Does Op-amp Rolling Work?

[Tranquility Bass]

Even lower noise, lower distortion....

How much lower ?

 

[wwenze]

So, you're saying that opamps don't matter, so if my audio gear had IC709 opamps in it, it would sound just as good as if it had Sparkos SS3602's? Hmmm. I'm not so sure about that.

If my power cable is made of wood, it wouldn't sound as good as one made of copper. So yes, mathematically and logically speaking, cables and opamps both matter.

But at the same time, will a 1AWG power cable make it even better? At that point, your maginal utility may even become negative, because diminishing returns in one performance aspect meets increasingly negative performance impact in another aspect.

So in practice we pay until performance reaches a plateau.

And for both cables and opamps, that value is $2.

And no, paying more does not guarantee better, which is what paragraph #2 explains in general. But that paragraph does not explicitly mention marketing and scam and sale of lower-performing yet higher-priced products.

 

[amirm]

Even lower noise, lower distortion....

Unless you measure, you have no idea whether the new op-amp has lower noise or distortion. Per my testing, the Sonic Imagery did not outperform the NE5532p that came with the amplifier.

 

[pma]

OPA1656 specs below. What's not to like ?

This. The 1/f voltage noise corner is too high.

 

[pma]

So, you're saying that opamps don't matter, so if my audio gear had IC709 opamps in it, it would sound just as good as if it had Sparkos SS3602's? Hmmm. I'm not so sure about that.

Sparkos SS3602 has some good and some bad features. As an audio opamp it is almost unuasable due its very high input bias current. Maybe usable as an output stage.

Re your note on LM709 - it is probably the worst existing opamp, design dated 1965 Bob Widlar and based on ancient technology of those days and good at the time. It is even much worse than 741/748. So yes, swapping for the Sparkos will make things better. You will get lower noise and distortion compared to 709 series represented by uA709, LM709 and other manufacturers. But same or better improvement you will get with SOTA monolithic opamps at fractional price.

 

[antcollinet]

That's why we need to fight against it by proper testing both ways

I’m not convinced that perceptive bias will prevent an audible difference being heard. That is not how it works. However, it doesn’t really matter:

You can’t prove anything with a negative result - only that that particular listener cant’ hear a difference. Of course an overwhelming percentage of negative results does say something

But the only way to positively prove something is with a positive result - which demonstrates that there is an audible difference. Surprisingly though - all those people who can hear “night and day” differences never seem to want to take the chance to stick it to the objectivists and demonstrate that in a scientifically valid way.

 

[antcollinet]

What exactly are the issues that these discrete opamps are trying to solve in their silicon chip counterparts ?

Exactly - lets see some engineering that demonstrates their superiority. Shout up or go home.

 

[Sokel]

I’m not convinced that perceptive bias will prevent an audible difference being heard. That is not how it works. However, it doesn’t really matter:

You can’t prove anything with a negative result - only that that particular listener cant’ hear a difference. Of course an overwhelming percentage of negative results does say something

But the only way to positively prove something is with a positive result - which demonstrates that there is an audible difference. Surprisingly though - all those people who can hear “night and day” differences never seem to want to take the chance to stick it to the objectivists and demonstrate that in a scientifically valid way.

Now, to be fair we have examples which demonstrated audibility.
A few, but we did, even after lots of scrutiny. Sadly, instead of getting some interest those tend to have 5-10 replies, 2 pages tops unless the person conducting them is of another kind of interest.

 

[pma]

One more comparison, Topping D10s with stock opamp LME49720, vs. replacement part OPA2134. Measurement of THD vs. output voltage at 10kHz. Please note that distortion with OPA2134 accelerates above 0.2V. There is no reason to change the stock opamp. We can also see the well known ESS hump, in both plots.

Note: 45kHz measuring BW.

 

[KL....]

With all due respect Amir, no Op-Amp can improve mediocre amplifier.

TI NE5532PTHD + N at 1 kHz (typ) 0.002%
https://www.ti.com/product/NE5532?u...MIuonBtuGajAMVvEdHAR0cihacEAAYASAAEgKB8PD_BwE
994Enh-Ticha Dual Matched Discrete Operational Amplifier
Distortion+Noise at 1 kHz 0.0003%
https://www.sonicimagerylabs.com/pr...e_HD_OpAmp/994Enh_DiscreteOpAmp_Datasheet.pdf

I tried many Class D amps with and without Op-Amps. Ended up with 8 Purifi 1ET9040BA and 8 Hypex NCOREx NCx500 amplifiers all with 994Enh-Ticha and can not peel my ears from the systems.

