Author Topic: DAC Project- build or modify or ?  (Read 22531 times)

Offline kajak12

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Re: DAC Project- build or modify or ?
« Reply #20 on: February 26, 2012, 03:36:17 AM »
what improvements in sound quality did you hear between receiver chips?
what system are you running amps,dac,speakers etc????
I made the S/PDIF receiver gizmo several years ago to experiment with DAC linearity. At the time, my audio system was CD-based, no PC, and the only way I could modify the sample data was with hardware.

The AD1865 is an 18-bit DAC. Shifting the sample data one or two bits to the right, preserving the sign bit, would not truncate the data but move the conversion into a different position in the R/2R network and perhaps change the sound quality. I wasn't expecting the new receiver chip to make any difference. The digital-analog conversion in the AD1865 is triggered by word clock, not the bit clock as it is in most other serial input DAC chips. The chips in the CS841x series all generate the word clock (aka FSYNC) based on the timing of the S/PDIF preambles and is not dependent on the PLL.

I was surprised by the improved clarity and resolution. An additional benefit was the ability to receive sample rates up to 192K even though the CS1815A is only rated to 96K. I attributed all that to the careful layout of the digital circuit surrounding the receiver chip. The experience also encouraged me to quickly migrate to PC-based digital audio and design my own DAC.

At the time, my audio system included:
Speakers: Avantgarde Acoustic Trio (Omega);
Amp: Art Audio Jota (monoblocks); 
Preamp: Hovland HP-100 with MC phono stage;
Vinyl: SME-30, SME IV-Vi, Cardas Heart;
CD: Sony 707ESD, Audio Note DAC 1.2;
Cables: DIY;
Power: Equi=Tech 1.5RQ & 2.0RQ;
Stands: Grand Prix Audio Monaco.

Tell us more about your dac?
what chip and output stage? (any photo's?)
still discovering the link between electronics and audio reproduction.so much to learn and so little time

Offline tam lin

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Re: DAC Project- build or modify or ?
« Reply #21 on: February 26, 2012, 04:55:57 AM »
Ensuring strong voltage at the source overcomes distance issues.
Regardless of the starting voltage, a single-ended clock, like the I2S clock, will degrade over distance. A good clock requires fast transitions because slow transitions lead to uncertainty in determining exactly when the clock changes logical polarity and that creates jitter. Not only is the I2S clock single-ended, it is not pre-conditioned and is rarely transmitted with a proper driver. Usually it’s just the output if a simple logic gate. That’s why my preference is to slave the digital source to the DAC clocks and not the other way around.

Tell us more about your dac? what chip and output stage? (any photo's?)
I don’t discuss work in progress and the DAC has been “in progress” for a long time. I am wrapping up what I hope is the last revision (I’ve heard that before) and when it and the new casework is finished I’ll have something to say about.

Offline ozmillsy

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Re: DAC Project- build or modify or ?
« Reply #22 on: February 26, 2012, 10:34:32 AM »
Regardless of the starting voltage, a single-ended clock, like the I2S clock, will degrade over distance. A good clock requires fast transitions because slow transitions lead to uncertainty in determining exactly when the clock changes logical polarity and that creates jitter. Not only is the I2S clock single-ended, it is not pre-conditioned and is rarely transmitted with a proper driver. Usually it’s just the output if a simple logic gate.
Tam, don't get me wrong,  I have no doubt that shorter distances will minimize errors.   In practise, my buffered i2s connections were a significant leap forward, over the previous spdif implementation.   I don't doubt that spdif could be better.  But by the same token, limiting the use of i2s to only 2cm distances is not necessary in my experience. 

Quote
That’s why my preference is to slave the digital source to the DAC clocks and not the other way around.
we can agree on this.  And if using PC as a source,  I see significant merit in leveraging async USB connections,  and reclocking at the Dac end. 

