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Valab NOS DAC - subjective listening and modifications - Page 2

post #16 of 2010
OK, if someone with zero soldering experience wanted to try some mods, where is the best place to start on this DAC?

Perhaps upgrading the parts in the analog signal path - like the I/V resistors and output caps, which I assume are the blue resistors and Kemet caps in the Phil's attached pic of the '09?

Also, as Phil was asking, what's the deal with changing the values and types of output caps?

The '09 has 10uF.
The '08 has 47uF, as Phil mentioned.
Some of you guys have used 4.7uF.
The Teradak has some blue caps, but I can't tell what they are. Link to pic here D22.jpg - Windows Live

Given the differences in the output caps' type and value, could someone please explain the function of these caps and why so many types/values can be used? Are the output caps also known as coupling caps?

Obviously, I don't know much about this stuff, but am willing to learn...

Thanks,

Adam
LL
post #17 of 2010
Adam2434, the blue caps in the link look like Sanyo Oscons, and the coupling caps also blue are 10uf Phillips. The MFR has said in the past that 4.7uf and larger are ok for coupling cap values, anything smaller will start to limit bass.

Get yourself a soldering iron, the wattage of which is debatable so you dont burn up solder pads, get some good solder and some solder dewicking braid. If you have an old VCR etc. kicking around take the circuit board out and practice removing parts from the board then resoldering them back into the board which is not quite the same as using new caps/resistors with clean leads but it'll give you some good practice. Take a look at some of the on line tutorials to give you a feel for how it's done, remember keep your tip clean.
post #18 of 2010
Thread Starter 

quick and fast

With no soldering experience you can tear up the board pretty easy.
So try for an easy in and out. Way to do that would be to keep the stock output caps as they are and bypass them. This means get a .1uF cap and solder it in place as the original cap. What is easy is to place the bypass cap on top of the stock one and hold it in place /w a bit of blu tac. The clip the leas and place them in contact with the stock leads but away from the board. Make sure the leads are in contact by whatever means makes sense.

Then solder a bit of of plane old solder, not silver as it needs too much heat, and get out of there.

After that get an old PC board and practice by removing component and replacing with cheap stuff from Radio Shack.

Best bang for buck and effort is those output caps.

And using the .1uF is a good choice as it will cover midrange up while the stock cap will then be taking care of bass.

Quote:
Originally Posted by adam2434 View Post
OK, if someone with zero soldering experience wanted to try some mods, where is the best place to start on this DAC?

Perhaps upgrading the parts in the analog signal path - like the I/V resistors and output caps, which I assume are the blue resistors and Kemet caps in the Phil's attached pic of the '09?

Also, as Phil was asking, what's the deal with changing the values and types of output caps?

The '09 has 10uF.
The '08 has 47uF, as Phil mentioned.
Some of you guys have used 4.7uF.
The Teradak has some blue caps, but I can't tell what they are. Link to pic here D22.jpg - Windows Live

Given the differences in the output caps' type and value, could someone please explain the function of these caps and why so many types/values can be used? Are the output caps also known as coupling caps?

Obviously, I don't know much about this stuff, but am willing to learn...

Thanks,

Adam
post #19 of 2010
Phil and Pat, thanks for the input.

What do the output caps actually do?

Block DC and filter the analog output?

Also, what's the benefit of using a bypass cap for the output? Would you somehow get some of the benefits of replacing the output cap with a higher grade part, assuming you used a higher grade part for the bypass cap?

Before I consider doing any mods, I'm just trying to understand the fundamentals of the function of the part and the benefits of replacing/adding parts.
post #20 of 2010
Thread Starter 

wherefor caps

The caps block DC.
Don't really need 'em at all if you have caps on the input of the preamp you are going to.

You would use a bypass in this case as a 4.7uF cap would be LARGE and bypassing with a smaller value would fit.

Why bypass at all?
Sounds better. Different caps impart a different signature. Some have lss noise and distortion over the stock and bypass will allow some signal to pass through the smaller cap while then allowing the larger cap to do it's job better.

Check this out: Bypassing



Quote:
Originally Posted by adam2434 View Post
Phil and Pat, thanks for the input.

What do the output caps actually do?

Block DC and filter the analog output?

Also, what's the benefit of using a bypass cap for the output? Would you somehow get some of the benefits of replacing the output cap with a higher grade part, assuming you used a higher grade part for the bypass cap?

