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VTV Purifi Eval-1 build

Rottmannash

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If you plan on using the VTV Eval-1 as it is shipped, then a 2-conductor cable with NL4* connectors on it would be fine (of the four terminals in the connector, 1+ & 1- are connected, but 2+ & 2- are not.)

If you plan on running a bi-wire set-up in the future (which will involve some soldering to connect jumpers from the circuit board to the 2+ & 2- terminals of the SpeakON jacks), then buy a 4-conductor cable with NL4 connectors.

* - NL4 is a 4-pole connector, but you don't have to use/connect all four.
2-core-speaker-cable-with-speakon-connector.jpg
Thanks. Don't plan on b-wiring so will get a pair of the 2-pole.
 

SCG

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They can't be too serious about it, otherwise they should've left off the banana jacks on the I/O board.
Completely disagree, Lars has done a lot of research in this area and from testing believes measurable magnetic hysteric distortion is an important but neglected area and where IMD may be hiding in plain sight and something All their transducers address.

'"Magnetic materials have something called hysteresis, If you test a magnetic core with a sinewave the distortion looks a little like soft clipping, perfectly benign. But what came out of testing was that hysteresis has a long term memory so you can get intermodulation between things that happen now and things that happened 10 minutes ago. With music this distortion sounds like half correlated noise."'

Most (not all) will be using these Purifi eval amps with passive consumer speakers. Being very conservative 95% (19 out of 20) passive consumer speakers don't come with SpeakOn connectors and instead use banana and/or spade connectors. So providing a non-magnetic connector for those that think it's important via SpeakOn while also providing a way for 95% of users to quickly/easily connect via banana jack doesn't mean 'they aren't too serious about it' - it's more about being flexible to the realities of the current market conditions. When I first hooked up my amp to test, I used the banana jacks as that's the connectors/cables I already had in abundance and didn't have to buy or make anything custom beforehand.

Topping has some products that have TRS instead of XLR connectors and there are some people in these very forums howling like hyenas that they will never buy them because they have (in their words) "a non standard connector".

I've also found no one who has tested if the banana jacks on the Purifi eval boards are non-magnetic or not, they very well may be. My earlier statement was about overall manufactures that use the Purifi power boards and build their own systems from the ground up including selecting the speaker connectors (e.g. NAD).

I doubt the purists would be able to get past the idea of using a class D amplifier, much less using any amplifier from a non-marquee brand.
I used the word purist (a person who has very strong ideas about what is correct) and not a fanatic (a person motivated by extremely unreasonable enthusiasm) and therefore you missed my point.

My point was that if someone takes a car to a test track with 4 flat tires and measures its performance it won't do very well. If they then replace them with 3 proper tires and remeasure its performance (while improved) it still won't be much better. The only way to get the improvements they're looking for is to replace all 4 tires, then (and only then) will they see the vast improvements the car is capable of and therefore get the much better measurements they're seeking.

In this case I have no data and therefore no idea if replacing 3 of the 4 magnetic items in the signal chain helps just a tiny bit (like only replacing 3 out of 4 flat tires) or if it has a cumulative effect and doing something is much better than doing nothing at all.

I don't have a horse in the race, nor any data to support things one way or the other, but it was only $20 to replace 3 out 4 magnetic items in the signal chain so I though why not do it.

In any case I suspect the point is moot as any improvements in this part of the signal chain are probably vastly masked by measurable magnetic hysteric distortion in the speakers/crossovers.
 
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Hello,
Sorry for the newbie question, what's the difference of the vtv's 1et400 and Eval1 models?
The VTV Eval-1 model sticks closely to the build of the Purifi reference design/demonstrator amplifiers that were made available to reviewers a few years back. It utilizes:
  • a Hypex SMPS1200A400 power supply
  • two (2) of the Purifi 1et400 single-channel amplifier modules
  • a Purifi I/O board/backplane that provides power/signal input/speaker output connectivity to the two 1et400 modules
  • a Ghent Audio case made for this particular component set
  • VTV offers an optional 12v trigger module for their EVal-1 build, but this is not something that was in the Purifi Eval-1 demonstrators.
This is the only VTV model that utilizes that Purifi I/O board.