Quote
Tell us more about your dac? what chip and output stage? (any photo's?)
I don’t discuss work in progress and the DAC has been “in progress” for a long time. I am wrapping up what I hope is the last revision (I’ve heard that before) and when it and the new casework is finished I’ll have something to say about.

Tam, if you are worried about IP, then it sounds like this is your profession, and that you intend to create a commercial product or design for sale when completed.    We welcome commercial interests, I'd just ask that you take a look at the following forum guidelines, in particular the 'Commercial Products and Vendors' section.
It's all about the music,, not the equipment.

Offline ozmillsy

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Re: DAC Project- build or modify or ?
« Reply #23 on: February 26, 2012, 10:37:03 AM »
Forum Guidelines

Quote
Commercial Products and Vendors

As this is a community based forum, we welcome any commercial vendors to contribute and be made welcome.

We have established a 'commercial vendors' forum where you are welcome to advertise your products. You are welcome to create the in that forum, the following:

- One thread for use as a general discussion thread regarding your products. Please use this thread in an ongoing manner
- One thread for use as a 'current specials', 'sale' type thread. Please use this thread in an ongoing manner.

You are of course welcome to participate in any other forums as you wish as any other member is. You ARE allowed to:

- Mention, discuss or direct people to your threads.
- Put your company details, contacts etc in your signature. Please be minimal and appropriate in this (no half page banners, flashing lights, embedded flash etc)

Too much flagrant self promotion will lead to warning, and then banning. Be nice and mindful that this is an information sharing site.
« Last Edit: February 26, 2012, 10:41:02 AM by ozmillsy »
It's all about the music,, not the equipment.

Offline tam lin

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Re: DAC Project- build or modify or ?
« Reply #24 on: February 26, 2012, 01:12:41 PM »
And if using PC as a source,  I see significant merit in leveraging async USB connections,  and reclocking at the Dac end.

I see no merit in USB. Adaptive USB is probably the worst digital audio interface imaginable. The same with Firewire. It's the same as USB: It's faster but doesn't have guaranteed bandwidth allocation. All async USB does is move the origination of the S/PDIF signal from the PC chassis to the end of a USB cable. It's still S/PDIF. In the end, your DAC is still using a VCO clock that is phase locked to the S/PDIF signal. Reclocking in the DAC doesn't change any of that. All it does is add jitter and noise.

Tam, if you are worried about IP, then it sounds like this is your profession, and that you intend to create a commercial product or design for sale when completed.

I'm a retired programmer. I have no IP! I have nothing to gain sharing my work in progress. Writing things up and taking pictures wastes my time because, by the next day, I will have decided to do things differently.


Offline ozmillsy

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Re: DAC Project- build or modify or ?
« Reply #25 on: February 26, 2012, 01:37:32 PM »
I was under the impression that the whole point of 'asynchronous' anything,  is that it is not locked to the source.

If you have any technical references that contradicts this, I'm happy to receive/read them.
It's all about the music,, not the equipment.

Offline tam lin

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Re: DAC Project- build or modify or ?
« Reply #26 on: February 26, 2012, 02:20:37 PM »
I was under the impression that the whole point of 'asynchronous' anything,  is that it is not locked to the source.
If you have any technical references that contradicts this, I'm happy to receive/read them.
Sorry, I don’t have any references. If you think having the DAC clock not locked to the source is a good thing I doubt there is anything I can say that will change your mind.


Offline ozmillsy

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Re: DAC Project- build or modify or ?
« Reply #27 on: February 26, 2012, 02:30:25 PM »
Sorry, I don’t have any references. If you think having the DAC clock not locked to the source is a good thing I doubt there is anything I can say that will change your mind.

Yes I do.   If you don't care to discuss it,  then that's fine.
It's all about the music,, not the equipment.

Offline tam lin

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Re: DAC Project- build or modify or ?
« Reply #28 on: February 26, 2012, 02:50:10 PM »
It's not that I don't want to discuss it, I love to talk about this stuff, it's just that I don't think you will be receptive to my way of looking at things. The tip-off was your mention of reclocking. If you believe reclocking is a good thing than, IMO, you don't have sufficient knowledge of digital circuits to understand what I would be talking about. BTW, this is getting way off topic. Perhaps you should move this discussion to another thread.

