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black_wing

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  • 3 weeks later...

I have seen both in commercial audio devices. I have also used the 1458 successfully in a large number of my own audio designs. It depends upon how you use them and how you incorporate them into your design. Filtering and shielding are key elements. Good board layout is also a place where many fail when it comes to noise levels. I would have to disagree with the comment that they are not suitable for audio projects since I have seen them used successfully.

MP

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MP,
I don't think that Black Wing wants to play "telephone answering machine mini-tapes" through his new audio mixer project. He probably wants to hear CDs clearly. Good opamps that are designed for audio are available and are not expensive so why not use them today?

A local audio equipment manufacturer has an upgrade modification service. They will replace all the older (a few years old) audio opamps in your audio unit with the latest better ones. Here is part of their ad:

"pcX only does mods in the following circumstances where the results are easily discernible, so that a marked improvement in overall sonic quality can be achieved:

a) OLDER Products -- Many older "vintage" products have good enough circuit designs... but lack the pedigree of parts now only available to us today... thus, these parts choices were simply not available to those designers.

b) BUDGET Products -- This is also true of some budget products made today as well ... in order to hit certain price points, parts quality usually suffers.

c) OBSOLETE Products -- Modifications are also very relevant to technologically sensitive products, which may benefit from the advances in various semi-conductor designs (op amps, etc.)... again, not available when the product was originally designed."

Personally, I think that a TL072 dual audio opamp (<$1.00US) is good enough but this company wants their upgrades to be the very best.
They sell as a DIY upgrade, an adapter board with two surface-mounted OPA627AP audio opamps (that are used in all their new products) that plugs into an 8-pin dual opamp socket to replace the older audio opamps. It is only $50.00US each.

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What are you going on about? None of this matters.

I stated that these op-amps are still used in design work and that this would obviously indicate that they "ARE" suitable.

If a guy wants to use a 1458 in an audio design, he can. There are places where audioguru's favorite op-amps are not available. To say it is not suitable, means you cannot use it. You can. And with satisfying results.
So, why don't you drop it? Whenever anyone disagrees with you on this forum you hound them until you get the last word. Whether you are right or wrong. I am so tired of this crap.

MP

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some of the opamp are crap but that doesn't mean it is not suitable for products.
I can tell, LM358 is still widely used in many everyday products..... why, because it is low cost....... (the price of IC is not what you seen in the local store)
Actully, no manufacturers will care about the noise and distortion but price.....

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Hi Trigger,
Have you heard the noise and crossover distortion from a "low power" LM358 dual or LM324 quad opamp? It is very noticeable at higher audio frequencies where it doesn't have enough gain for negative feedback to reduce it. Due to its low power, it doesn't have enough bias current for its output transistors so it operates as class-B with a big hole in the middle of its swing. Poor slew-rate is another problem. Terrible-sounding.
Today, I can buy LM358's, LM324's or low-noise, low-distortion and wideband TL072's for exactly the same price. The low price of the TL072 indicates its wide use in manufacturing of audio products.
We are talking about building a single audio mixer here, so why not use a good IC?

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We are talking about building a single audio mixer here, so why not use a good IC?


I see audioguru is trying to squirm out of this by changing the subject. His statement was that they are not suitable for audio application.

Trigger is absolutely correct. They ARE useable and suitable for audio applications. There will always be a better part that one can use. The industry will always come out with another part with better specs than the last one. That does not make all the other parts unsuitable.

MP
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I can tell, LM324 used as audio amp is much worst than using LM358.
As circuit designer, we always like to use the perfect components.. however, the reality will not let you to, esp. your boss is barking loud to stop you.

And I can tell, some of those opamp, are now produced by Korean or taiwan (some even china); some of them, also being modified by US fabless company with better specification.

So in some case, the chip is always improving rather than continuous with their noisy specificaiton.

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Which half-decent piece of manufactured audio equipment uses a noisy, distorted old LM358 or LM324 in its audio path? I am not talking about a narrow-band sub-woofer amplifier. Show its S/N ratio and distortion at full output from 20Hz to 20KHz like all audio equipment does.

Its datasheet shows it falling off above 5KHz (cheap AM radio quality) while a TL072 extends easily to 100KHz.

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audioguru,

May be you are National semiconductor supporter, but I am not.
Mostly used in products will no longer be NS brand, but some others.
Check the link here:

http://databook.kec.co.kr/Products/item_list.php3?type=X&key1=E&key2=100

Check what the specification on KIA358 and KIA324..... compared with what you found in NS. You will noticed what actually I mean previously. These ICs are pin to pin compatible with better specification.

And of course I know LM324 is quad version of LM358, don't just treat me as a fresh graduate..... :P

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Hi Trigger,
Yes, I am aware that far east semiconductor manufacturers copy American ICs and make them better. The KIA358 that you posted has an extended response all the way to 8KHz! Wow, that's nearly half the audio band. At what expense? How's its stability?
It still has the bases of its output transistors tied together for low power, so still has horrible crossover distortion.

New Japan Radio is highly respected in the Orient. They copied the TL072 and made its response out to 300KHz. They made a big mistake and admit that the thing is unstable and oscillates. They quickly replaced it with the NJM072B, with reduced high frequency response.
http://www.microelectr.com.hk/NJRC_datasheet/pdf/ae/ae04010.pdf

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not just east copy west.... but also some US fabless will copy and improve the chips.

One example is california microdevice (hmm... hope I haven't mistaken) .... they have single opamp with low noise and wide bandwidth which is pin to pin compatible with NS one..... but I forget the part number......

And that single opamp is used in an AGC video circuit with very fine performance....... even better the original one......

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MP,
Good point! Reducing the output level effectvely extends the high frequency response to well over 20KHz.
I was going to ask how are we going to keep the output level down during sound peaks (limiter?) until I saw on the mixer's schematic that it has a maximum gain of only one. With low-impedance microphones? Or a phonograph cartridge without RIAA EQ? The output level will be extremely low.

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