Transformer hum caused by Devialets?

[Digant]

Dear all,

while trying to improve the power supply of my system, a strange phenomenon occurred, the cause of which appears to be my Expert 220 Pro. I would be grateful if there was a clue to the cause or possible solutions here in the forum. So:

I first tested two different filter systems, one of which was a Puritan PSM156. (There are already other Devialet owners here who have had good experiences with it.) The phenomenon occurred that a linear power supply that was also connected began to hum when the Devialet was switched on.

This surprised me because the outputs in these filters are shielded from each other. However, the buzzing occurred in both filters, and so I assumed that the linear power supply might be defective. But then:

Since I wasn't really convinced by the sound of the filters, my dealer recommended a technically different solution, an Audes ST-1500 as an isolation transformer. This is really very satisfying in terms of sound - although clearly more expensive, but also a very clear step forward from any filter solution that I know of. BUT:

Now the Audes hums when the Devialet is turned on. And it's not quiet, so something you could tolerate, you can hear it at distances of up to 8 meters. In a kind of elimination process, the following can be said so far:

- the Audes only hums when the Devialet is switched on.
- This happens even if nothing else is connected to the Audes or Devialet.
- the Audes does not hum with other amplifiers, although we have only been able to test A/B amplifiers so far.
- An additional DC filter looped between Audes and Devialet does nothing (as expected).

We were able to reproduce the problem with a friend's Devialet 440 Pro Dual on an Audes ST-3000. Therefore I assume that my 220 is not defective, but that we are dealing with a quirk of the Devialet Experts.

Because of our work with filters, my friend and I already know that the Devialets return about 600mV of EMI radiation per device into the network. But here the phenomenon seems to occur that the Devialets also reflect DC, but we are not sure.

Does anyone here know this problem and can say something about it? I would be very happy.

Digant

[audio_engr]

Hello Digant,

That is really strange as I too possess the Puritan PSM156 but I use the Puritan to power my 2 x REL subwoofers. For my 440-Pro-CI Devialet, I tried
- Audioquest Niagara 5000
- Shunyata Denali
- PS Audio P12

And settled in for the PS Audio P12 (US ver) that has 2 x High-Current outlets hence they're for my 440-Pro.

I've had no issues using this arrangement since 2018. 

I also use Puritan Ground Master with 2 x 8-Ft copper rods into the earth as a dedicated Audio Earth. And also, the Puritan Route Master hooked to the Ground Master whereby I have dedicated earth wires to every audio component I use. The PS Audio P12 is also hooked to the Puritan Ground Master.  

The net result after getting the Puritan Ground Master + Route Master is that the sonic background is Jet Black ... and low-level sonic are just brilliant. I'm a classical genre listener and Puritan really helped me tremendously and was totally a 'bang for the buck' that other brands like Synergistic Audio would have cost me much-much more.

- Arup

[markush]

I liked the Niagra 5000 (EU) best and in both setups with 220 Pro or 440 Pro this considerably improved overall performance and works fine for years now.
The 5000 has 4 high current outlets so the Niagara 3000 might also work perfectly depending on your needs.

[hardcore]

I use Plixir balanced isolation transformers for the power conditioning of my Devialet 1000 Pro. The isolation transformers don't hum. I've not tried the isolation transformers with a 220 or 440 Pro.

However, I have an LG OLED TV, which *will* cause the isolation transfomer to hum if I connect the TV to the output of the isolation transformer. So my TV is connected via a regular power conditioner.

Transformer humming is usually caused by a DC offset it the AC supply.

You might want to try the ifi DC Blocker to see if it helps your case - although it doesn't fit directly into the IEC power port of my Devialet 1000 units.

https://ifi-audio.com/products/dc-blocker/

[Greg]

I use Plixir balanced isolation transformers for the power conditioning of my Devialet 1000 Pro. The isolation transformers don't hum. I've not tried the isolation transformers with a 220 or 440 Pro.

However, I have an LG OLED TV, which *will* cause the isolation transfomer to hum if I connect the TV to the output of the isolation transformer. So my TV is connected via a regular power conditioner.

Transformer humming is usually caused by a DC offset it the AC supply.

You might want to try the ifi DC Blocker to see if it helps your case - although it doesn't fit directly into the IEC power port of my Devialet 1000 units.

https://ifi-audio.com/products/dc-blocker/

Good reply. I’ve had exactly the same in the past. A DC Blocker sorted it. A transformer will not pass on DC but it will hum. DC offset can be readily measured on the mains with a basic multimeter.

[Digant]

I use Plixir balanced isolation transformers for the power conditioning of my Devialet 1000 Pro. The isolation transformers don't hum. I've not tried the isolation transformers with a 220 or 440 Pro.

However, I have an LG OLED TV, which *will* cause the isolation transfomer to hum if I connect the TV to the output of the isolation transformer. So my TV is connected via a regular power conditioner.

