V-PSU II
Will, I have found something which might be interesting for you. V-PSU II which you have is SMPS unit, and is much different from previous V-PSU which has toroidal transformer. As mentioned, it seems that the newer version is very noisy. Attached is the noise comparison between the V-PSU II and the ordinary LM-317 regulator, both under 100 Ohm non-inductive resistive and 100 uF capacitive load. These measurements are not mine. The vertical axis represents noise voltage multiplied by 100. It looks like that V-PSU II touches the 30mV ripple peak at around 120Hz.
Will, I have found something which might be interesting for you. V-PSU II which you have is SMPS unit, and is much different from previous V-PSU which has toroidal transformer. As mentioned, it seems that the newer version is very noisy. Attached is the noise comparison between the V-PSU II and the ordinary LM-317 regulator, both under 100 Ohm non-inductive resistive and 100 uF capacitive load. These measurements are not mine. The vertical axis represents noise voltage multiplied by 100. It looks like that V-PSU II touches the 30mV ripple peak at around 120Hz.
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Update on MF V-Dac 2 modd.
I'm back. My computer got devastated by a bott and had to start over. Got a new Mac Mini to replace my aged Mac Power PC G4. Anyhow I am darned pleased with my mod of my V-Dac 2. It sounds so sweet. Quite, smooth, dynamic. The stage is more refined. It's wider with more separation of instruments. Lots more detail and presence. It's a real pleasure to listen to my music now. Very worth while effort.
I forgot to photograph the opamp install before I soldered in the caps but the enclosed pics might be of some help to anyone else attempting this mod. I know I could not have done the mod without the pics provided by Will.
Will thank you for your help!
Best to you,Marvin
The output op amp in V-DAC is already bypassed: namely, C40 and C57 are ceramic capacitors connected between the supply pins and supply rails, which renders the third, in-between, bypass cap pretty much superfluous. In addition, for the purpose of bypassing I would suggest multilayer ceramic caps, instead of disc type.
Finally, I have also discovered that the supply voltages for op amps are not symmetrical: the DMM measures +10,5 vs. -13,5V on rails.
You're right about the bypass caps - so no additional caps under the board are required. I missed that in my original haste to mod. Thanks for the chart showing PS noise in the V-PSUii: That's a shame - MF must have cost engineered it (I feel another project coming on...). Nevertheless, it does improve the sound of the V-DACii. Speaking of which, what do you think of the sound of the VDACii with the mods? I'm now using OP1662 on other DIY projects - it's superb in my opinion, but does need hours of burn-in to sound its best. I'm wondering how the V-DACii + mods, compares with the new budget DACs? Schiit Bifrost and DACiT get great reviews for audio - it's mighty tempting to invest, but the modded V-DACii sounds superb with nothing to compare it against...
Musical Fidelity have gone from regular to SMT technology from first to second generation of their V-Series, obviously with cutting costs in mind and with a few trade-offs, one of them being the change from transformer-type to switching PSU. And while I trust you on saying that it improves the sound quality over the wall wart, I would still see the V-PSU II as mere three-prong power supply replacing the three wall warts and also as the weakest link in the V-Series chain. After replacing operational amplifiers, I see the PSU as the next key thing to improve on. I did mention SuperTeddyReg as my recommendation, but whichever you decide to build, it should be linear type and open-loop, that is, without voltage or current feedback because it really works the best with DACs.
Personally, once I find the sound I like, I stick to that component because that makes me return to listening to music instead to components, so I do not get that excited by new products, tests or listening at all. When I decided to go digital, the contenders were HRT Music Streamer, Arcam rDAC and Musical Fidelity. I have found MF to sound the best and I could immediately hear and see that there was potential for improvement. Even though it has its shortcomings (but only if compared to higher niche), V-DAC II doesn't show any digital "nervousness", harshness and is not tiring to the ears, the traits most often associated with digital sound. Finally, it is perfectly aligned to my system, sound- and price-wise (Revox B-200 series).
My mods include the new output op amp (LME49720), new PSU and new output caps (Nichicon Muse BP 47uF/16V). Their contribution to the sound quality goes in exactly the same order. Operational amplifiers are really a matter of taste (speed and slew rates are mere myths). Can't comment on 1662 because I haven't listened to it, but I have found that bipolar op amps give more true sound than FETs which tend to sweeten the sound but also to conceal nuances.
I haven't listened Bifrost or DACiT (not to mention the proliferating DACs on Hong Kong eBay), but I did listen to unmodded V-DAC90 recently. In my opinion, with the exception of convenient power and source switches, it is not worth switching to because it basically sounds the same as V-DAC II. Looking at V-DACxx as a whole, Musical Fidelity does know how to make great sound.
