Hi Peter
It looks pretty much Nelsons patent.
I think You need some inputresistors, or you have to trust the outputimpedance of signalsource.
May be the value of R8 is too high, try to short it, and add some more feedback.
Could You explain some more of Your point of views on this one.
I would like to do some sims, but it will be in the evening.
Could be an interting project.
🙂
It looks pretty much Nelsons patent.
I think You need some inputresistors, or you have to trust the outputimpedance of signalsource.
May be the value of R8 is too high, try to short it, and add some more feedback.
Could You explain some more of Your point of views on this one.
I would like to do some sims, but it will be in the evening.
Could be an interting project.
🙂
If You take away the folded cascodes, You end up with a simple XBOSOZ or a XSOZ for that matter.
As I remember, Nelson once talked about these folded casodes, and I thik his reason to implant these was to acheve better linearity at frequences higer than the audioband, >100kHz.
So do we need them at all?
As I remember, Nelson once talked about these folded casodes, and I thik his reason to implant these was to acheve better linearity at frequences higer than the audioband, >100kHz.
So do we need them at all?
Henrik said:
I'm not sure how high it stays linear, but perhaps it helps keep AM (medium-wave, in Europe? 550kHz to 1600 kHz) band signals from producing modulation products that end up in the audio band?
Erik
With the folded cascode the differential pair sees a constant voltage then the bandwith become better and the distorsion low.
Not to mention the output swing.
Sure it helps drive such difficult loads like some x-son of zen back in the x-soz thread.
Cheers
Not to mention the output swing.
Sure it helps drive such difficult loads like some x-son of zen back in the x-soz thread.
Cheers
I would agree the second cascoded stage is not so important for small signal, audio frequency and low gain application. In this circuit, I intended to level shift the output signal to eliminate the potential dc voltage to a quite low value. This can be done by adjusting the potentiometers VR1 and VR2 in the circuit. Thus, the output capacitor shown in the original bosoz project can be kicked away. I don't like signal capacitors.
In this circuit, the original bosoz parts is still remained in and only two p mosfet and three 750 Ohm resistors are added. It would be quit easy to modify the original bosoz, if you had constructed one. I constructed a bosoz without pcb and preserve some space to upgrade.
I don't like feedback either. I would take out the resistors, R4 and R10.
I hope somebody can help to analyze performances of this circuit.
Thanks.
In this circuit, the original bosoz parts is still remained in and only two p mosfet and three 750 Ohm resistors are added. It would be quit easy to modify the original bosoz, if you had constructed one. I constructed a bosoz without pcb and preserve some space to upgrade.
I don't like feedback either. I would take out the resistors, R4 and R10.
I hope somebody can help to analyze performances of this circuit.
Thanks.
When I played around with this circuit , some months ago, I did notice that it didn't work if R10 and R4 were out.
...but I may be wrong.
...but I may be wrong.
Peter, I can understand your concern for feedback but if you take out R4 and R10 does this not take out the "X" and was that not the whole point of the circuit to have it?
Maybe I am missing something again...
/UrSv
Maybe I am missing something again...
/UrSv
Thanks to stefanobilliani.
Since my CD player only has RCA outputs, I would drive it unbalanced in and balanced out, and connected to amp. SOZ or XSOZ.
Since my CD player only has RCA outputs, I would drive it unbalanced in and balanced out, and connected to amp. SOZ or XSOZ.
Gain, Distortion and Feedback
I found that the gain of the circuit should be adjusted to be higher when the feedback is increased, but the distortion of the signal may be increased with the gain,too. There must be a compromise. Could you have the idea or method to get an optimum feedback?
UrSv, thank you.
I found that the gain of the circuit should be adjusted to be higher when the feedback is increased, but the distortion of the signal may be increased with the gain,too. There must be a compromise. Could you have the idea or method to get an optimum feedback?
UrSv, thank you.
Although it may become most complicated when you will build it ,
the best way ( since you decide to use it as a unbal/bal converter also) is to replace the power resistor(s) with active current sources. The best example for this matter you can find is on the
Aleph P schematic at Passlabs.com aleph page.
the best way ( since you decide to use it as a unbal/bal converter also) is to replace the power resistor(s) with active current sources. The best example for this matter you can find is on the
Aleph P schematic at Passlabs.com aleph page.
Active current source
The amplitude deviation of two output signals could be concerned.
I would think the active current source invented by Pass highly improves efficiency perfomance of a class A power amplifier with heavy load.
In Aleph P1.7, I think that those are constant current sources.
A constant current source with temperature compensation will be preferred in this circuit.
Any suggestion is welcome and stimulate our brain. Thanks.
The amplitude deviation of two output signals could be concerned.
I would think the active current source invented by Pass highly improves efficiency perfomance of a class A power amplifier with heavy load.
In Aleph P1.7, I think that those are constant current sources.
A constant current source with temperature compensation will be preferred in this circuit.
Any suggestion is welcome and stimulate our brain. Thanks.
I built the circuit just 2 days ago .
First I say : it works with or without the R4 R10 (feedback / X ).
As a unbal/bal converter : I pull out R3 and R13 and add 2 resistors at the imput ( 2,2k ).
This circuit works , at my opinion , pretty good like a converter;
As usual I prefer to drive it balanced .
Well : it has a very defined soundstage , enormous from left to right , no noise (absolutely) and big dinamics.
It worths to be build and listen .
First I say : it works with or without the R4 R10 (feedback / X ).
As a unbal/bal converter : I pull out R3 and R13 and add 2 resistors at the imput ( 2,2k ).
This circuit works , at my opinion , pretty good like a converter;
As usual I prefer to drive it balanced .
Well : it has a very defined soundstage , enormous from left to right , no noise (absolutely) and big dinamics.
It worths to be build and listen .
Hi,
Nice to hear you build the thing! Do you happen to measure the output DC offset en input DC offset? How did you adjust them? Do you still use a 560 Ohm Diff pair feedback resistor? Why not go down to 47 Ohm and use feedback around the folded cascode?
gr,
Thijs
Nice to hear you build the thing! Do you happen to measure the output DC offset en input DC offset? How did you adjust them? Do you still use a 560 Ohm Diff pair feedback resistor? Why not go down to 47 Ohm and use feedback around the folded cascode?
gr,
Thijs
Good observations...
Yes , the diff pair resistor (set the gain) 47ohm , is exatly what I use.
Also 4 matched mosfets (2 irf9610 and 2 irf610) all with same VGS
do the thing right.
At the output , 10 millivolts ; at the input a fiew millivolts but I still use coupling capacitors .
For trimming the cascode fets : 100K ohm from the positive supply rail to the gate pin of Q1 and Q4 and then a 20k pot + 30k ohm to ground is pretty good.
Yes , the diff pair resistor (set the gain) 47ohm , is exatly what I use.
Also 4 matched mosfets (2 irf9610 and 2 irf610) all with same VGS
do the thing right.
At the output , 10 millivolts ; at the input a fiew millivolts but I still use coupling capacitors .
For trimming the cascode fets : 100K ohm from the positive supply rail to the gate pin of Q1 and Q4 and then a 20k pot + 30k ohm to ground is pretty good.
Ah...
yes for the feedback as shown on the schematic above.
100k ohm for the start . I remember that X works good if the amount of feedback is 20 db .
yes for the feedback as shown on the schematic above.
100k ohm for the start . I remember that X works good if the amount of feedback is 20 db .
- Status
- Not open for further replies.