VTV Purifi Amplifier Review with Weiss Buffer

[amirm]

This is a review and detailed measurements of the VTV Purifi class-D amplifier with the optional Weiss OP2-BA Op-amp (buffer/input gain stage). It is on kind loan from a member and costs US $2,090. I just reviewed the same amp but with SIL 994EnH-Ticha Pro buffer so you can compare them.

As with the other variation, I am a fan of the more slim rack mount case (it is a lot deeper than this photo shows):

Back panel as expected:

VTV Purifi class-D amplifier with the optional Weiss OP2-BA Op-amp Measurements
Let's start with our dashboard and see if the power supply noise we had with the SIL buffer also exists here thereby telling us if the problem was that or something else:

Sadly the issue remains with the noise in the FFT spectrum. So something else is at play. I tried to mess with grounding to see if it impacts it and it would get much worse. At one point one channel got unstable producing variable output. Maybe that was instrumentation error but I did not walk away with a good feeling on this. Nevertheless, overall ranking remains quite high due to stellar performance of Purifi amplifier module itself:

I am just going to post the rest of the measurements without text as they are similar as the other review:

When I ran the dashboard and saw the same problems with the other VTV amplifier, I wanted to rule out instrumentation error. So I dug up my Purifi reference design and it produced superbly clean output as it did in my original review. While I was at it, I also ran this test (which sadly I over-wrote) and it produced similar output to this VTV amplifier. So the choice of buffer doesn't have much impact here:

Conclusions
When I bought my latest car, it came with a fine scratch on the instrumentation cluster cover. Too lazy to take it back to be repaired. To this day it bothers me when I see it even though it doesn't impact anything on the operation of the car. Such is the case with this VTV Purifi amplifiers. In absolute terms they land way on top of the class. But looking carefully we see that something in the assembly and layout has caused performance to degrade objectively. It won't impact you in any way listening to it but just like my car, it shouldn't be there. Smaller companies building these boxes don't do any measurements and hence can't spot problems like this. So it is partly understandable but as consumers, we get to be ruthless in our demand in best in class execution. So I hope the company looks to resolve these problems as their prices are very attractive otherwise.

I can't recommend the VTV Purifi amplifiers based on these two versions I have tested.

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As always, questions, comments, recommendations, etc. are welcome.

Appreciate any donations using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/

 

[Vandemann]

VTV will hopefully figure it out and correct, thanks to your hard work.

 

[Ra1zel]

What a bummer that this issue persist and is not just a faulty unit

 

[Matias]

Opamps were not to blame.

 

[redshift]

First post here.

I’m thinking the input buffer section isn’t properly shielded/routed. The amp is quite high resolving (20+ bits) and likely need some more work there. Perhaps botching in some shielding cans/tape would do the trick?

 

[Kachda]

For a second I thought I was seeing double!

 

[Billy Budapest]

I can see two issues which could result in power supply noise:

1). VTV’s use of a Delta EFI filter employing y-capacitors, something that Bruno Putzeys explicitly warned not to do. This was brought up to VTV’s owner but I do not know if he plans to stop using the Delta filters;

2). The use of two power supplies, one for each Purifi module, is unnecessary and could contribute to suboptimal power wire routing and physical placement of the modules (ie, too close together, orientation unable to take advantage of using the power supply heat sink as a barrier, etc.)

 

[Billy Budapest]

VTV will hopefully figure it out and correct, thanks to your hard work.

I hope so!

However, offering “dual mono” power supplies and redundant EMI/RFI filtering feeds into audiophile neuroses and even though these “features” both contribute to lesser performance, they make good marketing copy to certain kinds of consumers.

 

[Billy Budapest]

Even if VTV insists on using two power supplies and the Delta EMI filter, I bet simply by moving the power supplies to the front of the case to put distance between them and the Purifi and buffer boards, and then turning them 90 degrees so that the heat sinks are able to form somewhat of a barrier against the EMI they generate and the Purifi and buffer boards, there will be measurable improvements. Currently, one pair of those thin unshielded wires from the output circuitry to the speaker jacks travels right over one of the power supplies, possibly resting on the heat sink. I sure that getting the power supply away from those wires would help performance.

