Does Op-amp Rolling Work?

[Buckeye Amps]

https://audioxpress.com/news/akm-pu...the-dac-with-new-ak491x-premium-audio-op-amps

AKM op amps AK4911 and AK4912 are here for rolling.

Thanks, I'll pass

According to AKM, the AK491x devices are intended to preserve transparency, spatial openness, and tonal weight rather than simply chase numbers on a datasheet.

 

[voodooless]

Thanks, I'll pass

And yet, they do chase numbers:

In the announcement, AKM says the AK491x series delivers a noise density of 0.96nV/√Hz and THD+N of −150dB at 1kHz, with ±100mA drive to support demanding DAC current-summing stages

So these things are as utterly transparent as almost any other opamp, just with even better specs than most.

 

[Buckeye Amps]

And yet, they do chase numbers:

So these things are as utterly transparent as almost any other opamp, just with even better specs than most.

Yea, I saw the actual specs. But their use of subjective drivel is a no from me. To each their own.

 

[voodooless]

Yea, I saw the actual specs. But their use of subjective drivel is a no from me. To each their own.

That’s obviously why they offer both

 

[Ruediger]

https://audioxpress.com/news/akm-pu...the-dac-with-new-ak491x-premium-audio-op-amps

AKM op amps AK4911 and AK4912 are here for rolling.

And the article gives good info too.

There is a part designed to "THD+N of −150dB at 1kHz". That is very far out for human ears.

Unless it replaces some very bad parts... the point of this device is to keep up/play with otherwise also outstanding specs of the surroundings.

 

[LTig]

And the article gives good info too.

There is a part designed to "THD+N of −150dB at 1kHz". That is very far out for human ears.

Such numbers make sense if you use many of these opamps in a chain, like in analog mixing consoles. Clearly this is (a) no longer needed as mixing, effects and mastering are all digital, and (b) this opamp is not designed as a standard opamp which won't need to drive 100 mA.

Unless it replaces some very bad parts... the point of this device is to keep up/play with otherwise also outstanding specs of the surroundings.

Yep. If the DAC chips get better and better the analog stage following it needs to do as well, otherwise the DAC is wasted.

 

[Sokel]

As a loyal AKM fanboi for at least two decades, I will already admit than any resistance from my part will be pointless

Where do I order???

 

[solderdude]

Just wasted money to create the illusion of hearing audible 'improvements' where in reality there aren't any to be had.

 

[CedarX]

AKM op amps AK4911 and AK4912 are here for rolling.

I haven’t read the product brief or other information but, are there conditions to meet in the implementation in order to get these performances? In other words, if you just by just roll an opamp without changing anything “around”, would you get… essentially the same performances?

 

[Sokel]

I haven’t read the product brief or other information but, are there conditions to meet in the implementation in order to get these performances? In other words, if you just by just roll an opamp without changing anything “around”, would you get… essentially the same performances?

That would be nice but very unlikely.
We have to wait and see the reference design.

(Edit: may we also have a REALLY nice ADC also? Please? )

 

[Billy Budapest]

https://audioxpress.com/news/akm-pu...the-dac-with-new-ak491x-premium-audio-op-amps

AKM op amps AK4911 and AK4912 are here for rolling.

We will probably start seeing these being implemented in designs by Topping, SMSL, and other manufacturers where AKM DAC chips are already in their supply chain and design process.

If the opamps are original to the design, I have nothing against them and are all for their use. But when people start “rolling” opamps with the intention to improve (or even just change) sound quality, it crosses into snake-oil territory. There might be minuscule measurable differences, but all far below the threshold of audibility. Money is better spent elsewhere where it can actually make a difference in sound quality: headphones/speakers, DSP, room treatments.

 

[PlanarSearcher]

Hi all,

Could you please help explain the high-level logic (for a beginner) in the following situation?