Offline kajak12

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Re: DAC Project- build or modify or ?
« Reply #29 on: February 26, 2012, 04:12:13 PM »
And if using PC as a source,  I see significant merit in leveraging async USB connections,  and reclocking at the Dac end.

I see no merit in USB. Adaptive USB is probably the worst digital audio interface imaginable. The same with Firewire. It's the same as USB: It's faster but doesn't have guaranteed bandwidth allocation. All async USB does is move the origination of the S/PDIF signal from the PC chassis to the end of a USB cable. It's still S/PDIF. In the end, your DAC is still using a VCO clock that is phase locked to the S/PDIF signal. Reclocking in the DAC doesn't change any of that. All it does is add jitter and noise.

Tam, if you are worried about IP, then it sounds like this is your profession, and that you intend to create a commercial product or design for sale when completed.

I'm a retired programmer. I have no IP! I have nothing to gain sharing my work in progress. Writing things up and taking pictures wastes my time because, by the next day, I will have decided to do things differently.


just give us a rough idea about the dac like the output stage at least it will fill some hunger for info
still discovering the link between electronics and audio reproduction.so much to learn and so little time

Offline tam lin

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Re: DAC Project- build or modify or ?
« Reply #30 on: February 26, 2012, 04:43:27 PM »
just give us a rough idea about the dac like the output stage at least it will fill some hunger for info

I've already said I don't talk about work in progress. Perhaps you could start a pool to guess the design parameters.

Input: S/PDIF, USB, I2S, TCP/IP, Firewire, other.
Oversampling: none, 4x, 8x, 16x, other.
Converter: multi-bit, delta-sigma, discreet R/2R, other.
I/V: resistor, opamp, transistor, tube, other.
Output: transformer, tube, opamp, transistor, other.
power supply: linear, SMPS, battery, other.

Offline kajak12

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Re: DAC Project- build or modify or ?
« Reply #31 on: February 26, 2012, 04:59:41 PM »
just give us a rough idea about the dac like the output stage at least it will fill some hunger for info

I've already said I don't talk about work in progress. Perhaps you could start a pool to guess the design parameters.

Input: S/PDIF, USB, I2S, TCP/IP, Firewire, other.
Oversampling: none, 4x, 8x, 16x, other.
Converter: multi-bit, delta-sigma, discreet R/2R, other.
I/V: resistor, opamp, transistor, tube, other.
Output: transformer, tube, opamp, transistor, other.
power supply: linear, SMPS, battery, other.

Are you serious? waste of time imho
when you do make a dac send it to australia for audition some people in audio are all show no go,when we press play its the only thing that counts the rest is bs.
still discovering the link between electronics and audio reproduction.so much to learn and so little time

Offline tam lin

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Re: DAC Project- build or modify or ?
« Reply #32 on: February 26, 2012, 05:18:57 PM »
when we press play its the only thing that counts the rest is bs.

Then why did you want to know what the output stage might be? I'm beginning to think this group is nothing but bs pushers who have memorized the latest buzzwords, like async USB, and reclcoking, but don't have a clue as what it means or how it works. I won't waste any more of your time or mine.

Offline ozmillsy

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Re: DAC Project- build or modify or ?
« Reply #33 on: February 26, 2012, 05:21:05 PM »
It's not that I don't want to discuss it, I love to talk about this stuff, it's just that I don't think you will be receptive to my way of looking at things. The tip-off was your mention of reclocking. If you believe reclocking is a good thing than, IMO, you don't have sufficient knowledge of digital circuits to understand what I would be talking about.
It's true that i dont. But that doesn't mean I won't understand.   And there are others here, who may understand what you say more deeply than I.

It's a commonly held view at the moment, that the best way to receive data from a PC is via an async data connection,  where the receiving end does not depend on the quality of the source clock.   I would like to hear why you think this view isn't correct.

