[J North]

There is some question as to whether or not the dAck will match up well with the NOH. Here are the output specs from the Ack website:

Output: Gold-plated stereo single-ended outputs
Output impedance: <100 Ohms
Downstream component should have >10KOhms input impedance
Signal amplitude:  2V peak-to-peak for 1KHz 0dB signal  
Quiescent current:  5.5-8mA per channel (matched)

Furthermore, Ack suggests that a tube pre with high input sensitivity ~20KOhms+ would work best and that if a TVC was used, then an power amplifier with HUGE gain would be required.

Has anyone tried this combo?

What are your thoughts John?
Would the 6db gain swtich make a difference?
Does the 6db gain have a detrimental effect on the sonics?


Thanks!

[John Chapman]

Hello!

A local friend with an Ack!Dac on order just pointed me to the post over at the asylum - I'm guessing that was you!

First I don't think an amp with HUGE gain is needed. I see where the idea came from - the tx102's output impedance goes down as you turn the level down and so the thinking is you should run the tx102 turned way down. Not the case at all. Even at the highest settings the tx102 has a lowish output impedance - lower than almost any passive pre-amp out there. It's just that you get the bonus of the impedance drop as you turn down the level.

There is a chart that shows the output impedance with a 1K source - note your output impedance will be much lower with 100 ohms source imp. It is here:

http://www.stevens-billington.co.uk/page102.htm

This chart also lists input impedance with a lowish 10K load on the tx102. Note that it is something like 50K or higher so well above the 10K or 20K recomended by ACK.

The 100 ohms of the Ack!Dac is just fine and plenty low. This means that should you need it the +6db option it is availiable to you. 2 volts will drive most amps to clipping so you would likely be fine without it. The +6 db option does make it a bit  harder load for the source but if the source impedance is low (like the 100 ohms you mention) this is not a problem.  +6db mode does not measure quite as pristine as the normal mode but I have to admit I have a hard time telling the difference in practice.


 As recall from the other post Thorsten had been using the Ack and 102 with good success. Once the ACK!DAC unit arrives locally my friend was kind enough to offer to mate it up with the tx102 and confirm operation on this end as well.


Thansk!

John Chapman
www.bentaudio.com

[J North]

I just got further information from dAck forwarded to me:

"the output voltage is 2.0V *peak-to-peak*.  That is 0.7VRMS, which is much smaller than standard CDP's which are at 2VRMS or greater"

That sounds fairly low to me. Does it change your thoughts at all?

[John Chapman]

Hello!

That is very low - lower than most any source. It does not mean that it would not be fine but we'd need to know about your amp and you speaker sensitivity as these play a huge roll in that.

Using +6db mode would make that 1.4V rms and put it more inline with a typical cd source. Once you know the amp / speaker specs let me know and we'll run through it.


Thanks!

John

[John Chapman]

Hello!

One other test you can do if you have all the gear there is to just pluf the ACK directly into the amp. Play a passage of music that starts very quiet and slowly builds (1812 is not a good plan with this test - you might get hit by a speaker cone....). This will tell you the loudest level you'd get with 0db mode.

Since there are no other 'issues' the only thing we are looking for is if you'd get the system to play at a loud enough level.

Thansk!

John

[csown]

Hi John and other AC folks,

I'm by no means the expert on TVC's here, so I will defer to John, but when I say TVC's operate best at low settings, I mean that from a pure impedance standpoint.  Your system may do things that can compensate poor impedance matching and you may, in fact, have built your personal system to do this without you knowing it.  There is also the possibility that your system sits in a "safe" regime where you cannot hear the differences between low and high settings for various reasons (both electronic and psychoacoustical).

Also keep in mind that when saying "impedance", this term refers to a general value that actually represents only one frequency (usu. 1KHz) or perhaps a key band of frequencies, and the "true Z" of the device - and this is any device - varies across the band.

When at a low setting, the input Z of the TVC improves (i.e., gets higher = easier to drive).  At full open, the input Z is the absolute lowest it will be.  From the output impedance standpoint, the TVC's output Z improves (gets lower = better at driving downstream component) at lower settings.  At full open, the output Z is the highest.  Like John said, the worst-case output Z of 1.4K@1KHz ain't bad at all, and better than many other passive devices which is part of what makes TVC's so alluring and cool.

I suppose using the word "HUGE" was an overstatement, perhaps over-compensatory.  From a manufacturer's perspective, one has no control over what a user plans to do with a piece of gear and what it will be used with, so it's in my interest to provide "safe" advice.  Definitely, super-high gain isn't strictly necessary and likely wouldn't sound as good anyway because there's not that much market interest to support such technology.  I'm glad to hear that people have been finding essentially zero problem with mating the dAck! with the tx102 in a variety of installations.  This is a potentially hairy problem if the transformers are not designed properly.

