Valab Dac-First Impressions - Page 51

The 2009 Valab Dac's have arrived.

My two 2009 Valab Dac's arrived this morning after being stuck in Customs for 1 week. The plan is to leave one in stock form for control (C-Dac) and mod the hell out of the other one (M-Dac).

The C-Dac has been running since noon today, there was a positive change in sound at the 4 hour mark. (Don't remember that happening with the old board). I suspect it will still take the full 180 hours to break in but the new board is off to a flying start.

(Hey, Paul)

I followed all the traces and drew out the dac/output circuit board on a piece of paper to see what gives. We are looking at your basic I2S input, Bit Clock, Word Clock and Data. As advertised there is only a 390 ohm I/V resistor and 10uf coupling cap in the short analog circuit path. The resistor is hooked to ground and the signal does not technically travel through the resistor. After the resistor, the signal actually does pass though two ferrite blockers on its way to the coupling caps. These FB's are hooked to ground via a 5600pf micro cap for noise filtering. (The FB's could probably be removed without any effect in most systems). The coupling caps are hooked to the RCA jacks with a very short piece of wire. (I'm thinking silver wire)The output side of the caps is loaded with a 47k resistor to ground. This will drain any DC voltage from upstream when no signal is present.

It just doesn't get any simpler than this my friends!

Here is schematic for the dac ah which is very similar.
http://www.audiodesignguide.com/DAC/...ircuit_new.JPG

Ok, now for great unknown ... that 500 ohm variable resistor everyone keeps talking about. It connects the Bit Clock to ground .... Loading of the Bit Clock. Humm!

Ok you got me; I have no idea why you would want to do this. Perhaps it’s just a simple way to control the voltage/current on the Dac chips, perhaps something cleverer.

Anyone???

Sorry for the dumb question but is the e-bay only place to get this dac.I googled it couldn't find another source.If so,when are they going to be on sale.Any dates?
I've been checkin e-bay for a few weeks but nothing so far..
Thanks

aka Paul replies

Bill,

Thanks for the word on the new layout. Since I ordered the mica I will swap the noise filtering caps and remove the ferrite. Also swap the caps on the DACs /w 4.7uF Rubycon's and call it quits.

The thing is so over the top now that I will be happy to call it a big win.

Well, I got some wire on the way from Bud Purvine. Pure voodoo. He says attaching it to the RCA ground will affect the dielectric in a positive way. Who knows? We'll see.

Mod Dac Upgrade Parts List.

I just got off the phone with Parts Connection and the upgrade parts are on there way. I decided to go all the way and order the best parts available for the Mod Dac. Total cost of upgrade parts exceed the original price of the Valab Dac, but if you want to play, you have to pay.

2 ea Jupiter 4.7uf- Silver Leads- Coupling Caps
4 ea Caddock UF340 200R resistors I/V Conversion
3 ea Blackgate FK 1000uf 16V Power SupplyCaps
16ea Blackgate FK 47uf 16V DAC/RegulatoCaps
1 ea Blackgate Fk 220uf 16V Dac Board Regulator Cap

I would like to thank Steve Nugent for helping me map out a parts upgrade plan for the Valab Dac. Steve suggests using all FK Blackgate caps for maximum performance. I will layout the plan in order of best bang for the buck.

1. Replace the small 10uf Mica caps on each Dac chip with Blackgate FK 47uf 16V caps. (8 total)

2. Replace the single 47uf cap for the big regulator with a Blackgate FK 220v 16V . (1 total)

3. Replace the 3 each 1000uf power filter caps with Blackgate FK 1000uf 16V. (Items 1-3 are about Soundstage Size & Bass Slam)

4. Replace the 2 each 390R I/V resitors with Caddock Persision USF340's. Parts Connection does not sell a 400 ohm UF340 so I had to buy two 200R and will wire these in series. (This will also provide the Teepee resistor circuit that will keep standing DC off the primary if I should ever decide to try output trannies)

5. Replace the 10uf Titanium Mica output caps with my favorite Jupiter 4.7uf Caps. (2 Total)

6. Replace the remaining 8 each 47uf regulator caps with Blackgate FK 47uf 16V Caps. (This is to supply more stable current to the various Digital Chips and reduce jitter)

Don't hold your breath waiting for the results of my Mod Dac, the 2009 Valab Dac is a no brainer in stock form.
I have about 30 hours on my Control Dac and it's sounding really really good. I would say it is already nearing the sound of last years broke-in Valab Dac.

Better get in line for the next round of offerings on Ebay. I have a feeling the the Year of the Ox is going to be a great year for Vintage Audio Labs.

?

I will tell you what they are after I remove them and have a look.
Read a few posts on caps + DACs. Some say using lowest value is best and suggest .1uF foil or 4.7uF Electro. I would have used the .1uF BG Non-polars but Partsexpress jacked up the price on them. I copped 4.7uF Rubycon's for the job. I think Bill is right for going with all BGs and I half wish I did but I hate getting gouged even for a few.

Anyway, the smaller value is said to speed things up. I used .1uF on all other opamps I have in use and it really helped with clarity and weight. I think the 4.7uF will be an improvement but I won't lose sleep over the .1uF. This thing has exceed my expectations by far already.

I can't wait to see pictures of how those Jupiters fit. Look how big 1uF's are on a Hagerman Clarinet board:

I got some rumors that a no compromise Valab DAC with independent power supply and new output stage with best output transformer will be available during the year of the Ox (just in a couple of months). I hope Kevin reserves one for me!

the word from above

That's what the almighty Kevin wrote me in an email. Rumored also is that the transformers will be available separately to back fit current DACs. The transformers are said to be large and the implementation will be interesting to see. Inside, outside, wider box?

im still waiting for mine, kevin emailed me on monday and said that it would arrive this week, here it is saturday and still nothing. Maybe it's stilling in china somewhere on that long holiday. I shipped my defective dac off on December 26th though, this is starting to get ridiculous, im thinking about just writing it off and going with a Keces at this point. Typical QA problems, exploding capacitors, and constantly changing design, beta testing on the public.. sigh.

Pat, Kevin spoke of a new wider box for DAC and tranny but he has still some problems to solve for this no compromise upgrade I hope even with better coupling and regulator caps.

Here I want spend some words about Kevin's kindness and professionalism too.

The delivered DAC had a problem on one channel, a constant hiss, even after about 200 hours of burn in.

Kevin decided, without any discussion, to ship me another DAC (the new model) for free. It arrived today and it sounds in a a superlative way even before starting to burn in as usual.
A unique customer service, after Kevin's carefulness I must admit that my prejudices on chines products are solved.
I ordered some days ago his solid core interconnect that separates in a galvanic way, with the 2 trannys in a wooden box, the line. If someone wants it I'll post my impressions when I get it.

To MikeW: sounds strange ... did you get the EMS tracking number from Kevin?

bleeding edge

Hang in there Mike. It's worth the wait.

The variable resistor in my DAC is in the path with the 390 resistors which were swapped out for KOA Speer.



I also swapped in Rubycon 4.7uF/50v for DAC decoupling. Previous caps were 47uF.

If anything the sound is rounder, more schmoozy, sweeter, rather than any increase in detail. The ability to unravel rhythm and degree of presence is still high. Still very clean overall. To rate the mods so far the biggest positive was the output caps, next the IC + clock caps.

Historicus, I saw those interconnects as well as the power cords with the trannies. So the interconnects have transformers? Is this the same as transformer coupling ....?