Valab NOS DAC - subjective listening and modifications

[roker]

Quote:

Originally Posted by Amertuollig /img/forum/go_quote.gif My bodybuilded valab dac : http://amcycloplouedern.free.fr/valabOut.jpg http://amcycloplouedern.free.fr/valabSide.jpg http://amcycloplouedern.free.fr/valabIn.jpg I like the Obbligato Premium capacitors (10 uF). The I/V resistors give also their own sonic properties to the sound of the dac. Actually i am using NOS 360R resistors for which i have no details except for the tolerance (+/- 2%). More smooth, accurate and natural sound with these resistors in comparison with the 350R fim metal resistors used previously. The wires have been replaced by Gotham shielded single strand cable and numerical shielded cable. Very very nice sounding DAC.

How much did that cost to mod?

Seeing stuff like this is what makes this forum awesome. Can you post your complete setup?

 

[tubes]

Amertuollig, very original and a nice clean job. Let us know exactly what changes you made and the sound improvements. Are you done or are there more changes to come?

 

[Amertuollig]

The main changes are :

replacement of the transformer by r-core 50 VA 230V transformer (no heat, no vibration) ~ 30 $

replacement of the output 10uF capacitors by 10uF Obbligato premium capacitors 2x22 $ (Obbligato Gold Premium Caps | Diy HiFi Supply)

replacement of the 390 R I/V resistors by 350 R metal film resistors (not completely satisfied by this modification in particular in the treble) and after by the unknown NOS 360R resistors (recovery equipment).

The wires have been replaced by Gotham shielded single strand cable (i prefer to sound of this wire in particular in the treble) and numerical shielded cable (recovery equipment).

The chassis has been cut on the bottom to permit to get the pcb out of the chassis without desolder them.

The alumium plate used is also recovery equipment.

The sound improvement i wanted was more fluidity in particular in treble and high medium spectrum and a little more refinement of the overall tonal quality. To my point of vue, the replacements of capacitors and resistors (not wire) have prior of other modifications.

Probably, i will test other I/V resistors but i am very pleased with the subjective listening actually.

My complete setup is :

1. CD player Icos Fado ICOS gamme hi-fi used as drive or Personal Computer
2. Modified tda1541A Satch Dac
3. Amplifier Lavardin IT Lavardin Technologies - Model IT
4. JM Reynaud Concorde Signature loudspeakers Jean-Marie Reynaud créateur d'enceintes acoustiques hautes performances

 

[krisno]

I have a question.

The 390ohm resistor 'clipping' problem. Is that the resistor which sits beside the axial ferrite bead links? Because, on my DAC, I have not got the march edition, the PCB says 340R beside the resistor. Does that mean that my resistors are 340R or is it just wrong writing on the PCB? ... Are these 390R or 340R ? if it's 340 I don't need to swap them out do i..

Second question, anyone know the diameter size of the holes the Tantalum's occupy. I plan to put some wire there. Is it 0,5mm holes or are they 1mm in the PCB that is ??

Thanks..

K

 

[Amertuollig]

You can deduce the value with a resistor color guide as : Electronics Reference: Resistor Color Code Guide

I think that the value for these resistors recommanded by the manufactuer (Teradak) of the pcb is effectively 340R but Vintage Audio Lab have implemented the dac with 390R value for reasons explained somewhere in an other thread.

The diameter of the hole is between 0.5 and 1 mm. The diameter was sufficient to solder my big caps but it will be usefull if you have de solder pump.

 

[krisno]

So 1mm cable won't fit into the holes where the tantalum are fitted?? .... I am just wondering what to buy... either 0.5mm silver cable or 1mm cable..

Do you know the mm of leads out of the obligato's premium..




Also...

My dac shows 47Kx2 it says written beside the 2 output resistors... I need replacement for these.

http://www.hificollective.co.uk/comp...resistors.html

I look at that pages, Holco seems cheap and its 'film'.. But I don't understand which one I should get. Do I look at the K rating or the R rating? If someone can find the one and paste in the spec under here I would be happy. Thanks guy

 

[Amertuollig]

After measurement, the diameter of the obbligato's lead is about 1mm.

 

[krisno]

THANKS!

But I still need to know the answer on that resistor question, can you have a look at that list and find a 47k ohm of them? eh.. sorry, I know its basic.

Amertuollig . Do you know if the obbligato lead's go into the hole where the old tantalum's where?

 

[r8833]

Hi Bill

What's the 47k idle resistors do? I bypassed mine by soldering caps straight to rca's and it sounds fuller

Rich

 

[krisno]

I ended up with 2 Tantalum(audio note) 47K ohm resistors, £2.80 each. Most expensive resistor I have ever seen. Some people say it's important and Meridian cd players have 47kohm resistors, so why not me too ..

 

[Amertuollig]

Quote:

Originally Posted by krisno /img/forum/go_quote.gif Amertuollig . Do you know if the obbligato lead's go into the hole where the old tantalum's where?

No problem, the lead of my 10 uF Obbligato cap go into the hole where the old tantalum's where.

 

[Amertuollig]

error

 

[krisno]

hmm.. I might have done a mistake here. Does the output from the output caps pass through the 47kohm resistor's on the valab board or not? .. If I solder a 47kohm resistor on the output lead of a output cap, would that be the same, or are these 47kohm actually not even in the signal path? ..

 

[Amertuollig]

I have to verify something i do not understand but this morning (i do not have enough time) i observed that the output AOL was connected to the + lead of the 10uF capacitor, the other lead being soldered to the rca and surprisingly the serial 340 Ohm et 47 KOhm were in parallel to the 10uF capacitor ???

 

[krisno]

I don't understand this either. Therfore I cancelled my order on the tantalum's etc... I will just solder the Obbligato's directly into the board. This is way above my understanding ..