VTV Purifi 1ET400A updates

[Rugger]

Hi all,
I have been a succubus in this forum for far too long, only taking and never giving so I figured that I would register and make a fool-hearted attempt at contributing.

Disclaimer - Rugger is not an audio professional and is simply attempting to hang out with some guys and learn something through osmosis, plz no make fun of.
"This is the forum where we try to impress each other with how much we know about audio. Heavy use of technical jargon is required for participation" ..... well shit

On to the task at hand. I am building a ground-up bang for your buck system with a goal of having that 30-50k sound for far... far less. (i will do a full thread about this and my build process)
After reading Amir's review of the Purifi modules and seeing the price I knew that these amps had to have the bang for your buck championship belt. A little googling later I discovered that VTV amplifiers were not only the least expensive supplier but also the only one based in the US. After a little more searching around and I found several poor reviews of VTV Purifi amps but seeing as they were the cheapest I took the leap with the expectation that I would just fix any issues myself.

I let the pictures speak for themselves but the amp arrived quickly with no issues in the ordering process. It was in good shape, there were no scratches, dents, or missing screws. The internals looked nice, there was no duct tape or loose connectors. The mains power connector was tight and the infamous pin 1 issues looked to be solved. The buffer boards and pin one were grounded to the chassis at separate spots. I even tested the resistance between all of these connections and the mains ground, everything read 0 ohms. There was nothing for me to fix so I buttoned it up and ran some tests through my JBL Studio 280's by way of the MiniDSP SHD and WOW! This thing is crystal clear for as much as I'm willing to crank it up.

More Disclaimer - I'm not affiliated with VTV in any way and I paid full price for this thing.

 

[Matias]

Nice! Welcome to the forum.

 

[Sebastijanovski]

Hi Rugger, thanks for that! Are those the stock Hypex buffers, or did you tick any option boxes?

Cheers,
Seb

 

[Rugger]

Stock Buffers, unsure if the benefit of fancy buffers is worth the cash, it would be interesting to see measurements of the Purifi modules with all the different Buffer options. That being said I will need another amp. what I'm essentially building is a JBL M2 clone (same drivers) that uses Dirac instead of that BSS deal, the crossovers from the MiniDSP SHD instead of the Crown Amps, and that has a far higher wife acceptance factor.

I'm going to build a test setup and see if the Purifi amp has the juice to push that 15" 2216Nd to my satisfaction, if it does then I will likely get another one, if not ill probably go with a hypex NC500 or NC1200.

If I do go with the all purifi setup ill order the next one with one of the buffer options and do an A/B comparison

 

[Aardappel]

Hi Rugger,

I am in a very similar position as you, looking to buy the VTV amp, a new DAC and a new pair of speakers (leaning towards the Klipsch RP-8000F at the moment). This is my first post!

First of all the amp looks well assembled, looks like the teething issues have been resolved. The price has also gone up a bit recently which could explain the difference in quality. At this quality/price level I think it is a no-brainer compared to other assemblers, even for someone from Australia like myself with all the additional costs. I would be keen to get the thoughts of a lot of the members here who have been bashing VTV (with a passion) recently.

I am contemplating the same amp however I have a few thoughts - with the stock input buffers the max capacity is reached at 2.35V, instead of say 4V which is the output Voltage of a typical balanced amp. Would a balanced amp work well with this amp? Is distortion higher at lower output Voltage of a balanced DAC? Is it better if I opt for an unbalanced DAC?

Furthermore, how are you finding the SQ and power levels of the amp so far? Have you hooked the amp up to your larger speakers already to give that a go?

The thing I noticed is that when the NAD M28 was tested (https://www.audiosciencereview.com/...8-seven-channel-power-amplifier-review.15939/) the power output was significantly higher - would it be worthwhile opting for mono-blocks to get more power out of the Purifi modules?

Cheers

 

[tmtomh]

After a little more searching around and I found several poor reviews of VTV Purifi amps but seeing as they were the cheapest I took the leap with the expectation that I would just fix any issues myself.

Thanks very much for this post - great to see that VTV appears to have worked out the previous issues. And kudos to you for the statement I've bolded - for folks with the skill and confidence, this is a great attitude to take and probably makes the hobby both more enjoyable and less nerve-wracking!

 

[Rugger]

I am contemplating the same amp however I have a few thoughts - with the stock input buffers the max capacity is reached at 2.35V, instead of say 4V which is the output Voltage of a typical balanced amp. Would a balanced amp work well with this amp? Is distortion higher at lower output Voltage of a balanced DAC? Is it better if I opt for an unbalanced DAC?

