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Old 14th October 2012, 05:02 AM   #11
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Quote:
Originally Posted by Jay View Post
Cool. I should put that in my footer signature
You can find more, we have a huge thread in the Lounge, about "Sound Quality and Measurements"
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Old 14th October 2012, 09:07 PM   #12
sreten is online now sreten  United Kingdom
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Quote:
Originally Posted by Wavebourn View Post
Some persons that design best in the world equipment know
better what to measure than the majority that does not
have a clue what and how to measure.
Hi,

Still one persons opinion obfuscating the basic facts.

The 5532 is faster, has lower noise, lower distortion and
better drive capability, and is dirt cheap to try compared
to buying discrete op-amps, and compare to the 4558.

I've no idea if "class A" bias improves it or not. I do know
when I've used it to replace dual op-amps in cases I've had
problems (I don't change op-amps for fun, if it works, fine)
the 5332 has fixed the apparent problem, mainly inputs.

Suck the 5332 and see is my opinion, you will get less noise.

rgds, sreten.
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Old 14th October 2012, 09:26 PM   #13
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Quote:
Originally Posted by sreten View Post
I've no idea if "class A" bias improves it or not.
I see.

But honestly, I don't see how replacing opamps in the EQ can decrease hiss, since both original opamps, and suggested as replacements, have better noise figures than required for "no hiss" on line levels. If to go for improvement of sound quality, as I suggested, biasing in class A gives more real improvement than replacing of opamps. Yes, THD+N figures of 5532 in datasheets look better, but it is not THD+N that matters in this particular case. It is what is below that "N", dynamically occurring, matters, that is hard to measure, and according some beliefs don't matter if below that "N", while it is against the nature of human perception of signals of levels below of noise levels. It is not in the human nature to prefer widening spectum of decaying sounds, like decay of strings, or reverberation. And it matters much more than what is easier to measure ignoring what is "below accepted threshold".

What else can be suggested for EQs? Most probably the EQ uses set of gyrators. On resonant frequencies in gyrators most probably opamps are loaded on very low impedances. That means, opamps with better drive capability may give better improvement than opamps with better noise figures, again in terms of audible distortions.
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Old 15th October 2012, 12:57 AM   #14
Jay is offline Jay  Indonesia
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Quote:
Originally Posted by Wavebourn View Post
That means, opamps with better drive capability may give better improvement than opamps with better noise figures, again in terms of audible distortions.
If I'm not mistaken, in (Burr Brown) opamp's pdf documentation there is a chart showing the source impedance where a (very) low noise opamps start to be better than high slew rate opamps. I think the impedance starts at around 15K for low noise opamps to be better. This is a relatively low number for most applications, so low noise opamps rule in term of "distortion".

To take benefit of that characteristic of very low noise opamps, I started to work with amplifiers where transistor's bandwith/slew rate/transconductance is not critical. It can be an opamp driving a phase splitter (like JLH69), but I'm recently working with opamp driving CFP output (where stability is more easily achieved with slower parts).

Slow but very low noise instrumentation opamps do have some good characters. I think with such topology the audible benefit will be more. Hopefully.
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Old 15th October 2012, 02:44 AM   #15
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All "high end" types resort to hand waving and obfuscation if you ask them to provide something so crude as scientific proof of their assertions, such is the way of things.
rcw
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Old 15th October 2012, 04:46 AM   #16
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Quote:
Originally Posted by rcw666 View Post
All "high end" types resort to hand waving and obfuscation if you ask them to provide something so crude as scientific proof of their assertions, such is the way of things.
Sure they do! But more often their explanations are in terms of precise perceptions translated into some (mis)understanding of technical terms. But if you try you can find scientific explanations that not necessary correspond to the technical language that they use. It is always more profitable to learn foreign languages instead of complaining that experts in other fields do not speak fluently yours.
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Old 15th October 2012, 05:25 AM   #17
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I've used the AD op07 to exellent effect.
Really an instrumentation amp.
Very slow...if you buy by the spec. sheet...you'd never use it...way too S L O W...
...That's just numbers though...
...sounds vandabidoseeee...

Si.
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Old 16th October 2012, 06:05 PM   #18
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Anyway, the question "Name better opamp than xxx for EQ in yyy because I know that xxx is guilty" has no answer, as jcx pointed in the beginning.
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Old 16th October 2012, 06:33 PM   #19
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Well, I proposed an experiment, after all. Put in a socket, try something else. I find in my 50x gain mag phono circuit, ST33078 is less hissy than NJM4558. Your results may very- particularly as the tone control circuits under discussion have low impedance sources (other amp stages). I've got the socket, have RC4560, TL082, and LM4562 in the parts box for other experiments some rainy day. I already tried the experiment of NJM4558, NJM4560, ST33078 in the input stage of a CS800s amp, driven by a low impedance 2k ohm output stage (33078) of a Herald RA88a mixer. Results, the latter two op amps are indistinguishable, the 4558 is hissy.
The only thing scientific about my experiments is my calibrator. I have a Steinway console piano in the same room as the hifi. I have always been of the opinion that recorded piano music sounded artificial, from the days of the Bozo the Clown record player with the paper cone "amplifier", forwards. With the SP2-XT speakers, the equipment is getting pretty close, now. On the premium brand LPs the records weren't the worst part of the distortion chain after the old ribbon microphones went out of fashion for classical recordings, my ears tell me.
Interesting about the class A use of the 4558. There are places that might be useful- like this 50x mag phono circuit. Having 300 ohms between part and both supply rails, and no cap afterwards, surely did something to supress the hum in this circuit before I modified it for more powerful op amps.
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Last edited by indianajo; 16th October 2012 at 06:43 PM.
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Old 16th October 2012, 06:50 PM   #20
sreten is online now sreten  United Kingdom
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Hi,

Came across the 33078 in a Rega Brio recently (phono input 1st stage,
the rest are TL072's), similar to the 5332, possibly not quite as good.

rgds, sreten.
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