Valab NOS DAC - subjective listening and modifications - Page 7

teradac. How can we check the reference voltage for that trimmer? Many times when mods are done it affects the voltage. It would be nice to know what the reference voltage is and where to check it.

Don't know if this what you're looking for.


Originally Posted by TeraDak
For those concering the clipping issue.
We current use a 390R resistor for the i/v conversion and it will output 2.19V at the full range audio data. It is impossible to listen the 0-db audio signal from the DAC , to pre/power amplifier and to speaker without any attenuation. It the source doesn't exceed -3db, there will be no clipping issue. However, if you would like to attenuate the signal in the preamplifier and keep the range as full as possible and without clipping. The i/v resistor in the TDA1543 output should be lowered to 340R ~ 350R to avoid clipping. The clipping issue is just a tradeoff for signal attenuation and it depends on the user listening condition. We will show the picture for analog output with i/v resistor 340R ~ 350R. For signal analysis, it should be 340R~ 350R, but it may not be the best for users in most real listening conditions.

(1) For user using the original 390R resistor, if you care about the clipping issue, you can reduce the resistor to 340R ~ 350R without loss the audio quality. If you don't have 340R ~ 350R resistor at hand ( 340R ~ 350R resistor is difficult to buy), you can parallel a 3.3k or 3.6k on the original 390R resistor. However, a 330R resistor is good aslo. The main difference is the maximum output voltage when a 0db signal is input.

(2) After that, connect the USB line to our DAC and repeat playing a 1kHz 0DB sine wave in PC. The wave could also be downloaded form our share space ( Public - Windows Live )
Use a meter and set it to measure AC voltage segment. Measure the RCA output or our DAC. The AC output is approximate 2.0V initially. Trim the VR nearby TDA1543 to find the maximum AC output. We usually trim the VR with the help of scope. But a meter is also good enough for tuning. If you have a scope, you can trim the VR such that the sine-wave is the most symmetric. The most symmetric output implies the maximum AC output in a meter.

The second step can be skipped it there is no meter or scope at hand. There is only few difference after step (2) adjustment.
/********************** Notice **********************/
The most important should be noticed is the VR trimming should be after the DAC power-on 30 mins. After that, the DAC will be in a stable state for adjustment. In the first 30 min, the TDA1543 was not in a stable stage. Trimming in the unstable state is no use.
/**********************************************/

Hi

Anyone knows where i can find a good r-core transformer 110-220 or 230 V for valab DAC? I have a hiss issue and it is due to the blue transformer.

Thanks in advance

may be : 50W R Core Transformer,115V//230V, for Preamp,DAC/R26-x - eBay (item 250393333112 end time Apr-19-09 15:50:15 PDT)

I changed mine yesterday by r-core transformer bought in France : SELECTRONIC ::: L'univers électronique :::

No vibration, no heat now and less noise.

This is weird... I get a sinus wave with my Canamp for some reason. Now instead of moving it further way so putting it on top do help but I need to find the sweet spot. As for my EF1 no sinus wave no matter what. Why would I get it with one amp and not the other? Canamp having it´s own PSU and the EF1 using what is it called a tranformator which is quite a bit away? But then why does it help bring it even closer

Hi guys

I got the Valab 2009 version(the distorting one people say).

After alot of testing, what is your recommended replacement for the Tantanium output caps?

Empirical audio recommended this solution:

"I'm going to share some trade secrets here for you:

3-4uFd V-cap oil caps bypassed with Sonicap Platinums .22uFd (in parallel)

V-Cap Oil Capacitors
V-Cap Oil Capacitors

Sonicap Platinum
Sonicap Platinum


Steve N.
Empirical Audio "

But it seems a bit too much hassle. So I ask you, do I have to bypass the v-caps, or can I just use the v-caps? Or can I just use the sonic caps?? Or what else you recommend if I just want to use 1 type of capacitator without bypass??

Just v-cap or just sonicap? and is the sizes correct? The emirical guy says: "3-4uFd V-cap oil caps" .... I find no size on that page which is 3-4uF ..

Can some of you help me... does it fix distortion also?

a big thanks!!!

Kris

Kris, I've also spent some time looking into output cap options.

Black Gate N caps have also been suggested, but they are hard to find.

I've been trying to find suitable caps that will fit in the existing spot and allow the case lid to be closed.

