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

Hi Doede,

Any progress in your trial with 8 boards?

Looking forward to your experience on this.

Cheers!

Ravi

Hey good Timing,

watch this Picture :) Made by my friend Dick. (as I had no time (again) :rolleyes:

He just built it and it did not work at first... Digital noise. meaning the I2S signals were loaded too much. The solution was very simple. Change the 3,3 Volt Regulator on the Mainboard for a 5 Volt Regulator. All Chips (The Isolator on the WaveIO, the VHC164 Registers and the PCN1704 are all 5 Volt compliant. This Little Change made it work seamlesley !

Too early to give a commentary on the Sound quality. But that will follow for sure...

PS. I also uploaded a nice example of a solo DAC in a nice Chassis solution ! :cool:
 

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by the way, this article is theoretically correct, but they leave the most important part away, the DC bias of the dac output.... the idea of this document works only, when the dac output is designed to work at zero volt DC output and swing around this point....

Hi Deode,

The DC bias is the reason to connect the center tap to common. This is the answer I got from a Chinese HiFi forum, the guy who gave me the answer used a transformer directly to the POS and NEG of 1794, and connected the center tap to common. And he used 1pc 1794 chip for one channel as well, and summed the output up exactly the same as your circuit. Your answer and his answer are just on the 2 side of this case and against each other, that made me a bit confused.
 
Hi Deode

Sorry for the previous post as you already answered the question. Actually the case I read from the Chinese forum was: the DC resistance for his transformer is around 120Ohms, so he just took all the resistor away, and used the transformer directly.

For this transformer: EDCOR - XS4400, the DC resistance of each winding is 116Ohms, I guess the winding can be used directly as a resistor.
 
Balanced outputs

I have a question about balanced output options which I would be grateful for advice on.

I have a DDDAC with single DAC board and standard output caps to RCA output. My preamp is an Ayre K-5xemp which apparently sounds best in all balanced operation. Before fitting balanced sockets to the DDDAC I want to be sure I'm on the right path.

The DDDAC has an output of 1.2v. The Ayre accepts a max input of 8v (bal) but I cannot find a figure for input sensitivity through single or balanced inputs. The input impedance is stated as 20k ohm single, 40k ohm balanced (20k ohm per phase).

So my questions/ concerns are:
1. How can I be sure that the 1.2v output will be sufficient for the Ayre's balanced input?

2. Given the input impedance of the Ayre are there particular output caps I should consider as a good match and upgrade over the standards? (As alternatives to the Mungdorfs)

3. Is balanced output possible when using Sowter transformers? (which I believe output circa 5v)

Many thanks.
 
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Joined 2003
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Hi Deode

Sorry for the previous post as you already answered the question. Actually the case I read from the Chinese forum was: the DC resistance for his transformer is around 120Ohms, so he just took all the resistor away, and used the transformer directly.

For this transformer: EDCOR - XS4400, the DC resistance of each winding is 116Ohms, I guess the winding can be used directly as a resistor.

Hi,

it is Doede by the way :p

the idea of using the DC resistance as the Bias Point is not so bad. 116 Ohm is than for one module kind of right. But do not forget, at AC the DAC needs to see a solid load to avoid wrinkled Transfer characteristics and distortion. Meaning, you need to calculate the AC load seen at the Primary. This MUST be round 100 Ohms over a wide frequency range. so take care the secundary load is right. I would even place a resitosr between POS and NEG for this purpose and Keep high resistance secundary. Pick your choice.

The proof is in the eating. Can't tell how good the transformer is at low and high ferquencies of course. Just give it a try :)
 
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I have a question about balanced output options which I would be grateful for advice on.

I have a DDDAC with single DAC board and standard output caps to RCA output. My preamp is an Ayre K-5xemp which apparently sounds best in all balanced operation. Before fitting balanced sockets to the DDDAC I want to be sure I'm on the right path.

The DDDAC has an output of 1.2v. The Ayre accepts a max input of 8v (bal) but I cannot find a figure for input sensitivity through single or balanced inputs. The input impedance is stated as 20k ohm single, 40k ohm balanced (20k ohm per phase).

So my questions/ concerns are:
1. How can I be sure that the 1.2v output will be sufficient for the Ayre's balanced input?

2. Given the input impedance of the Ayre are there particular output caps I should consider as a good match and upgrade over the standards? (As alternatives to the Mungdorfs)

3. Is balanced output possible when using Sowter transformers? (which I believe output circa 5v)

Many thanks.

No problem let me see if can answer this:

1. Use your ears and neighbors… if it plays loud enough it is ok By the way, balanced out is 2,4Volt
2. The brand is 100% personal choice…. For 20k 2,2uF is sufficient …
3. With the old ones not (there was no center tap) that has changed, new orders have a center tap, so YES, it can be used as balanced


Hope this helped!
 
Interesting project.

I used to run Doedes DDDAC 1543 years back. And still own it.


Some comments:


I've been using Rhopoints all the time with DDDAC1534. These are a must. ;)

I've been also running off 12V batteries. To really gain from those you need low ESR type and high capacities. Standard lead acid type give you a boring
sound experience. Of course those batteries show aging effects. Some people
are running those batteries over years. No wonder that these sound dull.

And I also prefer low ESR LiFepo4. Doede never really followed up on his page about LiFePo4, what happened to his Lifepo4 tests !?!?

If you guys like Sowther on the outputs. Try german Silvercore transformers.
However. All transformers will also change the sound.

I'm also wondering why a NOS DAC sounds worse on 44.1 then Hirez?!?!?
Isn't that the major disadvantage of NOS?
Similar feedback you can read about the Metrum DACs.

