A NOS 192/24 DAC with the PCM1794 (and WaveIO USB input) - Page 27 - diyAudio
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Old 31st March 2013, 08:25 AM   #261
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Join Date: Sep 2003
Location: West of Netherlands
My promised review between a one and 4 decks DAC. I had my onedeck dac and a good friend of mine had his 4 deck. We didn't do exotic modifications, but listen to it as it just is.
Both dacs use the Doede psu (2 for each dac) and the silver/gold/oil mundorfs.
Both dacs had its own macbook, and its own harddisk with the same music on it.
Further a very good tube preamplifier, a SE300B (Ceasar II) power amp, La Scala's 2005 speakers, coffee and later some white wine.

We started with Beethoven 3 symfonie the slow movement. By counting from 3 to 0 we started nearly eactly at the same time.....so switching from one to the other dac was easy listening.


First thing I noticed that the 4 decks dac didn't play much louder than the other (just a little bit..)
We heard a difference but it was first hard to describe what is was. We were listening to the same dac construction. And then it became clear. The 4 decks was even more analog, I can't describe it another way.
With both dacs I could live my life happy for ever after but....there was something in both dacs. The 1 deck was a bit more tight in the middle, the 4 deck dac seemed to be ......how to say....thinner...but it wasn't thinner....It was just a bit higher, and more transparent...
Then Berlioz cam, with Elly Ameling singing....she was standing there with 1 deck, and with the 4 there was even a bit more space around here, she seemed to became thinner, but it wasn't that, it was just that the little air around her seemed to ......mmmmm....difficult to describe very small differences without becoming to esoteric
Because D4 had a bit more air it seemed she became smaller, but with more presence.....
If you can still follow my experience..... Is it worth the money...mmmm as I said I can live with both dacs, and maybe I will change it deck by deck.....first I have to raise some funds for that....till then I am Enjoying my music....happy Eastern

Last edited by Jan Deckers; 31st March 2013 at 08:27 AM.
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Old 31st March 2013, 10:04 AM   #262
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Join Date: Feb 2013
Hi Jan,

I suspect you have compaired with the dac from (triode) Dick?
Nice review.

It makes me wonder what will be the best upgrade to do if you are on a budget and cannot do it all:
-go for more dac boards
-solder 4 tent shunt regulators on one dac board.

The shunt regulators make the sound much more dynamic and transparant, I suspect more so than with parallelling dac boards.
Only downside is you need some (de)soldering experience with the shunts.

Happy easter!
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Old 31st March 2013, 08:56 PM   #263
Tinco is offline Tinco  Netherlands
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Join Date: Feb 2013
Location: Enschede
Hey guys,

I just discovered that the Raspberry Pi has a i2s output. It takes an external clock. Does this mean that if I supply it with a high quality clock signal and drive it with the right software it will have minimal jitter, removing the need for an asynchronous reclocking circuit like the WaveIO has?

Granted ofcourse that I can get the software to reliably provide data for the i2s output.

I think maybe I can even get it to output the aligned format so even the mainboard is unnecessary?

Are there any errors in my line of thinking? I was wondering about it because the WaveIO is a lot more expensive than the Pi and the Pi has some other nice features (as it is a general purpose computer).
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Old 31st March 2013, 09:18 PM   #264
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Quote:
Originally Posted by Tinco View Post
Hey guys,

I just discovered that the Raspberry Pi has a i2s output. It takes an external clock. Does this mean that if I supply it with a high quality clock signal and drive it with the right software it will have minimal jitter, removing the need for an asynchronous reclocking circuit like the WaveIO has?

Granted ofcourse that I can get the software to reliably provide data for the i2s output.

I think maybe I can even get it to output the aligned format so even the mainboard is unnecessary?

Are there any errors in my line of thinking? I was wondering about it because the WaveIO is a lot more expensive than the Pi and the Pi has some other nice features (as it is a general purpose computer).
Hi Tinco,

I have also thought about this. I disregarded the Pi because it suffers package loss when used with an USB receiver, this because both USB and ethernet are on the same buss system and that's not fast enough for hi-res streaming. You would not have this bottle-neck using the I2S out.

I also wonder how it would sound using the I2S on the GPIO pins, the advantage of waveIO is it's galvanic separation of the PC and DAC. There is a lot of noise on the PI ground connection that would pollute the signal. If you test the analog output you will understand what I mean.

