version of the original bosoz and after listening to it for about 10 minutes I immediately changed back to your X-bosoz configuration. The difference was so large that I do not have to make this test again. I will stay with the x-bosoz version.
I am still finding it difficult to describe in words the very noticeable difference in sound other than very crisply focussed and very fast with no edge. The resolution and presentation of fine detail is also much more pronounced.
My x-bosoz set up is slightly different than yours, because I have two-output sets of caps; however, I am now down to a 10R gain resistor instead of a 0R.
Can you direct me to a link where you obtained your simulation software for this circuit?
I would like to simulate my exact configuration to optimize my trial and error experiments.
Thanks
Hi Ignatz
Glad you like the X-bsoz.
In my oppinion it is the much better deatails in the all over performance which makes this X Pass so special.
X´ing the SOZ is very similar.
BTW, are you still running yours without inputresistors?
You can download the simulator from this link:
http://www.catena.uk.com/Pages/download.html
Regards
Glad you like the X-bsoz.
In my oppinion it is the much better deatails in the all over performance which makes this X Pass so special.
I really reconice crispy withouth edges.
X´ing the SOZ is very similar.
BTW, are you still running yours without inputresistors?
You can download the simulator from this link:
http://www.catena.uk.com/Pages/download.html
Regards
Since the gain is quite high and any distortion and output unbalance is corrected by much feedback, I think this strategy is often used in the design of operational amplifier (OP).
However, I would say this may violate the major design premise of Zen.
stefano's x-bosoz
Stefano, regarding your image on post #29 of this thread on page2, what would need to change to run it off of +/-60V dc rails?
I am thinking of using it to drive a source follower FET with no voltage gain, so I need about 15V AC from the x-bosoz while staying in the linear region of operation. That is why I want the +/-60V supply.
And, why did the thread focus on Henrik's design more than this one?
What is the change in your circuit that allows its operation with no output capacitors?
Grant
stefanobilliani said:
Stefano, regarding your image on post #29 of this thread on page2, what would need to change to run it off of +/-60V dc rails?
I am thinking of using it to drive a source follower FET with no voltage gain, so I need about 15V AC from the x-bosoz while staying in the linear region of operation. That is why I want the +/-60V supply.
And, why did the thread focus on Henrik's design more than this one?
What is the change in your circuit that allows its operation with no output capacitors?
Grant
Hi Grant,
At 60 volt different values for R2 and R8 are probably what we want since Vr1 and Vr2 are there to set the outputs at zero volts.
The folded cascode, formed by Q1 and Q2, is the main difference from the Henrik version and allows to avoid the capacitors .
The thread did focus on Henrik's design more , becouse IMhappyO this one is more simple to implement if you have already build a BOSOZ.Second , I'm not sure but I think that the current amplification, like you are goin' to do, is essential out of the folded cascode circuit.
BTW the circuit at post #29 was incorrect since the sources and drains pins of Q1 and Q2 was inverted.
At 60 volt different values for R2 and R8 are probably what we want since Vr1 and Vr2 are there to set the outputs at zero volts.
The folded cascode, formed by Q1 and Q2, is the main difference from the Henrik version and allows to avoid the capacitors .
The thread did focus on Henrik's design more , becouse IMhappyO this one is more simple to implement if you have already build a BOSOZ.Second , I'm not sure but I think that the current amplification, like you are goin' to do, is essential out of the folded cascode circuit.
BTW the circuit at post #29 was incorrect since the sources and drains pins of Q1 and Q2 was inverted.
Attachments
Thank you Stefano, that is more help than I ever hoped for.
I am not sure what you mean by "the current amplification (presumably you refer to my intended source follower power amp) ....is essential out of the folded cascode circuit"? Do you mean that the folded cascode circuit is essential if the power amp has no gain? Why?
Grant
I am not sure what you mean by "the current amplification (presumably you refer to my intended source follower power amp) ....is essential out of the folded cascode circuit"? Do you mean that the folded cascode circuit is essential if the power amp has no gain? Why?
Grant
- Status
- Not open for further replies.