Topping A90 Headphone Amplifier Review

[JohnYang1997]

Actually isolating the power supply external to the signal path - reducing the influence - even separating into separate closed enclosures is common. Battery power for desktop audiophile equipment is also common.

Figuring out how to connect the grounds, or isolate the grounds between equipment is part of the design for getting paired components to work together without induced interference. Avoiding

Avoiding interference by pulling out the power generation components and using a common ground between components is basic design principle. If you ignore that then this is what we get. Random induced interference experienced by some and not by others, with the burden of figuring out a solution now put on the customers instead of in the design stages.

You'll figure it out

Plug it in AP and see what's the noise of it. The issue is the system not A90.

 

[JohnYang1997]

Why provide USB connectivity if you can't reject the noise through isolation? Why allow the source USB power to be pulled internal to the D90 when it doesn't use the power? Why provide RCA connections when you can't stop the ground loop interference between your own equipment?

These are valid questions as well, and I hope you consider them in future designs.

It's all one of the same. If you can't enjoy the excellent sound reproduction from your components due to failure to account for noise rejection from the outside, and design your components to work together, at the very least, without affecting each others ability to reject noise induced, then the original goal of providing sound reproduction isn't attainable, at least for all of your customers.

It's not an unusual configuration. D90 MQA + A90 + USB source from PC - is it? Many will run into the same issues, if not at first then later.

No hard feelings, but there is disappointment that has to be acknowledged. You'll lose customers and next time they will be wary to purchase without waiting for initial rollout to happen and see how the products work before buying. Losing that "unthinking support" that drives high product sell through initially can be more than disappointing.

Like I've said, I think you'll work it out.

All are considered. And you failed to understand what that post means.

 

[JohnYang1997]

Why provide USB connectivity if you can't reject the noise through isolation? Why allow the source USB power to be pulled internal to the D90 when it doesn't use the power? Why provide RCA connections when you can't stop the ground loop interference between your own equipment?

These are valid questions as well, and I hope you consider them in future designs.

It's all one of the same. If you can't enjoy the excellent sound reproduction from your components due to failure to account for noise rejection from the outside, and design your components to work together, at the very least, without affecting each others ability to reject noise induced, then the original goal of providing sound reproduction isn't attainable, at least for all of your customers.

It's not an unusual configuration. D90 MQA + A90 + USB source from PC - is it? Many will run into the same issues, if not at first then later.

No hard feelings, but there is disappointment that has to be acknowledged. You'll lose customers and next time they will be wary to purchase without waiting for initial rollout to happen and see how the products work before buying. Losing that "unthinking support" that drives high product sell through initially can be more than disappointing.

Like I've said, I think you'll work it out.

Extensive evaluation and optimization blew off by your single post? Do you have any idea? Is there a single person having issue with d90 + a90 with XLR ?

 

[JohnYang1997]

Plus engineers should know that external transformer is the way for best isolation and noise performance. That's what's on L30. But do you really think that will work on A90? A separate chassis like gsx mkii is possible. And it's been considered.

 

[Audimon]

This is going the wrong way without the faces. We should all have a beer

 

[JohnYang1997]

Why provide USB connectivity if you can't reject the noise through isolation? Why allow the source USB power to be pulled internal to the D90 when it doesn't use the power? Why provide RCA connections when you can't stop the ground loop interference between your own equipment?

These are valid questions as well, and I hope you consider them in future designs.

It's all one of the same. If you can't enjoy the excellent sound reproduction from your components due to failure to account for noise rejection from the outside, and design your components to work together, at the very least, without affecting each others ability to reject noise induced, then the original goal of providing sound reproduction isn't attainable, at least for all of your customers.

It's not an unusual configuration. D90 MQA + A90 + USB source from PC - is it? Many will run into the same issues, if not at first then later.

No hard feelings, but there is disappointment that has to be acknowledged. You'll lose customers and next time they will be wary to purchase without waiting for initial rollout to happen and see how the products work before buying. Losing that "unthinking support" that drives high product sell through initially can be more than disappointing.

Like I've said, I think you'll work it out.

Also talking about I'm losing customers without acknowledge that I'm only a designer and was only here from last December to bring some goodness to the market....

 

[JohnYang1997]

This is going the wrong way without the faces. We should all have a beer

You are fine. That guy really triggered me.