Regards,
Boris

Slew Rate Calculator

This calculator computes the minimum slew rate necessary to output a certain voltage at a certain frequency, calculates the maximum output frequency an op amp can deal with at a given voltage, and calculates the maximum voltage that an op amp can output at a certain frequency.

www.learningaboutelectronics.com

Because slew rate is a measure of input overload, its not in regular operation, you don't want to be anywhere near it. The rule of thumb is to calculate the slew rate required (for 15v rms and 20khz is 1.9v/us) and multiply by 5, so an opamp that has a slew rate of 10v/us can be used for any audio application without slewing.
The TI data sheet has the NE5534 SR as 13v/us, more than enough.

Most opamps slew rate is determined by the compensation capacitor, if this is an external cap the slew rate will change with the capacitance

Thank you, this is intrigueing, isn't it?.... objective measurement and (relevant) impressions....
The 994Enh-Ticha Dual Matched Discrete Opamp (Distortion+Noise at 1 kHz 0.0003%) measures better than the TI NE5532P THD+N at 1 kHz (typ) 0.002%, which implys that it is higher performing, but the Douk A5 measures a little worse with the 994Enh-Ticha, doesn't it? (Thank you @amirm for your efforts, very much appreciated :=)).

Perhaps the 994Enh-Ticha opamps higher performance (and the feeding circuit that it is in) is swamping the Douk A5 class-D output circuit (too fast/swamping) causing compatiblety/synchronousity issues (to timing/overlaying, filtering, PFFB application, etc) with the Douk A5 classD circuit/application. If yes, applying the Sherlock Holmes principle, perhaps a good alternative opamp, to the TI NE5532P, is an opamp that is a little lower in performance/speed of delivery (but still haveing equal/sufficiently close Distortion/Noise performance), for the circuit that it is in, when feeding the Douk A5 classD amplifycation circuit, couldn't it?. Further if yes, is there such an opamp that is readyly available and compatible, if yes which opamps could be applyed? @amirm, is this plausable/reasonable and if yes, measurement would provide an objective conclusion, wouldn't it?

If the above reasoning is reasonable/plausable (and even correct, in this instance with the Douk A5) then this could/would explain the (relevant) impressions, with @boristau, when the 994Enh-Ticha opamp is used with the Purifi 1ET9040BA/Hypex NCOREx NCx500 amplifyers, in that the 994Enh-Ticha is not too fast/swamping/even slower (not causing compatiblety/synchronousity issues, to timing/overlaying, filtering, FB application, etc), for the Purifi 1ET9040BA/Hypex NCOREx NCx500 classD circuits/applications. If yes, this would imply that it is compatible (perhaps even slower), for the Purifi/Hypex, and the (relevant) impressions are indicating beneficial, in this instance, but at some point (relevant) impressions would need to become objective and provide a repeatable conclusion, wouldn't they?

 

[pma]

Regarding Slew Rate and TIM/SID distortion, call it as you like. It starts increase distortion when the output dv/dt is about 1/5 (or more) of the rated opamp slew rate. Below the test with bandwidth limited 5kHz square signal and LME49720 vs. LM1458 opamps. LM1458 has rated slew rate of 0.5V/us. The test signal has dv/dt about 0.29V/us. Fast sampling (however low bit resolution) is used to demonstrate signal distortion in both time and frequency domain. Though the plots with LME49720 are what they should be, with LM1458 we can see signal corruption in both time and frequency domain, though the signal dv/dt is below the slew rate limit, but the rising and falling edges of the signal are affected with the LM1458. It reflects in frequency domain as well. This is also disclosed by DIM (TIM) test or THD at higher frequencies. Thumbnails attached, click on them.

