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Rolling (replacing) Op-amps in Topping D10 DAC

amirm

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#1
This is a study of whether changing op-amps in a DAC makes a measurable difference. Taking a lead form "rolling" tubes in tube products, a trend has started in replacing op-amps -- sometimes with much difficulty -- to improve performance of solid state products like DACs. A few months ago I tested the Topping D10 DAC and since it has a socketed op-amp, members asked if I could experiment with changing it to other pin-compatible parts. A couple of kind members supplied me with a good inventory of op-amps to test all the way up to esoteric discrete ones.

Here is the overall circuit diagram:

Topping D10 DAC PCB Board.jpg

You can see how the ESS DAC drives the OPA2134 op-amps that are soldered, providing current (I) to voltage (V) conversion. Their outputs in turn drive a pair of op-amps in the socketed Op-amp (circled) which are our output buffer/op-amps. That is the part we will be replacing.

EDIT: an earlier version of this review mentioned that we were changing the I/V op-amp due to misunderstanding of a statement from Topping. It is now corrected above.

The op-amps I had on hand were:


1536989665027.png


It retails for a whopping $94 each! The OPA2134 in contrast costs $4.79 in single units.

Measurements
For this testing, I thought any important difference would show up in THD+N (distortion + noise) versus frequency as this is what the data sheet for op-amps emphasizes a lot. We will see the effects of both noise and distortion in one measurement.

Here are the results:

Topping D10 DAC Opamp rolling distortion versus frequency measurement.png


This chart is hugely amplified (vertical axis) relative to what I normally show. Despite that, the differences are tiny. Assuming you want to go by that difference anyway, the best performance was achieved using the op-amp shipped with the unit, the TI OPA2134!!! In other words, the designer knows best. :)

I also looked at SINAD differences (not shown) and there was no difference to speak of there. The unit itself varied in performance by 1 dB there and that was what I observed as I changed op-amps.

Conclusions
With respect to Topping D10 DAC at least, rolling opamps is of no value at all. Fortunately nothing bad happens but nothing good either. I suggest leaving it alone as is.

I will try the same exercise with a different DAC in the future to see how consistent the results are.

-------------

As always, questions, comments, recommendations, etc. are welcome.

If you like this review, please consider donating using Patreon (https://www.patreon.com/audiosciencereview), or upgrading your membership here though PayPal (https://audiosciencereview.com/foru...eview-and-measurements.2164/page-3#post-59054).
 
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#2
Very interesting.

Would you care to make an opamp rolling review of the Objective 2 amp?
 

Sythrix

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#3
It’s interesting that they chose an area that would make little difference to be the user replaceable op-amp.

Also:
1621a (SMD part mounted to through-hole socket)
you have the 1 and 2 reversed. ;)
 

Sythrix

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#6

solderdude

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#8
Thanks, always wanted to see real measurements of such.

Why are the output buffers located further away from the output RCA's than the (rollable) I/V opamp, is that done as to make it appear the rollable opamp is the one that provides the actual output signal ?

How would a TL072 or the 4558 perform in comparison (in the DA10) ?
Maybe even the NE5532 ?

The TL071 and 4558 surely will measure much worse...
A good thing to know that at least this 'discrete' opamp performs equally well as 'normal' opamps.
At least, the tested one is very well documented.

Driving low impedance headphones demands a lot more from opamps (their limits) than driving a 10k or 100k resistive load.
I did a simple 'C'Moy' alike test a while ago.
 
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#9
Is that socketed? If so, yes.
All opamps in the O2 are socketed, though one is a comparator chip that has nothing to do with the sound. The gain stage opamp is an NJM2068, the output stage consists of two NJM4556AD in parallel.

NwAvGuy measured lots of opamps here: https://nwavguy.blogspot.com/2011/08/op-amp-measurements.html

Here are some subjective impressions of opamp rolling on SBAF, though of course it's heavily biased because the O2 is considered "crap" there: https://www.superbestaudiofriends.org/index.php?threads/o2-op-amp-rolling.2109/

I'd test the OPA1688 in the O2. It's relatively new and specifically designed for headphone amp purposes.
 