This discussion about the tx102 has gotten me quite interested!  I've been meaning to try one of these things out, so maybe now's the time...

-csown

[Al Garay]

I'm getting ready to place an order for the DAC as well. I am willing to take a chance that it will work well with my TX102S pre-amp, AKSA 100Watt amps and 1801 speakers (86db).

It has been awhile since I have spent time/resources on my audio system, so I'm really looking forward to this upgrade.

Any opinion on the digital interconnect? I'm not much into boutique cables. I'm happy with my Vampire ICs and Goertz speaker cables.

Thanks,

Al

[bubba966]

Any opinion on the digital interconnect?

Al,

When I heard the dAck! in the GR Research setup at VSAC Danny was using a very short (10") Bolder Cables digital w/copper Eichmann's. I had my Bolder Cables 1M Cryo'd Napalm Ultra digital (Silver Eichmann's, 2 Bybees, full ERS wrap, and a cryo treatment) with me and Danny was nice enough to allow me to swap it in.

While my digital was better, it was very, very slight. It's the slightest improvement I've yet heard when swapping in my CNU digital. I can only assume that the lack of large improvement was due to the dAck! being battery powered and thus having a very, very low noise floor to begin with. Mind you this is speculation on my part as I don't know for sure.

Anyway, I think a good solid digital is all you need for the dAck!, such as the standard digital that Wayne makes.

[Al Garay]

Thanks Brian. $75 doesn't seem outrageous for a digital cable.  

Al

[bubba966]

Yeah, $75 is pretty reasonable for such a great digital. That's certainly much, much less than the cost of the digital I'm using on my DV-AX10.

Will be interesting to hear what you think of the dAck! once you get it running in your setup. I found Danny's setup to be most impressive at VSAC, and I'd bet the dAck! had a lot to do with it.

[Marbles]

Got my dAck! this morning.  Played a few CD's, say 1.5 hours worth.

Took a break for lunch and powered it down.  The charger light is still yellow after lunch.  Can I play it safely again before it is fully charged, or will it be bad for the battery life?

I assume you will not get back to me in time to be of use today, but for future times like this.....

Thanks

BTW, with my Bent pre the sound is great, but I DO have to turn up the volume knob further than with my turntable or previous CDP's/DAC's.

This is just about 2 clicks.  Not bad, and nothing to worry about.

[csown]

Hey Marbles,

I didn't receive an e-mail from you so I assume things went OK.

The first charge using the standard charger usually takes quite a while.  There is the possibility that something was wired backwards by accident, either the charger terminals (you can check this yourself) or the internal jumper.  Refer to this picture for the way things should be - you will be able to see it just by looking through the holes on top of the dAck!:



Think about it like this:  for this type of battery, for every 1 hour you take out of it, you have to put about 1.5 hours back in.  So if you listen for 4 hours, to get it all back, you should ideally charge it for 6 hours.  This only applies for fresh cells - with age, the cells get more and more inefficient at charging, and the maximum amount of charge decreases.

With the rapid charger, we speed things up a bit, at the expense of life of the cells.

It is not terribly bad to use the dAck! multiple times a day as long as the continuous time used does not exceed about 8 hours.  For example, you could use 2 hours in the morning, another 2 in the afternoon, and 4 at night, then letting it charge overnight you'll be fine the next morning.

-Chris

[Marbles]

Thanks Chris..everything was wired fine...it just took a while the first time.

Thanks for that explanation.

It seems to be breaking in nicely.

[Marbles]

After a week I have decided that for the long term the Ack! is not all that compatible with the Bent.

The soundstage width and depth was there, but the midrange was a bit on the dull and lifeless side.

This is not a bad report on the Ack! though.  This is a bad report on the combination of the Bent pre and the Ack!

I have heard the Bent with other sources, TT's,  Dac's and CDP's and with those combinations it can sound very nice.  In fact I don't plan on changing this pre for a very long time.

A manufacturer that has a forum here, has tried the Ack! with a tube pre, and a Bent pre, and he thought the same thing about the midrange with the Bent.  He said that it was like a light turning on when he put the tube pre back in.

So I want to make sure this is clear.  The Ack! could be a very good dac.
The Bent is a very good pre.
The COMBINATION of the two was not to my liking, nor was it to the liking of a manufacturer here.

It just goes to show how two very good products when put together can make a less than good sound.

As always YMMV.

It is always important to try components in your own system to see if they work out as well as you hope.

