Battery powered DAC


Has anybody tried this new battery powered DAC?

Ack! DAC

It seems to be very promising...
psychicanimal
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
i have had private correspondences w/chris - wery responsive. he told me he could provide bigger batteries w/an enlarged case for ~$100 more, that would hold a charge a lot longer. he also said he could configure it to easily hook up to a lab-grade dc power supply, of which there are a myriad awailable on ebay for pennies on the dollar. this is what i would likely do, as i cannot realistically see myself *ever* being willing to deal w/a battery power supply. i presently use a ~$1200 hewlett packard 0-20vdc, 1-4a power supply to drive my turntable's origin-live dc motor kit. i picked it up for ~$100, & it's a noticable improvement over the stock o-l supply... chris sez he cannot say for sure how a typical lab p/s would compare w/the battery supply. i think he needs to try one & see - enquiring minds wanna know! are ya listening, chris? :>)

i may have to try an ack!, to see how it compares to my self-modded art di/o. but, to be honest, i don't really have any overwhelming urge, since the di/o has aquitted itself so well against the likes of resolution audio & electrocompaniet cd players. but, the ack! certainly *looks* cool! :>)

doug s.