Review : AUDINST HUD-MX1 DAC/amp - a promising newcomer (compared to Audio-gd FUN, AMB Gamma2) - Page 8

Quote:

Originally Posted by Dalamar 

I can't believe 8 pages, and comparing all these dacs, doesn't result in any RMAA posts.

Well ... RMAA tests are pretty much pointless if you want to asses the sound quality of a DAC/amp.

THD, DR, FR, Noise floor, Crosstalk cannot really tell you what you actually need to know.

Trying to quantify these into sound signature attributes is an exercise for the imagination, rather than a scientific approach.

I remember measuring once the RMAA "performance" of my cellphone ( Sony Ericsson W series) against my soundcard and my NOS DAC (Monica3). Although it didn't fare that well against the soundcard the phone did actually show better THD, flatter FR and lower noise floor and crosstalk than my NOS DAC.

Having said that, I bet that no audiophile in his right mind would prefer the cellphone to the Monica3 when listening to music.

Vinyl is another strong counter example for this RMAA thing.

Quote:

Originally Posted by MrTrotsky 

OKAY. So after reading about audiofil's experience with switching opamps with the MX1, I wanted to try it for myself. I did some research and decided to go with the AD797. I looked at the datasheets on AD's website and noticed that there was an 8-pin PDIP package of it, which was great because that is the form factor of the stock opamp and I wanted to avoid using an adapter if possible. I know audiofil used got two of the AD797BRZs and used an adapter. I sprung for the AD797ANZ (the PDIP AD797).

 

Today I got it in the mail and installed it easy as pie, and yes, it is definitely installed in the right direction, the notches are in the same place. Unfortunately, there seems to be something very wrong. The volume is now very low and muffled and there is a lot of distortion in the (very quiet) sound. In short, music comes out, but clearly there is a problem.

 

Please help! Is there really something so different between the AD797BRZ and the AD797ANZ or did I just install it wrong? Thanks so much in advance!

AD797 AN and BRZ are basically the same chip with a different package and tighter tolerances for the BRZ type.

There shouldn't be any electronic differences whatsoever.

Your post however does raise quite a few questions that I'd like to know the answers to.

Here are my opinions:

Things safe to assume are:

- you are using a faulty adapter

- either one of us is using non-genuine opamps

- differences in the electronic configuration of the DACs (different values for the caps or resistors, or missing parts). As far as I know there aren't any, since I've ordered a second Audinst and both look identical in layout and component choice.

Having a closer look at AD797 does reveal some interesting facts.

AD797 is known to oscillate if improperly matched with the circuit.

Analog Devices recommends adding a small capacitor over the feedback resistor or a resistor in series with the feedback capacitor.

All this happens in circuits with low gain values as AD797 is not unity gain stable.

If the Audinst's opamp gain would be a known factor then it would be easier to find an answer.

Since I've mentioned having a second Audinst with me there are a few interesting conclusions I've reached with this DAC/amp.

Before writing them down I must mention that I've allowed the second Audinst to burn in over a period of 2 weeks playing nothing but the XLO/Reference Burn in CD with almost no brake.

I began critical listening and making comparisons to my original unit in various configurations (re: opamps and PSU) in three different burn in stages: out of the box, at about 100-150 hours and well after the full two weeks (~350 hrs).

Also, a seemingly unimportant component of my PC has been changed since my original review - I've bought a new Enermax Pro82+ power supply.

Although it never really crossed my mind my former PSU (a rather old but still very decent Chieftec) has had an influence in my original assessments.

In short - a better computer PSU does make a noticeable improvement in sound quality, especially if you use USB power.

Here are my updated thoughts on the Audinst after 2 months of ownership:

1. It does improve with burn in, so much so that it has made a few of my original findings a bit obsolete.

2. It does improve with a better power supply but not as much as I thought. Part of the improvements must have been attributed to the burn in process and some influenced by my old computer PSU. Going from USB power to stock wallwart power does very little to the sound, if anything.

My original findings were not so favorable for USB power as I found the sound a bit fuzzy.

With my new Enermax PSU that fuzziness was never present.

The TREAD PSU does clear up the sound a bit, notably so in the upper half of the spectrum. The sound signature becomes slightly cooler and more open than USB powered.

3. Opamps do make a difference, however it is a subtle one and my top choice has changed - it's the original LME49860.

4. The sound signature of the DAC/amp fully burned in and in stock configuration is pretty much in line with my original description when using AD797BRZ.

There is definitely a relaxed and smooth character to the sound, but no coolness. I'd actually call it politeness as the Audinst does round off the edges, both in terms of dynamics and tonality.

5. What I didn't pay much attention to initially was the bass response. Out of the box up till' about 100 hours it's very well behaved, flat and unobtrusive. After some 2-300 hours on it, however, Audinst's bass is a bit more present than absolute neutrality and the sound is more rounded and "bassy". It is a pleasing coloration but it can loose that ultimate drop of control and detail at times.

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I'll update my original review in a few days.

I need some time to synthesize all my findings into one complete revision that will be my final take on Audinst HUD-MX1.

Let's not blow this argument out of proportions and stick to facts,

My point:

1. Vinyl measures badly in absolute terms but can sound extraordinary and without obvious coloration in a proper system.

If you feel differently I encourage you to experience it first and judge with your own mind after.

2. I'm an engineer by profession and I'm very much into DIY and figuring things out on my own scientifically. If you want a true scientific approach I suggest you look into what people like John Atkinson of Stereophile are doing . You'll take RMAA with a grain of salt after that, I assure you.

3. And lastly I regard RMAA tests as an oversimplified method of measuring real life sound quality. It can provide an insight into what's going on in there, but it's rather a glimpse than full disclosure.

PS: If you're trying to be sarcastic you've picked the wrong guy.

PS2: I'll politely remind you the subject of the topic is Audinst HUD-MX1 and I'll appreciate if we keep things on-topic.