Valab NOS DAC - subjective listening and modifications
May 20, 2011 at 6:58 PM Post #1,922 of 2,013

Having taken a look at the schematic, I can actually follow what you are saying now :)
What would doing this achieve? won't it be more susceptible to noise / EMI? I take it that's what you have in your own valab, any subjective findings on the audible differences between this and the default setup?
 
You got some BIG ASS capacitors there 
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Quote:
You could bypass the circuit board completely and solder your output cap directly to the dac chip. 
 



 
 
May 20, 2011 at 7:06 PM Post #1,923 of 2,013
I was just trying to get it all to fit in the case. It seemed easier to connect the caps there rather than run them down to the front of the board and then back again to the volume pot. I remembered someone (Bill Allen I think) suggesting connecting the output directly to the dac chip. Definitely no extra noise going this way.
 
 
May 20, 2011 at 7:13 PM Post #1,924 of 2,013
I would think those extra inductors and resistors are there for a reason? Well to rewire it like that I would have to rewire the already working left channel for symmetry. Don't wanna risk breaking something else in the process... Thanks for a cool tip though, that's another way to get it done I suppose
 
May 20, 2011 at 7:16 PM Post #1,926 of 2,013


Quote:
I would think those extra inductors and resistors are there for a reason? Well to rewire it like that I would have to rewire the already working left channel for symmetry. Don't wanna risk breaking something else in the process... Thanks for a cool tip though, that's another way to get it done I suppose


One of the first mods discussed for the Valab was removing all the output  filter junk. Even in the Chamelean they do the same.
 
 
May 20, 2011 at 7:56 PM Post #1,927 of 2,013
hmmm any reason you chose that particular kind of caps? Digikey doesn't carry the "ZA" type, unfortunately. Where did you buy them from? There are plenty references to Rubycon ZA/ZL for what it's worth, often comparing them to Nichicon HE.
 
May 20, 2011 at 8:18 PM Post #1,928 of 2,013
No reason for the ZA, I bought them from Farnell back in 2009.  Oops just checked back on my order history, They are Rubycon ZA's but the ones I bought aren't available anymore. I believe the Rubycon XYF's are recommended or better still are Blackgates but both are hard to find. If I had to get new ones I would probably just get Panasonic FM's.
 
May 21, 2011 at 3:35 PM Post #1,930 of 2,013


Quote:
No reason for the ZA, I bought them from Farnell back in 2009.  Oops just checked back on my order history, They are Rubycon ZA's but the ones I bought aren't available anymore. I believe the Rubycon XYF's are recommended or better still are Blackgates but both are hard to find. If I had to get new ones I would probably just get Panasonic FM's.



http://cgi.ebay.com/8-Rubycon-YXF-series-35V-47UF-Japan-Make-Capacitor-/290396807186?pt=LH_DefaultDomain_0&hash=item439cffa012#ht_2615wt_901
 
would something like this work? I found the 16v 47uf ones at a cheaper price at newark but they want $20 handling fee per transaction -_-
 
 
May 21, 2011 at 4:41 PM Post #1,931 of 2,013
where do you live? I bought some panasonics very cheaply in the Netherlands.....for these type and amount of caps local shops rule as S&H is likely to be more expensive than the items themselves....
 
May 21, 2011 at 10:49 PM Post #1,933 of 2,013

Quote:
where do you live? I bought some panasonics very cheaply in the Netherlands.....for these type and amount of caps local shops rule as S&H is likely to be more expensive than the items themselves....


I live in the US so the shipping isn't all that exuberant from US based sellers.
 
Well I got a little impatient and ordered those rubycons from ebay (35v 47uF) For $8 shipped I thought what the hell, why not. Hope they work well enough...
 
 
Jun 2, 2011 at 7:19 PM Post #1,934 of 2,013
The lil caps are here, should be able to work on it sometime next week. To be absolutely clear, do I solder pin5 (vdd) on the TDA1543 with the positive lead on a coupling cap and pin4 (gnd) with the the negative lead, respectively? Do I just leave whatever is already on there (some kind of square component) alone? Gonna be a hell of a struggle to get the lid to shut properly with less clearance to work with 
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Jun 3, 2011 at 4:49 AM Post #1,935 of 2,013
Yup just solder the new (not coupling) caps between Pin 5 (positive lead of the cap on Vdd) and ground...if need be use pin 4 as ground yet if you can you should try to connect to ground as close as possible to the power supply. creating something of a star ground using a decent wire to connect all Cap negative leads to the PSU ground (negative lead of the last cap in the PSU, C12)

Just leave the smd 10 uF capacitors in place or take em off if you feel cocky (quick heating at both ends and flipping them off the board with the tip of the soldering iron seems to work for me, never damaged a trace so far)

I'd take a bit of care soldering onto the TDA pins, I'd solder onto the chip socket taking out the DAC chips for a bit as you may do thermal damage (especially if your soldering skills are minimal or your soldering iron is big) Or you may use a clamp/pair of tweezers as a heat sink yet you'll probably find out that you are short at least one hand :wink:
(I usually take the tube of solder in my mouth using that as my third hand)

Not sure how hight your caps are, mine were approx 3.5 cm high and fitted just fine.

dying to hear your evaluation!


 

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