Personally, once I find the sound I like, I stick to that component because that makes me return to listening to music instead to components, so I do not get that excited by new products, tests or listening at all. When I decided to go digital, the contenders were HRT Music Streamer, Arcam rDAC and Musical Fidelity. I have found MF to sound the best and I could immediately hear and see that there was potential for improvement. Even though it has its shortcomings (but only if compared to higher niche), V-DAC II doesn't show any digital "nervousness", harshness and is not tiring to the ears, the traits most often associated with digital sound. Finally, it is perfectly aligned to my system, sound- and price-wise (Revox B-200 series).
My mods include the new output op amp (LME49720), new PSU and new output caps (Nichicon Muse BP 47uF/16V). Their contribution to the sound quality goes in exactly the same order. Operational amplifiers are really a matter of taste (speed and slew rates are mere myths). Can't comment on 1662 because I haven't listened to it, but I have found that bipolar op amps give more true sound than FETs which tend to sweeten the sound but also to conceal nuances.
I haven't listened Bifrost or DACiT (not to mention the proliferating DACs on Hong Kong eBay), but I did listen to unmodded V-DAC90 recently. In my opinion, with the exception of convenient power and source switches, it is not worth switching to because it basically sounds the same as V-DAC II. Looking at V-DACxx as a whole, Musical Fidelity does know how to make great sound.
What do the owners of V-DAC II think about the quality of electrolytic capacitors inside? I don't think I can recognize the manufacturer, but I was thinking about replacing them with Nichicon UQ series, which is their "for audio" series in SMD form factor. Does anybody have the list of values for electrolytes? Thank you in advance.
The capacitors used in the Musical fidelity V-DAC are not realy the best choice. I changed them all:
I used organic polymer types from mouser.
On the analog- side the OPAs changed to OPA 1644AID and 1642AID. I changed both ones for best results.
On position C37/C38 you should use the very very best capacitors you can get. I use HV PP- Types, 12uF /400V
at the position C40/C57 i use an 3,3uF 100V Polyesterfilm Panasonic Type. Sounds very well. For the C3/C103 i use an PP HV Cap 12uF.
Hope you get some Ideas for your projekt
Richard
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I used organic polymer types from mouser.
On the analog- side the OPAs changed to OPA 1644AID and 1642AID. I changed both ones for best results.
On position C37/C38 you should use the very very best capacitors you can get. I use HV PP- Types, 12uF /400V
An externally hosted image should be here but it was not working when we last tested it.
An externally hosted image should be here but it was not working when we last tested it.
at the position C40/C57 i use an 3,3uF 100V Polyesterfilm Panasonic Type. Sounds very well. For the C3/C103 i use an PP HV Cap 12uF.
Hope you get some Ideas for your projekt
Richard
Hi Guys, few years ago I have modded V-DAC v.1 with really good results.
All opamps and capacitor changes are minor when comparing to modding power architecture.
The key is to omit both switching power converters (in v.2 most probably these are IC2 and IC7) and supply all the sections directly from good voltage regulators.
I used 3 SuperTeddyRegs (2 x for analog output stage, 1 x for DAC chip) and LM317 for digital section, but I believe you can find better options and combinations.
Mentioned mod has bigger impact on sound than any opamp or capacitor swaping. First of all you'll get clean and black background, and lot of small details will show up. Listening will no longer be fatiguing. Then you can start replacing opamps, to see which one is better and not only different. As far as I remember I ended up with OPA1612 + LME49860. This combination had really clean and natural sound with good sound stage, but not the biggest one.
The only problem is that such mod will not fit into original case, but what you can do is to have PSU + voltage regulators in separate case, and replace power jack with some DIN input (multi pin) and distribute power wires inside original case.
All opamps and capacitor changes are minor when comparing to modding power architecture.
The key is to omit both switching power converters (in v.2 most probably these are IC2 and IC7) and supply all the sections directly from good voltage regulators.
I used 3 SuperTeddyRegs (2 x for analog output stage, 1 x for DAC chip) and LM317 for digital section, but I believe you can find better options and combinations.
Mentioned mod has bigger impact on sound than any opamp or capacitor swaping. First of all you'll get clean and black background, and lot of small details will show up. Listening will no longer be fatiguing. Then you can start replacing opamps, to see which one is better and not only different. As far as I remember I ended up with OPA1612 + LME49860. This combination had really clean and natural sound with good sound stage, but not the biggest one.
The only problem is that such mod will not fit into original case, but what you can do is to have PSU + voltage regulators in separate case, and replace power jack with some DIN input (multi pin) and distribute power wires inside original case.
