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Topping A90 Headphone Amplifier Review

EdW

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I noticed something, and was just curious if others have this too. When I turn the volume down to the bottom on the A90, there is still some sound, it's not muted. But as I approach the "0" value, at very low volume (and I mean very low) there is more sound coming out of the right channel. This happens on speakers connected via XLR out or the headphone SE jack out front. Is this normal behavior? Why won't both channels be equal at very, very low volume? The input is from the D90 in DAC mode via XLR.
I think you may be seeing the behaviour of an analog potentiometer here used to control the gain of the A90. Even very expensive pots do often have channel imbalance at low levels. The only way out of this is a some arrangement like a relay switched attenuator, which is considerably more expensive to implement than a pot. This may feature on the forthcoming PRE90?
 

3125b

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Simple solution inspired by typical Swedish house wiring - tape off the earth pin.
Is it safe? Theoretically no (unless you have a RCD), practically yes until something goes wrong ... and you might die.
Does it work? Yes.
How much does it cost? Nothing.
It's great all around :)

Disclaimer: Don't. Unless you want to die, in wich case above statement applies.
 
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Jimbob54

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Simple solution inspired by typical Swedish house wiring - tape off the earth pin.
Is it safe? Theoretically no (unless you have a RCD), practically yes until something goes wrong ... and you might die.
Does it work? Yes.
How much does it cost? Nothing.
It's great all around :)
Careful. Not everyone will read that and know not to try it.
 

hmscott

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Just tried XLR and RCA connected between D90 A90 and Preamp RCA out to my HiFi Amp Earthed present Cambridge Audio CXA 60 Amp to a Mordaunt Short Carnival 8 speaker.

Max Volume preamp out at the 9090, gain tried at L, M, H, CXA 60 also max volume (Replicate a powered speaker)
Can't seems to hear any ground loop noise at all of what i clearly heard on my Headphone setup.

So i guess is fine? @hmscott
A guy ( @burma ) before me posted he tried on a actual Powered ADAM Audio Active Speaker as well, same XLR between 9090, then A90 preamp RCA out to Adam Speaker, maybe his test would be even more accurate :)
The noise in my setup comes up through the USB cable - if I disconnect the USB cable the noise stops, but there is a tone that emanates in H Gain mode with both XLR and RCA cable connected - in XLR mode switched on.

You don't mention what source is used with the D90, what is it?

Thanks for the details :)
I noticed something, and was just curious if others have this too. When I turn the volume down to the bottom on the A90, there is still some sound, it's not muted. But as I approach the "0" value, at very low volume (and I mean very low) there is more sound coming out of the right channel. This happens on speakers connected via XLR out or the headphone SE jack out front. Is this normal behavior? Why won't both channels be equal at very, very low volume? The input is from the D90 in DAC mode via XLR.
Yes, it's normal to not be able to Zero out volume at the lowest setting, it is also variable via the drive from the D90 - so you could set the D90 in PRE mode and reduce the output until the A90 Zero Volume + L/M/H Gain has really zero audio output through your headphones / speakers.

There might be an adjustment for balance trim in the A90 / D90 that could get the L/R balance of volume the same so the Right and Left channel "go out" at Zero at the same time. My A90 in H Gain with D90 in PRE mode -00.0dB at Zero volume I still have sound in headphones, with Right side louder than Left side.

@JohnYang1997 - is there a channel balance trim in either the A90 / D90 we can adjust?
 
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Rigel

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I don't understand anything about computer science and electronics, if I understand correctly, the problem can arise by connecting a PC via the USB port to the A90 / D90 connected via rca.
if instead they are connected via xlr the problem does not occur, right?

Hi robertozappala

Effectively, that's right.

Roughly speaking, it could be said that the chassis / earth connections of each equipment and for example due to the leakage currents of the power supplies, etc. They are at an electrical potential "of noise" different from each other, so that when we connect them electrically using an RCA cable, in addition to the audio signal, the electrical noise signal is added by the shielding of the cable (return of the audio signal that sometimes are in electrical contact with the equipment's own chassis, hence the problem).

When the connection is made through an XLR cable, it would be like connecting them through two different pipes, one of which runs the audio signal and the other, electrical noise, minimizing the problem.

This should not happen, if the earth connections were perfect and absorbed all that electrical potential of noise, but in reality it is not perfect and although they are generally not a problem, at other times if the earth connections are not as they should be, Not only can noise be spread better, but even dangerous voltage differences can be found for people. It has already happened to me personally, although it is also true that these things usually happen only in extreme cases and not usual in a home.

That is why it is generally convenient, to have the power connectors on the power strips as close as possible to each other, to facilitate as far as possible, those currents circulating through the ground wiring between equipment and equipment due to having a lower electrical resistance by proximity and not the audio signal wiring.

By way of example, this is what would happen when connecting two water tanks located at different heights and connecting them by means of a pipe. But instead of having the water in each tank have different potential energy, it is different electrical potential.
If we add to this that we can have multiple different tanks and pipes interconnecting some elements with others, the question can be complicated. It is not trivial.

In this case, we could say that a PC is a large reservoir of water at high altitude, wanting to pour water everywhere.

I use a translator, I hope I can explain myself well.
 
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Hi all.

I understand people who have or may have noise problems and I feel sorry for them, but I think that it is impossible to design a specific equipment such as the A90 or another, I do not care about the brand and model, which can satisfy the Once, all the needs in terms of each person's personal design tastes and component installations so varied in our homes.

Leakage currents are common in all grounded equipment whether or not they are audio and generally PCs are literally huge generators in this case.
Especially when we work with analog signals produced by the same PC. It is inevitable that the ground / earth signal can be contaminated with the leakage currents created by the same PC depending on the installation. And that can happen with the A90 or with any other amplifier.