It's all about the music,, not the equipment.

Offline kajak12

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Re: DAC Project- build or modify or ?
« Reply #34 on: February 26, 2012, 05:27:04 PM »
when we press play its the only thing that counts the rest is bs.

Then why did you want to know what the output stage might be? I'm beginning to think this group is nothing but bs pushers who have memorized the latest buzzwords, like async USB, and reclcoking, but don't have a clue as what it means or how it works. I won't waste any more of your time or mine.
If you use opamps in the output stage i wont even try the dac why you may ask?opamps make me cry
as for bs pushers latest buzzwords i don't even use a pc as a source i think computer audio is not good enough yet(and my tda1541 dac is not the latest buzzword.
I can tell you now that the power supply for clocks is very important and so are the components around the clock to me smd resistors or caps are a no no they belong inside mobile phones.
still discovering the link between electronics and audio reproduction.so much to learn and so little time

Offline vitavoxdude

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Re: DAC Project- build or modify or ?
« Reply #35 on: February 26, 2012, 06:08:54 PM »
Go easy Oz, this bloke has a product coming up so will not be too keen on giving the game away.
We all like different things so lets all agree to disagree and if any common ground is found then worship it.  Mine is the KD hence being present on this forum.

Offline stevenvalve

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Re: DAC Project- build or modify or ?
« Reply #36 on: February 26, 2012, 07:21:44 PM »
when we press play its the only thing that counts the rest is bs.

Then why did you want to know what the output stage might be? I'm beginning to think this group is nothing but bs pushers who have memorized the latest buzzwords, like async USB, and reclcoking, but don't have a clue as what it means or how it works. I won't waste any more of your time or mine.
I am certainly interested hearing about your DIY dac and all the stuff you make. Your experiences are helpful, so we can all learn,

Offline vitavoxdude

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Re: DAC Project- build or modify or ?
« Reply #37 on: February 26, 2012, 07:30:45 PM »
when we press play its the only thing that counts the rest is bs.

Then why did you want to know what the output stage might be? I'm beginning to think this group is nothing but bs pushers who have memorized the latest buzzwords, like async USB, and reclcoking, but don't have a clue as what it means or how it works. I won't waste any more of your time or mine.
There are some knowledgable folk here on this site as well as the purveyors of key words as you pointed out, I'd suggest you stick around for some of the pearls that come up every now and then, they are not alway just about DAC's despite being called the KDAC forum ;D
v
We all like different things so lets all agree to disagree and if any common ground is found then worship it.  Mine is the KD hence being present on this forum.

Offline zenelectro

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Re: DAC Project- build or modify or ?
« Reply #38 on: February 26, 2012, 07:41:50 PM »
It's not that I don't want to discuss it, I love to talk about this stuff, it's just that I don't think you will be receptive to my way of looking at things. The tip-off was your mention of reclocking. If you believe reclocking is a good thing than, IMO, you don't have sufficient knowledge of digital circuits to understand what I would be talking about. BTW, this is getting way off topic. Perhaps you should move this discussion to another thread.

Hi Tam,

We endeavor to try and keep this place respectful - and work through differences of opinion using the combined experience here.

WRT reclocking versus whatever, I think we agree that the whole objective is to have as low jitter as possible at the DAC chip.

As such, the ultimate solution is to have a fixed clock -at the DAC chip-.

USB -> I2S can acheive this if done correctly.

There are many subtle differences between receiver chip / I2S / USB -> I2S.  I have pretty good experience and understand and working with this stuff but as always
there is more to learn.

IMO, generally speaking using just receiver chip is the worst option.

cheers

Z

tuyen

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Re: DAC Project- build or modify or ?
« Reply #39 on: February 26, 2012, 07:43:22 PM »
stick around if you have time, id be interested to learn more about your dac.   you seem very technically knowledged like our tech guru 'zenelectro'.   you guys would hit it off me thinks! :)

cheers
tuyen