 

[Ddd]

Whoa, Ok. Let me Clear it out for everyone!
I hope i'm right, but i may be wrong.
And sorry if i am wrong, i have much more to learn.
But just sharing

A90 power supply designed with Earth connection utilised.
So a potential ground loop issue is expected if you use it with the WRONG DEVICE
Simple to say, it is not the A90 fault design, but to know what interconnect devices you should use with and what devices you should'nt use with.

TLDR, Summary,
If you want to use A90 with a Earth Utilised Device, Use XLR interconnect ONLY
If you want to use A90 with a Non-Earthed Device, Use Either will be Good.

_____________________________________________________________________________________________________________

if one wish to use the A90 with a Earthed Device, Use the XLR input only,
and dont connect other Earthed Device to A90 RCA input while using XLR input

I was told that XLR connection can prevent ground loop issues,
thats why it is recommended XLR interconnection if you're using between two XLR capable grounded device

(Example of device like Topping DX7 Pro, D90)

Using RCA Interconnect between two Earth-ed device is definitely going to be suffer from potential ground loop issues.

And Off course if you still insist you want to use A90 RCA input with your Earthed Device,
only way to do it is to Earth-Lift your A90 or your Earthed Device!
But not sure if is safe, but is not recommended by @JohnYang1997
But if is ok or safe enough to do so,
John will you think is a good idea to implement a Ground/ Earth Lift Flick Switch on A90?

______________________________________________________________________________________________________________

if one wish to use the A90 with a Non-Earth device, You can use both RCA or XLR input no issues
(Example of Device like Topping D50s, Dx3 Pro)
Because the A90 will act as the Earth-ed station for your non-Earth DAC thorugh any cable

Those who used A90 with -

- RCA out from Desktop PC motherboard or Soundcard,
Your Desktop PC is producing a lot of noise and Desktop PC is Earthed!
Now you're Connecting to A90 RCA input
A90 utilised the Earth, so ground loop issue is one thing
Another is your Desktop PC dirty power noise will also leaked into the A90 and Earth through it
And thats the noise you heard when using RCA input,
Just to let you all know is not the A90 issues.

And Off course if you still insist you want to use A90 with your desktop,
only way to do it is to Earth-Lift your A90!
But not sure if is safe, but is not recommended by @JohnYang1997
But if is ok or safe enough to do so,

Again, @JohnYang1997 , will you think is a good idea to implement a Ground/ Earth Lift Flick Switch on A90?

________________________________________________________________________________________________________________________________

- Another is some using DAC that is eithered USB Powered or Draw power from PC using USB CABLE
or COAXIAL signal to your DAC

If your DAC did not reject the noise or Ground loop from your PC,
the signal send to A90 may suspect to noise or Ground loop issues as well if you are using RCA interconnect between them,
The way to solve it is to either get a USB Ground Isolater like the iFi iDefender+ to break the gound between your DAC and PC
For USB Powered device you will also need to get the iFi iPower 5V as well to Power your USB Powered device
And you may get sound quality improvement from doing so with a clean power supply from the iFi iPower
and end of the day you may potentially achieves even better sound quality to your DAC to the A90.

______________________________________________________________________________________________________________

- For All other user that compare the A90 with device like THX 789, 887, JDS Atom
The reason those device doesn't have the RCA noise is because THX 789, 887, Atom doesn't utilise the Earth Pin!
So they are designed to be used with a Earthed DAC!
So they Earthed through another Earth Device through the RCA Interconnect!

Simple to say, it is not the A90 fault design, but to know what interconnect devices you should use with and what devices you should'nt use with.
Try using Topping D90 with SMSL SP200 and you may get the same issues as well, maybe..
Since i guess SP200 is Earthed and designed to use with their Non-Earth DAC M300 M200 as well.
While M400 with SP200 amp may have potential Ground Loop issues too.

Just my finding and sharings.
I may be wrong
I'm still learning.
But hope i gave you an idea for reading XD
Thanks.
*Sorry that i wrote so long

 

[Ddd]

Extensive evaluation and optimization blew off by your single post? Do you have any idea? Is there a single person having issue with d90 + a90 with XLR ?

Through the XLR interconnect Zero Issues !


Thanks.