Now people seem to start resampling the materials. This makes NOS a fake. You apply filtering through the backdoor by resampling the material.
I havn't listened to resampled material that wouldn't suffer from it.

E.g. The Phasure "NOS" 1 DAC also "resamples" everything to insane high rates. It's still called NOS. Really funny.

Beside that comparing 44.1 vs 96 material is IMO a pretty questionable test.
44.1 usually gets downsampled, attenuated and dithered. It'll always
sound different.

I'm really asking myself if Doedes new project is worth the effort.
All the parts incl. 4 DAC boards , transformers, PS, WaveIO ... , that's a lot of effort.

I for myself switched to full digital amps (100$+) - after running a TP Sabre instead of DDDAC1543. My FDA solved many DAC associated (peripheral) issues at a fragment of cost.


Looking forward to read some Sabre DAC comparisons.


Just my 2 cents.

Cheers
 
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Joined 2003
Paid Member
I had already some feedback and had one at home. the sabre is no deal for the dddac 1794... it sound stoo thin, too digital. the 1794 sounds more natural, more analog.

I appreciate your feedback, but talking negative about something you never heard yourself is not worth the comment. just my 2 cents....
 
It's not that I wouldn't buy the rather euphoric feedback about your product. That kept me reading. ;)

In fact I read the entire thread and your webpage.

I'm not questioning the good quality of your product and I'm not showing up here for just bashing it. How could I.

I know your 1543 DAC, which according to your webpage is still delivering
pretty good sound in comparison. That's a kind of a benchmark at least.
I also know the WaveIO module btw.

My current FDA setup though is "lightyears" ahead of your (my) DDAC1543 at least.
And that FDA also left the Sabre with Silvercore transformers at a friends place ( I never bought those transformers myself) behind.

PCM/PWM amps do take the signal shortcut in comparison to traditional DAC setups.

Putting your 1794 DAC together will easily lift you up in a €1000+ region for a DIY product. That's a lot of money.

Since it is a DIY product it's not possible to just buy it and return it.

That's why I'd like to bring up and maybe discuss my concerns over here first.

If there is somebody in the Duesseldorf area running your DAC I might get a chance to hear what you guys are talking about!?!?


Cheers


PS: I'm a bit skeptical reading about characteristics like thin/digital vs. natural/more analog. I'm pretty sure there are highly tweaked Sabre implementations which do sound quite realistic and highly resolving too. A single well done opamp output or a great transformer a la Silvercore might change an experience from thin/digital to natural/analog. It'll always depend on the implementation.
 
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Paid Member
Since it is a DIY product it's not possible to just buy it and return it.

That's why I'd like to bring up and maybe discuss my concerns over here first.

thanks for elaborating your points, is appreciated!

on the quoted part, actually I do offer this..... anyone who build my stuff can return it for full refund, when they do not like what they bought.... works perfectly :) I want no one to pay for something they do not like afterwards. after all it is just a hobby....
 
Interesting project.

I'm also wondering why a NOS DAC sounds worse on 44.1 then Hirez?!?!?
Isn't that the major disadvantage of NOS?
Similar feedback you can read about the Metrum DACs.

Now people seem to start resampling the materials. This makes NOS a fake. You apply filtering through the backdoor by resampling the material.
I havn't listened to resampled material that wouldn't suffer from it.
Cheers

Hi Soundcheck,

I have a different experience; to my ears, and in my sound system, there does not seem to be a lot advantage in playing hirez above red book.
Listening carefully to 44.1 versus 192 there seems to be a, very, slight impovement in detail (atmosphere). This is however so small that I would not change my complete red book catalogue for it.

My system is build of: dddac with shunt regulators, balanced to a dht tube amp with audio consulting silver rock volume trannies and interstage coupled dual channell (Sakuma style) output stages, directly to a two way speaker system with Manger and dual woofers.

The tube amp and Manger makes the sound very natural, direct and (in comparison to dome tweeters and transistor amps) slightly recessed in the highs, just like live music.

I think it is strange that my experiences with hires are so different than the most people. This has me thinking that it has more to do with the complete audio setup and listening expreience than only the sampling rate.

I am very satisfied with the dddac now, it has a very high resolving power and sounds very detailed, dynamic and direct (wich is always a good indication for quality)

If you are sometimes in the neighborhood of Utrecht than you are welcome to have a listen!

Doede is also very coöperatieve and friendly with trying out the stuff, I speak from experience.......
 
LifePo4 Batteries

Interesting project.

I've been also running off 12V batteries. To really gain from those you need low ESR type and high capacities. Standard lead acid type give you a boring
sound experience. Of course those batteries show aging effects. Some people
are running those batteries over years. No wonder that these sound dull.

And I also prefer low ESR LiFepo4. Doede never really followed up on his page about LiFePo4, what happened to his Lifepo4 tests !?!?


Cheers
Hi Soundcheck,

I am currently using a 12 V lead acid battery for the main DAC boards and can't say the sound is 'boring' by any means.

However, I would be interested in details of the LifePO4 battery configuration, manufacturer you used if this is going to result in even better sound quality

Regards
 
I've been using 100Ah Northstar LA @ 2mR ESR. These got really expensive over the years. We compared those batteries to Optima Red Top as proposed by Charles Altmann. That was the reference for my earlier judgement.

As LiFePo4 I'm using A123 or 10Ah Headway cells.
Several Manufacturers meanwhile use those or similar cells to power their digital devices. Of course you're tight to a 3.3*x V scheme.

A nice alternative nowadays are Ultra/Supercaps as PS.

Cheers