Furthermore, how are you finding the SQ and power levels of the amp so far? Have you hooked the amp up to your larger speakers already to give that a go?


Cheers

I don't have the knowledge or equipment necessary to test output voltages etc. I can tell you I'm using the balanced output from my MiniDSP SHD (4v @ 0db) and it's pushing the poor duel 6.5 inch woofers on my JBL Studio 280s right into Xmax on any song that has lots of low-end, movie soundtracks etc. I have no idea how much power it's pushing other than to say it's plenty haha. If you are concerned, for some extra cash you can get VTVs custom input buffer with selectable gain that will let you cut the input gain in half with a jumper.

The sound quality on the amp is amazing, I can hear no distortion once so ever at any level until these JBLs start to give up from the power. they claim that they have 200W power handling but that is likely 40hz and up. I have no high pass filter on them, they are getting all the signal. That being said the 280s only have an 89db sensitivity and this amp will drive them to levels far above comfortable listening. Those Klipsch you listed have 9db more sensitivity at 98db. They are going to be 3x as loud at the same power level. I can not imagine you need even half the amount of power this purifi amp puts out. I'm pummeling these JBLs like a rented kia and this thing is bearly warmer than my desk.

Right now by far, the most limiting factor of this set up are the drivers but we will fix that shortly with the 2216nd and the D2430K just have a whole lot of design and wood work to do

 

[Aardappel]

There have been some reports on this forum that the Hypex stock input buffer is unsuitable for home hifi use, and only really useable for evaluation purposes. Supposedly an RF filter is required as a minimum, some additional information on the stock Hypex buffer can be found here for example.

Have you noticed any RF interference or issues at all in your setup?

 

[Rugger]

There have been some reports on this forum that the Hypex stock input buffer is unsuitable for home hifi use, and only really useable for evaluation purposes.

Sounds like bullshit. Why would hypex, designers of some of the quietest amps ever made, create a buffer for those quiet amps that would pick up noise in a standard home environment? Doesn't add up. Sounds like people are trying to hype up their product which uses the same amp module but costs twice as much because it uses a "super extra special RF shielded buffer board"

I have this amp and the mini DSP plugged into the same circuit as all of this computer gear on my desk which I'm sure all have super "noisy" SMPSs and just for good measure I sandwiched the amp between a Sonos amp and the SHD. There is no noise.

Beware of the HF boogeyman come to steal your fidelity!!! you must buy $20k RCA cables to ward him off, it is known.

 

[March Audio]

Sounds like bullshit. Why would hypex, designers of some of the quietest amps ever made, create a buffer for those quiet amps that would pick up noise in a standard home environment? Doesn't add up. Sounds like people are trying to hype up their product which uses the same amp module but costs twice as much because it uses a "super extra special RF shielded buffer board"

I have this amp and the mini DSP plugged into the same circuit as all of this computer gear on my desk which I'm sure all have super "noisy" SMPSs and just for good measure I sandwiched the amp between a Sonos amp and the SHD. There is no noise.

Beware of the HF boogeyman come to steal your fidelity!!! you must buy $20k RCA cables to ward him off, it is known.

Its not BS. Its an evaluation circuit for designers to use, not for use in final products.

That eval buffer has no input filtering or GBW limiting. Its wide open to external RF or that from DACs. You can find a couple of forum users here that had "digital noises" due to intermodulation with the class d switching signal. They fitted a filter and problem went away.

https://www.audiosciencereview.com/...ith-ncore-amp-apollo-twin-x.11771/post-400198

https://www.audiosciencereview.com/...ltralite-mk4-akm-dac-version.3796/post-400194

 

[Aardappel]

Its not BS. Its an evaluation circuit for designers to use, not for use in final products.

That eval buffer has no input filtering or GBW limiting. Its wide open to external RF or that from DACs. You can find a couple of forum users here that had "digital noises" due to intermodulation with the class d switching signal. They fitted a filter and problem went away.

https://www.audiosciencereview.com/...ith-ncore-amp-apollo-twin-x.11771/post-400198

https://www.audiosciencereview.com/...ltralite-mk4-akm-dac-version.3796/post-400194

Looking at those forum users it seems like they only had noise issues with certain DACs, and not with others. That could explain why Rugger hasn't experienced any noise with his miniDSP. Is there a way of knowing in advance which DACs would be problematic, and which DACs wouldn't be? Even if there is no audible noise, could the measurements be messy?