Most of the high-end film caps are huge compared to the stock caps.

I've been looking at the Elna Cerafines, which are supposed to be a decent electrolytic cap and should fit in the existing spot. 10uf 25v models are less than $1 US, so I wonder how much of an upgrade they can be over the stock caps.

So, I would also be very interested in suggestions for output caps, especially ones that would fit in the existing spot.

Is there an electrolytic cap comparable to Black Gate or a small film or PIO cap that would be a good choice to try?

Regarding the clipping distortion - that is fixed by replacing the 390 Ohm IV resistor with a 330 Ohm.

I tried a lot of capacitors and I don't believe in bypassing, it creates new proplems that I don't like.
I tried Black Gate bipolars and I think the standard versions sound better.
You can find them here:
Black Gate STD 10µ/16V bei eBay.de: Bauteile (endet 08.04.09 20:52:13 MESZ)

I hear thay many people really dislike black gate.. I dunno for what reason though. They really don't sound to good.

Can you tell me what sound difference you got with swapping out tantalum for black gate? Was the dac still warm? realistic? sweet sounding?

K

My (russian) tantalums was sounding very transparent but overbright.
The standard Black Gate 10uf 16V sounds quite balanced and clean and warmer than the tantalum.
When you spend a lot of money and time you will always hear a difference, probably not in but between your ears.
I think, but I am not sure, that the higher capacitance Black Gates sound slightly warmer, bigger.
After my last mod, 100uf 50V, I felt the sound was very relaxed and musical.

Dear Adriaan243...

I don't know if mine has got the russian, I am including a picture of mine here...

But, that sounds great, so the black gates are actually warmer and better than tantalum's?? I will get them then.

Anyone tried V-cap or Sonicap, what would difference be?? Those blackgates are so cheap also....

what is that 100uf 50v??

How did the non-Polar version sound btw, vs stock? I rather get stock from Germany, so cheap, but everyone else says NP blackgates are like heaven?

But this one... Black Gate Non-Polar N 100uf 16v Audio Grade Blackgate - eBay (item 130286373129 end time Apr-08-09 03:43:23 PDT)

.. it might be fake? But do you think this is the best match for the DAC?

Please guys.. some response The dac might be a bit harsh in stock form yes..

K

Bypassing the Jupiter Cap

In light of the current conversation I decided to try bypassing my Cryo'd Jupiter 4.7uf caps with .22uf Jupiter caps.Well Shaazam! Once again it looks likes Steve Nugent's magical formula works. (Bypassing 4.7uf film caps with .22uf film caps)

While the fully monty Blackgate FK power cap mods gave dynamic's to the lows and mids. The .22uf bypass cap extended this trend to the highs. This dynamic highs thing is very intoxicating and I listened to music so loud and so late my normally tolerant wife had to extract me from my throne at 2 am.

I let the Dac play all night and back up at 9 AM I have been sipping coffee and playing Ballet music to my wife's delight. "Dynamic Beauty" are the words that come to mind. Needless to say the bypass caps are staying in.

This could be the bang for the buck thing all you stock Valab Dac owners are looking for. A .22uf film cap will easily fit inside the case and should be easy to solder directly to the legs of the stock coupling cap. I will give this a try with the Control Dac and report back.

I know that Pat has already done something like this to his Blackgate output caps. Pat can you recap on your experience with bypass caps.

Since noone answerd me I just orderd 2 x (CAP-9324) - 33uF 16V Black Gate N Type...... was this a big mistake?? Is the 4.7uf the one I should have got?? honestly guys, was this a waste??

Are they 'ok' for replacing those Titanium tantalums? I don't know what the heck are those output cap's. But by putting in those black gates will i remove the 'tubiness' of the DAC?

Bill.... you think all types works well? Well the guy said use soniccap + v-cap.

K

Krisno,
while the stock output caps are 10uf the 33uf Blackgate N caps should work just fine, you should hear a more natural refined sound. In the future you could also try a bypass cap with the Blackgates. I believe Pat did a double bypass with his Black Gates.

Bypassing caps is more of an art versus a science. However when using film/foil caps I believe Steve Nugent may be on to something with the 4.7uf bypassed by .22uf. At least when it comes to low voltage output applications such as Dac's. I encourage everyone to give it a try.