VTV Purifi Amplifier Review with Weiss Buffer

[redshift]

Ha! Feel free to experiment a bit if you wish...

Here’s the shopping list:

1. Copper tape

2. Tinfoil

 

[Stoutblock]

^^^^ ha! ^^^^

 

[Billy Budapest]

I think that simply relocating and reorienting the power supplies would yield measurable results.

 

[redshift]

I think that simply relocating and reorienting the power supplies would yield measurable results.

Perhaps there is some trivial grounding issue that can be solved with some sand papering?

 

[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.

Unless VTV offers a good substitute, may be difficult to find another IEC with same size cutout. Another approach is to do inline...

AmazonSmile: KOLACEN Automotive Car Inline Screw Type 5x20mm AGC Fuse Holder 16 Awg Wire (Pcak of 10): Automotive

 

[boXem]

I think that simply relocating and reorienting the power supplies would yield measurable results.

I don't think so

 

[KSTR]

I don't think so

+1

My guess would be the hum/buzz we see is introduced in the buffer PCB. The input cables from the XLR's are short and shielded and there is little chance for catching up interference elsewhere, like from the sloppy wiring.
A specific is that the noise spectrum is that of a full-wave rectified mains signal, with rising amplitudes for the lower harmonics. This suggests capacitive coupling of a rectified mains signal into a reference ground polluting it, creating a GND error voltage that makes it into the 1ET400 input pins. Two SMPS1200A together will have at least 2nF of EMI capacitance from primary circuit "0V" to secondary...

 

[Matias]

+1

My guess would be the hum/buzz we see is introduced in the buffer PCB. The input cables from the XLR's are short and shielded and there is little chance for catching up interference elsewhere, like from the sloppy wiring.
A specific is that the noise spectrum is that of a full-wave rectified mains signal, with rising amplitudes for the lower harmonics. This suggests capacitive coupling of a rectified mains signal into a reference ground polluting it, creating a GND error voltage that makes it into the 1ET400 input pins. Two SMPS1200A together will have at least 2nF of EMI capacitance from primary circuit "0V" to secondary...

Could it be the non-recommended yet still being used IEM/RFI IEC inlet that is causing this?

 

[KSTR]

Could it be the non-recommended yet still being used IEM/RFI IEC inlet that is causing this?

It does make it worse. The PE-to-L and -to-N caps in an standard inlet filter will close the return path right in the device. Rather, a medical filter should be used (no caps to PE) plus a PE choke rated for this purpose. The connection from the inlet to the SMPSs should be lossy at RF otherwise there can be a risk of ringing (direct cascading two arbitrary mains filters should be avoided). Ferrite beads or cable insulation loaded with a ferrite powder grease can be used for the lossy connection.

But the main issue in my view atm is that the grounding scheme went wrong and only once that's fixed other cleanups would result in visible improvements. But I could be wrong, of course, not having the device on the bench...

 

[Gorgonzola]

I've read both reviews and the teardown.

Performance: "superb", "top of the class".
Price: unbeatable (lower than sellf-sourcing the components)

Recommendation: nope.

Compared to some other reviews I find this very harsh.

I would understand if it was out of security concerns, but are we even talking about audible sound degradation here?

VTV bashing has been going on for while around ASR -- not to say the negative comments have been invalid only maybe more severe than really warranted.

 

[Rick Sykora]

VTV bashing has been going on for while around ASR -- not to say the negative comments have been invalid only maybe more severe than really warranted.

ASR can be a tough crowd, but in the end, everyone has to make their own decision…

When VTV was first criticized, he posted and took steps to address the problems. That was years ago and new problems are found and no response. Otoh, Buckeye Amps puts himself out there, is responsive and continues to improve. No he does not do Purifi, but his price/performance is just as high for Hypex amps. If inaudibility concerns of test measurements are a non-issue, then seems like splitting hairs over Hypex vs Purifi would be comparably inaudible IMO.

Otoh, if you are willing to overlook some basics like no mains fusing, exposed shock hazards and other wiring issues, buy VTV. However, seems to me, the alleged bashing has some very substantial basis in facts.

 

[Rottmannash]

ASR can be a tough crowd, but in the end, everyone has to make their own decision…

When VTV was first criticized, he posted and took steps to address the problems. That was years ago and new problems are found and no response. Otoh, Buckeye Amps puts himself out there, is responsive and continues to improve. No he does not do Purifi, but his price/performance is just as high for Hypex amps. If inaudibility concerns of test measurements are a non-issue, then seems like splitting hairs over Hypex vs Purifi would be comparably inaudible IMO.

Otoh, if you are willing to overlook some basics like no mains fusing, exposed shock hazards and other wiring issues, buy VTV. However, seems to me, the alleged bashing has some very substantial basis in facts.

Not sure all VTV amps suffer from these issues. I guess I need to send my VTV Eval 1 amp in to Amir and let him put it through its paces and see how it performs.

 

[Rick Sykora]

Not sure all VTV amps suffer from these issues. I guess I need to send my VTV Eval 1 amp in to Amir and let him put it through its paces and see how it performs.

I have an older VTV that I got used and it has all three of the same issues mentioned in Amir’s recent teardown. I missed the fuse and am about to fix that issue. The trigger board had exposed AC and insulated it. Finally, the wiring for the trigger board was not secured and did add some strain relief.

