Valab NOS DAC - subjective listening and modifications - Page 110

mrdon, I am using a similair product, the musiland usd 01. I dont think there is much between it and the M2Tech from what Ive read. But I went for the Musiland because Its more mod friendly. After I filled it up with BG FK, cant live without it now, the Valab just sounds distorted without it.

Glad you like those NX, thought I was the only one who was using them here. I find them more transparent/neutral then films caps I have tried.

For anyone interested, I just posted up my valab for sale yesterday

The musiland is not compatible with OS X, correct? That is why I would need the M2Tech.

It is funny...there was a time on this thread when the BG's in the output stage was not discussed. Glad you are liking them. I never put films in that spot so I am not one to compare.

BG NX are mostly only rated for 6.3V so watch that, fine for the output caps, but pretty borderline for most other places in valab

Lundahl

Will the Lundahl transformer, you guys have been installing, provide any benefit when using the fiber optic input? Thanks in advance,

Not really, the whole point of the transformer is to disconnect the two electric circuits, you already have that situation as the electrical signal gets transformed into an optical signal is transmitted through the cable and transformed into electricity again.

Hard to tell but you might gain something using a digital interlink with the lundahl, sound quality might be better than with optical....but that is down to the quality of the execution of either option I guess (personally never have been a fan of optical cables).

mine finally got through customs.....
a quick listen proved no hiss no humm and the makings of a nice sound are definitely there. CD Player is on repeat, burn in has officially started.

marcelnl, on the other thread you said

I played with that option for the Valab....where the 75 Ohm is in the signal path as for the 0.1 uf cap

how did that work out and what is the wiring for it?

Thanks

well I played with the thought, my Valab just arrived and is in burn in now. I'll unscrew the lid as soon as it has 200 hours under its belt. Only 195 more hours to go

When I get to installing a coupling transformer I'll try this as it usually is an improvement to get rid of stuff in the signal path. A simple ladder resistor network as a volume attanuater sounds so much better when you put the ladder in the 'negative' and the single resistor in the signal path.

I put my old Valab 2.1 back to stock today, took my time and made everything nice and pretty, cleaned it up good with 99% alcohal, looks factory fresh Will probably sell it. Im actually listening to it right now, and it sounds better then I remember, I wonder if it was a mistake to put a 330 ohm resistor in it, as it seems there are elements of the Stock dac that sound better then when I had it modded, the big differences are the UF rating of the output caps and resistors.

Glad you pointed that out Mike,

My Valab at the moment is running on 44uf per channel, thats 2x22uf bg nx hiq in super H configuration, it sounds rich and the bass is tight to the very bottom.

I have texas 390r iv, and really cant hear any clipping in normal use. I chose to fork out on them at this spec despite the fuss about 390r clipping, I could of played safe and gone for 330r/340r (as its not cheap those texas) but I trusted my ears and the lower 330r I had tried just didnt have the oomph!

On these forums we concentrate on the Dacs and some tend to forget that we all have different systems and tastes. Of course a good cap will be better then the stock, but what value? The stock is 10uf not 1uf or 44uf. So whats good for the goose isn't necessary good for the gander. Bill and Pat have both pushed these dacs to the edge of performance, but look at the differences in there choices of components, prp vs caddock or obbligato vs jupiter? NO, this is a false dichotomy! This is not a case of which is best objectively, but subjectively.

There is no groupy peer pressure here, but we have still see the occasional charcter come and go who complain to us they are not getting miracles when the copy our mods, but thats going to happen. Now if I was designing a new Valab I might call it something like the Chameleon and put a space for unique sig of the modder at the back because everyone of them will be unique, is that enough of a hint?

the valueof the stock output cap is probably a guesstimate by teradak, in an attempt to accomodate the input resistance of most systems.

Has anyone measured the output with f.e an oscilloscope or with a good voltmeter(capable of handling the freq range) and a test CD? That way the required lowest capacitance in that given system can be established quite elegantly, I'll use that method to determine whether I need something as big f.e. the 8uF Relcaps I used in the analog tube output amp of my CD player.
Calculation of the required cap is also possible, but not as straigh forward imho.

There's a good chance that 4-6 uF is enough for most systems, the difference may be larger in case anyone has ripped out the output filter and 47Resistor at end of the analog output section as in that case the input resistance of the amp will drive the capacitance requirement (or lowest freqency the output cap will let through).
I have some 1uF Mundorf silver gold oils, but probably will need something larger for the output.

The trick is to get enough low end extension by using enough capacitance in order to stay away from the borderline area where phase linearity is not good at all yet the lowest freq. do get through.

What is 'phase linearity'. Ive got some old stock jupiter 5.5uf on the way to compare to the 44uf bgnx in the dacs. I think with lower value like 2.2uf you can hear the bass but there is still a loss of body/richness for me.

Its not simple, I have 2 amps at the moment one with Blackgate and one with Silmic2 on the decoupling psu, the Silmic are thinner sounding. I have a 100k pot on the way to change the impedance of the amps which use 50k at the moment, to again determine better what value caps to put in the Valab/Chameleon.

I think there is a tendency to go for lower value caps because they are physicaly smaller and it is cheaper for higher end film types. This, in some cases, this may be a false economy.

Another way of evaluating system changes is the Audionote 'contrast' method. When I first heard a full-on AN system what struck me was how very different each of my test cds sounded on it. I really felt I was hearing the recording session as it was. The soundstage in all directions was radicaly different as was the tone, clarity and balance with each recording. I cannot say what the AN setup itself sounded like, it just was not there!

The AN kit seemed to have no character at all, it was uncanny. Their methodology (I found out much later) puts less reliance on subjective evaluation and depends more on the idea, that if you hear more differences between different recordings, more of the original information is getting through. If a particular 'nice' cap gives similair character to all you music then it is colouring and filtering the sound. That 'nice' cap may be prefered but I will never forget that AN system.

Not sure I can explain phase linearity on caps in a couple of words, wikipedia might have an article on that (or some audio site) might do a better job.

5.5 uF might just do the trick, I'm quite sure you do not need 44 uF ;-) (unless you are using an amp with a very low input resistance and did cut our the 47k resistor at the output of the DAC),


In short; Caps affect the phase difference between current and voltage by nature, the larger a cap gets the lower the frequency roll of starts. If you use a 'borderline' sized cap of which the roll of value is close to the audible range you may hear/measure the full low freq range yet there is less power available, and subjectively you'll hear less ' slam'/'push' in the bass registers.

I'm not sure whether changing your pot is the best approach to get away with a lower sized cap, the pot influences input impedance for the DAC and the cabling so that would work, but only if the amps input resistance is not fixed(see later) BUT the first amplification stage may be affected when you use too high of a value (they did not use the 50k Pot just for fun, I hope).

IMHO the better method (and more linear too) is to connect a resistor of appropriate value between the input 'plus' and 'minus' of your amp (in your case 47k) as the changing resistance of the pot may influence sound quality.

Most tube amps have an input resistance of about 100k, while transistor amps typically use 47k.

Pat, I get the feeling that you are also noticing the effects of input-output resistance mismatch. In some cases a buffer amp can sort that out or indeed the good old transformer can help out and provide galvanic decoupling at the same time (BTW I love these chunky parts, though high quality parts are very pricey).
The resulting sound quality of either option can imho not be generalized to 'use a tranny for more bass' as the performance of either option will be depending on the efficiency of the resulting match between all equipment thus linked and the individual quality of the parts used.

perhaps as a tip; I always put two trannys at a 90' angle to each other as the magnetic fields may well influence each other