[GoldenSound]

What I found interesting is on the website that you credit for the pic of the U18 internals, there's a user reviewer who states he likes the U18 more than some of the other units you tested and he has owned with better numbers. I think reviews/comparisons like yours should be a combination of objective numbers testing and subjective listening comparisons. I think too many people base product like/dislike decisions based on numbers alone. Personally I think the U18 would be hard to beat in terms sound quality per cost. Thanks again for the time spent on this. 2 thumbs up!

I deliberately keep my objective testing and subjective thoughts separate, as I don't want people to think that I'm Amir 2.0 or something where higher number always is better.
I feel measurements are a way to explain trends or subjective findings, not a way to give a definitive better/worse ranking.

I'll sometimes put a bit of subjective description into objective testing if I think something is explicitly relevant to or could explain a subjective characteristic, but other than that I try to keep it as separate as I can.
Subjective reviews are posted either in video form on https://youtube.com/goldensound or in a separate website post.

I did post in a couple places and in discord etc about my subjective findings with the U18. It seemed to make things a little bit more crystalline/incisive but also actually hurt precision of imaging a bit.
I can totally see why people like it, but personally I felt other DDCs like a Singxer SU6 did a better job without the drawbacks.


In regards to objective 'rankings', generally I feel there are simply too many factors to consider and there is no single number that can determine the overall quality of a product. If that were the case Tube amps wouldn't exist.
This is more the case with DACs/Amps where there are countless factors to consider.

For example, the Gustard X18 outperforms the Benchmark DAC3B in THD+N/SINAD pretty comfortably. But then it falls on its face in the presence of intersample overs and that causes massive distortion, whereas the DAC3B handles them perfectly. So who is to say whether that extra few dB of SINAD is worth that drawback, or whether the differences in say Jitter performance, IMD, oversampling filters etc are more/less/equally important?

With DDCs though it's (a bit) less the case. They aren't analog devices, and so there are only really three factors to consider:

- Data integrity (so far I've not encountered a DDC that wasn't bitperfect other than the MScaler which ofc changes the data as it is an upsampling device)
- Noise
- Jitter

Level vs spectrum of both noise and jitter is a different debate and two DDCs with similar RMS jitter but very different structures can still sound different, but still, for the most part a DDC will either have overall higher or lower jitter than another.


(Also, there's of course always the issue of expectation bias. If a DDC is a big, expensive behemoth like the DI20HE, people will EXPECT and be more likely to hear a greater improvement compared to a smaller, less expensive but equally or better performing one like an SU6.
Realistically the differences with DDCs are usually very minimal, more minimal than DACs, and so expectation bias and placebo are bigger concerns.)

 

[T 1000]

For me, the U18 has made a shift in sound quality and it’s cheap.
I don't want to falsely support the Device, but the fact that there are users who like the sound more than the SU6 shows that there are other factors at play.
As far as I'm concerned, GD DI 20-HE with its regenerative power supply is attractive to me

 

[kumar402]

What a proper DDC does is the reduction of noise and jitter. It is clearly seen through measurements that U18 fails at both.

Well those numbers are down compared to other products but are still below something that can make significant audible difference

I have Pi2AES/ Digione Signature and U18 and since I started using U18, I haven’t heard any degradation in SQ. In fact I liked it a lot and ended up putting purple fuse in it and since getting it I haven’t used other DDCs I have and I have bought all of them with my own money so it’s not like I will gain something out of these claims.

 

[JaMo]

@GoldenOne :
Thanks for the measurements and the work done. It's much appreciated. I wonder if You have the possibility to add a good master clock to the DDC's. The reason I ask is that in my setup I get "a little better than average" with Gustard U18 I2s on its own internal XO's (Accusilicon AS338) but a much better result (Listerning wise) with my Mutec REF10 SE120 producing the clock pulse. Another thing I spotted on the U18 is the fact that it is equipped with a 75Ohm BNC connector input but a 50 Ohm resistor (R6). I removed and replaced the 50 Ohm resistor and soldered in a pretty exact 75 Ohm resistor. I have both 50 and 75 Ohm outputs on the REF10 BNC and I use very good true 75 Ohm BNC cable. When I was at it inside the box I also added a Black Gate Cap after the rectifier in parallell with the Nichicon. That said the difference is more than night -day on internal/external XO modes. It should be very interesting to read of Your findings if it could be tested at some point.

