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Valab Dac-First Impressions - Page 80

post #1186 of 1580
Quote:
Originally Posted by tubes View Post
Dcolak, you've had this problem with 3 dacs now, do you get distortion with the output of the Squeezbox or the CD player? What's the rest of your system, it seems strange that you get distortion with 3 dacs. Do you get distortion if you take the PC out of the system and just use the CD player as a transport into the Valab or Gigalab?

BTW, people that have modded their dacs never mentioned hearing clipping before or after modification.
I wrote it in previous messages, but, we can always resume it:

Sources: Nad C541i (SPDIF), Squeezebox (SPDIF), PlayStation3 (SPDIF), PC (USB), PC (M-Audio Revo 5.1 -> SPDIF)

Amplifiers: Trends TA 10.1, NuForce Icon, NAD C370 (have two of them, tried them in mono block mode and in stereo mode)

Speakers: Klipsch RF83, JBL S312II, JBL S38II, Klipsh B3

All those combinations show the distortion (clipping) produced by the DAC.

The "solution?"

Where was possible, lowering the volume to approx 60-70% eliminated the clipping with all the "bad" things that come with it. It was not possible to do with the CD player and the PS3.

Eliminating the DAC, of course results in no distortion what so ever, with any of the sources at 100% volume with, of course, the same music / test sounds.
post #1187 of 1580

running the voodoo down

I am not keeping time with the distortion thing going on because I don't have any distortion on my modified 2008 version.

I recevied some EMI paper. voodoo. I placed it in the transport aka NAD C541i above the transport thingy and transformer. I didn't hear a bit of difference when placing it on the outside top of chassis but with it glued to inside top there was a bit more clarity.

I didn't make a peep about it but asked my 15 yr old who was laying all over the chair. She says, and she is very bored with these kinds of questions from me and usually says "no difference", that you could hear Nina Simone's voice better. As if it was separated from the "background" music. [background music, sheesh!] She compared it to the EQs on the car radio when you get the right one. The kid doesn't care enough to lie.

So there is nothing but bits moving in that transport that is being affected and I supposed adding the EMI paper reduced jitter a wee bit. Something I was hoping for. Not a powerful difference but it is there. Is it worth $25? Well, I own it now so I will take it.
post #1188 of 1580
pat have you done an listening test with pure tones, or are you just assuming you don't have the distortion/clipping problem because you've never heard it in music? I never heard it in music either and assumed I did not have a problem. surprize it's there.
post #1189 of 1580
nt
post #1190 of 1580
I alerted Kevin at Valab about recent discussions in this thread via eBay asking seller a Q and asked him to comment. We shall see.
Funny thing is that knowing I heard clipping in test tone and learning problems other people have experienced, now I just can't stand this little "wonder" anymore. I start to hear "distortion" in whatever music I listen to I need a break
OK, does anyone else think C-media driver sounds brighter and thinner than others, e.g. WASAPI ?
post #1191 of 1580
Has anyone determined if the test tone distortion is in both the 2008 and 2009 models? Similarly, are the output levels the same for both?

Also, I assume this distortion is from clipping the output, not overloading the input. Right?

This does make me wonder if the "thickness" I've noticed in male vocals and piano is related to distortion - not necessarily clipping, as that has a distinct sound, but rather a lower amount of distortion, prior to clipping.
post #1192 of 1580

ignorance is bliss

Quote:
Originally Posted by MikeW View Post
pat have you done an listening test with pure tones, or are you just assuming you don't have the distortion/clipping problem because you've never heard it in music? I never heard it in music either and assumed I did not have a problem. surprize it's there.
Mike, I don't want to be a wise guy but I don't listen to tones. I just turn it on and listen to music. I take it apart a lot, too. Maybe there is distortion, technically, I don't know. But from what I am reading on this board I can safely say I do not share in the gestalt re distortion. I get no vibe that way.

I placed a small bit of that EMI paper on the big VALAB clock near the output caps on the 2008 version and it seems a little more ... more. It's the little things like more breath on a trumpet. The delicate things are more presented.

I read that you shouldn't use this EMI paper near the analog section but the clock is right next to those caps.

If what I am hearing is distortion then I like it.
post #1193 of 1580
Distorsion with tone test why not but question : what is volume for numerical data ?

Are these data suitable for the 16 bit quantization of the TDA 1543 whatever the volume ?