[Al Garay]

Oh MAN

My wife and I love our BentAudio TX102S pre. And I just ordered the Ack DAC - after saving for it for months. I hope your impression was impacted by other factors such as your amplifiers (mine are AKSA 100W) and speakers (mine are the Ellis 1801s which tend to be bright  up high and very detailed midrange). I'm also going to try Chris' digital cable which is supposed to be very lively, detailed mids.

So, I will not lose hope. I will have a friend's very modified ART DI/O to compare. The ART is a great match with the Bent, providing 7V of gain.  It gets plenty loud even at 11:00 o'clock as opposed to my usual 2:00 o'clock.  I am just looking for more.

I will report back once I have it.

Al

PS. Marbles did you get the latest version or the original? I ordered the new one.

[bubba966]

Al,

Will be interesting to hear what you think of the dAck! when you get yours. While I was very impressed by the setup I heard it in at VSAC, that was a Dodd pre & Dodd amps. So I didn't get a chance to hear it with the Bent. Though I probably coulda gotten Danny to take the dAck! upstairs for a moment to the Bent room as he was more than happy to go to great lengths to demo what I asked to hear while I was there.

Hopefully it works for you in your setup.

[Rob Babcock]

I'm interested, too.  A DAC isn't my greatest need at the moment (that "honor" must go to some room treatments! ).  But eventually I'll have to give the dACK! a try...

[Marbles]

Oh MAN

My wife and I love our BentAudio TX102S pre. And I just ordered the Ack DAC - after saving for it for months. I hope your impression was impacted by other factors such as your amplifiers (mine are AKSA 100W) and speakers (mine are the Ellis 1801s which tend to be bright  up high and very detailed midrange). I'm also going to try Chris' digital cable which is supposed to be very lively, detailed mids.

So, I will not lose hope. I will have a friend's very modified ART DI/O to compare. The  ...

Al,
I really hope it works out for you, and ALMOST anything including personal taste can effect how a component sounds.  The best way is to try it and see if it works in your system.  The Ack! I tried was with the new caps.  A week is not that long to break it in, so maybe it needed more break in as well.  My system is linked in my signature.

[John Chapman]

Hello!

I have not posted a reply because I would have only been guessing and I also knew I would get the chance to try myself soon. Today I took the day off and spent most the day listening to the Ack and the NOH at a freinds place. He just got the Ack recently and was kind enough to offer to let me come over and 'play'. We all need more days like this - good tunes and no solder fumes

I am a bit familiar with his system and I always enjoy listening to it. He has been kind enough to let me come by and try different stuff when I have a new experiment I'm eager to try in different systems. He has a Sony 777 player (top loader) as a transport to the newly aquired Ack to usually a sonic frontiers preamp to a Pass Aelph amp to Dunlavy speakers. Really nice set-up and a dedicated room. He also recently added a REL sub that adds a nice feel to the bottom end (did I type that?...).  We plugged the Ack to the NOH via single ended cables and then used the NOH to convert to ballanced to the amp.

First - the Ack is awesome! It is a really cool package and very very nice sounding. Amazing Value. I have a thing for battery power - the first dac I made years back  had a separate battery for each regulator stage and weighed about 40 Lbs. The Ack is a much nicer package!!

I sensed no incompatibility with the NOH and the ACK. The sound is very clear and what I'd call 'straight ahead'. Not a tubey fuzzy thing at all but not unforgiving either. We tried a bunch of mainstream (marginal) recordings and it was not harsh at all. The Aelph is a rather nice sounding solid state amp so a more ruthless amp could  leave you wanting something a bit more laid back in the system somewhere to ballance it out but in this system it was just fine to me. The low end and dynamics were great. I seldom comment on sound where my stuff is involved so I'd better not go on.....

The low output level of the Ack combined with the unity gain NOH could be a bit marginal on level. In this system (not particularly sensitive) it was just enough and although we did not have a +6db version handy to try we would have used it on one or two of the cd's we played. 95% of them we were listenning at about -6db.  A quick test if you have an Ack and want to see if a passive would be o.k. is to plug it direct to your amp.

The fellow (forgot to ask if I could use his name online!) may post his impressions as well either here or over at the asylum.

Summary - Don't worry Al - there is every chance it will work just fine for you!

Please post any questions


Many Thansk!

John Chapman
www.bentaudio.com

[Marbles]

John,

Since I have the transformers set in the unity gain mode, and the input impedence of my amps is rated at 10KOhms, I wonder if that's would could have caused my apparent incompatibility problems?  

Glad you liked the dAck! Chris Own was very nice to work with.