Measurements are good but I trust my ears and perception, emotions listening to the music and for me the U18 performs great on EXT XO setting. Way above its price. I think it is a bargain. By the way.. I also use the DI20HE I2S and the MC3+USB AES/EBU (on LPS) both (all) on EXT XO (REF10 SE120) As always the cables has to be of high quality and well paired to the signal producing gears. I have put in a lot of work and testing in this but I am not using any extreme priced cables. Just good ones. I use power filter -70 dB on the DDC's, the REF 10, -50 dB's on dacs and Preamp
Values from me: All used with EXT XO
Audio-gd DI20HE I2S - 10/10
MUTEC MC3+USB - 9,5/10
Gustard U18 I2S - 9.5/10

/Jan

 

[MartinWT]

Don't forget the overall connectivity of the U18 and how it will typically be used in real life.

I switched from a highly modified (by Coherent) Mutec MC-3+ USB after comparison with the U18. I started off comparing them in AES mode, as that is the best interface I could use with the Mutec. In AES with internal clock, the U18 sounded no better than the Mutec, but this alone seemed promising. Once I added my external AfterDark Emperor Triple Crown clock, it had already pulled ahead. Switching to I2S with a Blue Jeans HDMI cable was a complete revelation. It wasn't close, it was a staggering difference in the presentation of the music.

So, using the Mutec in its best configuration versus the U18 in its best configuration was a no-contest. In view of the Mutec's higher price and its modified form, the U18 gave me a step-change improvement at a lower price than I got back on trading the Mutec in. Measurements, in my case, were immaterial to my decision.

 

[T 1000]

@GoldenOne :
Thanks for the measurements and the work done. It's much appreciated. I wonder if You have the possibility to add a good master clock to the DDC's. The reason I ask is that in my setup I get "a little better than average" with Gustard U18 I2s on its own internal XO's (Accusilicon AS338) but a much better result (Listerning wise) with my Mutec REF10 SE120 producing the clock pulse. Another thing I spotted on the U18 is the fact that it is equipped with a 75Ohm BNC connector input but a 50 Ohm resistor (R6). I removed and replaced the 50 Ohm resistor and soldered in a pretty exact 75 Ohm resistor. I have both 50 and 75 Ohm outputs on the REF10 BNC and I use very good true 75 Ohm BNC cable. When I was at it inside the box I also added a Black Gate Cap after the rectifier in parallell with the Nichicon. That said the difference is more than night -day on internal/external XO modes. It should be very interesting to read of Your findings if it could be tested at some point.

Measurements are good but I trust my ears and perception, emotions listening to the music and for me the U18 performs great on EXT XO setting. Way above its price. I think it is a bargain. By the way.. I also use the DI20HE I2S and the MC3+USB AES/EBU (on LPS) both (all) on EXT XO (REF10 SE120) As always the cables has to be of high quality and well paired to the signal producing gears. I have put in a lot of work and testing in this but I am not using any extreme priced cables. Just good ones. I use power filter -70 dB on the DDC's, the REF 10, -50 dB's on dacs and Preamp
Values from me: All used with EXT XO
Audio-gd DI20HE I2S - 10/10
MUTEC MC3+USB - 9,5/10
Gustard U18 I2S - 9.5/10

/Jan

If I understood correctly, without intervention on U18, it is better to use BNC 50 ohms?

 

[MartinWT]

The AfterDark clock is a sinewave which makes impedance matching over short lengths irrelevant, especially with the excellent 30cm Belden 4694R double-shielded clock cable. I believe this is a factor in the U18's excellent performance, especially with the AD's -142dB @10Hz noise performance.

