Battery powered DAC

Has anybody tried this new battery powered DAC?

Ack! DAC

It seems to be very promising...
I am on the waiting list to try this thing out. I don't like the idea that it has to turned off before it exceeds 4 hrs of playing time or each succeeding play time will be shorter. I got the Nixon DAC now and is left on all the time. Chris Own claims the Ack! to be a much better design than the Nixon DAC. It certainly looks better. We shall see.
A review of this unit has been posted in the Digital Drive section of Audio Asylum:

I wonder how it compares to the Channel Islands DAC. I think Lak is contemplating on buying this unit for a second system...
Besides Vinnie's, I haven't read a out right positive review/impression of the Ack!. Then again, I doubt a simple non-oversampling DAC will be better than complexed upsampling or with more bits and khz in most people's systems. Best is to try it at home. Chris claimed everyone who did the home demo has kept the DAC. Then again, he sends out demo models...
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.


Chris Own
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.

Wow, fantastic responses! I have to hear this thing!!!
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.
are you guys honestly listening to only a cd source for 6 hours non-stop every day??? my god, where do you find the time! At first the 4 to 6 hour batter life worried my, then i actually took a log of how long i listened to cds at a time.. usually between 1 and 3 hours per day (for the most part much closer to the 1 hour). Then it was either change to vinyl or do something else. I cant fathom sitting for 6 hours + only listening to cd.. some people are just way more hardcore than me! :)

I'd say battery supplies are getting more common in hi-end gear for obvious AC noise reasons. My Merlin VSM's use the battery BAM. Most everyone whose heard it would agree the full on battery mode on the BAM is the most desirable setting available. More transparency, blacker background, etc.

Anyone else see the new Sutherland phono stage advertised in the newest Absolute Sound. For $3K you get a unit that has 16 "D" cells ringed around the circuit board. This guy makes superb gear and I'm sure he felt staying away from AC provided an improvement in sound otherwise he would of done something else.
Sedond is *special*. Ewe would have to go to his house--I mean--year round vacation ranch!!!
Thanks Chris--I'll look for the "new and improved" unit to solve the recharging issue.

ROOX: I wish I listened that much, but the fact is, the CD player is on that much for background-- cooking dinner, eating, working after dinner, reading and some real listening, too. I wouldn't want to have to suffer with built in DACs during this less critical listening. I've also got enough stuff to remember without having to make sure I put my dAck! to bed properly lest I harm its delicate batteries.

I'd be interested in a unit with AC power that didn't have to be put to bed every night, and maybe a switch for critical listening to disconnect the AC and run on battery power only.
colin, the stereo chez-sedon typically gets turned on at ~7 am, & doesn't get turned off 'til midnite, later on weekends. even if fm or winyl is playing, everything's always on, & i wouldn't wanna have to be futzing w/whether or not a battery needs charging. but, fact is, the cd *is* on a lot, the wife typically loads 5 discs into the changer & hits "shuffle", and has background music on all day.

i'm not the only one in the house that enjoys the rig - even the kids, 8 & almost 12, use it. fortunately, they are too short to reach the turntable! ;~)

doug s.
Sedond: it's great your family is always involved. At my house, we are used to listening 4-8 hours a day, 12-14 hours on weekends. I know how it is :). I usually have vinyl playing 7 out of 8 hours, but the dAck! has started taking over so it is now CD's on 50%-60% of the time. I used to listen to CD much less (before = NAIM CD5 + Hi-Cap). Obviously, the battery thing doesn't bug me. In practice, running the dAck! for 3 or 4 hours, it charges within 20 minutes - that is less than a single record side. For 5-CD changers, one could say it's almost perfect since going through the set tells you it's time to charge. Funny how usage is strong personal preference in a similar way to sound characteristic.

Against D/IO, I will let you form your opinions without giving you too many preconceptions. Only thing I will say is that I find dAck! more magical in the midrange than full-mod D/IO and while D/IO has fatter stronger bass, dAck! has faster punchier bass. As always, it is up to your tastes.

Thanks for everybody's feedback and will keep all your inputs in mind. Right now at the workbench we have more than enough to keep us busy but keep your eyes peeled. Imagine long-play add-on modules - they are on the distant horizon.

Tom - you know anybody who's heard the Sutherland? I keep seeing ads, no impressions yet. Phonostage is a reaaaal good thing to run off batts, especially for MC. Throw-away D-cells are kind of not-friendly for the environment though. A!I is a little more environment-conscious by virtue of the rechargeables :).

Nobody I know has played w/the Sutherland. I'd like to see you try your hand at a phono stage that complements the dAck! The market is waiting....
Has anybody tried the Ack! yet?

I Acked last night, but I'll spare you the details.
Does that mean it's not good?

I ate acking, thought everyone did.
I do not understand what you mean. You can do better...

I doubt if I could ave Ack'd any better (it was a damned good Ack, if there is such a thing), with both me neck and me lower back as well supported as they could be considering the circumstances.