VTV's other 1et400-based models employ that amplifier module but, depending on the specific model/configuration, use different combinations of I/O boards, signal buffer modules, and power supplies. The cases vary in response to the component count.
 
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Hi @SubsonicLurker
Thanks for your explanation.
I was planning to buy it with the sparkos I/o.
Have you heard it?
Thanks
No, I haven't.

In fact, for my own system, I had specifically ruled out amplifiers that employed custom opamp modules because each of them had been designed for a particular sound signature that their respective designers believed to be "more musical" than alternative offerings. I wanted an amplifier that is the proverbial "straight wire with gain."
 
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Here's hoping - for your sake - that you have more self-control than I do with regard to potentially loooooooong back-and-forths over whatever the build quality reveals itself to be. I will say that even though I disagree with one person on many points made in my own back-and-forth, he's right that VTV is definitely not doing their own heat sinking design and is relying on Ghent Audio for them. I have a VTV amp myself with nc1200s and a SMPS 3K 700 power supply and it's definitely in too small of a chassis w/o adequate heat sinking.*

* that said, I haven't run into any problems yet and my initial impressions/measurements of the operating temperatures have not caried through to daily use. Please let us know if you happen to think about monitoring that w/ your own VTV product.
The build quality of my sample was fine, not perfect, but nothing that I feel needs VTV's involvement in addressing.

As for the matter of heat sinks/dissipation, I've only sporadically bothered to do temperature checks (and am less inclined to continue doing so since my prior checks have not shown any marked increase in temperature at either idle or normal listening levels.)

I'm not sure if you've found differently but, aside from the Audiophonics unit reviewed on ASR in February of this year, I have yet to see a Purifi-based amp with any appreciable heatsink capacity. I found this both odd, and at odds, with Purifi's own datasheets which state how important proper heat dissipation is for device operation. But Purifi's own demonstrator units lacked dedicated heat sinks and (seemed) to rely on thermal conduction/dissipation via the lower chassis plate (it would've been informative to know if there was any heatsink compound or pad between the modules' base plates and the chassis.) I would've expected that demo units would be subjected to harsher that normal treatment in the course of the measurement & review process, but none of the reviews that I found mentioned anything about thermal or abrupt amplifier shutdowns occurring during the review process.
 
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Hi @SubsonicLurker ,
I saw that you are retiring your old big Emotiva. I am having the same problem. I have an old Parasound A21 amp.
How the Vtv compares with the Emotiva regarding SQ?
 
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Hi @SubsonicLurker ,
I saw that you are retiring your old big Emotiva. I am having the same problem. I have an old Parasound A21 amp.
How the Vtv compares with the Emotiva regarding SQ?
Aside from the lack of a very faint background hiss at idle when compared to the Emotiva, there's no discernible difference in sound quality. The VTV probably measures much better than the Emotiva, but that hasn't translated into an audible difference when actually listening to music or other material.
 

Rottmannash

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I can hear a faint hiss close to the tweeter with all my A/B amps but not the Purifi or the MP252 or the PA5. YMMV but typically Hypex and Purifi amps are dead quiet.
 
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I can hear a faint hiss close to the tweeter with all my A/B amps but not the Purifi or the MP252 or the PA5. YMMV but typically Hypex and Purifi amps are dead quiet.
Aside from the lack of hiss, would you say that you've noticed a change in sound quality versus your most recent amplifier? And, if so, how would you characterize the change?
 

Rottmannash

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The Purifi and MP252 amps are far superior to the onboard amps of my AVRs, my Emotiva PA 1 monoblocks (class D) and my old Rotel. Especially as power is needed. The VTV Purifi is the best of them all. The Topping PA5 sounds clear but not powerful enough for my F208s.
 

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I'm not sure if you've found differently but, aside from the Audiophonics unit reviewed on ASR in February of this year, I have yet to see a Purifi-based amp with any appreciable heatsink capacity. I found this both odd, and at odds, with Purifi's own datasheets which state how important proper heat dissipation is for device operation. But Purifi's own demonstrator units lacked dedicated heat sinks and (seemed) to rely on thermal conduction/dissipation via the lower chassis plate (it would've been informative to know if there was any heatsink compound or pad between the modules' base plates and the chassis.)

