A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input)

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J

Jan Deckers

Member
Joined 2003
Hi,

as far as I heard, or read on Audio Creative site, for balanced output you don't need output capacitors.
Dick (one of the owners of Audio Creative) tested a TVC "preamp" with balanced input and he directly plugged the dac into it.....and he was very, very enthousiastic about that. Stil have to try that too with a different preamp myself.
 
dddac

dddac

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Joined 2003
blog.dddac.com
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AudioH said:
Thank you Bas

I thought so, but how do I connect the XLR connectors ? Directly to the output pins ? If so is a DC decoupling capacitor required for both -ve and +ve legs ?

Regards
Click to expand...

hope I am not too late :D

the DC voltage between the POS and NEG output is indeed very low, just a few mV or sometimes even below it. If you use only these two to connect to a balanced system, than things are fine, as for DC blocking.

but, you should not connect the common terminal in that case, as than you will see two times 2,7 Volt DC. in this case you need the output capacitors.

I know from one DDDDAC builder who is using a tube amplifier stage directly after the DAC and actually uses the DC voltage in the bias from the first tube, avoiding coupling capacitors....

there are several possibilities and situations. Every one should check his specific situation and make the appropriate circuit connections.

in doubt, just email me .....
 
dddac

dddac

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zjaakco said:
Hi Doede,
I have read your explenation on your site, and make mine decision to make one.
Words are words, but still there is something , I think your design is right.
Mine knowwlegde is not sufficient to design the delay in the I2S line.
So, I have order a waveIO board, and collecting / buy parts.
Still a few questions, I can't determine what is the L or R channel, i have read the
blue line in the delay circuit. and,
you use a output trafo, are you still use the A B iv resistors on that position, or
a ristor on the sec side?
I have good experiens with an outputtrafo.
Regards,
Zjaakco
Click to expand...

Thanks for positive feedback :)

on the left right question. if you check my circuit diagram, you see on page 2 at the right the connections to the dac. they are indicated as right and left channel. the left channel is the one with the most delay ... hope this helps?

the resistors are needed to do the DC biasing of the DAC output, so they have to stay. I also use a secondary load of 10k.this has been very arbitrary and can be left out or lowered or whatever. it is only to dampen the transformer a bit for the small peak round 200kHz. I could not hear a difference, but could measure it, so I left the 10k in to go kind of sure ... :rolleyes:
 
A

AudioH

Member
Joined 2011
DAC Pictures

So here are two, progress so far :)
 

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A

AudioH

Member
Joined 2011
I2S Cable Length

I'd like to move the Wave IO Board to the back of the enclosure, along side of the main DAC baord, rather than directly in front as the short interconnect cable implies such that all signal inputs and outputs are on the rear face. Is there a limit to the I2S cable length from the USB board to the main DAC board before problems occur ?

Regards
 
I

IanS1

Member
Joined 2012
AudioH said:
I'd like to move the Wave IO Board to the back of the enclosure, along side of the main DAC baord, rather than directly in front as the short interconnect cable implies such that all signal inputs and outputs are on the rear face. Is there a limit to the I2S cable length from the USB board to the main DAC board before problems occur ?

Regards
Click to expand...

Take a look at post 156 on this thread. From the photos you will see I'm using a cable which is about 200mm ish without any known problems.
 
A

AudioH

Member
Joined 2011
I2S Cable Length And Initial Listening Impressions

Thank you for the responses on cable length, I can now plan my final installation. Will post some more photos shortly.

I have the DAC up and running, currently powered from a 12V lead acid battery and the WaveIO from the pc. Have to say so far very impressed! :). I have tried both the single ended and balanced connections (latter with direct connection no capacitors) and prefer the latter with my amplifier (Electrocompaniet ECI3, with factory approved upgraded power supply), it delivers a tighter, slightly deeper bass and removes a degree of veiling of detail over the single ended connection. This was apparent when listening back to one of my own recordings and noticed a degree of detail in the mix previousely unheard with my Focusrite Sapphire Pro 40. Excellent for final mixing then !

Next mod. is 5v supply to the WaveIO board.

Regards
 
dddac

dddac

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Joined 2003
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Almeg69 said:
I have noticed that some people are having trouble finding a suitable case.

I have two contacts, one is the supplier used by Doede which is: Home- Schaeffer AG - Frontplatten, Front Panels, Faces Avant

and another one from the UK: METCASE | Aluminium Enclosures | 19" Rack Cases

I hope these will be of use to you all.
Click to expand...

Indeed great HELP !! Thanks.... So now my turn ;)

I just added a link on my Website, which will let you download a set of files for a Schaeffer Chassis for the DDDAC1794. This should be used as a starting point and can be easily edited with their software .....

have a look: click here for the page link

doede
 
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