Purifi 3-Channel Amp has introduced radio Interference

[Acerun]

The site won't take the video but here is a link to it from my Google drive

New video by Doug Mitchell

photos.app.goo.gl

 

[MaxwellsEq]

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.

You really can't blame the power amplifier if you have anything else plugged in to the Denon. See my point in post 9.

If everything else is unplugged and switched off and you have noise, the problem is the power amplifier. If it is quiet with everything turned off, you need to work out what is the noise generator and work out what it's doing.

 

[Acerun]

You really can't blame the power amplifier if you have anything else plugged in to the Denon. See my point in post 9.

If everything else is unplugged and switched off and you have noise, the problem is the power amplifier. If it is quiet with everything turned off, you need to work out what is the noise generator and work out what it's doing.

That's a massive undertaking to try and unplug everything connected to the Denon...I do have delivery of a new entertainment center so I'll be needing to unplug and re-plug everything...so I'll have that opportunity soon. One challenge that I have is that I'm going on holiday on Tues. Audiophonics only has a 14 day return policy, so I either need to send the unit back by Monday, or Audiophonics needs to grant me more time to be able to work on this after my holiday. I've explained the situation to Audiophonics, so we'll see how they respond.

 

[Acerun]

You really can't blame the power amplifier if you have anything else plugged in to the Denon. See my point in post 9.

If everything else is unplugged and switched off and you have noise, the problem is the power amplifier. If it is quiet with everything turned off, you need to work out what is the noise generator and work out what it's doing.

On the other hand, my Hypex NC252MP didn't make any noise.

 

[MaxwellsEq]

On the other hand, my Hypex NC252MP didn't make any noise.

I'm aware of that. The point is, when you fault-find you break things down into sections and isolate a bit at a time, like a binary search. You simply can't blame the amplifier if it doesn't generate noise when it's the only thing powered.

What you have is a systemic noise problem when the system has the Purifi in it and no systemic noise problem when the 252 is in place. If the Purifi has no problem when its inputs are shorted, then it is not the problem, it's just showing the problem up. You then need to find the problem.

Or you find an amplifier that doesn't show up the problem.

 

[Acerun]

I'm aware of that. The point is, when you fault-find you break things down into sections and isolate a bit at a time, like a binary search. You simply can't blame the amplifier if it doesn't generate noise when it's the only thing powered.

What you have is a systemic noise problem when the system has the Purifi in it and no systemic noise problem when the 252 is in place. If the Purifi has no problem when its inputs are shorted, then it is not the problem, it's just showing the problem up. You then need to find the problem.

Or you find an amplifier that doesn't show up the problem.

Did you happen to listen to the recording that I linked to?

 

[mcdn]

Did you happen to listen to the recording that I linked to?

What happens if you disconnect the input cables from the Shure filters? If there is still noise then the power amp must have a problem.

 

[restorer-john]

I'm aware of that. The point is, when you fault-find you break things down into sections and isolate a bit at a time, like a binary search. You simply can't blame the amplifier if it doesn't generate noise when it's the only thing powered.

What you have is a systemic noise problem when the system has the Purifi in it and no systemic noise problem when the 252 is in place. If the Purifi has no problem when its inputs are shorted, then it is not the problem, it's just showing the problem up. You then need to find the problem.

Or you find an amplifier that doesn't show up the problem.

You can lead a horse...

 

[Acerun]

I'm aware of that. The point is, when you fault-find you break things down into sections and isolate a bit at a time, like a binary search. You simply can't blame the amplifier if it doesn't generate noise when it's the only thing powered.

What you have is a systemic noise problem when the system has the Purifi in it and no systemic noise problem when the 252 is in place. If the Purifi has no problem when its inputs are shorted, then it is not the problem, it's just showing the problem up. You then need to find the problem.

Or you find an amplifier that doesn't show up the problem.

Makes a lot of sense, thank you.

 

[Acerun]

What happens if you disconnect the input cables from the Shure filters? If there is still noise then the power amp must have a problem.

I will try that!

 

[mcdn]

The site won't take the video but here is a link to it from my Google drive

New video by Doug Mitchell

photos.app.goo.gl

For what it's worth, that sounds nothing like wifi or bluetooth interference, both of which I know the sound of pretty well.

 

[Acerun]

OK, so I uncoupled the XLR cables from the Shure RF filters, and left the Shure filters in. The light crinkle sound remained the same, so the light crinkling is not from the Denon but coming from the amp.

 

[HarmonicTHD]

OK, so I uncoupled the XLR cables from the Shure RF filters, and left the Shure filters in. The light crinkle sound remained the same, so the light crinkling is not from the Denon but coming from the amp.

I mean you have to ask yourself. Why did you buy this amp? If the answer is, because of the high SINAD, then return it because you are certainly not getting what you hoped for.

 

[Acerun]

I am mean you have to ask yourself. Why did you buy this amp? If the answer is, because of the high SINAD, then return it because you are certainly not getting what you hoped for.

