Bricolo,
The AX is a 3 stage-Design. In this front-end simply the mosfet IRF510 replaced the bipolars mpsa18 in Grey's design. Without now having had the opportunity to hear fets against bipolars, I read from a lot of sources that an all-fet-amp is much better in sonics than a similar design with bipolars. So, if someone would simulate the high-frequency-behavior of this front-end and if this is OK, it could be the best-sounding version around...
Thanks for posting the circuit.
The AX is a 3 stage-Design. In this front-end simply the mosfet IRF510 replaced the bipolars mpsa18 in Grey's design. Without now having had the opportunity to hear fets against bipolars, I read from a lot of sources that an all-fet-amp is much better in sonics than a similar design with bipolars. So, if someone would simulate the high-frequency-behavior of this front-end and if this is OK, it could be the best-sounding version around...
Thanks for posting the circuit.
Blitz, correct me if i´m wrong. The mpsa18 are part of the alpeh current sources feeding the output devices. They don´t affect the signal in any way, they only control the current over R5 / 40.
The differntial pair input is one stage. The bridged aleph output stages are the second stage. 2 stage design. The Jfet input pair doesn´t deliver enough current for the second stage because Jfets doesn´t like a lot of current bias. The 510 are nothing but followers so no voltage gain - no gainstage. If ZenV4 is one stage design the 510 are not a stage, they build one stage with the Jfets.
Do i see this right?
For the advantages of Jfets see some pages before, i gave a link in my posting before. Its intended for usage with hornspeakers >= 100dB/W
The differntial pair input is one stage. The bridged aleph output stages are the second stage. 2 stage design. The Jfet input pair doesn´t deliver enough current for the second stage because Jfets doesn´t like a lot of current bias. The 510 are nothing but followers so no voltage gain - no gainstage. If ZenV4 is one stage design the 510 are not a stage, they build one stage with the Jfets.
Do i see this right?
For the advantages of Jfets see some pages before, i gave a link in my posting before. Its intended for usage with hornspeakers >= 100dB/W
Can you explain how much current you want/get through the
newly introduced irf510?
Mr Blitz reports no voltage gain so no gainstage.
This I do not understand. Could it be, he means voltage gain of 1?
Then it would qualify as a gainstage, wouldn't it?
In short, until now I have not found a way to make this work.
I am playing with a jfet diff stage at this moment and will try to
finish a simulation in the coming days.
Regards.
newly introduced irf510?
Mr Blitz reports no voltage gain so no gainstage.
This I do not understand. Could it be, he means voltage gain of 1?
Then it would qualify as a gainstage, wouldn't it?
In short, until now I have not found a way to make this work.
I am playing with a jfet diff stage at this moment and will try to
finish a simulation in the coming days.
Regards.
X Aleph vs Aleph Comparisons,
My initial impresssions are much like those before me,
More apparent spark in the upper mid and top end, less mooph/wool in the bass and less warmth across the vocals with the X Aleph.
However warmth may be the wrong word, engaging and more romantic maybe more appropriate for theAleph.
The L100's are very good for bring out the good/bad of a recording and the differences were not sublt, even with on off air broadcasts.
If straight up A/B's are anything to go by, I would say the X Aleph is different but not better and it may come down to application.
Its possible that pure piston range speaker systems may need the more romatic of the two, aka the Rushmore.
No doubt more lengthy analysis will change my resolve.
Ian
My initial impresssions are much like those before me,
More apparent spark in the upper mid and top end, less mooph/wool in the bass and less warmth across the vocals with the X Aleph.
However warmth may be the wrong word, engaging and more romantic maybe more appropriate for theAleph.
The L100's are very good for bring out the good/bad of a recording and the differences were not sublt, even with on off air broadcasts.
If straight up A/B's are anything to go by, I would say the X Aleph is different but not better and it may come down to application.
Its possible that pure piston range speaker systems may need the more romatic of the two, aka the Rushmore.
No doubt more lengthy analysis will change my resolve.
Ian
R19 and R29:
It has been suggested that Grey's values of 68k are incorrect and that we should use 10k to 20k instead. I've tried all three values and must now report that the dc offset is initially lower with the 68k resistors and therefore drops to zero more rapidly. The sound is pleasant with the 68k value and this is where I intend to keep things for now.
Just food for thought,
John
It has been suggested that Grey's values of 68k are incorrect and that we should use 10k to 20k instead. I've tried all three values and must now report that the dc offset is initially lower with the 68k resistors and therefore drops to zero more rapidly. The sound is pleasant with the 68k value and this is where I intend to keep things for now.
Just food for thought,
John
Lowering the value of resistance to ground at the
Gates of the input diff pair affects a couple of things:
It lowers the tendency for common mode offset to
be amplified positively.
It lowers the open loop gain of the circuit, and thus the
amount of feedback.
If the source (preamp, cd player, what-have-you) has
a reasonably low DC impedance and you are DC coupling
the input, this resistor is unnecessary. If you are AC coupling
the input, it is essential.
Clearly there are optimal values for every circuit example
and taste, and the nice thing about it is you can fool
around with the values all you like and note the sonic
differences.
pass/ - he likes different sounds all the time.
Gates of the input diff pair affects a couple of things:
It lowers the tendency for common mode offset to
be amplified positively.
It lowers the open loop gain of the circuit, and thus the
amount of feedback.
If the source (preamp, cd player, what-have-you) has
a reasonably low DC impedance and you are DC coupling
the input, this resistor is unnecessary. If you are AC coupling
the input, it is essential.
Clearly there are optimal values for every circuit example
and taste, and the nice thing about it is you can fool
around with the values all you like and note the sonic
differences.
pass/ - he likes different sounds all the time.