Do you mind share with us in more step by step detail (better with pics) on how you mod the power architecture? Thanks
Only now it has come to my attention that there are no local capacitors surrounding the op amps in the analogue stage and that the 10uF electrolytics following the voltage regulators are pretty distant (reusing wiland1's photo as illustration). I added 2 10uF capacitors across C40 (Vcc- to ground) and C57 (Vcc+ to ground). The choice of 10uF is conventional wisdom for bypassing op amps and there is improvement in dynamics. But since one double and one quad op amp are fed from there, would more capacity, say 22uF or up to 100uF be more effective?
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Here is what I did in 2012:
Choosing quality over quantity will pay off for C40 and C57.
Polyester film caps like WIMA MKS2 between 2.2µF and 4.7µF can be applied easily.
This V-DAC setup - still with its original OpAmps - was superior to a Yulong Sabre D18.
Today, the OpAmps I use are OPA1642 (dual) and OPA1644 (quad)
- Johannes
Choosing quality over quantity will pay off for C40 and C57.
Polyester film caps like WIMA MKS2 between 2.2µF and 4.7µF can be applied easily.
This V-DAC setup - still with its original OpAmps - was superior to a Yulong Sabre D18.
Today, the OpAmps I use are OPA1642 (dual) and OPA1644 (quad)
- Johannes
I'd def recommend those tiny wima MKS caps for coupling the output. I always use these caps in the signal path where there are space constraints.
It's also worth looking at the Mundorf Evo caps as these are much smaller than many other boutique caps. They are still bigger than the elco's but much easier to manage. As stated go for 4.7uF (its possible that 2.2uF may be too low although it may be fine).
How many millivolts of DC are they actually blocking??
It's also worth looking at the Mundorf Evo caps as these are much smaller than many other boutique caps. They are still bigger than the elco's but much easier to manage. As stated go for 4.7uF (its possible that 2.2uF may be too low although it may be fine).
How many millivolts of DC are they actually blocking??
For output coupling, the best cap is no cap! �� (subject to <5mv on the output)
These MKS2 caps are about as close to boutique caps as you can get. They are not like the normal wima types and they will def outperform the green Muse BP's.
For local decoupling on analogue rails, I like the newer black cerefine. I tend to go for larger values often using 470uF. I then bypass again with 0.1uF Panasonic PPS as close to the device I can get. I've used this method in many mods I've performed with great success.
As you point out its all a matter of taste but those MKs2 are exceptional for their size (banzai music still sell them)
These MKS2 caps are about as close to boutique caps as you can get. They are not like the normal wima types and they will def outperform the green Muse BP's.
For local decoupling on analogue rails, I like the newer black cerefine. I tend to go for larger values often using 470uF. I then bypass again with 0.1uF Panasonic PPS as close to the device I can get. I've used this method in many mods I've performed with great success.
As you point out its all a matter of taste but those MKs2 are exceptional for their size (banzai music still sell them)
I have compared several types of capacitors over the past 30 years on really many HiFi devices.
Which type and which capacitance fits best depends on the specific position within the circuit. Many times, the capacitance of electrolytics is over-dimensioned by far to compensate for bad tolerance and projected aging losses. In addition, publications about capacitor usage have repeatedly indicated that over-dimensioned capacitances have less distortion than those operating at or near a time constant boundary with surrounding resistors (which I could ever believe). Anyway, one can take advantage and replace some of the electrolytics with much (!) smaller capacitances.
My conclusions:
1. For coupling capacitors it is best to avoid electrolytics completely. Film capacitors are always better by at least an order of magnitude (using dielectric absorbtion as the dominant criteria). In certain positions (high impedance, low signal level), we can even distinguish quality grades of different film capacitors and will prefer MKP / Polystyrene over MKT / MKS / Mylar.
Should we still need electrolytics for their high capacitance, these should be shunted with film. But removing the electrolytic completely will always be audible and positive.
I fully concur with UV101's statement:
I tried several MKT/MKS/MKT versions but ended up using 10µF Wima MKS2 as output coupling caps. The offset to be blocked is only 3..20mV for my opamps which would also allow to leave out (shortcut) the coupling caps completely and trust that the preamp will have input coupling caps anyway. A friend of mine did so successfully and claims to have improvements. Should you hear slight noise though in your volume knob you know you have some offset but certainly no damage is done.
2. For shunt / bypass of supply voltages I use combinations of electrolytic and film, however making shure to have at least 1µF, better 2.2 .. 4.7µF. I know that there is this ever-repeated notion of having 0.1µF (100nF) shunts everywhere. I wonder why that hardly anyone tries more film capacitance.
