Purifi 3-Channel Amp has introduced radio Interference

[restorer-john]

I’d be asking audiophonics about their front end RF filtering…

Did you ask @Audiophonics what specific RF filtering they have incorporated in their front ends? It is important and something only a few of the better assemblers do properly. It can be as simple as a few capacitors and resistors for each channel. Only costs a few cents.

 

[sam_adams]

@Acerun, if you still have the time and fortitude to test cables, try some of the WBC cables made with Gotham GAC-4/1 Ultra Pro cable. It's a star-quad design with double ruessen shielding (GAC 4/1 Ultra Pro 11301 spec). If the problem is really stubborn, you may need to seek out snap-on ferrites made with Fair-Rite Mix 75. Very expensive, though.

 

[sam_adams]

Did you ask @Audiophonics what specific RF filtering they have incorporated in their front ends? It is important and something only a few of the better assemblers do properly. It can be as simple as a few capacitors and resistors for each channel. Only costs a few cents.

Be careful there. Replying to yourself could have serious space-time continuum consequences.

 

[restorer-john]

Replying to yourself could have serious space-time continuum consequences.

That was backup John posting, not me.

 

[Acerun]

Did you ask @Audiophonics what specific RF filtering they have incorporated in their front ends? It is important and something only a few of the better assemblers do properly. It can be as simple as a few capacitors and resistors for each channel. Only costs a few cents.

Yes it's part of this thread. They said zero. They said in the hypex there's a resistor but none in purifi

 

[Acerun]

The horrible part of this though is that when the amp is playing, it's absolutely stunning. Does anyone have a different recommendation for a three-channel purifi amplifier? I also see the NCX500s testing good or better than Purifi and apparently don't have the RF interference problem so maybe there's my answer... But I wanted Purifi...

 

[Acerun]

Did you ask @Audiophonics what specific RF filtering they have incorporated in their front ends? It is important and something only a few of the better assemblers do properly. It can be as simple as a few capacitors and resistors for each channel. Only costs a few cents.

From Audiophonics:
"It's normal without XLR connected you have a little noise. You hear this sound because the input are in high impedance. You dont have this problem with Ncore because Ncore have 10k resistor grounded on the input, not the purifi amp."

 

[bo_knows]

If you don't mind asking me, is the sound better using the external Class D amps vs internal Denon amps?
I have the same AVR and just wondering.

 

[Acerun]

If you don't mind asking me, is the sound better using the external Class D amps vs internal Denon amps?
I have the same AVR and just wondering.

Substantially better. 104 SINAD with internal amps off. X8500 amps not very good.

 

[bo_knows]

Substantially better. 104 SINAD with internal amps off. X8500 amps not very good.

Hmmm. Ok, thanks. I guess I'm missing out.

 

[MaxwellsEq]

The horrible part of this though is that when the amp is playing, it's absolutely stunning. Does anyone have a different recommendation for a three-channel purifi amplifier? I also see the NCX500s testing good or better than Purifi and apparently don't have the RF interference problem so maybe there's my answer... But I wanted Purifi...

The problem with RF interference and also with mains hum (e.g. earth loops), is everyone's experience is unique. Factors such as proximity to transmitters, home construction and even kit orientation can make a difference, let alone equipment and cable choices.

I have a dual mono Nord Purifi amplifier which has inaudible noise even with my ear 10cm from the tweeter (better than the 30ish year old AB amplifier it replaced), and has no noticeable RF pickup at all. Nord make a 3 channel version. Nord design their own buffer boards.

BUT, my setup is balanced throughout. This approach should be much less prone to noise and interference.

From what I've seen here, you should not be able to tell the difference between a NCX and a Purifi. So, if the former, by default has better RF rejection, maybe that would be a better direction for you to go in.

 

[Acerun]

Here's the latest. I received the Shure RF XLR filters and plugged them in. No more radio interference. All that's left are light random static crackles from very close up to the tweeters. Not sure how to describe exactly. Like soft zz zzz crackle buzzes and light ticks. but you have to get really close to the tweeter to hear them. I can probably live with that now, I just don't want the problem to evolve into louder and louder noises over time and then be in a position where I can't even sell the unit. I'm wondering if the noises are coming from something else that's plugged into the Denon, like my AppleTV, Fire Cube, Wiim Pro or DirecTV unit. Maybe the amplifier is powerful enough that it's picking up that little bit of cross contamination? I'll experiment a bit more on that.

Funny enough, I'm irrationally, emotionally attached to this unit and I really want it to work out. Looks like the other main options for a three-channel Purifi are much more expensive. This unit was $1700 delivered and it looks like Nord and Apollon are $500+ more delivered.

 

[Acerun]

@Acerun, if you still have the time and fortitude to test cables, try some of the WBC cables made with Gotham GAC-4/1 Ultra Pro cable. It's a star-quad design with double ruessen shielding (GAC 4/1 Ultra Pro 11301 spec). If the problem is really stubborn, you may need to seek out snap-on ferrites made with Fair-Rite Mix 75. Very expensive, though.

I'm going to try them. If they do the trick I can send back the Shure RF filters. Thanks for suggesting.

 

[fatoldgit]

Like soft zz zzz crackle buzzes and light ticks. but you have to get really close to the tweeter to hear them.

Sounds like one of your power tubes is on the way out.

Peter

PS. Didnt include a /s cause we are all smart people here

 

[fatoldgit]

I'm wondering if the noises are coming from something else that's plugged into the Denon, like my AppleTV, Fire Cube, Wiim Pro or DirecTV unit. Maybe the amplifier is powerful enough that it's picking up that little bit of cross contamination? I'll experiment a bit more on that.

100%

If you have anything that spits out 2.4/5 wifi stuff or other noise that isnt well contained by its chassis then it could very well cause an issue.

If the ticks are periodic then its something that is polling.

Unplug/turn all off and if its gone, turn on progressively to find the offender.

Peter

 

[Acerun]

Sounds like one of your power tubes is on the way out.

Peter

PS. Didnt include a /s cause we are all smart people here

That would be odd as the unit is brand new

 

[Acerun]

100%

If you have anything that spits out 2.4/5 wifi stuff or other noise that isnt well contained by its chassis then it could very well cause an issue.

If the ticks are periodic then its something that is polling.

Unplug/turn all off and if its gone, turn on progressively to find the offender.

Peter

Little random static spits and ticks alternating with silence. You have to get within 3 inches of the tweeter to hear them now.

 

[AdamG]

Little random static spits and ticks alternating with silence. You have to get within 3 inches of the tweeter to hear them now.

A audio/video recording of what you are hearing always helps the Pro’s here to instantly know what the sound is. Using words to describe it doesn’t always help. Post up a short video.

 

[Acerun]

A audio/video recording of what you are hearing always helps the Pro’s here to instantly know what the sound is. Using words to describe it doesn’t always help. Post up a short video.

That's a good idea Adam. Not sure if it will come through but I will give it a try!

 

[AdamG]

That's a good idea Adam. Not sure if it will come through but I will give it a try!

Put the phone microphone right up to the tweeter.