Any issues when pairing Purifi or Hypex class D amps with home cinema AVR?

[restorer-john]

I mentioned "input sensitivity" and you explained "sensitivity". Those are different.

The input sensitivity is calculated as below (for NC252MP as an example):



View attachment 135623

You still don't get it. Your post is completely 100% wrong.

Edit your "too high" and replace with "too low" (twice) and delete this part altogether as it makes no sense whatsoever:

"The worst case is if the power amp's noise floor is higher than the AVR's nominal pre-out voltage, then you end up with a bad combo. I'm not saying that Hypex/Purify have high noise floor. I just cited that hypothetical scenario as an example."

There's no power amplifier on earth with a residual noise floor greater than the nominal pre-out voltage of any preamplifier.

For the record, residual noise floors of power amplifiers are measured in microvolts. uV. Millionths of a Volt. Typically in the low tens of microvolts.
Preamplifier nominal output voltages are measured in Volts. Typically 1-5 Volts.

 

[Gyroscopics]

and delete this part altogether as it makes no sense whatsoever:

"The worst case is if the power amp's noise floor is higher than the AVR's nominal pre-out voltage, then you end up with a bad combo. I'm not saying that Hypex/Purify have high noise floor. I just cited that hypothetical scenario as an example."

There's no power amplifier on earth with a residual noise floor greater than the nominal pre-out voltage of any preamplifier.

That's why I called it a "hypothetical scenario".

 

[boXem]

OK, so did I screw myself by going with the Sparkos Labs SS3602 input buffer?

You screwed yourself not going with a boXem

 

[patoulol]

It matters because AVRs have limited pre-out voltage and it varies by manufacturer and model. If the power-amp's input sensitivity is too high compared to the AVR's pre-out voltage, then you end up NOT being able to fully utilize the capability of the power amp in spite of how powerful that power-amp is on paper. In other words if the power-amp's input sensitivity is too high, the AVR would not be able to drive the power-amp to its full capacity without clipping the signal. The worst case is if the power amp's noise floor is higher than the AVR's nominal pre-out voltage, then you end up with a bad combo. I'm not saying that Hypex/Purify have high noise floor. I just cited that hypothetical scenario as an example.

the best is to have an external amp at 1.4 vrms for a Denon x3700 which outputs a voltage at 1.4 vrms?

 

[sg1838]

You screwed yourself not going with a boXem

Sorry, I didn't know. I'll post my VTV for sale immediately!

the best is to have an external amp at 1.4 vrms for a Denon x3700 which outputs a voltage at 1.4 vrms?

Though I currently have a Yamaha TSR-7850, it's funny you mention the Denon as my tentative plan was to upgrade to the 2021 version of the Denon X3700 or X4700 (X3800 or X4800, presumably) and then use the pre-outs to add at least one more Purifi amp for my center channel (I'm also now considering the new Yamaha RX-A6A). I'm running a 7.2 setup, with a L/R front presence setup rather than front height, so I may even consider adding a 3 more channels of external amplification to do those and the center channel. That would only leave the surround channels for the receiver to manage. So, there's hope for that boXem amp yet!

I'm sure some of you may be wondering, "Why the heck would you do that? Why not just get yourself a surround processor rather than pay for amplification that you're not going to use?" I'm open to suggestions, but the short answer is because when I've looked into quality Pre/Pros (like an Anthem AVM 70 or Emotiva RMC-1L), they want CONSIDERABLY more for theirs than Denon or Yamaha wants for an all-out receiver. Since the surround is a Dolby standard (Atmos), I don't believe any company will do it better than any other, and since I'm taking the amplification out of the equation by providing my own external amps, I don't see how I can justify the additional cost to use an "audiophile" grade pre-amp. The only difference at that point would be the DACs in the various units. Worst case would be that I would have to buy my own external ASR tested/reviewed DACs, at which point I would probably be at the same cost of a quality Pre/Pro (I could buy 3 Schiit Modius(es?) for $600 total and still be ahead.)

