Battery powered DAC


Has anybody tried this new battery powered DAC?

Ack! DAC

It seems to be very promising...
psychicanimal
This is Dusty's opinion taken from the Channel Islands forum in AudioCircle:

"Upsampler... i doubt it for the following reasons:
Although we could probably sell alot of them.. i haven't heard one that makes an across-the-board sonic improvement. The ones that do, usually have something else going on... jitter reduction, interpolation and higher bit rates (word lengths). The CS8420 is an easy way to do it but introduces alot of trade-offs. There is also rumor of the 8420 being discontinued and maybe the whole Crystal semi division of Cirrus Logic."
Here's the scoop IMHO....this ack dAck! is a great little DAC. I've had the latest version from the second production batch for about 6 days now. It was pretty obvious after the first day of use that is was a special piece. It's extremely detailed, wonderfully dynamic and is capable of that musical magic that makes you want to listen for hours. It's also the most non-fatiguing digital sound I've ever heard (although I can't say I've heard them all by any stretch). For $400 I can only think it's an extreme bargin. It also seems less dependant on needing a great transport. My Creek CD43 CDP works great. I also have a Muse Model 2 that I'm comparing it to and it's not even close.

I too wondered if the non-oversampling approach could yield great sound compared to all the newer upsampling/oversampling products out there. I am now a believer that this approach essentially gets rid of a lot of the digital artifacts I've come to expect from digital. You don't realize how much digital haze you have in a normal CDP until you hear this unit and it's missing. The background noise floor seems extremely black which allows you to hear a ton of detail.

The battery approach is somewhat controversial. Some users won't like to have to worry about it. But it's a piece of the design that allows it to sing as beautifully as it does. No AC noise, no over-sampling artifacts, etc.
As Chris will tell you, with good battery hygiene, the batteries will last up to two years. His recommendation is not to run it longer than 4 or 5 hours w/o a recharge cycle (which takes only 15 to 20 minutes). By not running down the battery as much and preventing "deep" charges, the batteries just last longer. I spin vinyl during the charge cycles!

No I haven't heard the CI or Nixon stuff. It's probably pretty good stuff. All I can say is I'm gonna buy this unit w/o a doubt or hesitation. I was skeptical it would be such a great improvement to my system, but the proof is in the listening. I had the advantage of having a few different IC's and digital cables to play with and found some that really made it shine. Hopefully the product is successful because at this price it deserves all the accolades I can come up with.
Hi folks,

Thanks, Tom, for your perspective as it is helpful for people who haven't had a chance to hear the dAck! yet. Viggen, we should be able to get your demo unit out to you shortly. And don't worry, it'll be brand new. I thought I'd clarify a few things for you guys regarding the battery operation because you guys seem to have some questions about this topics.

The 4 hour limit is RECOMMENDED, a cautionary and conservative estimate that is palatable to a wide range of listening styles. This does not mean that you will destroy the batteries by playing it 6 hours between sessions. Or 8 hours. In the 6 hour case, it will give you instead of 800 charges, perhaps 600 or 700 charges. The 4 hours is calculated based on a 30-35% discharge schedule for the main supply cell. You can take it down to 60% and still get quite a lot of charges out of it. It also depends on whether or not you actually play music through it, and what type of music. Some music is more power-hungry than others.

All rechargeable batteries have a slightly diminished charge after every cycle, even Li-Ion, which are designed for multiple cycling - that is chemistry and the laws of physics. Whether or not you will notice this depends on your habits. If you use the unit 10 hours a day, you will get very much diminished battery performance very rapidly. But then again they're pretty cheap to replace. And you get a wonderfully black background that is hard to imagine without hearing it.

Regarding up/oversampling: You cannot make a blanket statement saying which one is better. Up/oversampling is theoretically better if you consider only sampling theory. However, when dealing with very large data transfer rates, signal integrity becomes extremely important - and I'm not only talking about getting that data through your S/PDIF or I2S bus. Every aspect of the digital system becomes extraordinarily sensitive to minor variations in transmission lines, emi/rfi, and piezoelectric effects. By moving to non-oversampling, you can decrease the signal rate by 10-15x in extreme cases. Jitter sensitivity declines, and better yet, you can spend that extra money saved on a less expensive transport and buy more music.

In a related sense, throwing bits at the problem is also superfluous if you look at it from a realistic point of view. In theory it's wonderful - 120dB noise floor! It is a very engineering-type standpoint, but in the realm of esoteric hi-fi, few companies can afford the sort of R&D to properly optimize for these sorts of specs in the real world. Not only does it increase data rate, how many of those noise specs do you really trust? More companies than you would expect simply quote the S/N specs from the digital chips themselves without actually measuring real-world performance. Vinyl has an awful noise floor, yet the concensus is that it has greater apparent dynamics and is able to convey the musical message better than CD.

Apart from the difficulty with jitter and signal integrity, the single most important advance in the non-oversampling approach is complete circumvention of digital filtering in the reproduction. By avoiding digital filtering in the final output stage, one gains enhanced musicality, something quite hard to describe using the typical flowery language that audiophiles like to use. It takes longer-term listening to really begin to appreciate this, but some can spot it within a couple hours of listening. This is what most people buy the very expensive Audio Note and 47Lab for, and is something that is readily available in the dAck! and also the Nixon units.

In a nutshell, it can be done exceedingly well both ways. Compare Accuphase to Zanden, for example. Both are executed beautifully, both have remarkably different approaches, and both are top-notch performers. For the more down-to-earth market, the non-oversampling approach can be done much cheaper with quite stellar results.

Best,

Chris Own
Ack!Industries
Hey Chris--

The battery thing is a major drawback in the convenience department as far as I'm concerned.

Couldn't you just hook the dAck up to one of those nice dry cell batteries that serious car audio guys use for amp power? No fumes,no acid on the living room carpet, charge it once a month (or less) off the battery charger you already have in the garage. Designed as a deep cycle, so even full discharge wouldn't hurt it, stable, economical (well, $120 or so)- you could hide it in a closet and run a power lead to it.

Would there be any improvement in dynamics? If the thing sounds good with a tiny Li-ion battery pack that is rated 1.3ah, wouldn't a battery with 660 cold cranking amps basically be a super-stiff power supply, or is the little battery pack already plenty stiff?

No, I'm not kidding.
Hi Mike,

Just to clarify a little, the dAck! uses exactly what you're talking about - sealed lead acid - sorry if I was not clear in my previous post. Part of the design intent was to make something small, reasonably lightweight, inexpensive, and somewhat portable. I designed the thing with vinylphiles in mind with the knowledge that they're quite used to interactivity with their systems. Hence the small batteries - they are the largest that will fit inside the enclosure.

I could have easily spec'ed out large batteries, but like you probably know, engineering design is about compromise. It would quadruple the weight, move batteries outside the enclosure, and considerably increase the cost of the unit: extra enclosure requirements, need for durable and attractive wiring, and don't forget - overcurrent protection. This would give you a charging cyle of 24 hours to a couple days, depending on the size of the batteries.

This isn't an amp circuit or anything (it draws 100mA on average), so you're not going to get some night and day improvement by going to 42Ah. It's a bigger jump going from regulated AC-DC PSU to power cells. But yes, it does sound better (minorly) with larger cells.

Don't worry - I have some alternatives up my sleeve for you guys who just don't dig the battery thing. The system is designed modularly and new developments can be added to the existing system quite easily. What does this mean? Well you can probably figure it out from the above discussion :).

Thanks for the feedback.

-Chris