[Dutchamps]

Do you realy think musical fidelity give away schematics?
The first component in the V-Dac that is receive current is a diode strait to a TS7809 
Input is allways positive current
Pin inside connector is positive and outside connector is negative.
Thats easy to find back if you look at the pcb board.

 

[carlmart]

No, I expect MF to sell a V-DAC Service Manual, as most manufacturers use to do. As an owner you're entitled to have that manual, particularly if you live abroad and can't send it back for repairs.
 
My idea was that someone had already done that. It is much safer and effective to do mods when you know for sure what you are doing.
 
The only thing that diode before 7809 does is to protect the V-DAC from an inverted polarity supply, as they certainly should do.
 

 

[barmanekm]

carlmart
 
I've send schematic to your e-mail. It would be nice if you can clean it up a little bie (element positioniong etc.) as I have no time to do this.

 

[carlmart]

Quote:

carlmart
 
I've send schematic to your e-mail. It would be nice if you can clean it up a little bie (element positioniong etc.) as I have no time to do this.

Thanks.
 
I will what I can do, because my Eagle Light can only read the file, not modify it.
 

 

[CyberTheo]

Quote:

Two output caps replaced from 47uF bip elco to 3,3uF Mkp intertechnik audyncap
 

 
You guys are incredible!
 
I got my V-DAC last week.  I have it hooked up to the coax output of my 18 year old Proceed PCD2 CD player.  Out of box it nearly sounds as good as the internal DAC of the Proceed.  The most noticeable difference is that the Proceed has more body and air in the midband.  I wasn't expecting the V-DAC to beat the Proceed internal DAC, as I primarily bought the V-DAC to hook up to my PC for casual listening.  The performance of the V-DAC is a pleasant surprise.  I hope cap and opamp upgrades will push it over the top and improve on my Proceed.
 
Please help out a newbie on tweaking.  I'm not good in electronics but competent with a soldering iron.  I have a couple of technical questions for the veterans.
 
I'm planning to order the LME opamps.  I haven't removed IC from a PCB before.  What is the proper technique for removing IC without damaging them?  I want to install IC sockets so I can swap the original opamps back in for comparison.
 
The thread has examples of replacing the two 47uF output caps with 3,3uF or 4,7uF Mkp caps.  I happen to have a pair of Cornell-Dubilier 3,3uF Mkp in my parts bin.  How safe is it to use 3,3uF in these positions, as they are significantly lower than the stock 47uF value?  Would it damage the circuit though prolonged use?

 

[barmanekm]

It won't damage circuit, but if your amplifier (pre/integrated) has low input impedance you will get very audible distortions in the low frequencies, or you may even lost your bass sound at all.

 

[CyberTheo]

Oh well.  Thanks.  I'll stick to same value caps for starter.

 

[jaaptina]

 
[size=medium]

Power Mod:
 
It's told a battery is the best power supply for an audio component. So I modded a 12V powerless drill and added an out cable. The V-Dac still works fortunately. There is a noticably sound difference. It aren't the basses but more so the very high tones you can hear better. Little bells and sandy noises are more pronounced. I believe I don't like this effect so much. For now I use the standard power supply but I will try the battery later again.
 

​

[/size]

 

[Dutchamps]

To Cyber Theo
 

The thread has examples of replacing the two 47uF output caps with 3,3uF or 4,7uF Mkp caps.  I happen to have a pair of Cornell-Dubilier 3,3uF Mkp in my parts bin.  How safe is it to use 3,3uF in these positions, as they are significantly lower than the stock 47uF value?  Would it damage the circuit though prolonged use?

 
47uF is worse case possible the manufacture doesnt know what is behind the v-dac for resistor (pre-amp), so they take a value (overkill) 47uf
But i have made a little computing and came out on 2,5uF but knowing some users differ so 4,7 is more then enough.
Dont use elco or bip/elco USE MKP at least, elcos have a much higher distortion then MKP its called the D.A. factor, deelectric absortion
Read http://en.wikipedia.org/wiki/Dielectric_absorption
Aslong the cap gives values till 0,0002% are good over the 1 is like a elco some do make 10%
In other words, Mkp passes all audio freq. but elco is a one way conductor like a batterij, bip. elco is two ways -+ or+- ,Mkp is allways two ways.
Indeed when the value is too low the bass will disapear you need some capacity to load.
I hope you understand my explanation.
 
change opamps
Dis solder a opamp is little tricky when expensive ones, if you want to save a 5532 (costs 1-2 € looool)
Cut the pins on headside with side-cutter and dissolder the pins from the tin solder side, easier.
Note when you want to tweak with other opamps, you can place a dil8 foot so you can switch with other opamps later on.

