Purifi input buffers and OP amps

[Buckeye Amps]

First time poster, long time "listener" and overall A/V enthusiast. I am very close to getting a 3ch amp for my LCR setup (JBL HDI series speakers). Use is majority movie watching near reference levels.

After a lot of back and forth of reading reviews and comparing prices between companies, I am pretty set on getting a 3ch Purifi 1ET400 setup from Nord Acoustics. However, I am trying to figure out what truly is the difference between their Rev C input buffer that doesn't use "discrete voltage regulators and OP amps" vs their Rev D buffer that does (with the choice of either a Sonic Imagery or Sparkos Labs OP amp).

Nord describes the difference as "significant" and says the Rev D buffer "adds warmth" to the sound. And the few forum posts I can find Google searching are people raving about a big improvement going from the Rev C to Rev D setup for Nords NC500 amps. But the difference for the Purifi setup between the Rev C and Rev D is over $600.

Amir's review of the Purifi with the Eval board vs. the Purifi with Nords board shows negligible measurable differences.

So what truly gives with companies like Nord and others saying their own boards and discrete OP amps make a noticeable difference to sound output? And would any of it even matter for mainly movie usage?

Do I just go with the "lesser" Nord setup and pocket the extra cash without any second thoughts?

 

[tmtomh]

Unlikely to be an audible difference given Amir's test results - and it's more likely than not that a setup with discrete components, if it did sound different, would sound different because of reduced fidelity.

And for movies the chances that any difference, even if audible, will make a meaningful difference are virtually nil. Save the $600, is my advice.

 

[tw99]

There is quite a lot of subjective audiophile nonsense on Nord's site....

 

[Buckeye Amps]

What is the purpose of Purifi allowing companies like Nord and Apollon to add/use their own boards? This is more of an educational question I've had while reviewing the different Class D modules.

For instance, the NC400 is "all in one" (sans power supply) while the NC500 allows for different OP amps to be used. And now the Purifi is like that as well. What is the exact purpose of the OP amp/input buffer board and why allow for different implementation of these by 3rd parties?

 

[boXem]

What is the purpose of Purifi allowing companies like Nord and Apollon to add/use their own boards? This is more of an educational question I've had while reviewing the different Class D modules.

For instance, the NC400 is "all in one" (sans power supply) while the NC500 allows for different OP amps to be used. And now the Purifi is like that as well. What is the exact purpose of the OP amp/input buffer board and why allow for different implementation of these by 3rd parties?

The idea is to allow the companies using the modules to have something differentiating themselves from their competitors.
Second thing is that also allows to have something else than an input buffer, like in a example a DAC at this place. You could imagine an integrated amplifier with an USB input, a DAC board and these modules plugged to it in very compact dimensions.

 

[Buckeye Amps]

I just found an US based company, VTV Amplifier, that sells Purifi amps with the choice of the stock Hypex Input Buffer board which would save me even more money (while also being locally based for me in the US). Would this be the same buffer board as the Eval board Purifi used when it sent a sample to Amir?

 

[boXem]

No, it is not.

 

[maxxevv]

I just found an US based company, VTV Amplifier, that sells Purifi amps with the choice of the stock Hypex Input Buffer board which would save me even more money (while also being locally based for me in the US). Would this be the same buffer board as the Eval board Purifi used when it sent a sample to Amir?

There is a thread on VTV, worth a read if you are considering them.
Some rectifiable issues, though depends on how comfortable you are with DIY work.

 

[Buckeye Amps]

I'll give it a read.

This is where I've become overwhelmed thinking about it all: if I want a Purifi amp setup and I don't want any "flavoring" of the input buffer/OP amps, who should I be buying from? Because even the Nord Rev C buffer board is customized, no?

 

[March Audio]

I'll give it a read.

This is where I've become overwhelmed thinking about it all: if I want a Purifi amp setup and I don't want any "flavoring" of the input buffer/OP amps, who should I be buying from? Because even the Nord Rev C buffer board is customized, no?

The "discrete" op amps simply dont offer better performance from the significantly cheaper top end op amps from the likes of Texas Instruments. Amirs various test show this to be so, our tests too. Thats why we dont indulge in the marketing of alternative buffers.

As is mentioned so many times on this site, when making comparisions people dont apply any controls. They dont match volume and they do it sighted so the new super duper op amp they have thrown in is bound to sound better.

 

[Buckeye Amps]

The "discrete" op amps simply dont offer better performance from the significantly cheaper top end op amps from the likes of Texas Instruments. Thats why we dont indulge in the marketing of alternative buffers.