Simply mounting the module plate to the external chassis IS what Purifi's data sheet suggests. They're mainly wanting to make sure people aren't using the module without any thermal coupling.

While 1ET400A has very low idle losses and high overall efficiency, adequate cooling is essential for sustained power delivery. Careful considerations must be given to design of the thermal system in order to achieve desired output power specification.

It is recommended to mount the module on a heatsink, e.g., an adequately design aluminum chassis
 
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While 1ET400A has very low idle losses and high overall efficiency, adequate cooling is essential for sustained power delivery. Careful considerations must be given to design of the thermal system in order to achieve desired output power specification.

It is recommended to mount the module on a heatsink, e.g., an adequately design aluminum chassis
Not to be pedantic but, as written, that last statement implies something more than affixing yet another aluminum plate to the Purifi module's existing heat spreader*, such as either the attachment of an actual heat sink assembly (like NAD C298 & M28 devices do), or the use of an enclosure with integrated cooling fins/ribs like the Audiophonics HPA-S400ET (or the case below.)

I say this because the term heatsink** has a very specific meaning in the areas of electronics design & manufacturing***, and Purifi calls it out on their datasheet (that said, it's entirely possible that their marketing people got involved and were a little loose with their terminology.)

And, if anyone wonders why Purifi didn't do it themselves, maybe because they were development mules/press samples (they probably shipped them in something resembling a Pelican case, too.)

* - a plate (or block) of material is typically referred to as a heat spreader, and is used to increase surface area and facilitate the attachment of the heat sink(s) or other coolers.
** - a heat sink (heatsink) typically has fins or pins to perform heat exchange with the surrounding fluid.
*** - which is where I spent the early part of my professional career - electronics test engineering & environmental testing.
hit_02.jpg
 
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KMO

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Not to be pedantic

Indeed, because that would require being correct. ;)

So you're saying we should ignore the "e.g., an adequately design [sic] aluminum chassis" bit? Is that just decoration, do you think?

Sure, more fins can't hurt, but I'm not seeing any reason to suppose they're necessary for something of this level of power.


Purifi calls it out on their datasheet
Where? The only reference I can see is attached to "e.g., an adequately design [sic] aluminum chassis". Nothing about fins.

It's really not uncommon to see Class D devices just using a plain case as the heatsink. (And yes, dedicated "heatsinks" in a catalogue are the finny things, but other things are also heatsinks).

One pair of examples that springs to mind - the KEF KF92 and KC62 subwoofers, both of which are sealed (so no ventilation) and have 2x500W amps in them.

The KF92 has one of the finny things you'd recognise as a heatsink on the back.

The KC62 simply uses the non-finny aluminium case you don't recognise as a heatsink as its heatsink.

You just need sufficient area and airflow. Which may or may not involve fins.

The fins on the side of the box in your picture really aren't adding that much area, proportionately. They're not decorative, but they're not radically changing the box's properties.
 
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Indeed, because that would require being correct. ;)

So you're saying we should ignore the "e.g., an adequately design [sic] aluminum chassis" bit? Is that just decoration, do you think?
Neither said nor implied any such thing, but your cognitive ability seems to leave you swirling around that particular drain.

Do you think that the fins/pins on a heat sink are "just decoration"? Is NAD attaching "finny things" because they had a bunch of them sitting around that they needed to surreptitiously dispose of?

Did you actually read (and understand) my original comment on this topic? Specifically the part where I wrote, "Purifi's own demonstrator units lacked dedicated heat sinks and (seemed) to rely on thermal conduction/dissipation via the lower chassis plate"

Subsequent to that, I also wrote, "none of the reviews that I found mentioned anything about thermal or abrupt amplifier shutdowns occurring during the review process."

The clear implication being that thermal management did not seem to be an issue even though I would've expected the demo units to be treated more harshly than one that was actually owned by an individual. To spell it out for you, this is a positive.

Sure, more fins can't hurt, but I'm not seeing any reason to suppose they're necessary for something of this level of power.
You would need actual information such as the operating requirements (including duty cycle and environmental conditions) to make a meaningful supposition, but you do you.

