DIYHiFi.org

First of all I am aware of the sensivity of this topic, and I want to say I don't want to start another discussion about some esoteric qualities of certain OpAmps, I want to keep it at technical level (if possible).

I have looked into several DAC-OpAmp configurations in the commercial products (including my HK and Denon receivers/DVD-players).
Everywhere I see LM833, BA15218 and for the higher-end NJM2068, NE5532, NE5534. I would expect that the price is not the driving reason behind those selections, but... don't know.
I have swaped in my receiver the LM833 with LM4562. I think I heard an improvement, I like it better, so why the "big guys" don't use some of those "exotic" OpAmps (forums are full of examples)? It is just my immagination?

It is just cost? Or it doesn't matter at all? Are NJM2068 or NE5532 somehow better that the specs show? Or it is just "if is not broke don't change it" mentality in the design phase?

From the datasheets I would expect that OpAmps are an important piece of the puzzle - I/V stage (where is the case), 3rd order filter, +6dB boost for HDCD (where is the case). Noise, SR, BW, distortion (TDH), intermodulation... aren't those important?
What's your take on this?

The NE5532 isn't that bad. When you see a TL072/TL074 op-amp in your equipment, or a 4558, that's when you get angry.

Yes 5532 is not bad. But there is out the improved version 5534. Why is not used?

I am getting "angry" with LM833... I had that in my Philips CD473 (TDA1541 glorious days) and after 10 years I found that in my Denon AVR-3805 receiver (1200$ "list" price). Same OpAmp is used even in higer models. WTF?
Then... I see a lot of NJM2068 in higher models. And the specs are not that great. Sure, sounds all right...
In my Denon DVD-2390 they have NJM2068 ONLY on the stereo output, like they couldn't afford it on the surround ones (same DAC's with BA15218).
I had NJM2068 in my HK receiver too...

It is just something simple as a matter of supply chain? Not having to relay on some "fancy" OpAmp supply? Especially that I see the japan companies favoring NJR...

Or it is something else that I miss here?

It's all about cost.

I was thinking that it might be a factor. But... whan they ask more than 2000$ per a piece of equipment what are they saving? A few dollars on the front-end?

I wonder if it is also a matter of saving design hours by reusing the old schematics.

Remember that on that $2K unit, 25-50% goes to the store, x is part of the warranty, y is supporting the local division of the company, etc, etc.

A $1 part probably adds $100 down the line...

See, the store, local reps, those are fixed expenses for the manufacturer, they are not multiply with the actual production cost.
So... if they use 1$ op-amp or if they use a 4$ one, the actual net profit for the manufacturer drops with exactly 3$ per cip.
That's why I don't get it. Are those profit margins so tight that "loosing" a few dollars (20-50$ max) would break them?

Actually no, they aren't fixed costs. Costs are typically based on percentages. Adding $1 to the BOM price is multiplied down the line. It may not affect the manufacturer that much but the MSRP goes up and that affects the retailer.

Enough with the marketing lesson. Just accept it, modify the gear the way you want, buy old stuff from ebay cheap and rebuild it and be happy you're getting a deal.

Engineers have no ears

I have...
Just couldn't explain WHY other engineers seem not to care about this issue. I would LOVE to talk to a designer that works for for Denon, HK, Sony, Yaymaha... See what he thinks about analogic side of the electronics "world". Sometimes I have the feeling there are all DSP, asm, C++ type of "engineers". AKA programmers.

You try going to your boss and propose a change that costs more but yields virtually no improvement in measurements when you are in an increasingly low-margin business. Tell him you need to make the change because it "opens up the soundstage", then prepare to start looking for another job.

That I can understand. But I cannot belive that it makes so much difference to the final line. Regardless what you might think, an extra 10$ in the BOM doesn't inflate to 100$ to the final production cost. It stays at 10$ and it gets deducted from the profits of the sale. The sale price is determined by market forces and and marketing department, has little to do with the actual BOM.
At least that's how it is on other industries (electrical field).

A company might only make a $100 net profit on a $2000 piece of equipment once you involve production cost, transportation cost, retail margin, support, warranty, etc. Adding $10 worth of parts to a part with a $100 net margin isn't exactly smart.

Plus, we all know that lots of high end equipment isn't. If it looks fancy, has an uncommon name and has a high set retail price, people automatically assume that it is a good piece of equipment. And the great majority of people who buy these things won't notice the subtle difference an op-amp makes - most receivers are used to play back lossy Dolby/DTS/whatever encoded content in the form of movies with next to zero dynamic range, not for serious music listening.

Heck, lots of receivers have moved to class D outputs.

Because I was pleased of the results in my receiver, I tried the swap in my older Toshiba SD-6980 (DVD-A, SACD player).
The DAC is DSD1608 (BurrBrown), the PCM decoder is Zoran Vaddis 778 (36778HQCG), the SACD cip is Philips SAA7893HL and surprise... the OpAmps on all the channes are S4560. Nice jellybeans...
I swap all of them with LM4562. I love this little guy! The result is WOW...
When I swap the LM833 with LM4562 it was a small improvement, but from S4560 to LM4562 it is a sensible difference, a different animal.
I don't think it is at the level that I get from PCM1791A driven sound but hey... it cleaned the sound of DSD1608 a lot.
I am waiting for some LME49722 to play a little bit more Altough I don't think I will see too much improvement (law of diminished returns ).

....4560 cost cents and LM4562 cost dollars. At 10.000 units produced (or more) this is not negligible difference