Valab NOS DAC - subjective listening and modifications

[Bill Allen]

Spdif Input:

1. High quality low jitter transport (Money is better spent on a Pace Car or Off Ramp)
2. DIR9001 mods
3. Polish your CD with something like this. Mapleshade Audio Products - MikroSmooth
3. "Real Glass" Toslink Cable (Check Ebay $20)
4. Get lucky and find the "right" Coax Digital Cable. They will all sound different, some may actually lower jitter. (Read and re-read Steve Nugents white paper on jitter).
5. Upsample to 48/20 with Apple Computers, output via glass toslink to Dac. (This appears to offer "the" lowest jitter to the DIR9001/1843 Dac chips).

USB Input:

1. Solid State Hard Drive
2. Quality Rips to the Computer (This is a can of worms)
3. Quality USB cable to Dac
AudiogoN Forums: Best jitter free USB DAC
4. Software upsample to 48/20 using Mac computers & Upsample using SRC in FooBar for lowest jitter with Valab.


My estimate is that even with all the above jitter tweaks above implemented perfectly, you still only get 20% of the jitter lowering capability of the Pace Car or Off Ramp 3.

This is not to say these are must have products, au contraire, lowering jitter for free is even more rewarding in some ways. This list is by no means all inclusive, I will update this thread as more "proven" jitter tweaks are exposed.

 

[Newk Yuler]

It's understood that the Valab DAC requires a low jitter source to meet its potential. The USB circuit in the Valab is designed with special consideration for USB-based jitter. What are the issues with the USB circuit in the Valab?

- Rand

 

[Bill Allen]

Rand- see the link above, under item 3 for your answer.

 

[Newk Yuler]

Quote:

Originally Posted by Bill Allen /img/forum/go_quote.gif Rand- see the link above, under item 3 for your answer.

Steve mentioned the Valab in a thread at Computer Audiophile some weeks back, recommending it as the clear choice for a DAC in its price range. Web searching led me to the Valab DAC threads here and soon afterward I purchased one. I understand if we're bound to the typical troublesome USB protocols we really need to have something in line that can recondition the data and properly deliver it to the DAC. I'd love to have Steve's hardware as part of my system but I have to be frugal with my audiophile purchases.

Kevin, the people at Vintage Audio Labs and Teradak are selling the design primarily as a USB DAC with a better USB circuit. The design certainly sounds as if it should be better for dealing with the troublesome standard USB protocol. Data is taken by an independent receiver, then it's reclocked and sent via I2S to the DACs. I don't recall reading anyone addressing, comparing, and making issue of this design. I'm very curious to know what the experienced folks in this thread think about the USB circuit in the Valab DAC. (You too, Steve.) Other than it's obviously another relatively inexpensive design with the inherent problems.

- Rand

 

[adam2434]

Pat and Bill - thanks for the input.

Yes, the board does look very delicate compared to the board I was using for practice. So, I think I will take Bill's advice of soldering new parts to the legs of the existing parts. Even doing this, it will be pretty tight soldering, especially for the IV resistors, as they have very short and thin legs.

So for this approach, I assume it would be best to make a light mechanical connection between the old legs and new leads - perhaps bending the new leads into a "J" and lightly hooking them on to the old legs before soldering.

Sound right?

 

[Bill Allen]

Adam-sounds like a plan.

Here is a picture of my friend Tony's Valab Dac. This is as far as any sane man should take this Dac. Full Blackgate FS mod for Dac Chip power supply, DIR9001 fs mod, Caddock I/V resistor and Blackgate 22uf NX HI-Q coupling caps. (In super E configuration)

Attachment 15976

Notice the large caps that surround the large voltage regulator. He originally tried a Blackgate 47uf FK, then stepped up to a 470uf FK and finally added an additional 220uf Fk for a total of 690uf. His conclusion was that the speed of the Blackgate FK was the most important aspect, not the size. However he concludes that a 220uf FK is the best choice for this position. Thanks Tony.

I rest my case.

 

[PatOMalley]

adam2434,

Just be aware that when using in place leads with the component cut off, the in place leads get fiddly when you heat them up. Solder melts and they move around a bit. A good trick is put a small bit of solder onto the new component lead, set in place, then heat the in place lead. That will hold the in place lead steady and melt the solder on the new component. As soon as the solder melts pull away.

I just tried the in-place lead trick when replacing my generic Vishay resistors with PRP today.

A very small bit of improvement on focus again. Worth the small cost and effort.

 

[pcourtney]

Bill, the problem with the Pace Car is the $1250 USD price point, would the Pop Pulse PC-Link at $110 be an option for us less heeled lovers of Computer Audio like me for instance

Pc Link

The chain being PC to Pop Pulse device using USB2, then to the Valab using Coax or Optical (Toslink)

The SP-II looks like a very neat little box of tricks. When plugged into the USB port of a PC, music selected by the PC is fed into the SP-II and it takes this digital stream from the USB port,cleans it up and then outputs it into a pristine, clean, "jitter" free digital spdif data stream that can be fed directly into the Valab or indeed any DAC.

The SP-II is highly flexible in that as well as having coaxial rca, optical toslink and balanced digital xlr spdif outputs, it also features an I2S output.