 

[JohnYang1997]

Whoa, Ok. Let me Clear it out for everyone!
I hope i'm right, but i may be wrong.
And sorry if i am wrong, i have much more to learn.
But just sharing

A90 power supply designed with Earth connection utilised.
So a potential ground loop issue is expected if you use it with the WRONG DEVICE
Simple to say, it is not the A90 fault design, but to know what interconnect devices you should use with and what devices you should'nt use with.

TLDR, Summary,
If you want to use A90 with a Earth Utilised Device, Use XLR interconnect ONLY
If you want to use A90 with a Non-Earthed Device, Use Either will be Good.

_____________________________________________________________________________________________________________

if one wish to use the A90 with a Earthed Device, Use the XLR input only,
and dont connect other Earthed Device to A90 RCA input while using XLR input

I was told that XLR connection can prevent ground loop issues,
thats why it is recommended XLR interconnection if you're using between two XLR capable grounded device

(Example of device like Topping DX7 Pro, D90)

Using RCA Interconnect between two Earth-ed device is definitely going to be suffer from potential ground loop issues.

And Off course if you still insist you want to use A90 RCA input with your Earthed Device,
only way to do it is to Earth-Lift your A90 or your Earthed Device!
But not sure if is safe, but is not recommended by @JohnYang1997
But if is ok or safe enough to do so,
John will you think is a good idea to implement a Ground/ Earth Lift Flick Switch on A90?

______________________________________________________________________________________________________________

if one wish to use the A90 with a Non-Earth device, You can use both RCA or XLR input no issues
(Example of Device like Topping D50s, Dx3 Pro)
Because the A90 will act as the Earth-ed station for your non-Earth DAC thorugh any cable

Those who used A90 with -

- RCA out from Desktop PC motherboard or Soundcard,
Your Desktop PC is producing a lot of noise and Desktop PC is Earthed!
Now you're Connecting to A90 RCA input
A90 utilised the Earth, so ground loop issue is one thing
Another is your Desktop PC dirty power noise will also leaked into the A90 and Earth through it
And thats the noise you heard when using RCA input,
Just to let you all know is not the A90 issues.

And Off course if you still insist you want to use A90 with your desktop,
only way to do it is to Earth-Lift your A90!
But not sure if is safe, but is not recommended by @JohnYang1997
But if is ok or safe enough to do so,

Again, @JohnYang1997 , will you think is a good idea to implement a Ground/ Earth Lift Flick Switch on A90?

________________________________________________________________________________________________________________________________

- Another is some using DAC that is eithered USB Powered or Draw power from PC using USB CABLE
or COAXIAL signal to your DAC

If your DAC did not reject the noise or Ground loop from your PC,
the signal send to A90 may suspect to noise or Ground loop issues as well if you are using RCA interconnect between them,
The way to solve it is to either get a USB Ground Isolater like the iFi iDefender+ to break the gound between your DAC and PC
For USB Powered device you will also need to get the iFi iPower 5V as well to Power your USB Powered device
And you may get sound quality improvement from doing so with a clean power supply from the iFi iPower
and end of the day you may potentially achieves even better sound quality to your DAC to the A90.

______________________________________________________________________________________________________________

- For All other user that compare the A90 with device like THX 789, 887, JDS Atom
The reason those device doesn't have the RCA noise is because THX 789, 887, Atom doesn't utilise the Earth Pin!
So they are designed to be used with a Earthed DAC!
So they Earthed through another Earth Device through the RCA Interconnect!

Simple to say, it is not the A90 fault design, but to know what interconnect devices you should use with and what devices you should'nt use with.
Try using Topping D90 with SMSL SP200 and you may get the same issues as well, maybe..
Since i guess SP200 is Earthed and designed to use with their Non-Earth DAC M300 M200 as well.
While M400 with SP200 amp may have potential Ground Loop issues too.

Just my finding and sharings.
I may be wrong
I'm still learning.
But hope i gave you an idea for reading XD
Thanks.
*Sorry that i wrote so long

For transformer based, the secondary can be fully isolated. And only the chassis is connected to the earth. A lift switch is possible. And that would isolated the circuit from the earth.
For SMPS, it's not a good idea to isolate the secondary because leakage current can build up and cause problems, and it's much more noisy.
Yes, if you are comparing to other transformer based design. I would ask about the interference caused by the transformer (possible to isolate but PITA). Transformer is seriously considered in Pre90 which is responsible for interfacing two or more devices that it's very appealing.
And yes you get much heavier weight, much more heat generated, much larger for the same power, no voltage regulations right out of the output, needs extra regulators that also generated heat. For L30 it's adequate to live with that as it's external. For pre90 it's also ok because it's less power and have less circuitry to occupy area. Still not decided what to use eventually yet.
For the size the weight the power of A90, it's just the way to go.