How do I determine whether it makes sense to replace a soldered OP275 when it is used as a low-pass filter (LPF) after an ES9018Q2 chip? For example, I am considering replacing (resoldering) the OP275 used in the LPF stage with an OPA1612. After this LPF stage, there is an OPA1622 used as the output amplifier (before the 3.5 mm headphones jack). For sound listening, I plan to use planar IEM headphones with 16 Ω impedance and 9x dB sensitivity.


Should the following factors be taken into account? If so, could you please clarify which ones matter most and which are less important:

1. The surrounding components near the OP275 in the LPF stage (resistors and capacitors)
2. Power supply lines (it is a Hi-Res Chinese player powered by a 3.7 V Li-Ion battery, followed by an MT3608 boost converter to ~13 V, and then an RT9193-3.3 LDO)
3. Overall PCB quality (4-layer board)
4. Measured noise floor at the 3.5 mm output using a 12-bit oscilloscope (for example it is bad, then there is no any sence to replace LPF=OP275)

Second question:

Is there any proven and simple measurement method to check whether there is an actual improvement after replacing the LPF=OP275 with an OPA1612?

If yes, what equipment would be needed? For example, is a 12-bit oscilloscope sufficient, or is THD+N measurement required instead? If THD+N is needed, what kind of equipment would be appropriate for measuring improvements in a LPF OU replacement scenario? For instance, would a minimal setup like an Intel-based PC with an integrated Realtek audio codec be sufficient?

PS: If it makes sense, I could also attach PCB photos, more detailed information, and, if needed, measurements from a 12-bit oscilloscope.

Many thanks in advance for your help.

 

[solderdude]

Measured noise floor at the 3.5 mm output using a 12-bit oscilloscope (for example it is bad, then there is no any sence to replace LPF=OP275)

Ignore what you see on a 12 bit scope.

I don't think there will be a measurable nor audible improvement when swapping the OP275 for 1612.

 

[MAB]

Hi all,

Could you please help explain the high-level logic (for a beginner) in the following situation?

How do I determine whether it makes sense to replace a soldered OP275 when it is used as a low-pass filter (LPF) after an ES9018Q2 chip? For example, I am considering replacing (resoldering) the OP275 used in the LPF stage with an OPA1612. After this LPF stage, there is an OPA1622 used as the output amplifier (before the 3.5 mm headphones jack). For sound listening, I plan to use planar IEM headphones with 16 Ω impedance and 9x dB sensitivity.


Should the following factors be taken into account? If so, could you please clarify which ones matter most and which are less important:

1. The surrounding components near the OP275 in the LPF stage (resistors and capacitors)
2. Power supply lines (it is a Hi-Res Chinese player powered by a 3.7 V Li-Ion battery, followed by an MT3608 boost converter to ~13 V, and then an RT9193-3.3 LDO)
3. Overall PCB quality (4-layer board)
4. Measured noise floor at the 3.5 mm output using a 12-bit oscilloscope (for example it is bad, then there is no any sence to replace LPF=OP275)

Second question:

Is there any proven and simple measurement method to check whether there is an actual improvement after replacing the LPF=OP275 with an OPA1612?

If yes, what equipment would be needed? For example, is a 12-bit oscilloscope sufficient, or is THD+N measurement required instead? If THD+N is needed, what kind of equipment would be appropriate for measuring improvements in a LPF OU replacement scenario? For instance, would a minimal setup like an Intel-based PC with an integrated Realtek audio codec be sufficient?

PS: If it makes sense, I could also attach PCB photos, more detailed information, and, if needed, measurements from a 12-bit oscilloscope.

Many thanks in advance for your help.

I tested an OP275 earlier in this thread. While the results show absolutely inaudible levels of noise and distortion in the non-inverting application I measured, they do give an indication as to measurability with a 12-bit device.

A 12-bit scope is orders of magnitude too coarse to measure the difference between an OP275 and another OpAmp like a NE5532.
The differences are not audible, even if there is a benefit.