Before I consider doing any mods, I'm just trying to understand the fundamentals of the function of the part and the benefits of replacing/adding parts.
post #21 of 2010
HiHi
Haha i did it ~ swapped the output caps to BG np 33/16 and the power cap to BG 220/16 , took me 2 hours just to did that , not too bad for first timer a =P
post #22 of 2010

Best Bang for the Buck

Good Job Carlter.

I believe the most bang for the buck will changing out the IV resistors and coupling caps. I suggest the very small size Blackgate "N" 10uf in Super E L-cancelling configuration. (This is simply soldering 2 Blackgate N caps together with short leg to long leg and long leg to short leg. Parallel). You will need 4 total caps, 2 for each channel. This is especially beneficial in "low voltage" coupling cap situations like this. For the I/V resistors I would go with the 400 ohm Caddock TF020. This is not a place to cheap out ... go for the best resistor! These parts can be had at Michael Percy Audio Ordering Information.

For you guys who have limited or no experience soldering I highly recommend simply cutting out the old parts leaving as much of the original legs in place as possible. Soldering to these nubs is a much safer practice.

The reason being is the solder pads on the Valab boards are not very beefy and its easy to overheat them. This is especially true with the south leg of the I/V resistor. On my 2009 output board I found only a pad on the top. No through rivet to a lower pad on the bottom of the board. Very dangerous situation for a newbie.

If you want to stop at this point then it time for a trip to the Cyro lab. This will be your next biggest bang for the buck. Toss in all your cables while you are at it. Tell Charles I sent you.
1 Cryogenics, Cryogenic Treatment, Tempering, and Cryo Processing: Cryogenics International


I am going to start slowly modding the control Dac, however in IMHO, if you are going to modify the power supply delivery to the Dac chips this is an all or nothing type of scenario. Especially if you are going to use Blackgate caps. The break in time is a mind numbing 30 days. I just got done riding that bull and I can tell you its a real mind numbing experience. Totally worth it mind you ... but painful!

I will post a recap of the complete mod from the previous thread shortly.
post #23 of 2010

Bill Allen's Mod "The Bomb"

I would like to thank Steve Nugent of Empirical Audio for helping me pick the best coarse of action for modding the Valab Dac. Home : Empirical Audio

Here is schematic for the dac ah which is very similar.
http://www.audiodesignguide.com/DAC/...ircuit_new.JPG

I decided to go all the way and order the best parts available for the Mod Dac. Total cost of upgrade parts exceed the original price of the Valab Dac, but if you want to play, you have to pay!

2 ea Jupiter 4.7uf- Silver Leads- Coupling Caps
4 ea Caddock UF340 200R resistors I/V Conversion
3 ea Blackgate FK 1000uf 16V Power SupplyCaps
16ea Blackgate FK 47uf 16V DAC/RegulatoCaps
1 ea Blackgate Fk 220uf 16V Dac Board Regulator Cap

I will layout the plan in order of best bang for the buck according to Steve Nugent.

1. Replace the small 10uf Mica caps on each Dac chip with Blackgate FK 47uf 16V caps. (8 total)

2. Replace the single 47uf cap for the big regulator with a Blackgate FK 220v 16V . (1 total)

3. Replace the 3 each 1000uf power filter caps with Blackgate FK 1000uf 16V. (Items 1-3 are about Soundstage Size & Bass Slam)

4. Replace the 2 each 390R I/V resistors with Caddock Persision USF340's. Parts Connection does not sell a 400 ohm UF340 so I had to buy two 200R and will wire these in series. (This will also provide the Teepee resistor circuit that will keep standing DC off the primary if I should ever decide to try output trannies)

5. Replace the 10uf Titanium Mica output caps with my favorite Jupiter 4.7uf Caps. (2 Total)

6. Replace the remaining 8 each 47uf regulator caps with Blackgate FK 47uf 16V Caps. (This is to supply more stable current to the various Digital Chips and reduce jitter)

Here is a step by step picture tutorial of the mod process. (I have added captions to the bottom of each page)

Picasa Web Albums - Bill - Valab DAC Mod

"The Bomb" mod was an all out professionally planned assault on the Valab Dac. The sonic results after a Cryo treatment and 30 solid days of Break In are way beyond my expectations. A total success on all fronts and well worth you time and effort if your pocketbook and soldering skills are up to the task.

After Cryo treatment I was able to successfully remove the Bypass caps on the 4.7uf Jupiter's. It's amazing what Cryo does to these Beeswax/Foil caps, they just open up like a flower in the sunlight. Without a doubt my favorite caps on the planet. It's just a shame there is no way to fit them inside the Valab Dac. If you can live with the looks of the Valab DAC with the cover off and plan on a Cryo dip, than by all means the Jupiter's are a first class choice. Chris Young of Jupiter Caps Audio Capacitors assures me that he will be rolling some of the "new style" large value caps in the near future. Till then I believe that Michael Percy Michael Percy Audio Ordering Information still has some of the earlier version 4.7's like I used in stock ... and at a very attractive price too!