Anyone could explain me how works the volume ?

For both R and L line out of the dac, i have observed on oscilloscope pure sinus at -20 dB with frequencies ranging from 20 Hz to 20 KHz and i do not see distorsion.

I am not sure that the distorsions observed with a PC as source are the same that those observed with a cd player.
post #1194 of 1580
Quote:
Originally Posted by PatOMalley View Post
Mike, I don't want to be a wise guy but I don't listen to tones. I just turn it on and listen to music. I take it apart a lot, too. Maybe there is distortion, technically, I don't know. But from what I am reading on this board I can safely say I do not share in the gestalt re distortion. I get no vibe that way.

I placed a small bit of that EMI paper on the big VALAB clock near the output caps on the 2008 version and it seems a little more ... more. It's the little things like more breath on a trumpet. The delicate things are more presented.

I read that you shouldn't use this EMI paper near the analog section but the clock is right next to those caps.

If what I am hearing is distortion then I like it.
This is a fairly significant sonic detriment. All of the good things are still good things. But we are talking about enough distortion that it sounds like two notes are being played. I didn't notice it at all in spdif(didn't put tones across it in spdif yet, maybe it's OK?) but when I changed over to usb on Saturday the dynamics were so good I wanted to think the distortion in peaks was in my speakers(looking for an excuse to upgrade).

If you were to add up all of the tweaks you could do(caps, i/v resistor, ers paper, damping, isolation, etc) it would not make as much of a difference as getting this sorted out. Makes me think the 2008 on spdif are OK because you would definitely notice it Dialing back -3db in foobar makes the distortion go away but is missing some low level details and dynamics.
post #1195 of 1580
Can someone post a way to point out the distortion/clipping in the Valab- maybe a particular time in a track where it is noticeable. I have the 2009 version and so far have not noticed the distortion in Foobar using Windows XP via USB. I guess my ears aren't too well trained.
post #1196 of 1580
I get distortion on usb when I use the foobar test tone at 100% volume. My Valab dac come from the first production of 2009 (Jan-16-09 ebay auction). I will test spdif output of my soundcard tomorrow and let you know.
post #1197 of 1580
[QUOTE=dcolak;5481817]Don't forget that it appeared also when used SPDIF output of a soundcard to drive Valab! It's not only USB, SPDIF is the same.

SPDIF using Windows is not the same as SPDIF using a CD player.
Using a CD player SPDIF is pure and unmanipulated 16 bit 44.1 khz.
A computer may even resample your precious audio and do you really know what happens during level changes.
post #1198 of 1580
The distortion sounds like a loose material fluttering at the end of every test tone 40hz. The distortion does not sound that apparent, though it sure is weird. Anyway for the test tone I cant use wasapi to run, always have this error.

Unrecoverable playback error: Could not open device: unsupported data format: 48000 Hz / 16-bit / 1 channels

Any Idea, only direct sound allows my to play the test tone.
post #1199 of 1580
Just received a response from Valab. Briefly, he explained that the output range is purposely set "higher than normal" to overcome NOS DAC's "narrow dynamic sound" and smaller soundstage. But some records with very high output will clip. According to his experience, this should be rare. Also, he indicated if this is not acceptable to me, he would be happy to refund in full.

BTW, I have same error message running test tone using WASAPI. Also, to my ears the sound is richer when selecting WASAPI: USB digital out in Foobar than selecting C-Media USB digital out (no idea why)...
post #1200 of 1580
Ok guys,
the following attachments show photos of my CRO screen when generating various tones in foobar and running into the Valab through the USB.

The first photo shows that with the volume set to 100% in foobar that the negative half cycle of 40Hz is clipping. The clipping was eliminated when turning the volume down about 3dB.

The more concerning issue is what I saw when I incresed the frequency of the test tone whilst mainatining the voume at -3dB.

At 5Khz the sine wave(hmmm) is not a sine wave, it appears to be full of harmonics or I was thinking that it looks like there could be a delay in the i2s data lines which is resulting in the DAC's outputting different or delayed data??? - just a thought, no proof of this, maybe someone else could shed some light?

At 10Khz the waveshape is undescribeable.

22Khz looks as expected.

Well, this doesnt take anything away from the way people percieve the sound quality or take away from the enjoyment of the musical reproduction, but the weird stuff happening above 5Khz speaks for itself.
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