That is also my experience. Also Andrea Ciuffoli's MOSFET version provides excellent results (10mA - 500mA scalable idle current - depended from the number and capacity of the cable connector to the power amp).
the Power Folllower
The use of MOSFET version with extrem low input capacitance isn't very important by the source follower topology.
From the audible view, there is no justification for this effort. Despite the much more better measured results of such an audio line stage I am sure, that Andrea Ciuffoli's MOSFET version provides the better sound by a listening test, if the adjusted idle current is not too low (>100mA).
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If you download their software and keep your board size at 3.8" X 2.5", which seems doable for this design, you can order 2-3 boards for $50-$85.
I'm not sure where you got that price but that's outrageous.
Discrete high performance linestage design with 12v rails
kp93300,
The gain is unity, i.e., (1). Its is designed strictly to be used at unity. You could increase the values of R13 and R14 in like magnitude perhaps somewhat, although at a likewise increasing loss of high frequency linearity.
tiefbassuebertr,
I know nothing of Andrea Ciuffoli's MOSFET version and therefore I cannot comment much about it other than you state its idle current is adjustable to 500ma. It seems to me (and perhaps just myself, others have the right to their own opinion) that an idle current of 500ma for a preamp is quite high.
Best Regards,
Rich
kp93300,
The gain is unity, i.e., (1). Its is designed strictly to be used at unity. You could increase the values of R13 and R14 in like magnitude perhaps somewhat, although at a likewise increasing loss of high frequency linearity.
tiefbassuebertr,
I know nothing of Andrea Ciuffoli's MOSFET version and therefore I cannot comment much about it other than you state its idle current is adjustable to 500ma. It seems to me (and perhaps just myself, others have the right to their own opinion) that an idle current of 500ma for a preamp is quite high.
Best Regards,
Rich
That is correct. By the use of supply voltage from only 12V the power loss is 6W - not extrem for a preamp. But one disadvantage you must accept: A low value of undistorted line voltage output (mostly no problem, but in cases, where the power amp section also is a voltage unity gain device not usable.
actually this concept is only intended for a power amplifier, as you say. Nevertheless some user use this circuit as unity gain pre-amp with excellent sonic results. The adjust of the wanted idle current is very easy by variation of only one resistor.
Just my 2 cents 
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Im using the AMB Labs α20 since some weeks and I'm more than satisfied with it's performance. It needs a very, very good PSU as it has not any constant current source, so I dont know if it's "fairly simple to implement" for you.
...Im using the AMB Labs α20 since some weeks and I'm more than satisfied with it's performance. It needs a very, very good PSU as it has not any constant current source, so I dont know if it's "fairly simple to implement" for you.
I made a line stage as a headphone amp app. which could be used as a line amp as well. Published in latest issue of Linear Audio magazine. Also, discussed in the headphone amp section. pcb being made.
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