So, have actual experience with these VTV issues and, along with other‘s feedback, am not comfortable with what I see as apparent ongoing poor practices. Notably, not when there are safety problems that may put others at risk. YMMV and I can see how one might rationalize the EVAL-1 deal, but it comes with some major caveats from my perspective.

 

[Billy Budapest]

Not sure all VTV amps suffer from these issues. I guess I need to send my VTV Eval 1 amp in to Amir and let him put it through its paces and see how it performs.

I‘d be shocked if it measured profoundly differently (within sample-to-sample variation at most) than the Purifi reference design. The Delta IEC filter could possibly degrade performance a little bit via ground pollution.

 

[Rottmannash]

I posted images of the inside of my amp and no one seemed to feel it suffered many of the same safety and/or wiring issues as the amp in this review. So far I'm very satisfied. Similarly satisfied with Buckeye's amp as well. The sound identical to me btw.

 

[Rick Sykora]

I‘d be shocked if it measured profoundly differently (within sample-to-sample variation at most) than the Purifi reference design. The Delta IEC filter could possibly degrade performance a little bit via ground pollution.

I measured the amp with and without the Delta filter and found no real difference. There are versions of it that are fused though. Am just going with an inline fuse for mine. If mine were in warranty, would be asking VTV for a fused one!

 

[Rick Sykora]

I posted images of the inside of my amp and no one seemed to feel it suffered many of the same safety and/or wiring issues as the amp in this review. So far I'm very satisfied. Similarly satisfied with Buckeye's amp as well. The sound identical to me btw.

Thanks for sharing!

As for your pics, the filter label is not shown, so cannot see if yours has fuse or not. Mine does not nor does the review teardown unit have. The internal wiring looks comparable to the review unit so same judgments apply as Amir and others have already posted. The trigger board is mounted vertically and so this is likely less risky than my horizontal one. Mine has one screw holding it on. As my amp was used, cannot be sure it is entirely in “factory” state, but appears consistent with others posted/reviewed.

If you are satisfied, then would not expect it is worth spending the money to ship to Amir. If it is in warranty, would be interested to know how VTV would respond to the problems found. If it is not and you want to improve it, I can help. The shipping to me would be cheaper too. If so, PM me and will figure out how I can reasonably assist.

 

[Gorgonzola]

ASR can be a tough crowd, but in the end, everyone has to make their own decision…

When VTV was first criticized, he posted and took steps to address the problems. That was years ago and new problems are found and no response. Otoh, Buckeye Amps puts himself out there, is responsive and continues to improve. No he does not do Purifi, but his price/performance is just as high for Hypex amps. If inaudibility concerns of test measurements are a non-issue, then seems like splitting hairs over Hypex vs Purifi would be comparably inaudible IMO.

Otoh, if you are willing to overlook some basics like no mains fusing, exposed shock hazards and other wiring issues, buy VTV. However, seems to me, the alleged bashing has some very substantial basis in facts.

VTV has learned from mistakes in the past and let's hope he will continue to do so. Let's face it: he is evidently an assembler not an expert designer; (it seems he used consultants to design both the solid state and tube buffers he offers). One way to look at is, Does he do a worse job than the average, non-engineer DIY'er, (such as me), is likely to do.

I had an excellent personal exchange with him less than a year ago when I had issues swapping my original Hypex buffer for a VTV buffer (with Sparkos SS3602). He spent over an hour on the 'phone with me giving useful advice -- turned out the problems were entirely my own fault.

 

[Rick Sykora]

VTV has learned from mistakes in the past and let's hope he will continue to do so. Let's face it: he is evidently an assembler not an expert designer; (it seems he used consultants to design both the solid state and tube buffers he offers). One way to look at is, Does he do a worse job than the average, non-engineer DIY'er, (such as me), is likely to do.

I had an excellent personal exchange with him less than a year ago when I had issues swapping my original Hypex buffer for a VTV buffer (with Sparkos SS3602). He spent over an hour on the 'phone with me giving useful advice -- turned out the problems were entirely my own fault.

I agree.

Think you have cast it in the right light. Am not sure that everyone makes these distinctions about builders vs designers though. In the end, electrical safety should be addressed competently. Not only fixing the current products, but addressing the customer base too. So, the ball is clearly in his court.

 

[phoenixdogfan]

They measure as exemplary implementations. So much so that you would have to come up with a really good reason not to use them. Really good reasons will include their price and lack of flexibility. Putting the amplifier modules in a real product will likely be better served by a custom interface board that is exactly crafted for need. That might be a single board that provides buffering and interface for many more boards, or improves packaging and layout. In that respect this interface board is not suitable for production use, as, in particular, it dictates the precise layout of the connectors.

But for a simple box builder like VTV the only reason not to use it is to craft the sound away from perfect, or to add some undefined magic dust. I wonder if anyone has bought the version with a tube stage in the way?

Oh, I would hope not. There is a major difference between the Hypex buffer boards and the Purifi boards. The Hypex are not intended for production, but only something to be used by OEM's and DIYers for development purposes. The Purifi boards OTOH are suitable for end use as is.

They may not suit every user b/c they predetermine the location of the I/Os and where in the casing the boards need to be located, but their use makes for a maximally performing product. With the diy case from Ghent, the ease of construction of the stock kit exceeds the Hypex NC 400 monoblocks.