Transformer humming is usually caused by a DC offset it the AC supply.

You might want to try the ifi DC Blocker to see if it helps your case - although it doesn't fit directly into the IEC power port of my Devialet 1000 units.

https://ifi-audio.com/products/dc-blocker/

Good reply. I’ve had exactly the same in the past. A DC Blocker sorted it. A transformer will not pass on DC but it will hum. DC offset can be readily measured on the mains with a basic multimeter.

Thank you also for this tip. We also initially suspected that DC could be the cause. That's why, as I wrote above, we put a DC blocker between the transformer and the Devialet. This had no effect whatsoever. The transformer also has its own internal DC blocker. At least for the moment, I would therefore rule out DC as the cause.
But interesting that you had the same phenomenon, if I understand you correctly. Switching on the Devialets led to a transformer hum?

[Digant]

Hello Digant,

That is really strange as I too possess the Puritan PSM156 but I use the Puritan to power my 2 x REL subwoofers. For my 440-Pro-CI Devialet, I tried
- Audioquest Niagara 5000
- Shunyata Denali
- PS Audio P12

And settled in for the PS Audio P12 (US ver) that has 2 x High-Current outlets hence they're for my 440-Pro.

I've had no issues using this arrangement since 2018. 

I also use Puritan Ground Master with 2 x 8-Ft copper rods into the earth as a dedicated Audio Earth. And also, the Puritan Route Master hooked to the Ground Master whereby I have dedicated earth wires to every audio component I use. The PS Audio P12 is also hooked to the Puritan Ground Master.  

The net result after getting the Puritan Ground Master + Route Master is that the sonic background is Jet Black ... and low-level sonic are just brilliant. I'm a classical genre listener and Puritan really helped me tremendously and was totally a 'bang for the buck' that other brands like Synergistic Audio would have cost me much-much more.

- Arup

Thank you for the hint! That sounds like an impressive power supply installation.
But our problem is slightly different. As I already wrote, it's not about filter technologies such as the Puritan. And I had a Puritan in use - switching on the Devialet caused a transformer to hum through the Puritan's filters!
By the way - my friend was happy with his PS Audio 15 for a long time and has now sold it to finance the Audes transformer. It seems to have improved the sound for him too.

[Pim]

There was one review on an Expert that actually mentioned that the Expert's power supply causes distortion in the power supplying them. They found that out when they went from one stereo amp to a dual mono. Apparently something seemed off and they worked out it was the distortion coming from the power supply from one amp distorting the supplied power to the other and vice versa. So yes, the Experts can cause transformer hum.

The solution then is a power conditioner as some wrote above. I'm using a Furman IT Reference 16. It's a beast of a thing. One thing to note is that the transformer inside does hum a tiny bit just by itself (nothing turned on). I only heard it in the middle of the night when walking past it. That's with no wind, no traffic at all. just a really quiet night. I'd be surprised if it was audible at all in any other situation, it's that quiet.

As for the quality of sound from the Experts now they are connected to the Furman; in one word; sublime.

[hardcore]

I use Plixir balanced isolation transformers for the power conditioning of my Devialet 1000 Pro. The isolation transformers don't hum. I've not tried the isolation transformers with a 220 or 440 Pro.

However, I have an LG OLED TV, which *will* cause the isolation transfomer to hum if I connect the TV to the output of the isolation transformer. So my TV is connected via a regular power conditioner.

Transformer humming is usually caused by a DC offset it the AC supply.

You might want to try the ifi DC Blocker to see if it helps your case - although it doesn't fit directly into the IEC power port of my Devialet 1000 units.

https://ifi-audio.com/products/dc-blocker/

Good reply. I’ve had exactly the same in the past. A DC Blocker sorted it. A transformer will not pass on DC but it will hum. DC offset can be readily measured on the mains with a basic multimeter.

Thank you also for this tip. We also initially suspected that DC could be the cause. That's why, as I wrote above, we put a DC blocker between the transformer and the Devialet. This had no effect whatsoever. The transformer also has its own internal DC blocker. At least for the moment, I would therefore rule out DC as the cause.
But interesting that you had the same phenomenon, if I understand you correctly. Switching on the Devialets led to a transformer hum?

DC blockers only work to a certain value of DC offset. As Pim mentioned, the switching power supply of the Devialet probably creates strong distortion on the power supply 'kicking back' spikes to the isolation transformer.

My 250/1000 Pros don't have that problem with my isolation transformers though. I've used 2x250 Pro off one isolation transformer but am now using separate isolation transformers for each amplifier.

Have you tried changing the Devialet power saving settings? Many of us have disabled the power saving setting since it sounds better. I wonder if that would have any effect?

[hardcore]

More user experiences: A friend of mine has an Expert 440 Pro pair that is connected to a single Plixir Balanced AC power conditioner (isolation transformer) for several years and he hasn't mentioned any transformer hum.