[Pat95]

Hello.
I used 2,2 µF, and it works great. I didn't change yet IC7, Can't unsold it properly.

 

[kon5t]

This thread still alive?

 

[FalseMetal666]

I dug up this thread recently when I realized my old V-DAC was through-hole and could be easily modified. I fussed around with the output stage a bit, but little beyond that. The biggest deal was buying a Burson V5i opamp, which made a pretty significant difference. In any event, total spend on this thing is about $100 since 2011, so I think I'm ahead of the game.

Question for anyone in the know - what are the best caps to replace if I want to continue focusing on the output stage? Which of the electrolytics are feeding the opamps?

 

[Dutchamps]

Like I surgested at the first page of this thread the electrolytes at the output stage are 100uF electrolytes is the signal path are bad, replace them with polypropylene 2,2uF, yes they are big but I asure you your dac will sound much better.
Goodluck

 

[carlmart]

I'm not sure I still have the V-DAC schematic somewhere. but I think the best thing to do with this DAC is to replace the power supply completely.

The original supply was a single AC voltage, and inside it had a doubler, using diodes and capacitors and regulators to get +/- 15v. Also +5v, regulated directly from the input AC, if I remember well.

You can get ready made LM317-337 boards in eBay, small enough so you can put them inside the V-DAC box.

At the beginning of this thread it is suggested replacing both the original IC, which are a quad and a dual.

For the quad I would suggest using this adapter:

https://www.cimarrontechnology.com/browndog-070401-dual-to-quad-op-amp-adapter

And then pick one SMD to DIP-8 adapter from here:

https://www.cimarrontechnology.com/...-pin-interchange-adapters/smt-to-dip-adapters

Using modern low-offset ICs will allow you to eliminate the output capacitors, which are not good having.

If you still have the original ceramics, replacing them with film types would be a very good thing.

 

[FalseMetal666]

I bought an OPA4227PA quad op amp to replace the stock one, cost like $10 from Mouser. Crossing fingers that it represents an upgrade. Obviously won't allow for eliminating the output caps, so I'll replace those with 2.2, 3.3, or 4.7uf WIMAs, which are the only film caps I can find that will comfortably fit that location.

I'll also replace all the ceramics with film caps - any particular favorites that are economical? Looking at just getting a grip of WIMAs.

 

[Dutchamps]

Those wima caps you can get at eBay or your diy speaker shop. At this shop they have polypropylene types

 

[FalseMetal666]

I'm not sure I still have the V-DAC schematic somewhere. but I think the best thing to do with this DAC is to replace the power supply completely.

The original supply was a single AC voltage, and inside it had a doubler, using diodes and capacitors and regulators to get +/- 15v. Also +5v, regulated directly from the input AC, if I remember well.

You can get ready made LM317-337 boards in eBay, small enough so you can put them inside the V-DAC box.

At the beginning of this thread it is suggested replacing both the original IC, which are a quad and a dual.

For the quad I would suggest using this adapter:

https://www.cimarrontechnology.com/browndog-070401-dual-to-quad-op-amp-adapter

And then pick one SMD to DIP-8 adapter from here:

https://www.cimarrontechnology.com/...-pin-interchange-adapters/smt-to-dip-adapters

Using modern low-offset ICs will allow you to eliminate the output capacitors, which are not good having.

If you still have the original ceramics, replacing them with film types would be a very good thing.

I have the Musical Fidelity V-PSU power supply, so hopefully that will obviate the need to get too deep into the DAC power supply.

Any thoughts re. the OPA4227PA quad op-amp that I'll be swapping in? And assuming that I keep the output capacitors, do you reckon the WIMA MKS2 series is OK? They're the only caps with 2.2uf - 4.7uf values that will easily fit inside the DAC.

 

[carlmart]

Having the original MF PS doesn't mean much, as in fact what people did was to change that supply for a larger one.

The result was probably marginal, as the real problem was inside, on the internal power supply. Eliminating the external single voltage supply was the best way to go.

Also the gains from replacing the quad IC with types from the same time, like the OPA4227, or the output capacitors, were just marginal.

That's my opinion.

 

[FalseMetal666]

Having the original MF PS doesn't mean much, as in fact what people did was to change that supply for a larger one.

The result was probably marginal, as the real problem was inside, on the internal power supply. Eliminating the external single voltage supply was the best way to go.

