[marcelnl]

it might just be that the better bass is due to the low freq rollof, which might improve with the output filter because the impedance is then fixed at 47K
All wil depend on the characteristics of th eamp you;re using, ever tried a different one wo the output filter?
 
 

 

[Wood]

Could be,  I thought it was just a low pass filter and the resistors were for dumping dc return. I first noticed the high frequency 'distortion' after I changed the decoupling caps from silmic to bg. Perhaps the bg being more transparent or extended highlights it. The dac is running to a valve buffer as it is, had to because of impedance mismatch between direct dac - power amp. 
 
The sound is definitely rounder than before, but perhaps a tad more hifi, might try swapping some parts in the filter, see if changing the smd caps to polystyrene does anything.

 

[marcelnl]

blackgates as decoupling caps as in output caps or in the DC supply of the dac chips?
I"d personally invest in getting the sound optimized without the output filter, as it does all sorts of nastyness with the phase linerarity too
Your treble distortion being present without the filter and not with it makes me rather think there is a problem which the filter is hiding but not curing......

 

[jjlucas76]

Guys,
I need some help with the Valab DAC v2.1 I have dona all sort mods on it an after almost one year I have realised that the USB is not working. OS X does not see it and Windows XP / 7 find it just as Unknown USB device. Any idea on how to fix it?
 
Cheers
 
JJ

 

[marcelnl]

it would probably help if you listed the mods you did....

 

[jjlucas76]

The mods are the usual ones:
 
blackgate caps for the power section. 3x 1000uf 16v + 220uf 16v
 
Sanyo oscon 100uf 16v caps for the digital section
 
blackgates 47uf 16v for the decoupling the dacs
 
charcroft resistors for the output going into mundorf capacitor supreme 3.3V and then straight into WBT sockets. 
 
AMVECO power supply toroidal transformer.
 
 
I hoep this can help. 
 
The problem is that the dac although is discovered as devie but as unknown one for Windows XP and 7, on OS X it does not show at all.
 
Many Thanks
 
JJ

 

[marcelnl]

I'd say that your mods probably do not affect the USB part, unless f.e. the capacitor that powers the USB chip came loose...
 
I never used my Valab's USB port on any computer so far, so I can not tell how it should be recognized, I only know that it does not need any additional drivers....Hope someone else is able to help you out here!

 

[Wood]

Yep, loose capacitor, that happened to me.

 

[donpoon]

Need help trouble shooting my Valab.  Mine is a Late 2008 (Dec) version.  One of the very first generation. 
 
I have been using it with the Turtle Beach Audio Advance Micro optical output without any problem.  I usually run my computer under Linux.  I need to switch to Win7 to get something done and decide to setup my Audio Advance Micro under Windows.  I installed the driver downloaded from Turtle Beach and it ran smoothly.  However, Valab started giving out distorted and very low sound since then (the static noise is higher than the distorted sound of the song).  I switched back to Linux and it has the same symptom.  I test with both USB and Coaxial input and the symptoms are all the same.  I got static noise even if there is no signal input being fed.
 
All LED seems to light up normally and I don't see anything component burn after I remove the case.  How should I proceed to find out what is the problem?

 

[Wood]

It sounds to me that one or two of the TDA1543 have failed. I would try replacing all the chips with new ones , you can get of ebay for a buck each.

 

[donpoon]

Thank you so much for your suggestion.  Seems like it's not as bad as I thought.  I have ordered ten TDA1543 from Taiwan.  Will have to wait for the shipment. 

 

[realmassy]

Good luck with it, I too love my Valab!

 

[LosNir]

Hi, I just got my Valab Luxury with Independent Power and I'm ready to mod it

 
What are the most important mods?
 
I tried to find out but it's really hard keeping track with the latest versions on such a long thread.
 
Thanks.

 

[Wood]

The big 3 are;
 
i, change the output coupling caps to film.
 
ii, decouple the 8 TDA1543 with  decent electrolytics, 47uf 16v works well.
 
iii change the two I/V resistors to Texas Components TX2575.

 

[LosNir]

The output coupling caps are the 10uF on top of the 2nd board, right? What is recommended?
 
And where are the decoupling caps for the dac chips? Or do I need to add them by myself?
 
Thanks.
 
Edit:
 
Will this do the work?
 
2PCS 10uF 100V ERO MKT 1813 Metal Film Capacitor