Best opa604a opamp replacement?

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#21
juma said:
I wonder why no one mentions AD797 - when it comes to low noise and good sound, no opamp beats it (IMHO) ?
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the797 is excellent - in the appropriate application

as a heavily biased bjt input device it has relatively high noise current at the inputs so droping it into a circuit with feedback and source impedances selected for a fet input device will give high noise - the most common diy-audio use that matches the noise/impedance for the ad797 is low impedance mc phono input

further the 797 has unusual unity gain feedabck impedance requirements and may oscillate in unity gain circuits designed for typical unity gain op amps

also the 797 is unusually fast, the extended loop gain at high frequency can lead to oscillation in a circuit designed for slower op amps- improved ps bypass, high speed pcb layout as well as components may need optimizing for stability with a order of magnitude faster device

the ad797 is not a drop in replacement for just any audio op amp, certainly not just any fet input op amp - it requires the entire circuit to be designed with its strengths and special requirements in mind
 
#22
myhrrhleine said:
I think i'd go with the '827 if I could manage the package, otherwise the '134 would be my choice.
The '827 could also be a hf oscillation problem tho. The '134 would be better in that regard imo.
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OPA2134, OPA134 is a very stable op-amp.
I have not heard of any having stability problems with OPA2134.

Even if OPA2604, OPA604 is featured as unity gain stable,
I have read cases where it was not so stable.
 
#24
AD8599 is also a folded cascode amp. Low distortion, low noise and low DC-offset, cheap, easy to implement, and it sounds good. It's a bit warmer sounding than AD797, not as clean sounding but close. Not grainy like FET input opamps. There's now a single version, AD8597.All opamps have some colorations. AD8599 is on the dark side of neutral with slightly recessed mid. LM4562/LME49XXX is brighter and maybe more impressive, but in the long run it lacks "musicality".

AD825 is the very opposite with forward mids, some grain and grit but it sounds good if you like this presentation.

IMO the sound quality of OPA2132/2134 is not on par with the best opamps. The treble is quite grainy and dirty. The soundstage is very narrow. The bass is accentuated and "boomy".
 
#26
gaetan8888 said:
Hello

Which op-amps would have the best musicality and a 3D soundstage ?

Thank

Gaetan
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We all seem to experience sound different, but I think good JFET input amps like AD8620, AD825, AD8066 and AD744 have a more "pinpoint accurate" soundstage. I find good bipolar opmaps like LM4562, AD797, ADA4899 and AD8599 sounding "airier". It's a matter of taste.

I shouldn't have written "musical". It's too subjective, but I think JFET input amps have some kind of "organic" touch.
 
#27
nelsonvandal said:

We all seem to experience sound different, but I think good JFET input amps like AD8620, AD825, AD8066 and AD744 have a more "pinpoint accurate" soundstage. I find good bipolar opmaps like LM4562, AD797, ADA4899 and AD8599 sounding "airier". It's a matter of taste.

I shouldn't have written "musical". It's too subjective, but I think JFET input amps have some kind of "organic" touch.
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Hello

For me a good sound and soundstage give you a presence like it was really there, if you listen a jazz concert cd or vinyl, you really feel that the drum are in the back, the double bass in center, the piano in middle right and the singer in the center front with a good distance between them. And you have a clear and precise definition without any muddy sound.

Thank

Gaetan
 
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