[adydula]

John,

This is a thread on the ODAC...and in the course of reading items around the net I have run into a few concerned persons
that have some issues with what they think might be USB power related.

There is a lot of opinions etc and very little real facts....

Being an engineer and working with PC development since 1981 or so....I am familiar with the specs and what USB implementations
over the years are.

So I thought I would share the actual current that the an ODAC draws...when attached to a USB Buss on a PC.

The actual current is rather low with what most USB implementations can "source" if implemented to the spec.

Not trying to prove anything, just share real hard world facts and figures.

How, not by trusting someone, but by actually measuring it.

I the few cases I know about the issues seem to be related to having many devices connected to the USB ports....and getting close to
or over the 500ma limits....not really due to the quality of the DC voltage itself.

This is why I have stated in the past that I only have my USB dac attached on my HTPC because I know that there are limits and I dont want to even go there...

There may be some ripple in the Vcc of PC USB power, and I have not measured that with a scope....but take a look at the schematics and there
are inductors in the circuit to help out here....

In the case where a person replaces a the USB power supply with a 500 ma limit, with one that is 2 amps etc well that would fix any total power
requirements....but be careful on how you connect this and how much stuff is attached.

So the point once again kind sir of the current and voltage measurement I provided....is that the ODAC can run nicely on present day USB power and provide world class
performance that rivals other dacs at a price most of us can afford.....

All the best
Alex
 

[wushuliu]

Again, no one here has discussed pops, ticks or declared the usb power to be insufficient to meet performance specifications. What has been discussed and only by me is that I perceived *improved* sound quality with the external supply. Two separate things altogether. You keep taking one premise and trying to apply to another one altogether not because they are related but because you are personally opposed to it. So maybe your posts are best placed on those forums where there is an actual discussion of odac issues that may be power related.

There is really nowhere for this conversation to go (see pic) until someone else also tries an external power supply and hear for themselves to add another subjective data point. or somebody funds my double blind testing/measurement research (please allocate enough for lots of deep dish pizza).

m'kay, done with this, 'cause somebody's getting tired:









 

John,

This is a thread on the ODAC...and in the course of reading items around the net I have run into a few concerned persons
that have some issues with what they think might be USB power related.

There is a lot of opinions etc and very little real facts....

Being an engineer and working with PC development since 1981 or so....I am familiar with the specs and what USB implementations
over the years are.

So I thought I would share the actual current that the an ODAC draws...when attached to a USB Buss on a PC.

The actual current is rather low with what most USB implementations can "source" if implemented to the spec.

Not trying to prove anything, just share real hard world facts and figures.

How, not by trusting someone, but by actually measuring it.

I the few cases I know about the issues seem to be related to having many devices connected to the USB ports....and getting close to
or over the 500ma limits....not really due to the quality of the DC voltage itself.

This is why I have stated in the past that I only have my USB dac attached on my HTPC because I know that there are limits and I dont want to even go there...

There may be some ripple in the Vcc of PC USB power, and I have not measured that with a scope....but take a look at the schematics and there
are inductors in the circuit to help out here....

In the case where a person replaces a the USB power supply with a 500 ma limit, with one that is 2 amps etc well that would fix any total power
requirements....but be careful on how you connect this and how much stuff is attached.

So the point once again kind sir of the current and voltage measurement I provided....is that the ODAC can run nicely on present day USB power and provide world class
performance that rivals other dacs at a price most of us can afford.....

All the best
Alex
 

[JohnR]

So the point once again kind sir of the current and voltage measurement I provided....is that the ODAC can run nicely on present day USB power and provide world class
performance that rivals other dacs at a price most of us can afford.....

Hi Alex, thanks for responding and I'm sorry I was being a little snarky, that was at 1:30 am for me...

I have no issue with the ODAC. I don't have one, but I am thinking of getting one, simply because its measurements are well-documented and would serve as a point of reference. That is: I can't afford to buy proper test gear, so comparing an ODAC measured with a cheap soundcard, with ODAC measurements as supplied by NwAvGuy, would help confirm that I'm in the ballpark with my own measurements.

It's also possible that I will prefer the ODAC sonically to what I have here already. And it's possible that I may not. In either case, it will be interesting to see if I can find a correlation between what I can measure, with what I can hear. Because this is where threads like this (the direction it has taken anyway) always fall apart. Some people say they hear such-and-such; others say they (or someone else) measured such-and-such; and ne'er the twain shall meet.

