SMSL D1 - ROHM DAC for everyone

[Roland68]

Its marked A08QQAIx
View attachment 495945

This is just a switch to turn off the signal.

 

[KSJ]

Changed buffer opamp in d1 to opa1612 and I can confirm that it has made substantial difference in sound quality. I was not expecting this.
Wondering why SMSL didn't use opa1612/1656. Maybe because this is a low price category product.

I’m glad someone else tried swapping the OP amps and got results similar to mine. Earlier I mentioned that replacing the stock single‑ended, unlabeled OP with an OPA2134 worked out really well. one month Later I experimented with changing the two IV‑stage, unlabeled OPs to MUSES OPs — the sound signature shifted quite a bit, but honestly I didn’t like it. I quickly reverted to the original setup, and the sound went back to how it was before the mod. Of course, this could all just be placebo since I didn’t run any measurements, so take it with a grain of salt.

Nevertheless, I believe SMSL must have had solid technical reasons for replacing the unlabeled stock OP amp with an OPA1612, developing the D200, and positioning it as a high‑priced model. At the very least, it’s reasonable to assume they conducted proper measurements and validation. Haha.

 

[Roland68]

I’m glad someone else tried swapping the OP amps and got results similar to mine. Earlier I mentioned that replacing the stock single‑ended, unlabeled OP with an OPA2134 worked out really well. one month Later I experimented with changing the two IV‑stage, unlabeled OPs to MUSES OPs — the sound signature shifted quite a bit, but honestly I didn’t like it. I quickly reverted to the original setup, and the sound went back to how it was before the mod. Of course, this could all just be placebo since I didn’t run any measurements, so take it with a grain of salt.

Nevertheless, I believe SMSL must have had solid technical reasons for replacing the unlabeled stock OP amp with an OPA1612, developing the D200, and positioning it as a high‑priced model. At the very least, it’s reasonable to assume they conducted proper measurements and validation. Haha.

As long as people don't use genuine blind tests with identical original devices and/or meaningful measurements to verify modifications, they're deceiving themselves in 99% of cases and wasting a lot of time on nonsense.
That's precisely why I started working with a second, identical device without any modifications for comparison 25 years ago. It's much cheaper than wasting so much time.

Disguised components, including op-amps, primarily serve to conceal the fact that they've found a well-functioning and inexpensive op-amp, sometimes not even from the audio sector, thus securing this competitive advantage. Standard NE5532 op-amps were never disguised in the past by SMSL, Topping, or any other manufacturer.
The D200 also features two unidentified op-amps in the I/V stage directly after the DAC chip, in addition to the six OPA1612 op-amps.

SMSL typically uses the circuit diagrams and evaluation boards of the chip manufacturers as templates for its devices and modifies them to achieve good measured values, as can be clearly seen in the D1 and D300. Unlike other manufacturers, SMSL is not very innovative in its circuitry and usually limits itself to specific components with which it has experience.

The D200 is quite different. This device appears to have been developed by an external designer, as it is built completely differently than what is typical for SMSL, with different components and circuit solutions, and is significantly more complex in many areas.
For example, it features a true analog balanced preamplifier function with one NJU72315 per channel for volume control. This makes the D200 a DAC with an analog preamplifier section after the DAC chip. It's a shame SMSL missed the opportunity to add analog inputs.
The D200 also contains two unidentified op-amps in the I/V conversion stage. Since there are no coupling capacitors, the subsequent OPA1612s are presumably part of a DC coupling circuit.
The use of a toroidal transformer for the power supply is also unusual these days. The elaborate generation of numerous dedicated voltages for the various sections is also noteworthy.
The digital section appears to be divided into several areas, and a total of five crystals are used.

 

[kazuviking]

Disguised components, including op-amps, primarily serve to conceal the fact that they've found a well-functioning and inexpensive op-amp, sometimes not even from the audio sector,

If i had to guess its either locally manufactured or some cheap JRC branded opamp.

The OPA1612 became the de-facto standard for dacs as its one of the best performing opamp without external components. Yes the NE5532 can do -140dB distortion but it requires careful frequency compensation and input low pass filtering.

 

[kazuviking]

When i get my new multimeter im gonna reverse engineer the output stage as it looks like the bog standard TI recommended design. If thats the case them i'm gonna have to make a separate buffered LPF filter for the balanced out mod.

 

[Roland68]

When i get my new multimeter im gonna reverse engineer the output stage as it looks like the bog standard TI recommended design. If thats the case them i'm gonna have to make a separate buffered LPF filter for the balanced out mod.

Take a look at page 9/17 in the BD34302EKV Evaluation Board Users guide; Rohm seems to be suggesting exactly that there, as a kind of high-end version. It's a continuation of the circuit with the two I/V op-amps on page 8/17.

 

[kazuviking]

Take a look at page 9/17 in the BD34302EKV Evaluation Board Users guide

The schematic is so poorly drawn that its impressive. From the eval board the second half of the NE5532 is doing absolutely nothing.
This just showed that i will have to build the same buffer for the negative output or make my own buffer tapped after the LPF.

 

[Evgenliman]

 

[Evgenliman]

They finally fixed my DAC. They replaced the op amp.
But they couldn't replace the "A08QQAIx" chip.

 

[KSJ]

They finally fixed my DAC. They replaced the op amp.
But they couldn't replace the "A08QQAIx" chip.

it seems the SMAL D1 originally used the NE5532. Replacing it with the OPA1612 is clearly an upgrade, as the specifications are superior and may enhance certain aspects of the sound. Thanks a lot for the information!

