VTV Purifi Amplifier Teardown(SIL 994EnH-Ticha Pro Opamp)

[Feyire]

Interesting but which, if any of these mods will make an audible difference?

The second mod, in regards to modifying the output (LC) filter, is most likely the main and most signification contribution to any audible difference. This wouldn't be surprising, given that it is in the final stage of the amplifier through which the signal passes.

Any audible difference, which can be noticeably better or significantly worse, depends entirely on how you go about modifying the filter. Some options include replacing the capacitors with ones that have a lower dielectric loss and ensuring that all capacitors are oriented with their outer foil towards ground in order to minimize noise. Another option is to replace the standard hysteresis producing iron core inductor with a pure copper air core inductor (thus eliminating the issue of hysteresis) - although my understanding from Purifi is that any audible effect caused by hysteresis is reduced to inaudible levels in the updated feedback loop of the Eigentakt design, so this modification may perhaps be considered optional for the Purifi.

I haven't made any of these modifications to a Purifi module myself, but I have done the same procedure (i.e. modifying the output LC filter) in my NC400 modules. In my subjective experience, I had very noticeable and satisfying audible improvements with this type of modication.

 

[fluid]

That said, whats wrong with a user replaceable fuse with a clip on cover like so many other manufacturers use? Board real estate?

But it is what it is- all Hypex psu/amps (except for a few of the DSP plate amps) have non-replaceable (for the average punter) fuses.

They used to have a ceramic easily replaceable fuse in the earlier versions and some of the other supplies still do. I am not sure why they changed but the SMPS1200A400 is more reliable now than it used to be so overall they have improved the product over time.

 

[peng]

And this is why you build your own folks:

~$750 Amplifier board (https://purifi-audio.com/vare/eval1/)
~$250 Chassis (https://www.ghentaudio.com/kit/purifi-eval1-se.html)
~$250 Hypex 1200W PSU

That would end up costing a lot more than buying from VTV, no?

 

[Rick Sykora]

That would end up costing a lot more than buying from VTV, no?

Correct, not sure how he prices so low. Even with volume discounting does not leave much margin. May not be sustainable, so if you are willing to fix or put up VTV’s build issues, grab one while you can. Not convinced they are worth the price premium over Hypex, but pretty good value IMO.

 

[peng]

Correct, not sure how he prices so low. Even with volume discounting does not leave much margin. May not be sustainable, so if you are willing to fix or put up VTV’s build issues, grab one while you can. Not convinced they are worth the price premium over Hypex, but pretty good value IMO.

First of all, thank you very much for your posts that identified and deficiencies and the "fixes" you applied, that's very helpful if I end up with such an amp.

If I go for the single power supply model such as the one linked below, would some of your "fixes" become unnecessary because VTV would have fixed some of the things identified, and the long wire runs would naturally be avoided, assuming the size of the cases are the same?

VTV AMPLIFIER Stereo Purifi Audio 1ET400A Amplifier | VTV Amplifier

 

[tmtomh]

First of all, thank you very much for your posts that identified and deficiencies and the "fixes" you applied, that's very helpful if I end up with such an amp.

If I go for the single power supply model such as the one linked below, would some of your "fixes" become unnecessary because VTV would have fixed some of the things identified, and the long wire runs would naturally be avoided, assuming the size of the cases are the same?

VTV AMPLIFIER Stereo Purifi Audio 1ET400A Amplifier | VTV Amplifier

The single PSU version of any Purifi amp is a simpler and more economical option, with no downside that I'm aware of - the dual PSUs are not, as far as I know, necessary.

The inside shot of that VTV generally looks good to me, though I defer to others who are more expert. The one change that Rick or others might recommend - and I am not sure about this - is flipping the PSU 180 degrees so the heatsink/shield is between the PSU and the amp boards rather than up against the inside left wall of the case. But every configuration has its cost - doing so would likely require a new internal power wire from the AC input, as the current one is not long enough to make the run if you turn the PSU 180 degrees. And the black cable from the PSU to the amp boards would then have to run over the top of the heat sink.

This internal-layout stuff is important, but I also personally feel like there's a point beyond which it doesn't really matter in practical use. As long as things are grounded properly and there are no obviously over-long wires, no untwisted pairs that should be twisted, the rest isn't super-important - IMHO of course.

I have - and really like, and still strongly recommend - an Audiophonics amp that I got in May 2020. But were I in the market today, I'd probably get the lowest-end/cheapest VTV Purifi amp, since it's an amazing deal and the current builds of it seem solid (and it's based in the US for lower shipping).

 

[Rick Sykora]

The single PSU version of any Purifi amp is a simpler and more economical option, with no downside that I'm aware of - the dual PSUs are not, as far as I know, necessary.

The inside shot of that VTV generally looks good to me, though I defer to others who are more expert. The one change that Rick or others might recommend - and I am not sure about this - is flipping the PSU 180 degrees so the heatsink/shield is between the PSU and the amp boards rather than up against the inside left wall of the case. But every configuration has its cost - doing so would likely require a new internal power wire from the AC input, as the current one is not long enough to make the run if you turn the PSU 180 degrees. And the black cable from the PSU to the amp boards would then have to run over the top of the heat sink.

This internal-layout stuff is important, but I also personally feel like there's a point beyond which it doesn't really matter in practical use. As long as things are grounded properly and there are no obviously over-long wires, no untwisted pairs that should be twisted, the rest isn't super-important - IMHO of course.

I have - and really like, and still strongly recommend - an Audiophonics amp that I got in May 2020. But were I in the market today, I'd probably get the lowest-end/cheapest VTV Purifi amp, since it's an amazing deal and the current builds of it seem solid (and it's based in the US for lower shipping).

While I agree that smart electrical practices are essential, if you want the best possible performance, you need to be able to test each route of wiring with a spectrum analyzer comparing different routing alternatives. In some tighter cases, routing differences as little as a centimeter yielded several dB of lower noise. Based on my measurements, I am confident that a Hypex that is built with the wiring tested may likely be as good as a Purifi amp that is not tested.

The question over how to orient the power supply is a good example. When I tried reorienting the power supply with the heat sink away from the amp, the measured performance was better. Clearly this is counterintuitive. Did not analyze in detail, but others have said that the heatsink is a poor shield. My takeaway was that the shorter wiring must have helped more. See my VTV teardown thread for more info.

 

[Gregss]

While I agree that smart electrical practices are essential, if you want the best possible performance, you need to be able to test each route of wiring with a spectrum analyzer comparing different routing alternatives. In some tighter cases, routing differences as little as a centimeter yielded several dB of lower noise. Based on my measurements, I am confident that a Hypex that is built with the wiring tested may likely be as good as a Purifi amp that is not tested.

The question over how to orient the power supply is a good example. When I tried reorienting the power supply with the heat sink away from the amp, the measured performance was better. Clearly this is counterintuitive. Did not analyze in detail, but others have said that the heatsink is a poor shield. My takeaway was that the shorter wiring must have helped more. See my VTV teardown thread for more info.

Hello, Agree that placement of parts can have an influence on the result. Major reason I used a much larger case than is strictly required, so that I can have space between the supply and the amp boards and between the two amp boards as well. Energy transfer operates by the inverse square law of the distance and increasing the spacing can make a real difference. Also help things run as cool as possible, for a long life. Only downside - with proper cable routing of course, is the case will likely cost a little more. IMHO.

 

[peng]

Interesting but which, if any of these mods will make an audible difference?

To golden ears.., absolutely!!