 

[JaMo]

Yes, It is sold as a 50 Ohm EXT XO input gear. But I have a hard time to accept a 75 Ohm connector installed on it. I don't understand why Gustard do it. It is just wrong. And for a square wave signal it can ruin the time pulse signals's shape and therefore introduce jitter. I don't hesitate to correct these things even if I know it will ruin the warranty. I have the REF 10 and it produces a very clean square wave so it wasn't much to argue about..
If You are using 50 Ohm sine wave it should be fine as it comes but with Square wave, I recommend my treat. How the K2 synthesizer works with a slightly damaged signal, I don't know but I took the safe route here. I am very pleased with how the U18 performs. A great buy. I am waiting for my second one. But that one will be untouched, it will be used with a 50 Ohm sine wave EXT XO.
/Jan

 

[GoldenSound]

Thanks for the measurements and the work done. It's much appreciated. I wonder if You have the possibility to add a good master clock to the DDC's. The reason I ask is that in my setup I get "a little better than average" with Gustard U18 I2s on its own internal XO's (Accusilicon AS338) but a much better result (Listerning wise) with my Mutec REF10 SE120 producing the clock pulse.

A 10mhz clock is something I'd definitely like to get in to test various devices with. Unfortunately I don't know anyone personally whom I could borrow from and am not in a position to be able to afford one myself. So definitely will if the opportunity arises, but I don't know when that might be.

10mhz clocks are something that's likely to vary from device to device though for a few reasons.

Firstly, a LOT of devices won't actually run from the 10mhz clock when in use. They simply adjust their own clock speed slightly to prevent long term clock drift.
And in this situation you'll either get the same jitter performance (cause you're still using your DAC/DDCs own clocks) or potentially slightly worse due to the additional processes required to make this work.

In the situation of devices like the gustard u18 though, where the k2 apparently synthesizes the new clock signal directly from the 10mhz input, then there is much larger potential for the external clock to make a difference. But also now you have additional challenges as you're using a clock that cannot be cleanly divided to 48khz/44.1khz so it'd be interesting to see how it affects performance.

10mhz clocks were intended for use particularly in professional setups where you may have dozens of DACs, ADCs, and digital processors which all need to be aligned and not drift in relation to eachother.
This is particularly important for video where you need audio to be aligned exactly with frame capture.
They weren't ever really intended to provide a jitter performance benefit. But have made their way into the high end audio market regardless. Whether this is valid or not I honestly have no idea but would be keen to try some.

Another thing I spotted on the U18 is the fact that it is equipped with a 75Ohm BNC connector input but a 50 Ohm resistor (R6). I removed and replaced the 50 Ohm resistor and soldered in a pretty exact 75 Ohm resistor. I have both 50 and 75 Ohm outputs on the REF10 BNC and I use very good true 75 Ohm BNC cable.

I'm on a train currently so can't look at the PCB, but be aware when you see '75 ohm' when referring to spdif/bnc/coax cables and connectors, that doesn't actually mean 75 ohm DC resistance. In fact a typical 75 ohm bnc cable should have close to 0 ohm DC resistance.

Characteristic impedance is given by the formula Sqrt(L/C).
For example I've got some Wave Storm BNC cables at home at the moment. The parallel (open) capacitance is 71pF and the series (shorted) inductance is 0.4uH.

So they have a characteristic impedance of 75 ohm even though just testing with a multimeter they show near 0ohm DC resistance.

It's possible that 50ohm resistor is not related to the characteristic impedance on the connection. I'd imagine (or at least very much HOPE) that they'd designed it with a proper 75ohm termination

EDIT: sorry was thinking of the spdif connection. Just realised you were talking about the 10mhz clock which would indeed be 50ohm
God I need a coffee

 

[T 1000]

I am also interested , why despite the obvious advantages of I2S, this type of connection is not generally accepted in all DACs.

 

[milkdudd]

What a proper DDC does is the reduction of noise and jitter. It is clearly seen through measurements that U18 fails at both.

Sorry if this is a dumb question but is there a chance this is where the upgraded fuses help?

 

[JaMo]

Sorry if this is a dumb question but is there a chance this is where the upgraded fuses help?

I don't think You should be afraid at all of the measurements on their own. The fuses are a balancing part equal important as the cables choices to aim for the final result.

A perfect measured gear is very seldom funny to listen to for longer periods of time. They will probably leave You with a listening fatigue. A few guys here will probably comment or argue/differ on this. Trust Your ears. If You find it good even after a time of listening.. It is good! Whatever the measurements says.

Were Your head high and decide for Yourself..