If there is stabilization using a voltage regulator or gyrator (C-multiplier) already in place (like with V-DAC II), we can leave out the electrolytics near the opamps. The focus then is on impulse capability near the supported circuit. With the V-DAC II I tried 2.2, 3.3, 4.7 and 10µF Wima MKS2 or Panasonic MKT and ended up using 4.7µF.
If you are a perfectionist, you may want to film-shunt the electrolytic cap C62 at the base of the gyrator transistor TR2 for the positive opamp supply voltage in V-DAC II. The quality of this cap - multiplied by the current gain of the transistor - arrives at the opamp supply. Try it
And if you are already at it, try this with TR1 and C29 as well, which stabilizes the analog (!) supply voltage of the DAC chip.
... And then you know why I use WIma MKS2 so much .. prefering the taped version with long leads.
- Johannes
Which type and which capacitance fits best depends on the specific position within the circuit. Many times, the capacitance of electrolytics is over-dimensioned by far to compensate for bad tolerance and projected aging losses. In addition, publications about capacitor usage have repeatedly indicated that over-dimensioned capacitances have less distortion than those operating at or near a time constant boundary with surrounding resistors (which I could ever believe). Anyway, one can take advantage and replace some of the electrolytics with much (!) smaller capacitances.
My conclusions:
1. For coupling capacitors it is best to avoid electrolytics completely. Film capacitors are always better by at least an order of magnitude (using dielectric absorbtion as the dominant criteria). In certain positions (high impedance, low signal level), we can even distinguish quality grades of different film capacitors and will prefer MKP / Polystyrene over MKT / MKS / Mylar.
Should we still need electrolytics for their high capacitance, these should be shunted with film. But removing the electrolytic completely will always be audible and positive.
I fully concur with UV101's statement:
however ...
Mundorf Evo are polypropylene (PP) types opimized for loudspeaker crossover networks. High current and voltage throughput, vibrations and high pressure within the enclosure. A different animal. In electronic circuits I prefer regular metallized polypropylene types (MKP) from Wima/Vishay/Panasonic. The higher the voltage the lower distortion.
I tried several MKT/MKS/MKT versions but ended up using 10µF Wima MKS2 as output coupling caps. The offset to be blocked is only 3..20mV for my opamps which would also allow to leave out (shortcut) the coupling caps completely and trust that the preamp will have input coupling caps anyway. A friend of mine did so successfully and claims to have improvements. Should you hear slight noise though in your volume knob you know you have some offset but certainly no damage is done.
2. For shunt / bypass of supply voltages I use combinations of electrolytic and film, however making shure to have at least 1µF, better 2.2 .. 4.7µF. I know that there is this ever-repeated notion of having 0.1µF (100nF) shunts everywhere. I wonder why that hardly anyone tries more film capacitance.
If there is stabilization using a voltage regulator or gyrator (C-multiplier) already in place (like with V-DAC II), we can leave out the electrolytics near the opamps. The focus then is on impulse capability near the supported circuit. With the V-DAC II I tried 2.2, 3.3, 4.7 and 10µF Wima MKS2 or Panasonic MKT and ended up using 4.7µF.
If you are a perfectionist, you may want to film-shunt the electrolytic cap C62 at the base of the gyrator transistor TR2 for the positive opamp supply voltage in V-DAC II. The quality of this cap - multiplied by the current gain of the transistor - arrives at the opamp supply. Try it
And if you are already at it, try this with TR1 and C29 as well, which stabilizes the analog (!) supply voltage of the DAC chip.
... And then you know why I use WIma MKS2 so much .. prefering the taped version with long leads.
- Johannes
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I have had a very instructive correspondence with poetry2me and I tried his advice on shunting/bypassing certain positions in the DAC. But I also tried my own method which I have used in digital sources, by employing solid tantalum as output capacitor after every voltage regulator, as well as local filtering around digital ICs. Now, I know that mentioning tantalum capacitors here is heresy but, in my experience, when used in this way, the are the best for smoothing out digital "nervousness" and delivering beautiful top end with tight bass, lots of spaciousness and transparency. I warmly recommend this upgrade, it sounds like V-DACIII.
On SMD capacitors: using the hot air to remove them may be the standard but it also heats up other innocent components without reason. I removed them by gentle wiggling perpendicularly to the legs axis while applying downward pressure. They come off very easily without lifting or damaging any pads. The thing is that the thin soldered leg parts are stronger than the free ones which run upwards, so they snap rather easily.
On SMD capacitors: using the hot air to remove them may be the standard but it also heats up other innocent components without reason. I removed them by gentle wiggling perpendicularly to the legs axis while applying downward pressure. They come off very easily without lifting or damaging any pads. The thing is that the thin soldered leg parts are stronger than the free ones which run upwards, so they snap rather easily.
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