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Wombat

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#10
All opamps in the O2 are socketed, though one is a comparator chip that has nothing to do with the sound. The gain stage opamp is an NJM2068, the output stage consists of two NJM4556AD in parallel.

NwAvGuy measured lots of opamps here: https://nwavguy.blogspot.com/2011/08/op-amp-measurements.html

Here are some subjective impressions of opamp rolling on SBAF, though of course it's heavily biased because the O2 is considered "crap" there: https://www.superbestaudiofriends.org/index.php?threads/o2-op-amp-rolling.2109/

I'd test the OPA1688 in the O2. It's relatively new and specifically designed for headphone amp purposes.
I would credit NwAvGuy above SBAF subjective content. :cool:
 

derp1n

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#11
It’s interesting that they chose an area that would make little difference to be the user replaceable op-amp.
Amusingly, you could make that statement no matter what the design.
 

Thomas savage

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#12
As useful as this is all it will serve to do is convince those who believe that the measurements don’t show the whole or any part of the Audio story .

Still, I think it’s really intresting and personally find it useful so thanks amir .
 

Sythrix

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#15
Amusingly, you could make that statement no matter what the design.
If it was at least the buffer stage, as Amir was saying, I think there would be measurable results. Here they are all feeding the exact same op-amp before output. Kind of homogenizes them, being forced into the same buffer.
 
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amirm

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#16
Why are the output buffers located further away from the output RCA's than the (rollable) I/V opamp, is that done as to make it appear the rollable opamp is the one that provides the actual output signal ?
Agree it is an odd configuration. It is possible they have that layout for other products and are reusing it. Alternatively the information we have from Topping that it is the I/V stage may be wrong. I could try to reverse engineer it but it is a multi-layer board so it is not easy at all.
 

solderdude

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#17
Based on the schematic of a standard DAC output config and looking at the parts around the op-amps as well as layout I would (almost) bet my life that both the fixed op-amps are I/V converters and the roll-able component is the LPF/output stage.
I think the info supplied by Topping is suspect and makes little to no sense.
 

amirm

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#18
Based on the schematic of a standard DAC output config and looking at the parts around the op-amps as well as layout I would (almost) bet my life that both the fixed op-amps are I/V converters and the roll-able component is the LPF/output stage.
I think the info supplied by Topping is suspect and makes little to no sense.
Looks like collectively we may have misunderstood Topping's answer:

Just received reply from Topping:

"OPA1612 is better than OPA2134. Though we did not test it before but we believe OPA1612 is a better choice.

The other OPA2134 is for I/V convert. These two OP amp has great impact on performance so we don't want our users to change it."
By "other" they may mean the soldered ones and hence the one we replaced is indeed the output buffer!

I will have to open it again to test to be sure as the answer without the question asked is still a bit ambiguous @Krunok, what did you ask him exactly?
 

sonci

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#19
I thought the discret opamps would measure much much worse, maybe that opamp in the Dac is not doing anything or the 994Enh-Ticha are IC Opamps and all those components are not connected anywhere,
but yes replacing opamps is just null.. Lord forgive me for all the boards and soundcards I destroyed replacind smd components.
This may be the best review ever!
Thank you Amir,
 
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solderdude

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#20
The 994Enh-Ticha are discrete op-amps that perform just as good as other op-amps but can handle a higher voltage rail and have a higher output current capability.
The 'opamp' on the PCB may well be a voltage reference or something else entirely. The SO-8 enclosure is used for a myriad of components.
An op-amp can be made quite well with discrete parts but matching parts is essential.
On one chip this is much easier to do.
The component in the D10 is not doing much, it is just a simple low-pass filter doubling as an output buffer.

There are a lot of (also expensive) 'audiophile' discrete op-amps that indeed are performing a lot less. This is not one of them.
 
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