To your question about what specs (among those you quoted) would be improved with a different power supply. Possibly none. The ODAC has regulation and filtering on-board, from what I can tell. However, nobody (not even NwAvGuy, I'm fairly certain) would go as far as to tell you that this makes the ODAC "perfect." It's a circuit; power supplies are a circuit; nothing conforms exactly to an idealized model. And, all of those specs that you quoted are constant stimulus signals - just regular sinewaves or a combination of them. In other words, an easy job for any power supply. What would the specs look like comparatively with transient signals? I don't know, and neither do you.

Plus, I didn't notice where NwAvGuy quoted the specs of the USB power supply that he was using when he made his measurements. Do you know what they are?

With regard to claims that the ODAC offers incredible performance from a USB power supply - well, maybe, but I'm not at all convinced that it's unique. I think the days of "it's USB-powered therefore it must be noisy" are well and truly over. I've been measuring some audio interfaces (aka soundcards) and I really don't see that I would gain anything in the "objective specification" department by buying an ODAC. Here, for example, is the CCIF IMD measurement of a USB soundcard that you guys in the US can buy for $149 - the same as the assembled ODAC:



You can compare this to NwAvGuy's measurement of the ODAC:



The scales are different but hopefully it's not too hard to compare (?). Perhaps you can tell us which you would prefer, based solely on these measurements?

Yeah, it could be that my measurements are wrong.  But if not, the measured performance of a cheap "home studio" USB sound card bests the ODAC. And you get two mic preamps thrown in as well. So what's going on?

Hope this was not too long

[adydula]

Hi John!

Nice reply and not too long, and actually a nice reply, Its good where we can share stuff and get on with life!

I was going to actually measure the ripple on the Vcc line but I got lazy and dont have a o'scope at home anymore, but do at work in the lab. I would think that for the most part the ripple that would be present (and yes I do think there would be some) is probably not a real issue any more but unless you measure etc you never know.

I have run into a few people that again have issues with popping and ticking and other playback stuff and they indeed do think that it is USB power related good or bad. Who knows in their cases maybe they have a crappy USB supply in the pc. The one person who I do respect that was telling me about his issue had another brand dac that did not exhibit the issues on the same pc and it had several supplies...and thought that this was the problem.

So whether someone posted this or that in thread, this being an ODAC thread its nice to have people post stuff that they experience etc..where it be objective or subjective. Yes people do get wrapped around the axle on things even me!! But I hope the good outweighs the bad...move on.

I actually have sent a note to the designer on some issues and have not received a reply. If I do I will share with you guys.

NWavguy has stated that the ODAC is not perfect but compares well with other dacs more expensive I beleive the one he refers to it the $1600 Benchmark DAC1? But in his blogs, and they are long and deep...he does mention other dacs with superior anti-jitter "circuitry"....the design goals he uses from my viewpoint are just wonderful....whether he is right or wrong will be debateable etc...so the old blind A/B testing etc seems to be one way to try to see if something really matters and that leads to heated debate.

I agree that the ODAC with its specs is not the one and only DAC that has great specs ...its not unique, but at the price point and its simplistic design point its definitely in the running for a best in this price point class for performance....when you compare it to a $1600 Benchmark DAC1at $1600 or so? with a $99 dac and honestly have a hard time telling the difference...well maybe the DAC Magic is a better DAC, better built, more supplies, real copper chassis??, better shielding....(I am guessing here), weighs more, looks better etc...makes you feel better etc...great.

Heck I compared it to my HRT MSii+ which cost me $350 with the ODAC and I cant hear any difference. But the lights on my HRT sure look cool when they light up with the various bit depths and sample rates.... But sonically with my ears, cans and loudspeakers its a wash....to me.

The IMD CCIF chart that you posted is interesting. But their are more specs than that on the list NWavguy "thinks" are important and affect the potential audio etc.
So yes there are other audio devices that measure the same, better and worse than the ODAC. Its hard to get from a vendor all the specs in this list....another debate.