And there are two, very straightforward, reasons to implement conservative thermal management:
  1. to paraphrase Purifi's datasheet - continuous output power is limited by thermal management
  2. capacitor service life roughly doubles with each 10C reduction in temperature. As these are the components that frequently fail age out/fail in amplifiers, cooler is better.
If you neither require much power for your listening, nor are concerned about the longevity of your gear, then this won't matter to you. I tend to keep my gear around for 10-20 years.

Where? The only reference I can see is attached to "e.g., an adequately design [sic] aluminum chassis". Nothing about fins.
Again, here's what they actually said, including the piece that you like to exclude, "It is recommended to mount the module on a heatsink, e.g., an adequately design aluminum chassis."

Engineers, good ones at least, tend to speak with precision (the rest design high-end speaker cable and interconnects.) While I have no doubts that Purifi's engineers are very, very good, their datasheet is lacking detail/clarity in some areas (such as an actual RMS rating [even if it's couched with temperature envelope data], along with the inclusion of some typos.) Perhaps they have/use slightly different terminology, or perhaps it may have originally been written in Danish and something didn't quite translate the same.

Yes, Purifi used "adequately design aluminum chassis" as an example of a heat sink, but their datasheet doesn't provide any guidance regarding thermal dissipation requirements, so the example is not useful from an engineering perspective. Without that information, how does one know if the aluminum chassis in use is "adequately designed" aside from repeated prototyping & environmental testing?

It's really not uncommon to see Class D devices just using a plain case as the heatsink. (And yes, dedicated "heatsinks" in a catalogue are the finny things, but other things are also heatsinks).

One pair of examples that springs to mind - the KEF KF92 and KC62 subwoofers, both of which are sealed (so no ventilation) and have 2x500W amps in them.

The KF92 has one of the finny things you'd recognise as a heatsink on the back.

The KC62 simply uses the non-finny aluminium case you don't recognise as a heatsink as its heatsink.
Well, that explains why neither the 1.2KW class-D amp in my Velodyne sub (that I've owned since 2009) nor the 200W class-D woofer amplifiers in each my ML mains (~2010) have "finny" things.

But we're not talking about Kef, are we? Perhaps you'd like to go off on a tangent about the color red while you're at it?

You just need sufficient area and airflow. Which may or may not involve fins.
I never said that, depending the specific circumstances, a properly spec'd heat spreader couldn't work to keep a device within its operating envelope.

What I did say is that I had not found may Purifi-based devices, aside from a limited few, any that had much in the way of actual heat sink area. As I've said, heat sink has a specific meaning in the electronics world, and my use of that specific term was not accidental.

Since you're having such a mental block about that, I'd suggest that you ask an engineer, one that has both the time and crayons, to explain the difference between a heat sink and a heat spreader to you (hint, it's the finny things), and why cooler operating temperatures are (generally) a good thing.

The fins on the side of the box in your picture really aren't adding that much area, proportionately.
Based on the mechanical prints for that particular chassis, those fins have more than doubled the effective surface area of left & right sides of that particular chassis.

Please tell us what your statement is based on.

They're not decorative, but they're not radically changing the box's properties.
A 200%+ increase in effective surface area is not insignificant.
 

SCG

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In my opinion this thread has a lot of great info so far and while it's good to have spirited debates on key issues of disagreement, it's important to make sure the thread doesn't derail into character assassinations or insults of other people's intelligence, otherwise it becomes something to avoid like Covid hospitalization.

From a DIY perspective, I would never put the nc1200s & SMPS 3K 700 psu into that small of a Ghent Audio case without heatsinks, but its good to hear that there hasn't been any issues under normal use with VTV's build.

I also think it's important to make sure we're not talking semantics, I agree that a heatsink has a specific meaning vs a heatspreader but tech people do sometimes use them interchangeably. A prime example is Amir who is an Engineer and does testing & teardowns on a daily basis - yet he referred to the heatspreader in the VTV Purifi amps as a heatsink (see attached photo) and no technical people noticed it nor got into a heated debate in that 103 page thread. Although, I do think there's been some good info in this thread regarding this topic, minus the personal insults.

