Question on DAC's: internal components / weight, indication of quality?

[xenithon]

Hi all. I have a question that's been sitting on my mind for a while. There are a multitude of DACs available, and it seems that some of the higher end offerings look relatively simple inside and do not weigh much (relative to others). I wanted to ask what the correlation is between the internal components (specifically power supplies / transformers), weight, and indication of the quality / sonic performance of the DAC.

For example, here is a compilation of some interal DAC photos:

DAC1 - simple, but fairly large toroidal

Aqvox - no large toroidals / transformers, is this bad?

DA100 - similar to the DAC (simple, large toroidal)

DA220 (mkI) - a bit more complex than DA100, but I don't see large toroidals/transformers...is this bad?

The same thing seems to be the case with weight - some do not weigh much such as the DAC1 (3.5lbs), some are in between such as the Aqvox (8lbs) and some weigh a lot more such as the DA220 (16lbs).

I am intrigued as to whether the presence of the large PSU's/transformers and/or the weight of the units are any indication of how good they are?

Cheers,
X

 

[StanleyB1]

Weight has no bearing on sound in a DAC. There is no physics formula I know of where sound quality and weight are in the same equation.

 

[Zorander]

I think the design of the board and choice of components is of more crucial importance than the combined weight of the package. If weight was taken as a general indication of quality, I'm sure many manufacturers would sort to things like heavy caseworks, sizeable heatsinks or even filling with leads.

 

[mrarroyo]

Put a brick inside! Sorry, I could not resist.

I concur, weight is no indication. The designer's ability and implementation including good parts choice is what matters most.

 

[jp11801]

while weight is not an indicator of quality a well implemented power supply is usually a major plus.

 

[xenithon]

Apologies if the question came across wrong (especially in terms of weight). It was indeed more about the internal power supplies / transformers etc. which seem to be lacking in some higher end DAC etc.

 

[1UP]

DACs need good:

1 - power supply - this is critical for the digital circuitry; tight regulation, low-noise and ripple - a big, heavy toroid isn't enough to guarantee either of these

2 - robust input circuitry - let's assume standard S/PDIF - you'd want to see a BNC connector for starters, ideally transformer driven; imepdance matched and terminated correctly

3 - Clock recovery - many more expensive commercial designs do it with ASRC circuitry - many less expensive designs omit the ASRC, but there are other ways to recover a clean clock

4 - Analogue output - the DAC may be current output or voltage output (more common). In the former, you'd want to see a good I/V conversion stage and in both, a serious analogue output to amplify the signal. You would expect a well-designed discrete output to be better than an opamp stage, but again, it's all in the implementation, but again, the power supply for the analogue circuitry will be a factor.

PCB layouts, grounding, bypassing on DACs are important, too.

None of these have much to do with the mass of the unit!

 

[mrarroyo]

Here is a picture of the Monarchy NM24 DAC, it weights about 27 pounds.

 

[Michgelsen]

Quote:

Originally Posted by xenithon /img/forum/go_quote.gif DA220 (mkI) - a bit more complex than DA100, but I don't see large toroidals/transformers...is this bad?

See the two large things in the back? There are your toroidal transformers.

If you don't see a transformer inside, this can mean two things:
1. The unit uses an external adapter with a transformer inside it, so you'll have a large and heavy block attached to the plug.
2. The unit uses an SMPS, which does not use a heavy iron transformer. This can again be internal or external. External will look like a block attached to the plug, but since there's no iron in it, it will be much lighter.

Audiophiles love classic (heavy) transformer-based power supplies, because they are much quieter, supposedly. SMPSs require extensive filtering, as to not pollute your electricity and other signals with high frequency noise. Shielding and filtering can cure this. Each type of power supply has their advantages and disadvantages and I think all that matters is the implementation.

So, to answer this question:
Quote:

Originally Posted by xenithon /img/forum/go_quote.gif Aqvox - no large toroidals / transformers, is this bad?

No, it doesn't have to be, but it can be.

