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AD825 module from LC Audio
AD825 module from LC Audio
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Old 17th July 2002, 09:09 PM   #21
Helix is offline Helix  United Kingdom
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Thats why i said "The caps are not essential but prefrable."
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Old 18th July 2002, 12:56 AM   #22
MRehorst is offline MRehorst
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Originally posted by Bom
Thank you everybody for your good opinions.

Here is my understanding. I can replace the 5534 with any single opamp which has same leg (DIP, I guess). Not talking about the difference in sound, all opamp will work properly by doing so right? I mean without any other mod.
Yes and no. Yes, opamp pin-outs are more or less standard, however, some op-amps have more DC offset than others, some produce more noise than others, some will not be able to handle more than +/- 5V, and etc.

The opamp in the original circuit was chosen by an engineer, presumably an expert in the field. Do you really suppose you can choose a better one without knowing anything about the circuit or the opamp? Randomly plugging opamps into a circuit is unlikely to result in an improvement in the sound. You must study the specs and choose wisely. That means know the circuit the original op-amp is used in and the specs of that op-amp.

Don't plug a +/- 5V part into a socket with +/- 15V applied.

Beware of DC offsets- some circuits will have trimmers to allow offsets to be nulled, others won't. Plug in an op-amp that has more than a couple mV of DC at the output and you may have problems with the following stage.

The noise produced by an op-amp is a function of the source resistance and the design of the input stage and feedback network surrounding the opamp. Some, like the AD797 like low source resistance for minimum output noise. Others like high source resistance.

Some circuits will be designed so they suck quite a bit of current out of the opamp output stage. Plug in another opamp that can't handle the current and it might go "pfffft".

To summarize, the opamp itself is only a part of the total circuit. The input and feedback network are designed to match the opamp being used. Getting optimal performance from another opamp in the same socket will require that you reengineer the rest of the circuit. Contrary to what many purveyors of "high-end" equipment and accessories will tell you, good audio is not art or magic, it is science.

Good luck!

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Old 2nd August 2002, 12:25 AM   #23
Wombat is offline Wombat  Germany
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Just some more findings about switching other OPs into my DAC:

Today i had the chance to verify my findings a bit.
I was listening to Avntgardes Trios and compared my DAC
with an Audio note.

I first listened with the 2134 in the output and we found
that the room it creates was unnatural wide and sizes were
messed up. Also the highs were "too fine", almost synthetic.

So i threw in the cheap NE5532 from Philips (i had it working a
week long at home before for burn in)

The room was much more precise and the sizes of all instruments
and things were very good. It produces a very unspectular but
real sound.

But against the Tube exit in the Audio note both sounded lame.

All i can possibly conclude now is that the jFET 2134
does a very good job directly behind the D/A converter
but in this output stage that was designed for the 5218A
the Philips 5532 does a better job than the Burr Brown
maybe due to his bipolar input.

Like prophet MRehorst says, you can´t generalize OP amps sound
improvement when switching them into existing parts.

I can´t speak for the much praised AD parts cause i haven´t
them around for testing.


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