Regarding the benefit, it depends on the application and the surrounding elements, like the feedback and the load.

Modern Op-Amp Distortion Tests: Part 1 - BJT-Input Devices

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audioxpress.com

https://www.analog.com/media/en/technical-documentation/application-notes/AN-356.pdf

It takes some time to understand the many tradeoffs. Think of getting a degree in engineering, and having some years of experience actually designing and testing devices. And most people lack the fine skills and equipment to properly de-solder and replace.

If I had a DAC with an audible issue, I would trade it for a DAC with inaudible noise and distortion rather then try to re-engineer a LP-filter. Also, swapping OpAmps isn't re-engineering. If the designer can't apply a simple low-pass filter properly, then the entire circuit is suspect. Filters are foundational circuit elements that shouldn't be mis-applied. Is the device you have a messed-up design?

 

[Mnyb]

https://audioxpress.com/news/akm-pu...the-dac-with-new-ak491x-premium-audio-op-amps

AKM op amps AK4911 and AK4912 are here for rolling.

Or for careful implementation in the right use case by a competent designer

 

[Mnyb]

I haven’t read the product brief or other information but, are there conditions to meet in the implementation in order to get these performances? In other words, if you just by just roll an opamp without changing anything “around”, would you get… essentially the same performances?

That’s essentially not how to do it you must know the circuit and basically be able to design it from ground up before attempting any component exchange , implementation is everything you must know what you’re doing.

The OP rolling paradox if you know how it’s done you don’t do it

 

[LTig]

That’s essentially not how to do it you must know the circuit and basically be able to design it from ground up before attempting any component exchange , implementation is everything you must know what you’re doing.

The OP rolling paradox if you know how it’s done you don’t do it

Even looking at the high cost of the equipment to measure the result of the opamp rolling, it's cheaper to buy a better device in the first place.

 

[Mnyb]

Even looking at the high cost of the equipment to measure the result of the opamp rolling, it's cheaper to buy a better device in the first place.

Yea I totally forgot about that one you must verify the results aka measurements . Folks who design circuits have this equipment even DIY enthusiasts . Otherwise it’s just not a good idea.

 

[PlanarSearcher]

Is the device you have a messed-up design?

In my humble opinion (although I only have an engineering degree in Computer Science — logic-level design rather than electronics), probably yes.

I am attaching photos, including annotated PCB images with labeled key components. The device is a Hires (at least according to the product description, typical Chi-Fi) portable audio player with a fairly simple architecture:

DAC ES9018Q2 → LPF (OP275, soldered) → OU (amplifier, DIP-8, replaceable).

As far as I understand the power path (please correct me if I am mistaken):
3.7 V → 13 V boost converter → 2× LDOs (DAC and OU supply rails).

I assume the PCB has a maximum of 4 layers.

I am also attaching some very primitive measurements taken with a 12-bit oscilloscope (tip = probe, sleeve = ground), without load (16 Ω resistor disconnected), mainly in the hope of showing a general “noise picture.”
Sorry if this is not particularly relevant. I still have the device (bought it for researching) and could redo the measurements more properly if further investigation is required.

The background story: I found several modding communities (I could post a summary of the most common modifications for this device if needed; replacing the LPF-stage OP275 (typically OP1612 or muses89xx, sometimes even opa1656) is one of the key recommendations) claiming that this modification transforms the device from a ~$2x player into something comparable to a ~$5xx one.
From my skeptical perspective, such claims sound rather extraordinary, especially because they are usually based on subjective impressions and are never supported by objective measurements.

 

[solderdude]

Ignore your scope measurements it seems to be full of coupled (common mode) noise and 12 bit is not accurate enough.

Also ignore the 'claims' of improved sound quality.
Changing op-amps is NOT going to do that, regardless how many people claim to hear definite differences (ranging from subtle to night and day).
Well.... unless you put a really crappy in or one that is not suitable for the design/application in there.