Taking orders :)

[madbrayniak]

Question,

Will using the USB input sync the clock from the computer to the DAC? I read somewhere that this is possible and results in better sound quality.

Not entirely sure how this works though.

 

[John Swenson]

There are two different clock "topologies" for a DAC:

Source is master, DAC is slave
Source is slave, DAC is master

What matters is the jitter at the DAC chip (in the DAC). Having a fixed frequency clock in the DAC, right next to the DAC xhip is the best way to implement this.  You can do this when the DAC is master, it has the "master clock". USB can do this in "asynchronous mode". The BH DAC uses asynchronous mode so it can do the DAC as master. In this mode the source (usually a computer) sends the data out, but the DAC can tell it to speed up or slow down so tha average data rate matches the clock in the DAC.

There is another USB mode called adaptive, in which DAC is the slave, but the BH DAC does not use this. SOME other DACs use this mode.

The S/PDIF inputs (coax and optical) just work with the source as master and the DAC as slave. Thus the DAC has to somehow synchronize its clock to the data rate from the source. This is traditionally done with a device called a PLL, which is built in to all the S/PDIF receiver chips. PLLs have much higher jitter than a good fixed frequency clock. The BH DAC does not do it this way. It cleans up the S/PDIF signal, and sends it into an FPGA (field programmable gate array) which does the S/PDIF decoding. But the special part is a digitally controlled ultra low jitter clock. This is almost as good as the best fixed frequency clocks. The FPGA tells this clock to speed up or slow down so it is synchronized to the average data rate of the source.

The result of this is that both S/PDIF and USB produce ultra low jitter to the DAC chip. This combination of ultra low jitter from BOTH S/PDIF and USB doesn't exist in any other DAC. On other DACs one or the other will be significantly worse than the other input.

John S.

 

[xcortes]

Cool

 

[madbrayniak]

Thanks for that detailed response John.

I am a computer guy but DACs go over my head a bit...must be all those video games.

I am looking forward to this though. I see in my head a small PC build into a Streacom case sitting next to a Bottlehead DAC and my Quickie(maybe BeePree in future?).

Only bad thing is that one thing that I MUST have is HT Bypass since I will be running my receiver through it as well to the amp. I will have to do this with a splitter I think though so that I dont waste any tube life for tv watching.

Music has to be tubes though!

 

[Paul Birkeland]

Only bad thing is that one thing that I MUST have is HT Bypass since I will be running my receiver through it as well to the amp. I will have to do this with a splitter I think though so that I dont waste any tube life for tv watching.

You could add a switch and extra jacks to the Quickie for this.

The BeePre's larger chassis and plentiful jack field make this a bit easier. 

-PB

 

[madbrayniak]

That is something that I have considered. A way to bypass the preamp without it having to be on if possible.

We will see, I am waiting to see what happens with a few things before I go after this further.

 

[tdogzthmn]

If the DAC is limited to a single pair of outputs will using an RCA splitter reduce the sound quality?  I have both a SEX and Stereomour which I plan to use with with the DAC.

 

[jrebman]

Tom,

If I were you I'd use a second set of output rcas and a 4pdt switch to switch between them -- switches both hot and ground for both outputs -- you would'nt want a dirty ground from one device to spoil the other, if such a condition existed in your gear.

-- Jim

 

[Paul Birkeland]

If the DAC is limited to a single pair of outputs will using an RCA splitter reduce the sound quality?  I have both a SEX and Stereomour which I plan to use with with the DAC.

I wouldn't sweat it, splitters should work great.

 

[mcandmar]

If only somebody would design a switchbox kit to match our amps *hint hint*

 

[madbrayniak]

If only somebody would design a switchbox kit to match our amps *hint hint*

Couldnt the Submissive work like that?

 

[Evan]

The Submissive allows for 3 inputs and one output. I have the same issue as I use a Crack and a Stereomour with the same DAC. I built a small switchbox using a project box with one input and two outputs and a 4PDT switch. I'm planning on building it into the BH Dac if there is enough underhood real estate. If I remember correctly there wasn't too much underneath to get in the way.

 

[Paul Birkeland]

If only somebody would design a switchbox kit to match our amps *hint hint*

So you want us to design a kit that serves the same function as some RCA splitters?

 

[physicsmajor]

Any update or refined estimate(s) on the DAC kit price?

 

[Doc B]

Any update or refined estimate(s) on the DAC kit price?

We should have a price pretty soon. There are still a few items we need to do costing for.

 

[mcandmar]

If only somebody would design a switchbox kit to match our amps *hint hint*

So you want us to design a kit that serves the same function as some RCA splitters?

Better than that. Ideally i would want 2-3 inputs, and 2-3 outputs, and i would want the ground lines switched too so all the devices attached are disconnected from each other unless in use.  Basically a knob to pick your source, and a knob to pick your destination, mounted in a chassis the size of the Fix would be ideal.  The hardware from the quickie would be good enough for me, but leave enough room to upgrade to goldpoint switches if somebody wanted to.

Maybe i'm the only one with a need for such a thing, i seem to be constantly re patching RCA cables switching from speaker amp to headphone amp, DAC, to Set top TV box, to computer etc..

 

[Doc B]

You really want a patch bay.

 

[PassionForSound]

If only somebody would design a switchbox kit to match our amps *hint hint*

So you want us to design a kit that serves the same function as some RCA splitters?

Better than that. Ideally i would want 2-3 inputs, and 2-3 outputs, and i would want the ground lines switched too so all the devices attached are disconnected from each other unless in use.  Basically a knob to pick your source, and a knob to pick your destination, mounted in a chassis the size of the Fix would be ideal.  The hardware from the quickie would be good enough for me, but leave enough room to upgrade to goldpoint switches if somebody wanted to.

Maybe i'm the only one with a need for such a thing, i seem to be constantly re patching RCA cables switching from speaker amp to headphone amp, DAC, to Set top TV box, to computer etc..

I'm with you on that one. It'd be great to have a kit like this that provides lots of input / output flexibility without any significant degradation of signal.

 

[Paul Joppa]

Well a switchbox like that would be easy enough. Two 4P3T switches with knobs, a dozen RCA jacks, and some wire.

I'll even design the circuit and write the manual, for free. Switch positions 1-2-3-4-5-6 are hot1, hot2, hot3, ground1, ground2, ground3 for one channel. The other channel is the same using positions 7-8-9-10-11-12. Duplicate for the output switch. Connect the switches to each other, A-A, B-B, C-C, D-D. OK, my part's done.  :^)

 

[johnsonad]

Thanks Paul! Let's get back on the topic of hounding the BH team to get this product to market . Happy Holidays to the BH team and family!