 

[Ddd]

Ah! I see! Good to know, was always wondering why the Transformer is only used in the D90 and not in the A90. Now I get it, no wonder D90 case is much warmer due to transformer's heat I supposed? Which suggested why A90 as a high power amplifier is much cooler compare to its transformer utilised dac

 

[hmscott]

Extensive evaluation and optimization blew off by your single post? Do you have any idea? Is there a single person having issue with d90 + a90 with XLR ?

Through the XLR interconnect Zero Issues !


Thanks.

That's also reported by me - XLR masks the problem and cuts the noise - but at the expense of losing use of my RCA connections. And, that only works with my current headphones only configuration. Now I have to change my powered speakers to XLR from RCA, or to another configuration entirely.

The failure to assure RCA connections work between the D90 / A90 / PC USB before production has put me (and others) in the position of needing to rethink our system build. The connectivity we thought we had to work with isn't usable.

Now I'm considering a separate amp connected with XLR and using non-powered speakers to help firewall passing on the noise problems.

I'm trying to share with you what your customer is going through with this situation, you are telling me everything is fine, and I'm letting you know that no it's not fine, except in a limited way - different from the original intention of my build.

But, I think you get the idea, it's not an attack on you - it's that I hope you carry this feedback back to Topping to make sure this doesn't happen again in future separates products.

Thanks for listening.

I'll report back when I've decided what to do with my build configuration. It will likely be a while

 

[JohnYang1997]

That's also reported by me - XLR masks the problem and cuts the noise - but at the expense of losing use of my RCA connections. And, that only works with my current headphones only configuration. Now I have to change my powered speakers to XLR from RCA or to another configuration entirely.

The failure to assure RCA connections work between the D90 / A90 / PC USB before production has put me (and others) in the position of needing to rethink our system build.

Now I'm considering a separate amp with XLR's and non-powered speakers to help firewall the passing on the noise problems.

I'm trying to share what your customer is going through with this situation, you are telling me everything is fine, and I'm letting you know that no it's not fine, except in a limited way - different from the original intention of my build.

But, I think you get the idea, it's not an attack on you it's that I hope you carry this feedback back to Topping to make sure this doesn't happen again in future separates products.

Thanks for listening.

I'll report back when I've decided what to do with my build configuration. It will likely be a while

Who not use A90's preamp output for separate amp?

 

[hmscott]

Who not use A90's preamp output for separate amp?

"Now I'm considering a separate amp with XLR's and non-powered speakers to help firewall the passing on the noise problems. "

Yup, that's where I'm headed.

 

[JohnYang1997]

"Now I'm considering a separate amp with XLR's and non-powered speakers to help firewall the passing on the noise problems. "

Yup, that's where I'm headed.

I thought you were to use XLR from D90. I think I remember the discussion here. And using A90 as preamp was the final solution. Yeah.

 

[Ddd]

That's also reported by me - XLR masks the problem and cuts the noise - but at the expense of losing use of my RCA connections. And, that only works with my current headphones only configuration. Now I have to change my powered speakers to XLR from RCA, or to another configuration entirely.

The failure to assure RCA connections work between the D90 / A90 / PC USB before production has put me (and others) in the position of needing to rethink our system build. The connectivity we thought we had to work with isn't usable.

Now I'm considering a separate amp connected with XLR and using non-powered speakers to help firewall passing on the noise problems.

I'm trying to share with you what your customer is going through with this situation, you are telling me everything is fine, and I'm letting you know that no it's not fine, except in a limited way - different from the original intention of my build.

But, I think you get the idea, it's not an attack on you - it's that I hope you carry this feedback back to Topping to make sure this doesn't happen again in future separates products.

Thanks for listening.

I'll report back when I've decided what to do with my build configuration. It will likely be a while

Just wondering, if you connect the D90 to A90 with XLR... solving the ground issues

Then A90 RCA to your powered speaker, is the noise still present?