I have tried a few solid silver based fuses and they leave me too soft and too diffused sound wise. I am still on original fuses and they works fine for me.

I am using Gustard HDMI cable I2S between U18-X26pro,
The Di20HE to the R7HE Mk2 with the silver based HDMI cable. https://www.aliexpress.com/item/100...1009.64;-1;-1@salePrice;SEK;search-mainSearch

With the modded MC3+USB I use the DH Labs Silver Sonic D-110 with XLR's
/Jan

​

 

[Crypt Keeper]

Hello,
I had no Idea the connector on my U18 is 75 Ohm … I’m currently using Gustard C2 (50 Ohm BNC connectors) Clock cable to AD Double Crown Clock (50 Ohm Sine wave) and it seems to be better than the stock clock cable.

I just dbl checked Gustard C18 clock has the same 75 Ohm connectors (2 sq and 2 sine wave) . I guess b/c U 18 was made to use with C18 clock they just decided to use 75 Ohm Connectors with 50 Ohm "Chain"…

A lot of great info on this thread . Thank you all.. Much appreciated !

 

[GoldenSound]

Hello,
I had no Idea the connector on my U18 is 75 Ohm … I’m currently using Gustard C2 ( $167) Clock cable to AD Double Crown Clock (50 Ohm Sine wave) and it seems to be better than the stock clock cable.

I just dbl checked Gustard C18 clock has the same 75 Ohm connectors (2 sq and 2 sine wave) . I guess b/c U 18 was made to use with C18 clock they just decided to use 75 Ohm …

A lot of great info on this tread . Thank you all.. Much appreciated !

The connector will be 50 ohm.
Apologies. I was thinking of bnc spdif inputs which are usually 75 ohm. Not clock inputs which are usually 50 ohm. Though it'll depend on the specific device

 

[tamahome77]

@GoldenOne :
Thanks for the measurements and the work done. It's much appreciated. I wonder if You have the possibility to add a good master clock to the DDC's. The reason I ask is that in my setup I get "a little better than average" with Gustard U18 I2s on its own internal XO's (Accusilicon AS338) but a much better result (Listerning wise) with my Mutec REF10 SE120 producing the clock pulse. Another thing I spotted on the U18 is the fact that it is equipped with a 75Ohm BNC connector input but a 50 Ohm resistor (R6). I removed and replaced the 50 Ohm resistor and soldered in a pretty exact 75 Ohm resistor. I have both 50 and 75 Ohm outputs on the REF10 BNC and I use very good true 75 Ohm BNC cable. When I was at it inside the box I also added a Black Gate Cap after the rectifier in parallell with the Nichicon. That said the difference is more than night -day on internal/external XO modes. It should be very interesting to read of Your findings if it could be tested at some point.

Measurements are good but I trust my ears and perception, emotions listening to the music and for me the U18 performs great on EXT XO setting. Way above its price. I think it is a bargain. By the way.. I also use the DI20HE I2S and the MC3+USB AES/EBU (on LPS) both (all) on EXT XO (REF10 SE120) As always the cables has to be of high quality and well paired to the signal producing gears. I have put in a lot of work and testing in this but I am not using any extreme priced cables. Just good ones. I use power filter -70 dB on the DDC's, the REF 10, -50 dB's on dacs and Preamp
Values from me: All used with EXT XO
Audio-gd DI20HE I2S - 10/10
MUTEC MC3+USB - 9,5/10
Gustard U18 I2S - 9.5/10

/Jan

@JaMo Thank you for the impressions on adding an external clock to your DCCs. It's very helpful! I'm also very interested in adding an external clock in the future. I've heard a user over at CAM, who had added the Mutec SE120 to their two Mutec MC3+ USB ddc units connected in series and the sound quality improvements for that individual were massive. He mentioned it was similar to jumping from a low end dac to a high end dac. He can't stress enough of how important it is to improve one's system clock. According to your ratings, the DI20HE seems to benefit the most from the Mutec SE120? Just curious, were you using usb or coax input on your DI20HE? Can you expand a little on the night and day difference of adding the Mutec SE120 to the ddc, especially the Di20HE? Do you feel there's improvement in timing of music, clarity, imaging, air, & soundstage?