•Frequency Response: +/- 0.1 dB (10 hz - 19 Khz 24/44)
 •THD+N 100 hz 0 dBFS: 0.0029%
 •THD+N 20 hz -1 dBFS: 0.003%
 •THD+N 10 Khz -1 dBFS: 0.003%
 •IMD CCIF 19/20 Khz -3 dBFS: 0.0011%
 •IMD SMPTE -1 dBFS: 0.0004%
•Noise A-Weighted dBu 24/44: --102.8 dBu
 •Dynamic Range: > 111 dB A-Weighted
 •Linearity Error -90 dBFS 24/44: 0.0 dB
 •Crosstalk 0 dBFS Line Out 100K: --93.5 dB
 •USB Jitter 11025 hz J-test 24/44: Excellent
 •Maximum Output Line Out 100K: 2.0 Vrms
 •Distortion: < 0.005%
 •PCB Dimensions: 49.0 x 58.0 mm

I being the engineer type would choose the better measurement or the one that you provided if that was the only measurement etc...

The thing is here John, which one sounds better to you?

The sound might not be the only thing that influences a person to buy one item or another.

The great news is this is a cheap dac...and you can buy one love it or hate it...and its sure made other vendors take note....and many of us as well.

Now let me go find my Jerome supply ( and yes I really do have one!!) and I will go in and hotwire one of my odacs and see if I can hear anything for the better or worse?

John!! Thanks for the nice reply I look forward to your personal experience with this Dac.

All the best
Alex
 

[JohnR]

Well, I dunno if I want to buy one now. Doing so to prove a point to you would be completely pointless. One minute you're specs is all that counts, the next you're personal experience is where it's at.

Really not sure where the DacMagic came into this.

[jtwrace]

Well, I dunno if I want to buy one now. Doing so to prove a point to you would be completely pointless.

What do you think it would cost to ship a small (5" square) parcel to you from the USA? 

[JohnR]

What do you think it would cost to ship a small (5" square) parcel to you from the USA?

Small flat rate parcel is $15 I think.

[jtwrace]

Small flat rate parcel is $15 I think.

Ah.  That'a an option then....

[JohnR]

Sure, let me know if you want my address to post something to.

[adydula]

John,

Maybe someone is going to send you one!!! 

If your happy with what you have I agree dont spend bucks for the ask of spending bucks!....I was totally happy with my HRT MSii+.

But....I wanted to see for myself if this ODAC thing was real or not with my ears, amps and cans....

Theres no proving a point to me...I know what I am hearing,  so dont do this for me!! 

Specs are important to me, its an engineering level set.

The sound is also important.

The two go together (IMO).

If I see a item with great specs, published and verified the at least "I" have a better feeling that
the design might be at some level that I can trust...and if it sounds good then its a win / win for me.

If I see a product with no specs, that to me are important I have to question what are you hiding.

Alex
 

[JohnR]

Theres no proving a point to me...I know what I am hearing,  so dont do this for me!! 

Then why are you blathering about specs.

I regret (like wushu) getting involved in this thread. It was just the mindless claim that because a power supply meets some basic current spec that it can't possibly sound different that drew me in. See ya.

[jtwrace]

Sure, let me know if you want my address to post something to.

Will do.  It has two more stops first. 

[doug s.]

“If it measures good and sounds bad, it is bad. If it measures bad and sounds good, you have measured the wrong thing.”
- Daniel von Recklinghuasen, an engineer at H.H. Scott and editor of the Journal of the Audio Engineering Society



good measurements are nice, but it's not what i listen to.  which is why i am interested in what wushu had to say here.  alex, not so much...

doug s.

[JohnR]

I'd like to add another measurement. I apologize to Alex, but it's hard to have a discussion when the terms keep changing. But if an item is brought up then I think it's OK to discuss it and not expect to have the argument changed in the meantime. So this is a measurement of a different soundcard, this time the SMPTE IMD distortion:



Here's the ODAC plot:



So, why is the ODAC better exactly?

[adydula]

I agree with that statement doug, as long as your understanding what your measuring and whats in the chain.

John, I give up.

Like you told me in your PM.....I dont have the time to waste.

You enjoy your stuff...I will just go back to my cave!

All the best
Alex

[JohnR]

You enjoy your stuff...I will just go back to my cave!

The odd thing is that I'm not listening to these, I use them for loudspeaker measurements. I suppose I should tho (listen to them) to see.

[JohnR]

By the way... here's a DAC using the same chips (I think) for only $39...

http://hifimediy.com/index.php?route=product/product&path=62&product_id=83

A comparison would be interesting...

[Speedskater]

What is NwAvGuy up to these days?  His last blog was in May and since the he has only added a few short replies on his page.

[jtwrace]

These ODAC cases are pretty cool.

http://www.diyaudio.com/forums/swap-meet/220114-cases-odac-bamboo-acrylic.html

[jackman]

Thanks, those are cool looking cases!