 

[Maniac]

Circuit design is rather like cooking, good quality material is only part of the equation, skill of the designer can sometimes turn weird/bad sounding parts into fine sounding products if they are really good, more or less like two wrongs combined to make a right. But that is not always guaranteed, and of course, good parts with good design will often do magic. However, the best way is still to compare it yourself, because you may like some aspect of a DAC that others might not like and so on.

On a side note, the internal AQVOX's DAC looks remarkably like CEC's DA53... Output circuit layout, component choice, etc... I'll see if I can dig up some photos that I took of DA53 a few years back...

 

[Maniac]

Here it is, have fun.

 

[JamesL]

There has to be a transformer somewhere along the path, unless everything is running off the USB-power.

If the transformer is not encased inside the dac chassis, it most likely means it's in the form of an external adapter.

There are pros and cons for both, but I prefer having the transformer inside the case, simply because it means that theres no other bulky brick outside the case. On the other hand, an external transformer introduces less EMI.

I'm sure you've heard the phrase "correlation does not infer causation".
Well, a obviously, a DAC does not sound better because it's heavier. However, there does seem to be somewhat of a correlation. A designer will very rarely go with a more complicated design with more parts if it doesn't have any positive effect on sound quality.

 

[SleepyOne]

For me as long as the designer are not restricted by the size of box or size of component, then all is well. Ideally high quality parts too but that is a matter of economic.

I think the issue of weight/casing is important for speakers system due to external vibration.

 

[audioengr]

1UP and Maniac are quite right. A photo or weight of a DAC will tell you little about how it sounds and how good the design is.

There can easily be lots of cuts in the ground-planes of the circuit boards that disrupt the digital paths on these boards that are not visible from the top or even the bottom, and there usually is. There can also be poor power delivery to both the digital and the analog path IC's. There also can be poor selection and location of coupling and power decoupling caps. And finally, it is really easy to insert 10 or 12 op-amps in the signal path, which really adds a lot of noise and usually compression. I've been modding lots of DAC's for 7-8 years, so I've seen almost everything. I've modded the Bremen, DEQX, Benchmark, Electrocompaniet, Birdland, dAck! both versions, Northstar 192 and Extremo, Thetas, Perpetual P-3A, assemblage, Van Alstine, Audio Note and others I cannot remember. I only mod the Northstar 192 and Benchmark now and will stop these soon. Using good parts is no guarantee either. It's the board design and the parts selection that are the main indicators. Really outstanding DAC's have revolutionary designs, such as the Bremen DAC, which uses a ton of shunt regulators, all discrete analog stages and runs like a toaster. Even it has power delivery issues that cause compression in the highs.

The best indicator is to hear it in your own system. Even reviewers cannot be trusted. I have heard reviewers systems that were terrible and they have no business being a reviewer. I'm extremely picky about who I send things for reviews. Some companies avoid reviews completely, such as Audio Note UK. I cannot blame them.

Steve N.
Empirical Audio

 

[Maniac]

Oh yeah, I recalled one fact on the transformer.

Does transformer have to be HEAVY and big to be good? NO!

High quality iron alloy/steel alloy core can allow a transformer to be made smaller while retaining the same capacity or better then ones using lower quality core. Also careful attention to winding will also pack the wire in neater will also result in better performance and efficiency.

With a Toroidal transformer, you can actually see if the winding are carefully put on, if it looks like it is winded on very neatly and carefully, with very little unevenness or overlapping of wire in the same winding, then chances are that the transformer isn't too bad.

One down side with Toroidals, you can't see the iron core, as my friend at KECES had found out, there are many grades to a Toroidal transformer's core. All the way from premium to scrap, depending on how much you want to spend on it.

Premium grade core will be rolled from a continuous "tape" of the steel core material (usually silicon steel). there will be no seams anywhere other than the beginning and end of the entire core.

Slightly below is ones made with a seam in the middle of the core, basically joining up two sections of the steel tape that is used to roll the core with.

And way at the bottom of the pile, is the crap core, as when you make premium core, you can have a little bit of scrap at the beginning and ending of each spool of steel tape. Instead of sending the scrap to a recycler, it is recycled in house to make a core that is full of seams and joints. As the material was intended for recycling anyways, the price of this kind of core will be very cheap, but efficiency and performance suffers greatly.