You will also have to do some programming if you want to send the signal asynchronous to the DAC. All this is too much for me (I am not a programmer, I only like to heat a soldering iron now and then )

I think however it must be possible and I hope you can figure it out. I for one am very interested in this idea!

Regards,
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Old 31st March 2013, 09:30 PM   #265
Tinco is offline Tinco  Netherlands
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Hey Supersurfer,

I am a programmer, though I haven't done much in the way of driver development (it doesn't appeal to me :P). Someone has already written an I2S driver, iterating on that if necessary should not be much of a problem.

I wonder, if the clock signal is on a different power supply (and ground) than the Pi, wouldn't it be rather accurate? I am totally new to hardware, in my mind it would go like this: The cpu puts a value in the i2s buffer, which is put on the line when on the next clock tick.

If this is the way it works, the noise of the Pi has no effect on the quality of the signal as it is entirely driven by the external clock.

I have no idea if its even possible to have an external clock be on a different power supply, I'll have to read up on how that chip works.

Vrolijk pasen btw
(Happy Easters)
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Old 31st March 2013, 11:33 PM   #266
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Location: Cologne, Germany
Quote:
Originally Posted by Almeg69 View Post
Has anyone tried out different IV resistors. Would it be worth trying the Audio Note non magnetic type ?
yes, but with the bufallo dac and tube output...neoohm ww over texas components and an tant. best regards
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Old 1st April 2013, 09:15 AM   #267
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Quote:
Originally Posted by Tinco View Post
Hey Supersurfer,

I am a programmer, though I haven't done much in the way of driver development (it doesn't appeal to me :P). Someone has already written an I2S driver, iterating on that if necessary should not be much of a problem.

I wonder, if the clock signal is on a different power supply (and ground) than the Pi, wouldn't it be rather accurate? I am totally new to hardware, in my mind it would go like this: The cpu puts a value in the i2s buffer, which is put on the line when on the next clock tick.

If this is the way it works, the noise of the Pi has no effect on the quality of the signal as it is entirely driven by the external clock.

I have no idea if its even possible to have an external clock be on a different power supply, I'll have to read up on how that chip works.

Vrolijk pasen btw
(Happy Easters)
Hallo Tinco,

The clock ground needs to be connected to the pc ground because the clock signal needs to be referenced to something. Also the I2S data signals will be referenced to the pc ground.

There is another way to overcome the ground pollution; put an isolator on the GPIO output signal, on the waveIO a GMR isolator (IL715 from NVE) is used for this purpose. However I expect the ground pollution will still raise jitter.

Groeten,
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Old 1st April 2013, 12:29 PM   #268
dddac is offline dddac  Germany
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Location: Wiesbaden
The idea is not bad and as it is generic ( every dac could work with this) you could make an own thread of it. lets stick here now on the DAC. I know how quickly we can get off topic

To Jan, thanks for the comparison which is really apples with apples this time. normally you need to look back in your memory....

to super surfer, were the 8 volt shunts a special, or can you adjust them, what about the 5 volt which guido specs as minimum voltage for the regulator to work optimally, did you chek with him?
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Old 1st April 2013, 12:57 PM   #269
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Originally Posted by dddac View Post

to super surfer, were the 8 volt shunts a special, or can you adjust them, what about the 5 volt which guido specs as minimum voltage for the regulator to work optimally, did you chek with him?
Hi Doede,

The 8v is a special, tentlabs modifies the 15v version for this, together with the used current. The 8v works with your 12v supply, it has about 10,3v on the input of the shunt after local regulation on your board (Guido has confirmed this).
The 3,3v version is also adjusted by Guido to match the consumed current of the dac chip. The raw voltage here is higher than Guido states on his application note but this is OK because the current is low. I have soldered an extra drop resistor on the shunt but that should not be needed according to Guido.

the shunts can not be adjusted with a pot or so, you need to change resistors for this, and as the design is not published by tentlabs, they will do this for you.

After the sowters have burned in and the two extra dac boards are ready, I will fiddle around with the raw voltage settings to see if this makes an audible difference.

Regards,
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Old 1st April 2013, 04:11 PM   #270
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Join Date: Oct 2010
Location: Slovakia
Hello friends.
Today I finished and turned on the DAC. I'm ready to test it. And pic my Htpc.
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Last edited by jeremysk; 1st April 2013 at 04:36 PM.
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