Luckily, I have no problems in this regard using or not using RCA connections, both through headphones and with Edifier active speakers.



I know that it should not be necessary to buy anything, but this would be a reasonable price option to solve or at least minimize the problems if we use a PC and the problem that we detect is the one that appears in the video.

For the record, I have nothing to do with iFi audio, I have simply been experimenting with USB audio for several years and tried many devices with more or less fortune in my previous systems, this included.




What is the side entrance for?
 

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Hi all.

I understand people who have or may have noise problems and I feel sorry for them, but I think that it is impossible to design a specific equipment such as the A90 or another, I do not care about the brand and model, which can satisfy the Once, all the needs in terms of each person's personal design tastes and component installations so varied in our homes.

Leakage currents are common in all grounded equipment whether or not they are audio and generally PCs are literally huge generators in this case.
Especially when we work with analog signals produced by the same PC. It is inevitable that the ground / earth signal can be contaminated with the leakage currents created by the same PC depending on the installation. And that can happen with the A90 or with any other amplifier.

Luckily, I have no problems in this regard using or not using RCA connections, both through headphones and with Edifier active speakers.



I know that it should not be necessary to buy anything, but this would be a reasonable price option to solve or at least minimize the problems if we use a PC and the problem that we detect is the one that appears in the video.

For the record, I have nothing to do with iFi audio, I have simply been experimenting with USB audio for several years and tried many devices with more or less fortune in my previous systems, this included.



what differences are there between Idefender and isilencer?
Thank you
Roberto
 

JohnYang1997

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is it necessary or does it work without it?
Thank you
Roberto
Depends on your dac. If your dac is usb powered then it needs it. If not then there's still a chance that you need it. I recommend just try it out if you want to use one. I have not personally used one. But that's logical.
 
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Depends on your dac. If your dac is usb powered then it needs it. If not then there's still a chance that you need it. I recommend just try it out if you want to use one. I have not personally used one. But that's logical.

Thank you, John, another question: I would like to try the project kameleon, which works between amp and dac only in unbalanced, if I use cables with xlr and rca connectors, would a90 / d90 always work in balanced?
 

Matias

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Simple solution inspired by typical Swedish house wiring - tape off the earth pin.
Is it safe? Theoretically no (unless you have a RCD), practically yes until something goes wrong ... and you might die.
Does it work? Yes.
How much does it cost? Nothing.
It's great all around :)

Disclaimer: Don't. Unless you want to die, in wich case above statement applies.
I lift the grounds of my power amplifiers and I don't want to die. I think the security fears are exaggerated. After all these are new products with grounding through interconnect cables. It's not like an old rusted equipment with wires hanging out, isolated without any grounding at all. The ground loop problem is excessive ways of grounding anyway, not lacking grounding.
 
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Audimon

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Someone may correct me but the purpose of this device is to reroute 2 data pins of USB and cut off the 2 pins responsible for power and ground, which eliminates any internal power/ground related noise coming from the source.

The side socket for external power supply is only needed if the receiving device is actually powered by USB and has no power supply of it's own. So you can emulate power coming in via USB by plugging in an external adaptor.

However if your receiving device has internal or external power supply and therefore does not need USB power you can achieve the same result as this device provides by simply putting a piece of electric tape over the contact in your USB plug.

No need to spend $$-$$$ on some magic devices o_O Just magic tape covering ground contact to eliminate noise coming from PC to the DAC, which has external power supply.
 

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Rigel

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what differences are there between Idefender and isilencer?
Thank you
Roberto

The idefender minimizes ground loops. The isilencer no. It is not necessary to power the idefender for its operation. It is simply to facilitate external power to the DAC. In the case of the Topping D90 for example, it is not necessary since it is powered by internal voltage.
 

Rigel

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Someone may correct me but the purpose of this device is to reroute 2 data pins of USB and cut off the 2 pins responsible for power and ground, which eliminates any internal power/ground related noise coming from the source.

The side socket for external power supply is only needed if the receiving device is actually powered by USB and has no power supply of it's own. So you can emulate power coming in via USB by plugging in an external adaptor.

However if your receiving device has internal or external power supply and therefore does not need USB power you can achieve the same result as this device provides by simply putting a piece of electric tape over the contact in your USB plug.

No need to spend $$-$$$ on some magic devices o_O Just magic tape covering ground contact to eliminate noise coming from PC to the DAC, which has external power supply.

The magic tape does not work magic either, although I agree that in certain cases it is effective as I have said and recommended on several occasions.
In the USB theme, not everything is snake oil, it is not convenient to generalize in all cases.

I have a USB cable without connection in the factory shield and with external power and the noise is still produced, so then it is not only enough to tape the connector. The idefender also works on the voltage, I suppose with the mass, to somehow decouple the noise.

¿Can be tested first by taping the connector? Of course, I have recommended it once, but it is not a guarantee and you can be sure that there are audiophile cables, just as expensive or more, that are less useful for sound.

If you had the Topping D90-A90 in my case along with an idefender, you could try just listening to the background noise, which is not always enough to tape the connector.

In my case, I have to have the maximum gain and maximum volume on the A90, which I never will, to hear very little background noise from PC processing. It's not a problem for me even using RCA connections. I normally use balanced connections and the silence is absolute.
In other cases, as colleagues who have had problems, the difference will be greater.

You can see the previous video, it is real. Different thing is that we do not need it because we do not have any ground loop or the PC is not the cause of it.
 

Severian

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There is nothing magical about the iFi iDefender IMO. It it a way to sever a ground loop when using a USB connection. Nothing more, nothing less.
 
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