 
Most important dont overheat the pcb board then you will loose some copper from the pcb board

 

[Dutchamps]

Quote:

 

Power Mod:
 
It's told a battery is the best power supply for an audio component. So I modded a 12V powerless drill and added an out cable. The V-Dac still works fortunately. There is a noticably sound difference. It aren't the basses but more so the very high tones you can hear better. Little bells and sandy noises are more pronounced. I believe I don't like this effect so much. For now I use the standard power supply but I will try the battery later again.
 

​

What you hear is most likely the preformance of your amp, witch you have never experianced take it a good 3 weeks, dont set the power off let it "burn in"
The Dac sounds much more precise, witch give ME the kick of the tweaks.
I bet my live for it to say that a very stable powersupply is a must for having a good copy of the original sound and how its been recorded.
A battery makes the best kind of stable power, but not all kinds of only certain types like nic/cad
I tested that power sup with earier dac`s with great improvements.

 

[CyberTheo]

Thank you, Dutchamp.  Very helpful hints.
 
I have a couple of 3.3uF MKP and a couple of 47uF Elna elco to try.  I suppose the only way tell which works better is to try them both.  The MKP are real big, however.
Cutting the opamp legs sure beats the possibility of damaging the traces.  I'll install DIP socket for opamp experiments.
 

 

[carlmart]

I'm planning to order the LME opamps.  I haven't removed IC from a PCB before.  What is the proper technique for removing IC without damaging them?  I want to install IC sockets so I can swap the original opamps back in for comparison.

 
Definitely install gold plated, good quality IC sockets to swap them, both for 8-pin and 14-pin types.
 
IMHO the best tool for desoldering parts, particularly ICs is this RS tool:
 
http://www.radioshack.com/product/index.jsp?productId=2062731&filterName=Type&filterValue=Soldering%26amp%3B%23047%3BDesoldering
 
Also buy an extra thinner tip.
 
Let it heat up and be quick in sucking the solder, so as the part or the pcb won't get hot. Also look for solder small drops that might cause any shorts. Use a light and magnifying glass for that.
 
When installing the IC sockets also be quick and check for any "cold" solders afterwards.

 

[CyberTheo]

Thanks!  All are good tips.

 

[Dutchamps]

Quote:

Thank you, Dutchamp.  Very helpful hints.
 
I have a couple of 3.3uF MKP and a couple of 47uF Elna elco to try.  I suppose the only way tell which works better is to try them both.  The MKP are real big, however.
Cutting the opamp legs sure beats the possibility of damaging the traces.  I'll install DIP socket for opamp experiments.
 

 I suppose the only way tell which works better is to try them both
 
No, Mkp is better  its a law by nature

Oke one disadvantage is the bigness of those mkp`s but sound much better then elcos include the best you can find like elna
 
For mounting the mkps look for a good place where you can glue the boddy to a other component and direct the conducting leads to the right original traces on your board.
That way you provide the mkp a never moveing place, witch will prevent breaking lose from the pcb board.
 i used a plastic gluegun from Henkel  http://doitbest.com/Glue+guns-Do+it+Best+Imports-model-349755-doitbest-sku-349755.dib
I am convinst the mkp will please the sound quality dramaticly
Goodluck will tweaking the v-dac

 

 

[jaaptina]

Battery power box design

 
I plan to build a box that houses my V-DAC a SLA battery and a battery charger. Purpose is to have a need looking box with a front that matches my amplifier. On the front a main power switch and a selector switch. 
 
See schematic below. The main power switch is positioned before the battery charger. That way I can disconnect the charger. I use a three position rotary switch to make the following connections:
 

• Charger to battery; DAC disconnected; main switch switches charger
• Battery to DAC; charger disconnected (dac is "on" even if main switch is "off")
• DAC to Charger; DAC is "on" when battery is empty; main switch switches DAC

 
I like to hear your opinions on this schematic. Also I like to know if a charger for a 12V battery can be used as power unit for the DAC.
 
Battery: http://www.batterymart.com/p-12v-5ah-sealed-lead-acid-battery.html
Charger: http://www.batterymart.com/p-12v-500ma-sealed-lead-acid-battery-charger-2.html