Taking orders :)

It is exciting that the DAC may be getting closer to release!  I would like to hear more about the analog output stage.  It has been stated "no tubes".  Is it op-amp or discrete? Basic topology? 

I have heard several DAC's with the latest chips providing pretty amazing numbers. But I always go back to an early 2000's DAC with a tubed output stage.  Why, when its numbers parts are antiquated? Because the analog output stage makes it play closer to music than the new super numbers machines. 

I AM NOT saying that the output stage has to be tubes. I am saying that I assume that BH has spent an equal or greater amount of time on the critical output stage.  I would like to hear some details about it.

Cheers,
Geary
 
OK, I'm sold on the DAC and need to start saving my pennies, literally.

John,

I have a ST and wanted to know if you did any mods to the SPID/F out? The only thing I have done is build a PS based on your design using a Teddy Pardo reg and EDO.

Again can't wait.
 
John is really busy with his day gig now, so it will take a little time to complete what needs to be done. He is laying out the final PC boards and then we will need to have samples made and test them. So we are talking early 2014.
 
There is NO output stage! That is one of the reasons I like this DAC chip so much, it was designed to drive an output directly, no extra active stages and NO coupling caps! The output from the DAC chip goes through one resistor, the output of which has a cap to ground, this is the final analog filter for the DAC, that is IT!

I'm not exactly sure how they did it in this DAC chip, but it really does work and sounds amazing.

John S.
 
Sounds Brilliant John :) With the ever changing DAC world... You HAVE to take your time to get it right.. we get it... And you are certainly doing it... kudos...
 
And...... I do not know.. BUT... maybe.. for you tube output stage curious guys "me included"... MAYBE.... The Bottlehead team can/will release an independent/dedicated tube output stage product for the DAC, cd players, tuners, tape players etc..... to make and experiment with??  in our own systems........
 
John, what's your source? I'm wondering if I'll need to upgrade my computer when I get the DAC. I have an old PC with a Juli@ card. No separate power supply. Not fanless.
 
Great!! Doc... thank you !... My bad... thank you for the post, I was aware of people trying it as an experiment, but as a finished product?  .. but I guess it is not necessary... ok , I get it.. ?)
 
We have discussed the notion of a version with tube outputs and Nixie display. It would be very expensive.
 
John Swenson said:
There is NO output stage! That is one of the reasons I like this DAC chip so much, it was designed to drive an output directly, no extra active stages and NO coupling caps! The output from the DAC chip goes through one resistor, the output of which has a cap to ground, this is the final analog filter for the DAC, that is IT.
Click to expand...

Ahh so its an ODAC in a wooden box.    ...joke :P

I certainly cant wait for you guys to show off the finished product, really curious to see the PCB's and what chips are in there.  I already have an IOU from Santa in the bank..

Nixie tubes idea made my laugh, i have a bunch of Nixie tube alarm clocks in my ebay watch list that i cant get out of my mind.  Expensive, but very cool looking..
 
If I am mistaken... and I usually am here :)... I read that DOC said that tubes DIDNT make the DAC sound any better...  So, this is of course a great thing because the end result will be simpler and CHEAPER... Who cannot love that... IF you want a tube output stage..?? I just learned, ADD a quickie...... Brilliant as hell because the quickie is what???? wait for it.... Battery powered as well... haha superb.....
 
xcortes said:
Someday in the future I'll build a Soul sister with MQ transformers at the input (B7 10k:10k Ni) and output (B7 8k:600 Co) and a pair of Co SR45s for which I have most parts. 'Cause contrary to my main system philosophy, for digital I think the mo' transformers the better to tame the digital beast.
Click to expand...

Dear Xavier; You won't regret building the Soul Sister you have in mind. My PB-built version is wonderful whether driving the BH 2A3 amp and Blumensteins, or directly driving my HD 600's Cardas-cabled. I too have Mike's cobalt B7's but with IAG Sowter/Shallco transformer volume controls at the inputs. Vinyl is still my favorite source, and since PB built my custom Eros, I am re-acquainting myself with a large collection of mint discs.

Cheers, Hank in Eugene



 

Attachments

The DAC has three inputs. S/PDIF coax, S/PDIF optical and USB. They are all just as good as the other. (there might be very slight differences, but they will be small).

So anything that can output S/PDIF or any computer whose USB port can be used for UAC2 audio will work.  What is going to sound BEST, I don't know at this point. I have put a TON of effort into making this as immune to outside influences as possible, so I expect that it will very good on just about anything without needing the extreme source tweaking that many other DACs require to achieve their best.

But nothing is perfect so you probably will be able to make it sound better with some sources than others, but at hi point I have no idea what that will be. The way I have done this is so much different than most other DACs that there is nothing else out there that can be used to make an educated guess at this.

Right now there are just two out there (mine and Docs), and I have not nearly enough time to actually try it with lots of different sources and computer combinations. I don't think Doc has done too much of this either. So it's really going to have to wait until lots of them get out into your hands and you guys can start doing some testing on this.

Currently I'm either using a Squeezebox Touch (S/PDIF coax or USB) or a wandboard running Community Squeeze software (squeezebox emulation) via USB. To me these sound identical.

This design is rather unusual in that it has both an extremely good S/PDIF input AND and extremely good USB input. In most DACs that have both types of inputs, one or the other will be significantly better sounding than the other.

John S.

 
To Sam -- that means you can probably ddump the noisy PC and replace it with a single, fanless one board computer like an Alix or Cubox I, control it from an iPod/Pad/Phone and just run a usb cable to the bh dac and move thee pc to another room and use it as a fileserver. Or continue to use the PC until you want to use DSD when it becomes available.

No need, as John says, for a souped up mac mini or such to get stellar performance. Though I will hold on to mine until I can verify for myself that the alix or whatever can do as well as my over the top mac mini.

HTH,

Jim
 
Jim,

I really like that idea! I'll shoot you an email off line with questions on how to accomplish it.

Regards,

Aaron
 
John,

On the subject of USB interfaces and the article linked a few pages back i would interested to hear your opinion on USB isolators, specifically those built around the ADuM4160.  I have heard people claim that they are problematic in that they increase jitter. Is there any truth to that?

Thanks,

Mark
 
First off those isolators only work with full speed DACs, thus only work with UAC1, thus are only good up to 96 sample rate.

They definitely increase the jitter of the data signals. The technology used in ADUM can add a large amount of jitter. It's one of my least favorite isolation schemes. (I much prefer the GMR isolators from NVE, I use them in the BH DAC).

How that increase in data bus jitter winds it's way into the audio signal is complicated and will be different for different implementations.

The isolation CAN cut down on noise coming across the power and ground connection to the USB host, but it's difficult to say which will be worse, the decrease in noise or increase in jitter.

John S.
 
Thanks John, informative as always, i need to re-evaluate my little isolator box solution now.

Also good to know the BH DAC will have some form of isolation built in, so no need to worry about such things in the future.

Cheers,

Mark

 
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