The Gradomeister
Jul 9, 2007 8:55:07 GMT
Post by FritzS on Jul 9, 2007 8:55:07 GMT
We ignore Linear Technology www.linear.com/ ???Now I use two LT1056 in place of the both AD847 :(There are very little differences ....Treble (cymbals) are a little bit softer, silkier, darker, more natural Micro Dynamics - more than AD847 - more in background too.From the first tick I hear - I am snoopy why after a burning in time :PAnd all this with an "old design" 5.5 MHz, 14V/us OP - silmilar to the OPA602 :-[Next I will test LT1022 if I get some samples
2nd & 3rd test - as far as I can see the LT1056 is a "big player" like AD843 too
Natural, detailled sound with good micro dynamics, open wide and deep stage.
I think one must be changed: The WNA design use a ferrite bead between the output of the OPA and the powerstage. This is not calculated for other OPA's. The datasheet suggestions of LT1056 use a little cap 10 ... 33 pF in NFB:
"When the feedback around the op amp is resistive (RF), a
pole will be created with RF, the source resistance and
capacitance (RS, CS), and the amplifier input capacitance
(CIN ≈ 4pF). In low closed-loop gain configurations and
with RS and RF in the kilohm range, this pole can create
excess phase shift and even oscillation. A small capacitor
(CF) in parallel with RF eliminates this problem. With RS
(CS + CIN) = RFCF, the effect of the feedback pole is
completely removed."
But I dont hear oscillation in audible range or distortion. Only very good sound