DACs that are fed an I2S signal are supposed to offer a slight improvement in sound quality compared to being fed a spdif signal.

I2S eliminates time related errors that cause "jitter" (a certain type of audio distortion). Usually the lower the "jitter" rate, the more "analogue" a device sounds as opposed to sounding harsh and "digital".
exceptional.

Specifications

* SPDIF Input - Output 24-96kHz
* USB Input - 24-48kHz
* C-Media CM-108 Chipset
* Pulse isolation transformer ( reduces common mode noise and EMI )
* Plug-and-Play with Windows and Mac machines
* The unit can either run on power provided via USB or a supplied 12VDC power supply


NB It would be nice is TeraDAK added an I2S input on their design, I think Bill has mentioned this before that I2S is the way to go to elimate jitter.

 

[pcourtney]

Cryo stock the PC-Link SP-II by the way

CryoParts Pop Pulse USB to SPDIF Converter

I know Bill has used them in the past !

 

[MikeW]

cm-108, well what do you know, that's the same chipset the valab uses.

 

[Angsila]

Pcourtney,
"It would be nice is TeraDAK added an I2S input on their design"


As I2S is a standard between chipsets on the same board, what are you talking about?

 

[zzodhi]

"Software upsample to 48/20 using Mac computers"

Bill. How is that done? I only see 48/16 as the highest in iTunes prefs. The 22uF NX caps I see at only 6.3V. Is that high enough for this?

 

[Bill Allen]

Z Man- Applications-Utilities-Audio Midi Setup-Properties for "Built-in Outputs"- Now you change to 48/20. (iTunes must be turned off when changing output settings in Midi) The 6.3V BG's work fine.

Angsila- Yes I agree an I2S input would be deluxe.

P.C.- I see no gain in using the PC-Link> the Valab uses the same USB chipset, a good clock and also converts directly to I2S. Proper termination of I2S is crucial for lowest jitter, one size does not fit all with the I2S bus. PC Link gets by this by using isolation transformers, but I question the quality. Perhaps there is "a little" to gain with a Monarchy Dip but now comes the expense and guess work with 2 Coax digital cables. Termination/Galvantic isolation is just as crucial with Coax. That's why I am a fan of "real glass" Toslink with the Valab Dac. Best bang for your buck.

Getting jitter to vanishing levels takes serious gear and serious experience. Sorry I don't know of anything out there that can get you even half way to the Pace Car or Off Ramp 3. I suggest you do what you can for free and then start saving your penny's for a real solution to jitter. Look at all the money you saved with the Valab Dac. Seriously lower the jitter and you have one madman of a Dac with the Valab.

 

[zzodhi]

Quote:

Originally Posted by Bill Allen /img/forum/go_quote.gif Z Man- Applications-Utilities-Audio Midi Setup-Properties for "Built-in Outputs"- Now you change to 48/20. (iTunes must be turned off when changing output settings in Midi) The 6.3V BG's work fine.

I never knew that existed. I can change that with built in but if I select the Dac as the output it immediately changes to 44.1/24 What?

I wonder if PLAY sounds so good because it bypasses this app? Where can I read up on how it works? Is iTunes always going through this?

 

[Bill Allen]

Z Man- Lets move any further Computer Audio talk over to here. http://www.head-fi.org/forums/f7/val...55/index2.html Best to keep this thread clean for discussions on hardware modifications. I have posted a few updates on the Computer Audio Thread (The CAT) to keep it going, maybe you could lend a hand over there too.

Meanwhile I made some progress using battery power on the Valab Dac and Pace Car. I picked up a couple used Lithium Battery Packs that are used for Laptop backup. These large chocolate bar looking devices work great and output 16.8VDC. The regulators in the Valab have no trouble with the extra voltage. Mine are made by Polarmate, one is 8ah, the other 4ah. I used the 4ah on the Pace Car and 8ah on the Valab. The 8ah can run the Dac for about 3 days. Nice!

Starting with the Pace Car, didn't think it was possible but yes ... an even cleaner window into the sound. I.E.Lower Jitter. Interesting, when using Lead Acid Battery's I could hear no difference with the Pace Car. Must be something to do with the lower internal resistance of the Lithium Ion battery's.

Now for the Valab Dac, well lets just say that it was like a "change of venue". With A/C power, imagine a Jazz Trio at a small jazz night club, dynamic performance to go along with the festive mood and overcome the background noise. With battery power, this same Jazz Band is now at a quiet lobby bar. Detail, decay and nuance is in spades but somehow the performance lacks the immediacy or drive of the night club. Both valid, you pick the venue depending on the music and your mood. Not! I want it all, both crystal clear and dynamic drive. I didn't like the sound at all using sealed type or car type Lead Acid battery's. This may shed some light.

Speaking with Steve Nugent he suggests using a lot more capacitance when using DC power. Upwards of 40,000uf when using sealed lead acid battery's. Remember with A/C power we are using the three 1000uf caps mainly for filtering the noise. With DC power we need quick recovery from transients, obviously the Li-ion battery are far superior in this respect.

Plan is to find "just" the right amount of capacitance using the 8ah Li-ion battery pack to achieve that perfect dynamic venue excitement for ... "my" tastes ... in "my" system.

Stay tuned!