Valab NOS DAC - subjective listening and modifications
Jul 31, 2009 at 1:20 PM Post #736 of 2,013
Quote:

Originally Posted by PatOMalley /img/forum/go_quote.gif
Then I just added a pulse transformer to the coax input. Now cymbols, when hit, float and trail above/over the rest of the music at it plays. The do not disappear into the background or get in your face but they are now more fully realized as trailing transients.


Pat, sorry if I'm asking a basic question here. So is the pulse transformer inserted between RCA connector and output cap here? You may have said someting about this in the previous posts...

Thanks
 
Jul 31, 2009 at 1:24 PM Post #737 of 2,013
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Jul 31, 2009 at 1:56 PM Post #738 of 2,013
Quote:

Originally Posted by PatOMalley /img/forum/go_quote.gif
rhodes54,

I was looking at that Lundahl transformer. Looks big so I went with this small job to see if it made any difference and for size. Let me know if that Lundahl works out ...

It's all about about galvanic isolation, as I heard someone say recently.



I just checked the size of the lundahl. It's 15x9x11mm so that shouldn't be a problem fitting it in the case.
 
Jul 31, 2009 at 1:58 PM Post #739 of 2,013
Quote:

Originally Posted by hifi2001 /img/forum/go_quote.gif
Pat, sorry if I'm asking a basic question here. So is the pulse transformer inserted between RCA connector and output cap here? You may have said someting about this in the previous posts...
Thanks



You are confusing two stories here. Pat has been experimenting with output transformers on the analog output of the DAC.
The above picture is from a pulse transformer on the digital RCA input of the Valab.
 
Jul 31, 2009 at 4:29 PM Post #741 of 2,013
Does anyone know where to get the PE 65612 transformer in the UK? Mouser charge £12 to ship to the UK, but they only cost £3 each! If other people want them, I could buy a few, post them on, and split the total postage cost equally. Or if someone else wants to do it, I would pay for 2.
Bill, would you ship the DC-30W to the UK?
Thanks
 
Jul 31, 2009 at 11:02 PM Post #743 of 2,013
Quote:

Originally Posted by awkwardbydesign /img/forum/go_quote.gif
Sorry, I mean Norm.


I don't see why not. It is being shipped from Taiwan to your country. Or better yet it is being shipped from TeraDak to your address... PM/email me privately and I can let you know what it will cost. I seem to recall it costs the same.

Cheers,
Norm
 
Jul 31, 2009 at 11:04 PM Post #744 of 2,013
Quote:

Originally Posted by zzodhi /img/forum/go_quote.gif
HiFi - its on the input. In this case the coaxial.

I use this transformer on my USB interface in my giant dac. It works quiet well and reduces jitter



Thanks for the clarification guys! I must have missed the starting point where this topic first started in the thread :)
 
Jul 31, 2009 at 11:36 PM Post #745 of 2,013
Quote:

Originally Posted by hifi2001 /img/forum/go_quote.gif
Thanks for the clarification guys! I must have missed the starting point where this topic first started in the thread :)


Here is a good thread discussing a pulse transformer application.

http://www.head-fi.org/forums/f6/add...ransit-129132/

Two things I am taking away from it this time is that the S22160 is a bit better than the PE-65612 that I am now using. And so then it is most probable that the Lundahl may again be a bit better. I think I will opt for the Lundahl since I have proved concept to myself.

Second is that different cable lengths contribute to impedance matching. This can get goofy. Different lengths of Belden. Then what if you try silver? It's time for wire and connectors in bulk from ebay.
 
Aug 1, 2009 at 12:27 AM Post #746 of 2,013
In looking at the PE-65612, S22160, and LL1574 it looks like the the Liundahl is 100ohms on secondary and 75ohms on primary. I don't see any specs re the other two being any different at primary/secondary.

The VALAB has a 100ohm resistor onboard so that you can put the Lundahl with 100ohms facing that resistor and with 75ihms out to the cable. THAT would be impedance matching, no?

It may be that my PE-65612 should be flipped around. I will give that a try ... just to see. Then I will get me the Luindahl for sure. In looking at the datasheet for the Lundahl, the pins are telling me to flip my current transformer. It may be that most applications of these transformers are in reverse not giving best match.

I just assumed 75ohms on both.

EDIT: Just had another look at the datasheets and the PE-65612 is 1:1 @ 75ohms each side. The Lundahl being 1:1.2 @75/110ohms. Their ya go. Lundahl it is for better matching.
 
Aug 1, 2009 at 3:43 AM Post #747 of 2,013
Hey Paul/ Norm,

Thanks for the input about the DC-30W. I was tempted to get one by what was written by you guys.
But I need advice of a question, I have already replaced the original Blue transformer to a toroidal, any changes in SQ by replacing the DC-30W?

Thanks.
 
Aug 1, 2009 at 3:19 PM Post #748 of 2,013
I need some help again...

I have the Valab 2009. Changed the output I/V. Got some 0,5mm silver hookupcable and attached some Jupiters. Also have tried some Obbligato's.

The obbligato's are a bit sharp, edgy. The jupiters are a bit more realistic and has this added 'thickness' to the sound. Making it fulled sounding, but the jupiters looses out the pinpoint accuracy, spatial reproduction of the obbligato's.

How would a Mundorf SIO work in this dac compared to obbligato and jupiters? Anyone tried both?? Is the mundorf SIO almost as smooth as jupiter but with good soundstage and spatial positioning? The jupiters sometime sound just too dark and slow, though realistic.

Any thoughts??

K
 
Aug 1, 2009 at 8:57 PM Post #749 of 2,013
K,

I don't think those Mudorf's are going to work out either. The last thing that the Obbligato's or Jupiter's do is 'edge' or 'sharpness.' You can probably try 20 different caps and make 30 more posts but it is not the caps, IMO.

I would look somewhere else for the problem and leave the DAC alone. Once you figure out the core issue then the DAC will sound fine as is, with whatever caps it now has in it.

Do not buy any more caps. You _could_ try adding the pulse transformer on the USB input. It is most probably jitter coming in from whatever you are feeding the DAC with. I have no advice on adding the transformer hookup to the USB. I don't know what it involves as it is not my concern.

And don't go asking about Mudorf input caps on the USB. Just don't even thing about doing that. ;-(

-P

Quote:

Originally Posted by krisno /img/forum/go_quote.gif
I need some help again...

I have the Valab 2009. Changed the output I/V. Got some 0,5mm silver hookupcable and attached some Jupiters. Also have tried some Obbligato's.

The obbligato's are a bit sharp, edgy. The jupiters are a bit more realistic and has this added 'thickness' to the sound. Making it fulled sounding, but the jupiters looses out the pinpoint accuracy, spatial reproduction of the obbligato's.

How would a Mundorf SIO work in this dac compared to obbligato and jupiters? Anyone tried both?? Is the mundorf SIO almost as smooth as jupiter but with good soundstage and spatial positioning? The jupiters sometime sound just too dark and slow, though realistic.

Any thoughts??

K



 
Aug 2, 2009 at 12:36 AM Post #750 of 2,013
Jupiters are super smooth, but lack spatial precision, and feels like lack of detail.

The obbligato's are sharp / edgy at times...... Probably the AKG K 701 which are a bit bright.

Anyways, I might try the Claritycap MR ....

K
 

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