As is mentioned so many times on this site, when making comparisions people dont apply any controls. They dont match volume and they do it sighted so the new super duper op amp they have thrown in is bound to sound better.

At this point in my search, I am ready to pay more for a correctly assembled, as Purifi/Hypex intended unit (meaning no discrete OP amp). From my readings that seems to put your products on my short list. Any chance you have a 3ch solution either using the Purifi or NC500 modules?

 

[March Audio]

At this point in my search, I am ready to pay more for a correctly assembled, as Purifi/Hypex intended unit (meaning no discrete OP amp). From my readings that seems to put your products on my short list. Any chance you have a 3ch solution either using the Purifi or NC500 modules?

Sorry no we dont offer multichannel amps. Obviously you can go monoblock , however if you want to keep costs down you can do what a number of our customers have done and used something like a P252 or P502 stereo amp for left and right and bridged a P122 or P252 stereo amp into mono for the centre channel. A P122 will provide 250 watts into 8 ohms bridged and a P252 will provide 500 watts bridged.

The latest version have 12 volt trigger input (not on the website yet) so all the kit can be turned on/off together.

 

[Buckeye Amps]

Thanks for the input all. It helped me realize I don't want any of the 3rd party offerings for buffer boards or discrete OP amps. Just want whatever constitutes "stock" for whichever route I go.

 

[jalejos]

The idea is to allow the companies using the modules to have something differentiating themselves from their competitors.
Second thing is that also allows to have something else than an input buffer, like in a example a DAC at this place. You could imagine an integrated amplifier with an USB input, a DAC board and these modules plugged to it in very compact dimensions.

Effectively. Our option has been to add a buffer with a triode valve. We have managed to mix valve sound with the power of class D.
https://atm-audio.com/input-buffer-for-hypex-and-purifi-audio-with-triode-korg-nutube/
https://atm-audio.com/200w-hybrid-power-amplifier-with-nutube-valve/

 

[tw99]

Effectively. Our option has been to add a buffer with a triode valve. We have managed to mix valve sound with the power of class D.
https://atm-audio.com/input-buffer-for-hypex-and-purifi-audio-with-triode-korg-nutube/
https://atm-audio.com/200w-hybrid-power-amplifier-with-nutube-valve/

So comparing the graphs on your site with the graphs in Amir's original Purifi amp test, it looks like adding the valve buffer stage has added a whole load of distortion that isn't there with a "normal" buffer. Presumably this is the aim of your product ?

 

[jalejos]

Effectively. Many people like the sound of the valves. But powerful tube amps consume a lot of energy and get very hot. We, what we have done, has been a mixture of tube sound with class D power.

 

[CDMC]

Effectively. Many people like the sound of the valves. But powerful tube amps consume a lot of energy and get very hot. We, what we have done, has been a mixture of tube sound with class D power.

I like the concept and that you actually have measurements to show the effect. Yes, it results in higher distortion, primarily 2nd and 3rd order which gives a warm sound. For people looking for a tube sound, it gets the control of solid state, a lack of heat, and far lower maintenance, as a doing it at the gain stage allows for less tubes and less stress on them resulting in longer life.

 

[mgwloka]

Effectively. Our option has been to add a buffer with a triode valve. We have managed to mix valve sound with the power of class D.
https://atm-audio.com/input-buffer-for-hypex-and-purifi-audio-with-triode-korg-nutube/
https://atm-audio.com/200w-hybrid-power-amplifier-with-nutube-valve/

Very clever device! My first reaction was "I can't believe they dare to do this". But then I realized that this gives me a 130W@8ohm SE tube amp upgrade that has no noise, and will not overheat my living room or try to electrocute me. Extra points for not invoking pseudo science and showing the AP graph.

How do you deal with the reported microphonics of the Nutube device?

 

[jalejos]

When I introduced this kit to my friends, they did not understand the concept and asked me: why do you add distortion to an amplifier as perfect as a class D? My answer was: Do you know of any tube amplifier of more than 100W that does not heat up, does not weigh and that its size is that of a shoe box? They imagined the "thermal power station" Jadis and understood it immediately.
I have solved the microphonics with two adhesive Velcro tapes.

 

[Manojrc]

Anyone tried this ?

https://vtvamplifier.com/product/vtv-amplifier-custom-vacuum-tube-input-buffer-new/

Interested to see a comparison between ‘real’ tube buffer stage from VTV & ATM audio’s NuTube buffer ( only subjective evaluation because we know that both the buffers add (May be pleasant) distortions & that’s the precise intention also )