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Valab NOS DAC - subjective listening and modifications - Page 43

post #631 of 1994
7/8/09 at 5:41am
I wonder if this is discussed before. The NOS mode of tda1543 has high frequency roll off at about 3db 20khz. in fact it rolls off as early as 10khz. so half the spectrum (but only 10% of the energy) is gone. i wonder if this has been discussed before?
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post #632 of 1994
7/8/09 at 1:43pm
I am using 2xTDA1543 with passive IV followed by tube output. I have tried replacing the IV resistor with Vishay VTA55 series, blackgate cap for power supply, 2stage voltage regulator (with TL 431).

The sound of low and mid is fantastic and loads detail but high freq is soft and lacks attack. Just wonder if the sinc compensation would help.
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post #633 of 1994
7/9/09 at 2:49am
Maybe try bypassing the tube output?

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post #634 of 1994
7/9/09 at 1:07pm
Do you have the ability to run something like RMAA on it? That would at least give you a frequency response and show if the HF is rolling off or not. Being NOS, I would suspect that it is.
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post #635 of 1994
7/9/09 at 1:29pm
I have tried the jupiters. I have swapped them out 5-10 times now for Obbligato 4.7uf, also tried the obbligato's bypassed with 0.22uf Sonicraft Gen 2.

The obbligato solution is alot clearer, but with AKG K 701 headphones, even through a tube amp, they are a bit sharp and sometimes fatiguing on high volume. On speakers I would have gone for the obbligato solution. Bypassing with 0.22uf sonicraft makes it a bit lusher and 'fuller'.

But with these AKG K 701 I just have to stick with jupiters, it is the most magical, also very realistic. But I must admit, they do sirup together the instruments a little, and bass is a little less 'explosive'.

Anyone tried the Jupiter HT, i doubt any difference?

K
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post #636 of 1994
7/9/09 at 2:58pm

Off topic from capacitors

A newbie question: It seems that a lot of people have doubts about spdif reclocking circuit of the mid 2009 version, so is there a simple way to bypass it?
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post #637 of 1994
7/9/09 at 7:39pm
Thread Starter 

no wait, i want to hear way way more about capacitors

Has anyone around here swapped any lately. arf.
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post #638 of 1994
7/9/09 at 11:14pm
Not sure if Pats comment is legit or sarcastic but I have changed the dac decoupling caps to 47uf Rubycon XYF's and bypassed each with a MKP1837 0.01uf. Almost all the other caps on the board have been bypassed with either 0.1 or 0.01 uf caps. Still burning in but it actually seems to have revealed a bit of high end harshness.

Now this may be the preamp as it does this crazy ADC then DAC conversion which I only just realised (to allow digital volume control). So, I may actually be hearing the limitations of the pre-amps DAC.

Cheers,
Rift.
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post #639 of 1994
7/9/09 at 11:45pm
Thread Starter 
Realrift,

I think you have lost all the benefit of the Valab going into another DAC.
Can you bypass that second DAC?
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post #640 of 1994
7/10/09 at 3:08am

Desolder the board!

Quote:
Originally Posted by ms142 View Post
A newbie question: It seems that a lot of people have doubts about spdif reclocking circuit of the mid 2009 version, so is there a simple way to bypass it?
I guess the simple way is to desolder the 8 links to the reclocking board and see how it sounds but becareful of overheating the pads. I might try this one day as I have modded my Valab but now it gives out only a v distorted sound!!!

tom w
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post #641 of 1994
7/10/09 at 7:54am
Quote:
Originally Posted by PatOMalley View Post
Realrift,

I think you have lost all the benefit of the Valab going into another DAC.
Can you bypass that second DAC?
Yes, I believe this is the case Pat. I will play around with another pre-amp. In initial testing with the other pre-amp I am getting some ground hum I think. This happens as soons as I connect the usb cable. Even if the dac is off and connected to the pre-amp, if I connect the usb cable, I get a hum. I may try and ground the dac, preamp and computer.

Cheers,
Rift.
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post #642 of 1994
7/10/09 at 8:00am
Hello
I passed the 220 bg at the lt1084 with a .22 m-cap mkp getting very good result .
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post #643 of 1994
7/10/09 at 9:51pm
Thread Starter 

chump tries to hookup a transformer

Gents,

I got the CineMag transformers in and screwed them to a boad and wired them to some RCAs but I am doing something wrong because alls I get is a slight buzz thru the speakers.

How I did hookup was

in red positive / brown neg
out yellow positive / orange neg

I did this with both, plugged in, and nada.

reference the schematic: http://www.cinemag.biz/output/CMOB-2.pdf

I moved the things between my phon pre and preamp and got the same falure so it has to be the wrong way I hooked up.

I would take a picture but the wife took off with the camera...

any help would be greatly appreciated.
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post #644 of 1994
7/11/09 at 3:44pm
Thread Starter 

"i want to cook you a soup that doesn't disolve"

so i got the wiring sorted out and it's nice.very nice. very old school. I have Bill's comments about simplicity in mind as i think about it all. what i mean is that the sound is very old school, fish eye lens on the midrange. Sade's voice is very real and you can imagine putting your arms around her waist, that's what I'm talking about.


The top end or the whole range does seem as 'extended' rather theose sounds are now placed in a spacial field. Meaning that a sliding hand on guitar is not in your face but closer to the back wall, where i suppose it really was. and that is my point about simplicity ... is this closer to whatever? i don't know, just musing.

Deep bass does just do the pipe organ rollout. The bass impact is more lush and, well, impactful, rather that )tight( as latex. Much more character, nuance, texture, to the ever loving bass. you get that nice pebbly thing on electronic bass and tons of radiance from acoustic bass.

one thing is that you are much more captured by the sound. more narcotic. i used the solid steel core looking for old school sound and i know that this core has more distortion than the hi nickel ... so i am getting what i asked for, supposedly. and i vote 'yes' on it.

the mistake i made in wiring was to reverse the wires and to plug in incorrectly with interconnects. whenever my wife gets back from New Hampshire with the camera is when i can show a shot of the breadboard.

man, i like this. i wonder how the tube buffer will compare.

cost? ~50 shipped from CineMag.

Another small thing is that at first the sound seemed faster and slower at the same time. there is a serious reorder of the PRaT thing. very colorful. i guess you can tell that i am digging this. is it the bee knees, Don? could be.

EDIT: i moved the transformers between my phono preamp and the line preamp and there really doesn't seem to any shrinking of extension top or bottom and it delivered a similar increase in the midrange impact. what the hell!
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post #645 of 1994
7/12/09 at 9:18am
Pat,

It sounds like a delicious soup. Thanks for the review. When I get some cash (I start my new job tomorrow ), I may go this route.

A few questions:

1. If you had your druthers, would you go for the Hi-Nickel instead?

2. If you intend to keep these wired in, how do you plan on permanently placing the trannies? They are small, but I don't believe small enough to fit inside the VALAB. Again, trying to keep the wiring as short as possible, I can possibly, in my mind's eye, see them sitting atop the VALAB.

3. Last question - knowing that you have tried a number of film caps and being honest with us, are the trannies that much better than the caps? I know you are going to say "different not better," but I thought I would ask anyway.
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