[dcolak]

Quote:

Originally Posted by Kenobi /img/forum/go_quote.gif Hi, I have two Valab DACS, one Christmas 08 series and the other, the new 09 revised board series. Both worked as advertised w/o a hitch and oh so musical. I am alternating between optical and coaxial and both sound wonderful if slightly different. Have not tried USB at this point. A friend bought an 09 version on my recommendation and experienced no downside as well. That said, I hope the noise issue reported by some will be resolved quickly so we can move on to enjoying music with this wonderful DAC. Kevin: please take care of these folks and all will be well again. Kenobi

You should try the test tones, because, the clipping is there, SPDIF or USB

I'll upload soon the test songs so that you can burn them on a CD and try them.

As Kevin said, he is aware that the DAC is clipping with _some_ songs (or anything that has volume 100%).

So, maybe you just had luck, or not knowing what to listen for, thought that the sound was "so musical" when in fact it was just distorted

Edit: The problem is not noise, it's a clipping distortion. You can see how it looks on an oscilloscope at the end of the page 80.

 

[adam2434]

Really just thinking out loud here…

How does the level of ‘100% volume with a test tone’ relate to the levels in music?

In other words, if you play a track that has ‘Peak Level 100%’ as determined by ReplayGain, is this the same ‘100%’ as when folks are testing at 100% with test tones?

If ‘100%’ above mean the same thing, then, would that be equivalent to the max voltage allowable for 16 bit’s possible 65,536 levels?

Where I am going with this trying to understand the circumstances where the Valab would clip/distort with music. For example, I wonder if the Valab can “keep up” when the music only occasionally peaks at 100%, but has real problems when the recording stays around 100% for a longer duration, as with a particularly “hot” and compressed track.

Or, is the distortion always there, but at varying degrees depending on the track, with clipping resulting in the worst-case tracks?

 

[dcolak]

Quote:

Originally Posted by adam2434 /img/forum/go_quote.gif Really just thinking out loud here… How does the level of ‘100% volume with a test tone’ relate to the levels in music? In other words, if you play a track that has ‘Peak Level 100%’ as determined by ReplayGain, is this the same ‘100%’ as when folks are testing at 100% with test tones? If ‘100%’ above mean the same thing, then, would that be equivalent to the max voltage allowable for 16 bit’s possible 65,536 levels? Where I am going with this trying to understand the circumstances where the Valab would clip/distort with music. For example, I wonder if the Valab can “keep up” when the music only occasionally peaks at 100%, but has real problems when the recording stays around 100% for a longer duration, as with a particularly “hot” and compressed track. Or, is the distortion always there, but at varying degrees depending on the track, with clipping resulting in the worst-case tracks?

Volume 100% means no attenuation (0dB) applied to the source.

Using as a source a sound card with SPDIF output (or squeezebox) with its digital volume at 100% (no attenuation) DAC will produce clipping on the test signals (e.g. 40Hz tone).

The problem is, although I can apply attenuation on my sqeezebox, I have no way of doing it on my CD player.

Attenuation of the signal by 3dB will eliminate the clipping, as far as we know.

There is more, as someone else here noted, the oscilloscope does not show a clean signal on other frequencies (see the end of page 80).

So, yes, depending on the type of a song you will notice the clipping more or less. First time I noticed it was in a trumpet section of a song.

I thought my tweeters were busted

As far as I know, it has nothing to do with a digital compression.

The manufacturer (Kevin?) said that it is an intentional fault of the DAC, and suggested we should make hardware modifications in order to make it stop clipping.

Edit: Imagine buying a sound card and reading in the manual "please do not move the volume in the windows over 50% or it will start distorting music." That is the case with this DAC.

 

[Sex Bomb]

Quote:

Originally Posted by dcolak /img/forum/go_quote.gif The manufacturer (Kevin?) said that it is an intentional fault of the DAC, and suggested we should make hardware modifications in order to make it stop clipping.

This has to be validated for sure, cause I'm quite sceptical now. Maybe the modder folks on this forum could replace the output resistor (I guess it's something trivial for them) and then post back the result of the 40hz tone test?

 

[adriaan243]

This kind of DAC does not use any kind of filtering like commercial DAC's.
Your sine waves will always show all kinds of harmonics because of the missing 20khz brickwall filter.
This is also one of the reasons this DAC sounds different from commercial DAC's.

 

[microzyma]

Quote:

Originally Posted by adam2434 /img/forum/go_quote.gif Really just thinking out loud here… How does the level of ‘100% volume with a test tone’ relate to the levels in music? In other words, if you play a track that has ‘Peak Level 100%’ as determined by ReplayGain, is this the same ‘100%’ as when folks are testing at 100% with test tones? If ‘100%’ above mean the same thing, then, would that be equivalent to the max voltage allowable for 16 bit’s possible 65,536 levels? Where I am going with this trying to understand the circumstances where the Valab would clip/distort with music. For example, I wonder if the Valab can “keep up” when the music only occasionally peaks at 100%, but has real problems when the recording stays around 100% for a longer duration, as with a particularly “hot” and compressed track. Or, is the distortion always there, but at varying degrees depending on the track, with clipping resulting in the worst-case tracks?