Another potential solution maybe the future Pre90 may solve your problem since according to @JohnYang1997 the unit maybe using a transformer and may eliminate the ground loop issue and function as preamp.

Hope it helps.

 

[Ddd]

"Now I'm considering a separate amp with XLR's and non-powered speakers to help firewall the passing on the noise problems. "

Yup, that's where I'm headed.

Yeah. Or some powered speaker with XLR speaker input like those Eve Audio or Adam Audio speaker?

 

[hmscott]

I thought you were to use XLR from D90. I think I remember the discussion here. And using A90 as preamp was the final solution. Yeah.

Yes, I'd already bought 0.5m XLR cables with the A90 / D90 purchase, along with 0.5m RCA and 1.5m RCA powered speaker cables, but now with the noise problem I don't want to risk investing in powered speakers with RCA only inputs - even though I was trying to reduce the cost by limiting myself to that interconnect.

Now I'm down the road a bit and thinking if I am going to spend big bucks on a higher end powered speaker with XLR inputs, why not built out a more traditional AMP / speakers configuration. And, now that I am back on the path to reconfigure, it will take me a while to settle on a build.

Just wondering, if you connect the D90 to A90 with XLR... solving the ground issues

Then A90 RCA to your powered speaker, is the noise still present?

Another potential solution maybe the future Pre90 may solve your problem since according to @JohnYang1997 the unit maybe using a transformer and may eliminate the ground loop issue and function as preamp.

Hope it helps.

Thanks, every little bit of idea and experience exchange adds to the solutions

No I haven't tried that myself - I don't want to risk it without confirming it works for someone else.

I've asked a few times if anyone else had tried this, used XLR between the A90 / D90 and used RCA to powered speakers - or even an intermediate amp - but noone responded with their experienced results.

I'm already out the cost of a nice set of 0.5m RCA interconnects and a 1.5m coil of RCA terminated cables I planned to connect to powered speakers. I've decided I'm not ordering RCA powered speakers without hearing someone else's experience / results first.

With the quarantine there aren't any local outlets I could bring in my A90 / D90 / cables to try an RCA connected powered speaker configuration before buying.

Going with XLR interconnects to the powered speakers or an intermediate amplifier is more of a sure thing right now, but I've only recently thought of the intermediate amp.

I was reading up on the new Brystan 4B Cubed amp, and was looking at various floor standing speakers to pair together...
https://bryston.com/amplifiers/4b3/

That would cost me a lot more than my original "inexpensive" powered near field speakers... there are hidden costs to your original "planned build" going awry. So, now I'm scaling back that thought and looking at less expensive amps and speakers.

That's why it's going to be a while before I decide what to end up getting. First I've got to wrestle with my own desires - reign in my desires once again - I had already done that nicely, but now the "horse is out the gate" again.

 

[GeorgeWalk]

I have the D90/A80 combo. I am using USB from my MacBook Pro, with RCA cables, RCA cables to the A90, single ended to my headphones, and RCA to my Bose powered speakers. I am also using generic RCA cables and interconnects as well as a non-boutique USB cable. I am not having any noise or ground loop problems. I have used my HD660s and IEMs. No noise. This sounds like system/usage specific problem.

It is not possible for a designer/engineer to consider and build a general product for every possible consumer use and configuration. It is built for the majority of the market. Compromises ar always made. If the configuration can't be adapted easily to the particular configuration then you need to either change the configuration or get something else. Not every product fits every configuration. That doesn't make it bad or defective.

 

[Ddd]

I have the D90/A80 combo. I am using USB from my MacBook Pro, with RCA cables, RCA cables to the A90, single ended to my headphones, and RCA to my Bose powered speakers. I am also using generic RCA cables and interconnects as well as a non-boutique USB cable. I am not having any noise or ground loop problems. I have used my HD660s and IEMs. No noise. This sounds like system/usage specific problem.

It is not possible for a designer/engineer to consider and build a general product for every possible consumer use and configuration. It is built for the majority of the market. Compromises ar always made. If the configuration can't be adapted easily to the particular configuration then you need to either change the configuration or get something else. Not every product fits every configuration. That doesn't make it bad or defective.

Yeah. With no offense ya. Just my experience, while I heard the noise when connected with RCA. Some other people or even my friends some doesn't hear it. So I guess is only a sad case for sensitive ears people