 

[pma]

Perhaps the 994Enh-Ticha opamps higher performance

I have checked their datasheet

https://www.sonicimagerylabs.com/products/product_images_docs/994Enh_Discrete_HD_OpAmp/994Enh_DiscreteOpAmp_Datasheet.pdf

and it seems that the 994Enh-Ticha has higher distortion than LME49720 measured in the D10s. GBW is not higher, slew rate is not higher than that of LME49720. Noise - I would need to test it. So, my question is, why to use these discrete “opamps”? They are big, expensive and implementation with sockets is highly questionable. Just a potential trouble. I am with @amirm in this case. And the datasheets are not strictly engineering datasheets, but rather advertising to attract audiophiles.

 

[Old_School_Brad]

Regarding Slew Rate and TIM/SID distortion, call it as you like. It starts increase distortion when the output dv/dt is about 1/5 (or more) of the rated opamp slew rate. Below the test with bandwidth limited 5kHz square signal and LME49720 vs. LM1458 opamps. LM1458 has rated slew rate of 0.5V/us. The test signal has dv/dt about 0.29V/us. Fast sampling (however low bit resolution) is used to demonstrate signal distortion in both time and frequency domain. Though the plots with LME49720 are what they should be, with LM1458 we can see signal corruption in both time and frequency domain, though the signal dv/dt is below the slew rate limit, but the rising and falling edges of the signal are affected with the LM1458. It reflects in frequency domain as well. This is also disclosed by DIM (TIM) test or THD at higher frequencies. Thumbnails attached, click on them.

View attachment 438129 View attachment 438130

Thank you, Pavel. I appreciate the information.

 

[HaveMeterWillTravel]

There are certain more demanding applications where discrete components can be objectively superior such as higher voltage/current/power/frequency/etc.

But as a gain stage or filter in an audio amplifier with a properly selected and implemented op-amp?
I highly doubt it.

Nice VU meters or milled and polished aluminum knobs would have a higher chance of improving the 'sound'.

I have checked their datasheet
. And the datasheets are not strictly engineering datasheets, but rather advertising to attract audiophiles.

It seems similar in nature to TI's datasheets for their "audio" operational amplifiers which also have some 'marketing fluff' in them
I think the significant difference is the lack of proper CAE/CAD models such as PSPICE or the like.

I noticed they are using a feedback compensating capacitor for the pulse measurement circuit.
Decompensated opamps have their place, I just fail to see that place being an audio frequency opamp with only moderate gain.

 

[TNT]

Amir clarified his statement later in post 22.

Does Op-amp Rolling Work?

There's nothing "state of the art" about the Douk A5. Exactly what do you think plugging an alternative opamp into a cheap class D amplifier with ordinary performance and then running a few tests proves about either opamp specifically? Nothing to see here. It's the rant against Class D amps...

www.audiosciencereview.com

I don't saw how.

//

 

[TikBLang]

BTW- IMHO, I can order customized Converse sneakers. Why don't the manufacturers of this so-called TPA3255 Class D amp put a choice on the op-amp before placing order? For example - customize it with: 1. "meh" chip, 2. good chip, 3. better chip, 4. best chip, and 5—you can't beat this cheap I meant chip. . Dell e-commerce site started this way for selling home PCs, I'm wondering why Aiyima and Fosi Audio (and the latecomer Douk) can't do it? Why do I need to DIY it myself? If I want a certain signature of music where lots of reviews and recommendations are already done, why can't I pre-ordered it with the chip I think will work to my taste and just try them into my speakers?

That way I don't potentially destroy (or scratch it up) enclosures and the main board and most importantly. Also, I would like to save my very-very precious time!

 

[AaronJ]

I don’t understand why they wouldn’t just design the amp around the exotic chip in the first place. If the sound is so much better why purposefully design a worse sounding product?

 

[amirm]

TW- IMHO, I can order customized Converse sneakers. Why don't the manufacturers of this so-called TPA3255 Class D amp put a choice on the op-amp before placing order? For example - customize it with: 1. "meh" chip, 2. good chip, 3. better chip, 4. best chip, and 5—you can't beat this cheap I meant chip

They are not making them to order. The ones that do, companies making Hypex/Purifi amps, do offer alternatives at the time of ordering

 

[milosz]

He posts some example with audible differences. I suspect these are also measurable. Danny gets some things wrong but also he gets some things right.

 

[Buckeye Amps]

Please don't give clicks to that shill