It's audible with music. I also thought the fault was in my speakers. Apparently a simple fix. Just ordered some 340ohm resistors. It's annoying that I had already ordered some nice i/v resistors but whatever. We bought a dac from a company we never heard of at a cheap price from a far away land known for erratic quality control. There is no point whining about it. It is our responsibility as consumers to vet our purchases.

That said, I will not be buying anything else from Valab. I don't think they have the technical expertise or auditory acuity to be credible in this business. Lesson learned. New customers may decide Valab just spent a good deal of time learning more about what they are doing and decide it's a worth wagering. Both opinions are valid and caveat emptor.

 

[microzyma]

I'll also reiterate that their ad copy is misleading. Anybody who doesn't have the stomach to read 80 pages of this thread should know the Valab reclocks only USB, not spdif.

 

[Sex Bomb]

Quote:

Originally Posted by microzyma /img/forum/go_quote.gif I'll also reiterate that their ad copy is misleading. Anybody who doesn't have the stomach to read 80 pages of this thread should know the Valab reclocks only USB, not spdif.

Even more misleading when the DAC is sold in a combo with a Pure Silver Coaxial Digital Cable.

 

[tubes]

Just curious, have you guys with the distortion problems tested any other dacs? There are all kinds of sources of distortion with digital, you have jitter, upsampling, filters etc.. As far as I'm concerned I hear distortion with every piece of digital gear I've owned and the Valab to my ears is the least offensive yet. I have the 2009 Teradak which is basically the same as the Valab with a few different caps. I looked into the LT1084 Voltage Regulator as a possible source of distortion, if the 1084 adjust pin is bypassed you need a 150uf cap on it, I have a 220uf Rubycon ZL cap so I replaced the 47uf Sanyo Oscon and the sound fleshed out nicely and is sounding nicer in my system than other digital I've had including the Benchmark and the CA 740C CD player.

 

[MikeW]

it's not really distortion, it's clipping, have you tested a 40 hz pure tone tubes? this is not a debate any longer, we have word from kevin himself that it's an intentional design flaw, there's no reason to defend it, or pretend like it's defective units here and there, unless modified, they will all do it... "working as intended" so we have 2 options, live with the clipping, or reduce the volume via attenuation and lose details and bitrate.

edit: perhaps im being harsh here, even with all the problems, it's still a fine sounding dac in the end, and I think it will cost me alot to best it, but i'll eventually replace it, I really miss my old CIA VDA-2, which sounded better for sure, but at 3x the price.

 

[Angsila]

Quote:

Originally Posted by dcolak /img/forum/go_quote.gif You should try the test tones, because, the clipping is there, SPDIF or USB I'll upload soon the test songs so that you can burn them on a CD and try them. As Kevin said, he is aware that the DAC is clipping with _some_ songs (or anything that has volume 100%). So, maybe you just had luck, or not knowing what to listen for, thought that the sound was "so musical" when in fact it was just distorted Edit: The problem is not noise, it's a clipping distortion. You can see how it looks on an oscilloscope at the end of the page 80.

decolak,

Can you just provide a list of CD's and what tracks have this issue? I don't want a file that you provide.

 

[PatOMalley]

Mike, you were so happy with the sound of the DAC before all this PC noise started happening.

I got something from Bud Purvine in the mail. He makes this loop of Litz wire in heatshink that is cut/vented in certain ways, then sheathed in cotton. It is a treatment for the ground plane and seeing as the 2009 had robo ground plane improvement I thought the 2008 might benefit from Bud's treatment. (To get the full story on how it works you will need to search out Bud and talk to him. It is an experience.) I soldered it to the outputs ground.

There is an improvement: More of the same things like the EMI paper but more pronounced. More dynamics, itty bitty detail things, better bass, and more presence. The kid jumped thinking it was a real person when Oliver Nelson shouts "How Down!"

Is it worth $30? Well, now that I own it, yes.

 

[tubes]

Not trying to defend it and i'm not into pretending. If my dac has distortion it doesn't reduce my enjoyment of the sound I get and testing it with a 40 HZ tone won't change anything for me. I wouldn't say they purposely designed a defect into the dac, that just doesn't make sense, it's probably more like a a part of the NOS design and the resistor values they use. I wouldn't think changing the values would take the life out of it. Like I said before I hear distortion in every digital piece I've had making it almost unlistenable for me, I don't get that with the Valab.

I would love to see some other dacs tested to see what shows up. BTW, if it's something as simple as changing the resistor values someone with the distortion problem should change them out to see if that does the trick

 

[Lornecherry]

Perhaps someone with a Havana (another very well reviewed NOS DAC) could see if they experience the same test sweeps. Is the perceived design limitation limiting your enjoyment psychologically, or is it truly a flaw audible in real, everyday use? Sometimes it's very hard to tell.

 

[tubes]

This discussion of distortion sure wouldn't get very far with users of Single Ended Triode Amps. There very well be distortion imbedded in the signal, my question is to what degree is it there and is it the same on all Valab dacs and how many people hear it. Other than the recent complaints I would say feedback on the sound of the dac has been overwhelmingly positive, some of the QC problems are another issue.