Also, Amir did have the Purifi 1ET400A amp shut down under his testing conditions but they are not realworld use conditions for me in a desktop application (or I think for most people).

"'I ran this test multiple times, tuning the input voltage. This eventually upset the amp and caused it to shut down when producing 274 watts into 4 ohm before our (4th and final) sweep was completed (see green trace in attached photo). Their documentation clearly states that extra cooling is needed for continuous power."'

With that said, I could add a heatsink to the Hyperx heatspreader but have zero desire or need to. I also have no data nor plan to do any testing, but based on mine and others' previous testing on CPUs/GPUs (demonstrating the vast improvements) I will add thermal paste between the Hyperx psu plate and the Ghent aluminum case (once my VTV is a known keeper). It's only $10, can't hurt, will last for several years, and will definitely help based on other thermal transfer applications.

Heat is the enemy of extended life for all electronics so if doing something so simple can silently help keep things cooler then it's value added for me. Plus reorienting the PSU put the Hyperx heatspreader almost right above the Ghent's bottom plate vents which is another cooling bonus.




VTV Purifi Amp 994EnH-Teardown.jpg Purifi Distortion versus Power versus Frequency Measurements 4Ohms.png
 
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In my opinion this thread has a lot of great info so far and while it's good to have spirited debates on key issues of disagreement, it's important to make sure it doesn't derail into character assassinations or insults of people's intelligence, otherwise it's something to avoid like Covid hospitalization.

From a DIY perspective, I would never put the nc1200s & SMPS 3K 700 psu into that small of a Ghent Audio case, but its good to hear that there hasn't been any issues under normal use with VTV's build.

I also think it's important to make sure we're not talking semantics, I agree that heatsink has a specific meaning vs a heatspreader but tech people do sometimes use them interchangeably. A prime example is Amir who is an Engineer by training, does testing and teardowns on an almost daily basis - and he referred to the heatspreader in the VTV Purifi amps and as a heatsink and no tech people noticed or got into a heated debate about it (see attached photo) though I think there has been some good info in this thread regarding this topic, minus the insults.

Also, Amir did have the Purifi 1ET400A amp shut down under his testing conditions but they are not realworld use conditions for me in a desktop application. "'I ran this test multiple times, tuning the input voltage. This eventually upset the amp and caused it to shut down when producing 274 watts into 4 ohm before our (4th final) sweep completed (in green). Documentation clearly states that extra cooling is needed for continuous power."' (see attached photo).

With that said, I could add a heatsink to the Hperx heatspreader but have zero desire or need. I also have no data nor plan to do any testing (but once my VTV is a keeper) based on mine and others' previous testing on CPUs/GPUs demonstrating the vast improvements, I will add thermal paste between the Hyperx psu plate and the Ghent aluminum case. It's only $15, can't hurt, will last for several years, and will definitely help based on other thermal transfer applications.

Heat is the enemy of extended life for all electronics so if doing something so simple can help silently keep things cooler then it's value added for me. Plus reorienting the PSU put the Hyperx heatspeader almost right above the Ghent's bottom plate vents which is another cooling bonus.




View attachment 207206 View attachment 207216
I agree, considered discourse is always preferable, but when someone comes at you with snark and unsupported BS, it warrants a response lest they continue to think that that sort of behavior is okay just because it's over the Interwebs.

Moving on from finny things, now that you've had you amplifier for a bit over a week, what are your (initial) thoughts on its sound/performance?
 

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So far really happy with the VTV, it sounds exactly like the PA5 & Outlaw 2160 (thou without any AB hissing) which is to say neutral without any coloration of the original signal. The only issue is when turning on/off via the rocker switch* I get a slight click sound thru the speakers even with no input devices connected.

It's not a loud sound and it happens immediately after the relay click sound coming directly from the amp (or practically simultaneously). I have no concerns about speaker damage but none of my other amps (PA5, Outlaw, ATI, Monoprice, Denon) make any on/off sound thru the speakers.

Is anyone else experiencing this?

*no longer use the standby sw because the front panel lite was always on and now using the rocker sw - lite-on/amp-on; lite-off/amp-off.
 
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