 

[conuss]

it seems the SMAL D1 originally used the NE5532. Replacing it with the OPA1612 is clearly an upgrade, as the specifications are superior and may enhance certain aspects of the sound. Thanks a lot for the information!

And where does it come from about such a replacement?..

 

[RandomEar]

Changed buffer opamp in d1 to opa1612 and I can confirm that it has made substantial difference in sound quality. I was not expecting this.
Wondering why SMSL didn't use opa1612/1656. Maybe because this is a low price category product.

Your changes are extremely unlikely to have made any audible difference. They also likely made the DAC perform and measure objectively worse than with the original op amps. See [1] or [2] for some additional info on this topic.

If you tested this by sighted testing like listening, then switching op amps and then listening again, you can't reliably judge the two configurations. Remember that echoic memory is only a couple of seconds long, but it takes minutes to switch the chips. In addition to numerous additional pitfalls, sighted testing is also strongly affected by bias - even when you are aware of the bias existing.

 

[KSJ]

Your changes are extremely unlikely to have made any audible difference. They also likely made the DAC perform and measure objectively worse than with the original op amps. See [1] or [2] for some additional info on this topic.

If you tested this by sighted testing like listening, then switching op amps and then listening again, you can't reliably judge the two configurations. Remember that echoic memory is only a couple of seconds long, but it takes minutes to switch the chips. In addition to numerous additional pitfalls, sighted testing is also strongly affected by bias - even when you are aware of the bias existing.

But from the page[2] you provided, replacing the NE5532(-124dB+0.0032%) with OPA2134(-137dB+0.0028%) or OPA1612(-138dB+0.0028%) in the LPF slot resulted in positive improvements.doesn’t that prove there is evidence of measurable improvement?

 

[RandomEar]

But from the page[2] you provided, replacing the NE5532(-124dB+0.0032%) with OPA2134(-137dB+0.0028%) or OPA1612(-138dB+0.0028%) in the LPF slot resulted in positive improvements.doesn’t that prove there is evidence of measurable improvement?

I didn't say improvements would be impossible, but as you can see from the large number of op amp combinations performing worse or at best equal in that simple test circuit, it's unlikely. And in a more complex circuit in a real DAC, without understanding how it works and simulating or at least testing the results of a swap, you are simply much more likely to make it worse than to improve it.

 

[Roland68]

But from the page[2] you provided, replacing the NE5532(-124dB+0.0032%) with OPA2134(-137dB+0.0028%) or OPA1612(-138dB+0.0028%) in the LPF slot resulted in positive improvements.doesn’t that prove there is evidence of measurable improvement?

It proves absolutely nothing.
These figures come from the datasheets assuming optimal op-amp configurations. If these aren't taken into account, these values can plummet.

A simple example: look at various Topping devices like amplifiers, headphone amplifiers, and DACs, where Topping also uses NE5532 and OPA1612 op-amps. Often, other manufacturers don't even come close to the measured performance of Topping devices using the NE5532 when using the OPA1612.
What does that tell you? At least the op-amp alone doesn't seem to be the deciding factor.

That's also one of the reasons why op-amp rolling is so pointless as long as the rest of the circuit isn't considered and optimized.

Furthermore, based on over 30 years of tuning and development experience, I can tell you that you'll quickly get lost in such projects and have a good chance of making the modified device worse, even if you perceive an improvement.
Without a second, unmodified device for regular monitoring, most of your time will likely be wasted, and that's much more expensive than a second monitoring device.

 

[sabih]

Changed both I/V opamps to opa1612.

Now device sounds like a 500 dollar DAC. I know that's a bold statement but it's true in my case.

Opa1612 are not just opamps these are revolution that will completely change the audio industry.

Thanks to chatgpt for properly analyzing the circuit and giving proper guidance.

Now all three opamps in my d1 are opa1612 and DAC is working perfectly fine.

 

[VientoB]

Changed both I/V opamps to opa1612.

Now device sounds like a 500 dollar DAC. I know that's a bold statement but it's true in my case.

Opa1612 are not just opamps these are revolution that will completely change the audio industry.

Thanks to chatgpt for properly analyzing the circuit and giving proper guidance.

Now all three opamps in my d1 are opa1612 and DAC is working perfectly fine.

 

[Svend P]

Now device sounds like a 500 dollar DAC. I know that's a bold statement but it's true in my case.

Since all properly designed DACs sound the same, and changing op-amps does nothing, you could even claim it sounds like a 5000$ DAC and be right.

 

[Roland68]

Changed both I/V opamps to opa1612.

Now device sounds like a 500 dollar DAC. I know that's a bold statement but it's true in my case.

Opa1612 are not just opamps these are revolution that will completely change the audio industry.

Thanks to chatgpt for properly analyzing the circuit and giving proper guidance.

Now all three opamps in my d1 are opa1612 and DAC is working perfectly fine.

We conducted several blind tests with the SU-1, including one with the DO400, which uses nine OPA1612 tubes in its output stage.
Even our most experienced testers couldn't achieve results other than 6:4, 5:5, and 4:6.
Shouldn't the DO400 have been easily identifiable?
By the way, that's a €500 DAC.

 

[JSmith]

Opa1612 are not just opamps these are revolution that will completely change the audio industry.

JSmith