Cut me some slack.
Re charge cycles vis-a-vis discharge time:
Am I missing something in the math, or is 6 hrs x 600 charges more than 4 hrs x 800 charges? So aren't you ahead of the game with a 6-hour discharge?

I am keen on this DAC, but just like Sedon, we run the changer for several hours at a time. Sometimes more, sometimes less than 4 hours. Sometimes we go out and forget to shut it off!

Per Sedond's 7/24 post higher capacity batteries are available for a $100 upcharge (this includes a larger case to house them).
wow , does this dac sound close to the more expesive Audio note (which has tubes output ).
Can anyone comment . And how close in% does it get as forget about the $ .. Thanks js
pianojoe, i don't have direct experience, but the comments towards the end of the following thread may be of interest to ya:

doug s.
I compared the Nixon with the similar Ack! and immediately chose the Ack!. I have since compared it favorably to the EAD DSP 7000 III and with a very nice and smooth recent Van Alstine. The Ack! runs on batteries, always a major improvement, with the added advantage of no powercord to imrove upon. I've upgraded my Ack! significantly by replacing the 3.3 mF AuraCaps with Dynamicaps, a pair of 5 mF and a .01 bypass per channel. It really opened up and the bass improved big time. I use it with an EAD T1000 with a Mapleshade/Insound Zepher dig link. Extremely open yet smooth, dead silent with wonderfull dynamics; the best I've heard.
Thanks for your contribution Piedpiper. May I ask what are the sonic differences you heard between the Ack and the Nixon? Which Nixon did you audition? And, briefly, what's your system like?
Sold my MF A324 and kept the Ack!Dac. You can search AA and read my review. It's great.
Dear Viggen, I was outa town.

I can't remember which Nixon. It was tubed and in a black plastic case. Incidently, Pierre Sprey of Mapleshade would insist that it would sound much better in a maple wood box. He's very strong about the negative qualities of plastic as a dialectric. I just was discussing the ack and the cap mod with him and he suggested that the extra 5 microfarad on each channel was most likely unnecessary, stating that the DynamiCap and particularly the bypass might have been the real poiint here. I don't remeber whether I added the second 5 or the bypass first. I'll revisit it.

I did the Nixon/ack comparison with stock units of both. The Nixon was softer, grundgier, not as clear, not as silent a background. I didn't take alot of time with it because it was pretty clear to me which I prefered. It's not suprising to me given the battery and simpler circuit of the ack.

My system consists of the above mentioned transport and dac into a modified Cary SEI LX20 giving 20 watts single ended into modified Gallo references using all Mapleshade/Insound cables and power cords; pretty tweeked and well set up, halfway into the long length of the room with the listening position fairly nearfield at the apex of a right triangle in a 13x24x9 room with roomtunes.
Another thought, gleaned from musings on the Sutherland PhD: it seems there would be great sonic and logistical advantages to having a cheap AC/DC supply that could be simply switched in for convenience listening and to keep the circuit warmed up. The sonic advantages of batteries are huge and way cheaper to boot than a properly designed AC PS. It's a no contest if you ask me. Until you've heard a battery supply you won't get it, perhaps.
For 11 months I've been listening with the Scott Nixon tube dac+ and for about 2 weeks with the Ack dAck! The transport and the amp have been the 47 Labs Shigaraki, though sometimes I stick in my Decware Zen Zen amp or my Consonance 2a3 push push. Speakers have been the single full range Jordan JX92s in a transmission line that goes to a solid 50 Hz. At first, I was taken aback by the more laid back, less round and airy midrange of the dAck! Okay, I told myself, it doesn't have a tube so doesn't sound like a tube machine. With the dAck! the background is so quiet and black it spooked me and I thought, at first, that it did not have subtle detail. Took me a week to convince myself that the dAck! could reveal the hall acoustics, but it can. During the past couple of years I've really pursued a digital front end (within my budget). I've had an Ah!Tjoeb99, Sony SACD-777es, Cary 308, conrad-johnson Premier 9 and DR-1. The Scott Nixon with his better power supply and the nice Shigaraki transport was easily better than the above. Now the dAck! It excells in speed and timing--but perhaps a less responsive amp might not reveal this; the Nixon would sound better with a tube amp--sharing the good qualities of tubes in the midrange. The dAck! can throw hard and deep punches when the music calls for this--bruising my ears with the discovery of new erogenous sensations. The massed violins of an orchestra play melodically to an amazing degree though the dAck! The string basses too. The sweep of strings with the viola and cello slide lush and whole. Percussion: wow, was that snap my solid hardwood speaker cabinets cracking? The waves of the sea of dynamics hypnotize with crests and troughs, then splash one in the face with passionate surprise. Each musician can be heard listening to the other musicians, so precise is the timing (one would swear there exists telepathic communication between masterful musicians). The Ack! dAck! is !!!