Also the gains from replacing the quad IC with types from the same time, like the OPA4227, or the output capacitors, were just marginal.

That's my opinion.

Thanks, good to know. If I were to go with the DIP8 adapter, as you suggest, which ICs do you reckon would be the best choice?

 

[carlmart]

Unfortunately there are only dual SMD IC to quad DIP adapters to be found. But the chips are large enough to be carefully soldered.

https://www.cimarrontechnology.com/browndog-070401-dual-to-quad-op-amp-adapter

Or you could try this other way, using a small prototype board. More tricky to assemble.

https://www.diyaudio.com/forums/chi...8-socket-converter-quad-opamp-dual-opamp.html

Also read, with translator, this V-DAC mod story:

https://translate.google.com/transl...je-met-de-musical-fidelity-v-dac/&prev=search

Now, about the chips. I would first consider the LME49870, which is the one used in the mod above. But the OPA1612, used in the Topping DACs, definitely deserves a try. Pick the larger SOIC version, easier to solder.

The 1612 has much better specs all over, particularly on the DC offset, which would allow eliminating the output caps.

Another option would be to look for a quad SOIC, but I have not found people using any. Probably because quads are rarely seen nowadays in audio equipment, mostly duals.

 

[FalseMetal666]

Unfortunately there are only dual SMD IC to quad DIP adapters to be found. But the chips are large enough to be carefully soldered.

https://www.cimarrontechnology.com/browndog-070401-dual-to-quad-op-amp-adapter

Or you could try this other way, using a small prototype board. More tricky to assemble.

https://www.diyaudio.com/forums/chi...8-socket-converter-quad-opamp-dual-opamp.html

Also read, with translator, this V-DAC mod story:

https://translate.google.com/transl...je-met-de-musical-fidelity-v-dac/&prev=search

Now, about the chips. I would first consider the LME49870, which is the one used in the mod above. But the OPA1612, used in the Topping DACs, definitely deserves a try. Pick the larger SOIC version, easier to solder.

The 1612 has much better specs all over, particularly on the DC offset, which would allow eliminating the output caps.

Another option would be to look for a quad SOIC, but I have not found people using any. Probably because quads are rarely seen nowadays in audio equipment, mostly duals.

Thank you! I assume there's no harm (apart from cost) in ordering the pre-soldered offering from Cimmaron and plugging 'er in?

 

[carlmart]

If Cimmaron has that part assembled, certainly go ahead!

Much safer than buying it on eBay. That's an expensive that is cheaper.

 

[FalseMetal666]

If Cimmaron has that part assembled, certainly go ahead!

Much safer than buying it on eBay. That's an expensive that is cheaper.

Rad, I suppose I'll just do that. And in regards to overhauling the power supply, what would you recommend as far as a "minimalistic" approach? I've done nothing to the power section thus far, but don't want to sink more than a little bit of money into it - are there maybe 2-3 obvious parts to replace?

In case you've not picked up on it, I have absolutely zero experience with electronics apart from soldering/desoldering, so the electronic principals are completely alien to me (e.g. I would have no idea how to install a LM317-337 board).

 

[carlmart]

You have one thing on your favor: the parts are all through-hole. So soldering/desoldering should be easy.

The hard part, which I already tried and failed, would be to find the V-DAC schematics, which I once had and probably threw away.

From what I remember, and something I read on the Dutch mod article (which I do recommend you to read), there was a chip that converted the input voltage to negative (apparently it was -8v) in order to power the output chips with +/- 8v. The rest of the power is positive. (+5v, +3v). There should be regulators for each.

The Dutch guy did two important things: replaced all ceramic capacitors with film types, particularly those close to the coaxial input. That you should do.

The other thing he replaced is the quad IC. This you should also do, with any option you find available.

Now the supply question. I do not remember if Musical Fidelity did implement a virtual ground supply, because that would mean there will always will be DC offset and will demand output caps.

To do a thorough job on the V-DAC, the whole supply system would have to be lifted off, and use a 20v + 20v transformer to feed in AC, filter it all and use several separate regulators inside.

The major problem is the wiring inside in such a mod, and you would need some DIY experience to accomplish it. So let's no go into that.

Using larger and better caps at the main power supply might be a good choice too. And of course: replace the output caps for some film type.

Pay attention for any ceramic cap on the output stage and replace it.

That should bring a good audible improvement.