You are right. I irrationally kept trying to fix it when I should have just sent it back immediately.

I will try another vendor for either Purifi or NCX500.

 

[HarmonicTHD]

You are right. I irrationally kept trying to fix it when I should have just sent it back immediately.

I will try another vendor for either Purifi or NCX500.

Just had a look out of curiosity

Is this the amp you have?

AUDIOPHONICS HPA-T400ET Power Amplifier Class D 3 Channels Purifi 1ET400A 3x400W 4 Ohm - Audiophonics

We are proud to offer you the AUDIOPHONICS HPA-T400ET, a 3 way class D power amplifier based on three PURIFI 1ET400A modules. This ready-to-use version is aimed at audiophiles who want to equip themselves with a foolproof amplification solution.

www.audiophonics.fr

What happens if you engage the buffer board (it seems to be off by default) and set the gain to 20dB? (+7.5dB)

Set Gain & Bypass on Purifi Amplifier module - Audiophonics Blog

Find the blog of Audiophonics!

www.audiophonics.fr

If nothing happens, send it back for sure.

 

[Acerun]

Just had a look out of curiosity

Is this the amp you have?

AUDIOPHONICS HPA-T400ET Power Amplifier Class D 3 Channels Purifi 1ET400A 3x400W 4 Ohm - Audiophonics

We are proud to offer you the AUDIOPHONICS HPA-T400ET, a 3 way class D power amplifier based on three PURIFI 1ET400A modules. This ready-to-use version is aimed at audiophiles who want to equip themselves with a foolproof amplification solution.

www.audiophonics.fr

What happens if you engage the buffer board (it seems to be off by default) and set the gain to 20dB? (+7.5dB)

Set Gain & Bypass on Purifi Amplifier module - Audiophonics Blog

Find the blog of Audiophonics!

www.audiophonics.fr

If nothing happens, send it back for sure.

Sorry my first response was on mobile and I didn't see that. That was the three channel. Yes that is the amp. Do I really want + 7.5 dB going into my Denon? I think I'm supposed to keep it around +2 db, and the higher gain will degrade the SINAD as well. Will it not?

Edit: sorry I don't know what I'm talking about. I read the buffer section and I got confused with regards to volts. I think that Denon puts out about 2 volts before it starts degrading. In any case, I think I need to just close this chapter.

 

[HarmonicTHD]

It's basically the same but it's the three channel version. Do I really want + 7.5 dB going into my Denon? I think I'm supposed to keep it around +2 db, and the higher gain will degrade the SINAD as well. Will it not?

What do you mean going into your Denon?

Shouldn’t your Denon connected to this power amp?

Your Denon puts out a maximum of 2V at its preouts

Thread 'Denon AVR-X8500H AVR Review'
https://audiosciencereview.com/forum/index.php?threads/denon-avr-x8500h-avr-review.15266/


In order to fully take advantage of all the power (400w) of your power amp you need to set the gain to ca 25dB using the jumpers as described here

Set Gain & Bypass on Purifi Amplifier module - Audiophonics Blog

Find the blog of Audiophonics!

www.audiophonics.fr

I don’t know where you got the 2dB from.

Just try it. What is there to loose. Maybe the buffer board contains an RF filter and by engaging it you get rid of your noise.

 

[HarmonicTHD]

… and don’t worry about the slightly increased noise due to the additional gain.

Amir measured the 1ET400A also with a buffer board engaged at even 27dB gain with a resulting Signal to Noise ratio of 124dB. This is also dead quiet when you put your ears next to the tweeters.

Thread 'Review and Measurements of Purifi 1ET400A Amplifier'
https://audiosciencereview.com/foru...easurements-of-purifi-1et400a-amplifier.7984/

 

[Acerun]

What do you mean going into your Denon?

Shouldn’t your Denon connected to this power amp?

Your Denon puts out a maximum of 2V at its preouts

Thread 'Denon AVR-X8500H AVR Review'
https://audiosciencereview.com/forum/index.php?threads/denon-avr-x8500h-avr-review.15266/


In order to fully take advantage of all the power (400w) of your power amp you need to set the gain to ca 25dB using the jumpers as described here

Set Gain & Bypass on Purifi Amplifier module - Audiophonics Blog

Find the blog of Audiophonics!

www.audiophonics.fr

I don’t know where you got the 2dB from.

Just try it. What is there to loose. Maybe the buffer board contains an RF filter and by engaging it you get rid of your noise.

Yeah sorry I completely screwed up my response and tried to fix it by editing above. The truth of the matter is I'm going on holidays starting on Tuesday so this unit has to get in the mail on Monday.

 

[HarmonicTHD]

Yeah sorry I completely screwed up my response and tried to fix it by editing above. The truth of the matter is I'm going on holidays starting on Tuesday so this unit has to get in the mail on Monday.

Setting the jumpers correctly shouldn’t take more than 30min.