Ideally the potential issue wouldn't be there to begin with, such as by adding filters (March Audio) or choosing a buffer with filters built in (like the EVAL1 if I'm not mistaken) - I'm just trying to understand how much of an issue it really is.

 

[March Audio]

Looking at those forum users it seems like they only had noise issues with certain DACs, and not with others. That could explain why Rugger hasn't experienced any noise with his miniDSP. Is there a way of knowing in advance which DACs would be problematic, and which DACs wouldn't be? Even if there is no audible noise, could the measurements be messy?

Ideally the potential issue wouldn't be there to begin with, such as by adding filters (March Audio) or choosing a buffer with filters built in (like the EVAL1 if I'm not mistaken) - I'm just trying to understand how much of an issue it really is.

Its an impossible question to answer. You never know what the RF environment is going to be like, so the only solution is to have input filtering. BTW this is relevant and important for all amps, not just class d.

Ever heard a mobile phone come out your speakers? badup badup badup baaaaaaaaaa

 

[Rugger]

Its not BS. Its an evaluation circuit for designers to use, not for use in final products.

That eval buffer has no input filtering or GBW limiting. Its wide open to external RF or that from DACs. You can find a couple of forum users here that had "digital noises" due to intermodulation with the class d switching signal. They fitted a filter and problem went away.

https://www.audiosciencereview.com/...ith-ncore-amp-apollo-twin-x.11771/post-400198

https://www.audiosciencereview.com/...ltralite-mk4-akm-dac-version.3796/post-400194

I guess pick a quality DAC.

MiniDSP SHD is confirmed to send no noise that I can detect. If I put my ear in the tweeter waveguide I can hear the slightest hiss, moving my ear even 2 inches away results in the hiss being undetectable. This is not coming from the DAC as I disconnected it to make sure haha. We will see how this works out when it's hooked up to horns with 100db+ sensitivity.

All this being said I'm leaning toward picking up a Schiit Freya so I have the option to inject come tube qualities (read distortion) into the horns when I feel like it for funsies. If I do I may figure out a way to engineer in a buffer bypass switch and just send the line level direct to the Purifi module, maybe even hack it up more and use a 12v powered relay that kicks over when I flip the magic tube switch, the possibilities are endless.

I'll keep yall updated.

 

[Rugger]

badup badup badup baaaaaaaaaa

Marsh, thats just Cardi B hahah

 

[Doodski]

Its an impossible question to answer. You never know what the RF environment is going to be like, so the only solution is to have input filtering. BTW this is relevant and important for all amps, not just class d.

Ever heard a mobile phone come out your speakers? badup badup badup baaaaaaaaaa

I had a department store stereo from Sears and it would pickup the RF from aircraft and I could hear conversations. The first time it occurred I was very surprised to be hearing voices.

 

[boXem]

If I do I may figure out a way to engineer in a buffer bypass switch and just send the line level direct to the Purifi module, maybe even hack it up more and use a 12v powered relay that kicks over when I flip the magic tube switch, the possibilities are endless.

Out of curiosity, why would you bypass the input buffer?

 

[Rugger]

Out of curiosity, why would you bypass the input buffer?

Better performance technically. If you check out Amir's review of the Purify Eval https://www.audiosciencereview.com/...easurements-of-purifi-1et400a-amplifier.7984/

You can see that by bypassing the buffer board he cut the THD+N in half and he put 5db on the SNR. that being said if you can tell the difference between 0.0006% THD+N and 0.0003% THD+N .... well you have better ears than me sir

 

[boXem]

Better performance technically. If you check out Amir's review of the Purify Eval https://www.audiosciencereview.com/...easurements-of-purifi-1et400a-amplifier.7984/

You can see that by bypassing the buffer board he cut the THD+N in half and he put 5db on the SNR. that being said if you can tell the difference between 0.0006% THD+N and 0.0003% THD+N .... well you have better ears than me sir

At the cost of a 9,2V RMS sensitivity. Do you have an idea of the Freya max output?

 

[tmtomh]

At the cost of a 9,2V RMS sensitivity. Do you have an idea of the Freya max output?

At least 10V if memory serves.

 

[boXem]

At least 10V if memory serves.

I believe you. I had a quick look at Schiit website and they don't specify anything above 2V. Next question is it's ability to drive 4kOhm.