Understand thare are numerous ways to go about modifying the Valab Dac. Don't go making it a chore or you are really missing the point. Everyone involved with modding the Valab Dac on this forum are having a blast and enjoying the results. The ability to hand tweak your system is a very rewarding experience. Have fun, I know I am!
post #24 of 2010
Yup, I took out a solder pad while changing the V Reg cap, It didn't take much heat at all but I did give a slight sideways pressure that was enough for it to go bye bye. I retrieved it and slid it over the lead and soldered it back in place, at least it wasn't connected to a trace.
post #25 of 2010

Broken Solder Trace

It's not the end of world if you do break off a solder pad hooked to a trace.

What you need to do is to take a razor blade and carefully scrape away the sealer untill you get down to the bace metal. If its a small distance sometimes you get away with just flooding the area with solder.

If flooding is not an option you can use a small piece of bare wire and solder it between the damaged area. You then push your solder leg though the wire. Voila a homemade solder pad.

If you actually lifted the pad and trace together (it happens) its best to repair this situation with a piece of insulated wire directly from one solder leg directly to the next next solder leg.

Hope this helps.
post #26 of 2010
Bill and all,

I've read that the BG N 10uf can be hard to find.

Any other suggestions?

I guess a nice film cap would be too big to close the case, huh?

Does anyone know what the stock I/V resistors are? Just run-of-the-mill carbon?

I would say that my overall sound improvement goal from mods would be to add some high end extension, detail, and transparency. Compared to my other outboard DAC and CD player, this is where the Valab is lacking IMO. Much of this could just be a NOS thing though.

Did anyone notice a high freq extension/detail improvement with the I/V resistor and output cap upgrades?

I know, a lot of questions...tryin' to get my learn on before heading down the path of mods.
post #27 of 2010
Thread Starter 

what i did on my summer vacation

I wanted to close the lid so I kept the cap at 4.7uF and bypassed it with Obbligatos and Russian PIOs.



Now if you don't care about that lid then the 4.7uF Jupiters, like Bill did, are do-able.

But I like the lid:



The whole story: VALAB NOS DAC
post #28 of 2010
[QUOTE=adam2434;5513646]Bill and all,

I've read that the BG N 10uf can be hard to find.

Any other suggestions?

I guess a nice film cap would be too big to close the case, huh?

Does anyone know what the stock I/V resistors are? Just run-of-the-mill carbon?

I would say that my overall sound improvement goal from mods would be to add some high end extension, detail, and transparency. Compared to my other outboard DAC and CD player, this is where the Valab is lacking IMO. Much of this could just be a NOS thing though.

Did anyone notice a high freq extension/detail improvement with the I/V resistor and output cap upgrades?


- The stock resistors are run-of-the-mill, I used Caddock resistors but I don't think the sound improved, it was fine already
- I tried the BG N but I did not like them, I prefer the standard BG's,
the sound is clean and quite warm, not overbright (I measured the frequency response: -0.5db 10khz and -1.2db 20khz)
_ I tried many capacitor combinations but I can always identify the small capacitor like a tweeter that is not perfectly integrated, I had the same problem with microphone preamps and famous microphone Guru Klaus Heyne had the same feeling.
At the moment I am quite happy with a standard 10Mf/16V Black Gate, all Black Gates (different values) sound slightly different and I have the impression that the higher values sound slightly duller.
I also don't believe the 2009 version needs any modification except the output capacitor and resistor (270-330 ohm).
post #29 of 2010
Hi Bill Hi everyone
Thx for the tips i used those photo u post for reference and they really help me out .
Next i gonna try the super E setup which should be easy enough for me to do since i leaved some length at the output cap legs hehe but the question is will BG n 33/16 x 2 too much for the job ??
I got an extra pair of BG n 1/50v should i also put them in there for a 3s E ? :P Any suggestion are well come.
Thanks

Solder pad ?___? didn't see any when i was there...
post #30 of 2010
Adriaan, have you tried any film caps?


Carlter, I don't think there is any definitive answer for the coupling caps, it's all about experimenting, no I wouldn't add the 1uf cap, you can get spectral overlap, a .1uf might work. Solder pads are what you solder the leads of a part to like the capacitor leads, they're round and shiny with little holes in em.
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