Probably more than any of you really wanted to know. But again, I'm open to suggestions...

 

[Gyroscopics]

the best is to have an external amp at 1.4 vrms for a Denon x3700 which outputs a voltage at 1.4 vrms?

Exactly. And I'm glad and impressed that you got the point of my post. It is best to have an external amp with "input sensitivity" close to your AVR's rated pre-out voltage. A little over is fine, but not 3x or 2x because you would end up paying for that extra power rating you can't use.

 

[Desmo]

Something like this?

https://www.xtzsound.eu/product/edge-a2-300?technical

 

[Gyroscopics]

Something like this?

https://www.xtzsound.eu/product/edge-a2-300?technical

It does have 1.39 Vrms input sensitivity, but it's an ICEpower based Class D amp. In this day and age, I would pick a Hypex/Purify based amp over ICEpower based amp. There are many discussions in ASR that explain why. A good choice for AVR/HT application would be the NC252MP or the mono NC250MP.

 

[Desmo]

Do all the NC252MP based amplifiers have the same input sensitivity?

The Audiophonics MPA-s250NC RCA has 3.2V. So that is double for the Denon.

 

[Gyroscopics]

Do all the NC252MP based amplifiers have the same input sensitivity?

The Audiophonics MPA-s250NC RCA has 3.2V. So that is double for the Denon.

3.2V peak or rms? It's better to talk to the assembler as input sensitivity may vary depending on implementation/input buffer. As boXem stated earlier:

The input sensitivity is determined by the input buffer. Each manufacturer using it's own buffer has a different sensitivity.

 

[datrumole]

I have asked to Amir what would be the ending SINAD when pairing the new Denon 3700H with a purifi amp.
Please find below its disappointing answer:
Well, I tried to test this scenario but failed completely.
Hooking up the output of 3700 to Purifi using RCA to XLR adapter generated worse results than the internal amps! Some of this I traced to increased ground loop. But even when I filtered this out, the Purifi still performed worse.
I then tested the Purifi using my Audio Precision unbalanced (RCA) outputs. To my surprise, its performance was worse than it was with balanced input. It was still much better than what I could do with 3700H though.
After an hour of messing with it, I gave up. It is possible there is ultrasonic noise from the 3700H DAC that is disturbing the Purifi amplifier (wild guess).
In abstract, you need to have the amp be 10 dB better to have it almost be transparent (0.5 dB loss in SINAD). In your scenario we don't have that so the SINAD will drop to around 96 to 97 dB (my guess).
Since I am envisaging such set-up, I would like to know if anyone has already successfully associated an AVR (especially a Denon) with either hypex-based or purifi amps?
I am looking forward reading your feedbacks!

late to the gate

i have a UDAC8 which is 8ch unbalanced feeding a ICEpower 500ASP (and 2 500A hangers), 2x inukes, 2x aiyima A04

seemed fine since the module documentation states the gain is the same on both unbalanced v balanced, but i always wanted to get it to balanced

with the ART cleanbox coming in at $40 a ch, you can see how it gets expensive quick

enter the THAT1646 unbal to bal converter: https://www.sparkfun.com/products/14003

paired that with a smps and voltage regulator, voila. currently only using it for 5 of the ch (icepower and inukes) but it's made all the difference

granted this project might not be available to some folks, but its an option i dont see discussed very much, you could even get into the DENON and retro fit to see if you can find some suitable power lines to power the modules and tap them right into the chassis

 

[patoulol]

Exactly. And I'm glad and impressed that you got the point of my post. It is best to have an external amp with "input sensitivity" close to your AVR's rated pre-out voltage. A little over is fine, but not 3x or 2x because you would end up paying for that extra power rating you can't use.

If one day I decide to hang an external amp (I returned the purifi) I will go to a crown with its 1.4 vrms
Crown XLS 1502