 

[Matias]

Even if VTV insists on using two power supplies and the Delta EMI filter, I bet simply by moving the power supplies to the front of the case to put distance between them and the Purifi and buffer boards, and then turning them 90 degrees so that the heat sinks are able to form somewhat of a barrier against the EMI they generate and the Purifi and buffer boards, there will be measurable improvements. Currently, one pair of those thin unshielded wires from the output circuitry to the speaker jacks travels right over one of the power supplies, possibly resting on the heat sink. I sure that getting the power supply away from those wires would help performance.

Two power supplies is an optional, they also have single power supply for sale.

And aluminum used in heatsinks is weak for magnetic shielding, almost like air.
https://en.wikipedia.org/wiki/Permeability_(electromagnetism)#Values_for_some_common_materials

Steel is a cheap solution, just like Apollon did with the Purifi Mini.
https://www.apollonaudio.com/apollon-1et400a-mini-stereo-amplifier/

 

[Helicopter]

Thanks Amir. I guess the one to get is the Purifi with one power supply... and made by a different company.

 

[gonzoucab]

what a boomer.

i bet the NAD C298 does the same.

and i bet they even fucked the no buffer entry

whos wanna bet?

 

[Koeitje]

Two power supplies is an optional, they also have single power supply for sale.

And aluminum used in heatsinks is weak for magnetic shielding, almost like air.
https://en.wikipedia.org/wiki/Permeability_(electromagnetism)#Values_for_some_common_materials

Steel is a cheap solution, just like Apollon did with the Purifi Mini.
https://www.apollonaudio.com/apollon-1et400a-mini-stereo-amplifier/

It's still better than air and basically a free upgrade in performance.

 

[GWolfman]

Thanks. Good to know the stock buffer holds its own. Any issues running the stock buffers indefinitely (as I do)?

 

[Rick Sykora]

Lol, @amirm I had a comparable issue with an Accord I bought used from a “trusted” dealership. Along with a scratched display, later found out the car had been crashed despite a clean Carfax. I drove the car for years and still enjoyed it for the most part. However, am never going back to that dealer.

After the marginal reviews and other’s experiences, VTV seems a lot like that car dealer to me. I am pretty sure I could address most of the issues if I bought another one of his amps, but do not need the hassle or lingering doubts.

 

[Gorgonzola]

Thanks. Good to know the stock buffer holds its own. Any issues running the stock buffers indefinitely (as I do)?

I'm curious to know just what you mean by "stock" buffer: are you referring to the Hypex buffer? I first order my VTV Purifi stereo amp, (i.e. single PSU version), with the Hypex buffers. Much to my surprise the high frequencies seemed bright and harsh, especially at higher volumes which I found intolerable. I replaced the Hypex cards with a pair of VTV buffers with Sparko SS3602 op amps which solved the problem.

 

[Stoutblock]

Looks like VTV has some work to do. I would hope they take this review seriously.

 

[Rick Sykora]

Btw, just as with the earlier model just reviewed, there is no AC line fuse on this amp either. If you have bought or plan to buy, please consider replacing the IEC socket with one that has a fuse!

If you are wondering whether Hypex would recommend, look at the IEC socket used in the NC400 kit here. Also note there is no line filtering supplied with their kit.

 

[Billy Budapest]

Any tear down pictures of this particular sample to see if the workmanship, wire routing, etc., is consistent between both VTV units?

 

[Billy Budapest]

Thanks Amir. I guess the one to get is the Purifi with one power supply... and made by a different company.

Actually, the VTV to buy is the one based on the EVAL1 board in the Ghent case. Just ask VTV to make it with a standard fused IEC inlet rather than the Delta filter. For U.S. customers, it is the least expensive Purifi amp I’ve seen sold by anybody. It is essentially the reference design, minus a control cable used for the reference design’s push button on/off switch and LED.