Topping A90 Discrete Review (Headphone Amp & Preamp)

[ObjectiveSubjectivist]

I can replicate it by just having the device powered on and plugging/unplugging a 6.36mm cable . It sometimes powers off the device and others it shows a "-5" on the screen before powering off including the pops of course. This happened sometimes even on the 4.4mm jack, I surely informed Topping about it before shipping the amplifier for adjustments.

One of the reasons I'll be returning my unit.
I prefer benchmark hpa4

 

[Gggggas]

One of the reasons I'll be returning my unit.
I prefer benchmark hpa4

I am curious to see the results of their adjustments , I have a feeling that it will be working perfectly. Nonetheless it is a big problem having to return or ship the device overseas for a repair.
I have never used a HPA4 , unfortunately for me there are no stores where I can go to and try audio gear here in northern Greece. They thought I was an alien when I asked if they have headphones and audio equipment for testing.

 

[tarikuz]

@tarikuz you can't compare "half volume" on Amp 1 with half volume on Amp 2. That doesn't work.

Solved! It should be an impedance problem of the RCA output of the SMSL SU-9 DAC... Today I installed a couple of topping TCX-1 XLR balanced cables.. With same setting at 40 (high Gain) it's very loud.... Definitely too high impedance of SMSL SU-9 on RCA output.

 

[Molina]

I can report that this bug is still happening alas only when music is playing.
When I click pause on roon, I couldn't replicate that issue.

Ohh, it's just on the unbalanced out? Well, I can live with that. I'll probably still be getting it since it allows me to easily switch between the outs and memorises the volume level.

Maybe I'll wait until @amirm manages to find some time and get his hands on an L70. Also, you never know what's on sale during Black Friday.

 

[Veri]

Solved! It should be an impedance problem of the RCA output of the SMSL SU-9 DAC... Today I installed a couple of topping TCX-1 XLR balanced cables.. With same setting at 40 (high Gain) it's very loud.... Definitely too high impedance of SMSL SU-9 on RCA output.

Wait, erm. Isn't it completely expected that those XLR cables bring much higher loudness? Why would you assume the RCA has any impedance problem at all??

 

[staticV3]

Solved! It should be an impedance problem of the RCA output of the SMSL SU-9 DAC... Today I installed a couple of topping TCX-1 XLR balanced cables.. With same setting at 40 (high Gain) it's very loud.... Definitely too high impedance of SMSL SU-9 on RCA output.

using the SU-9's Bal out instead of RCA will naturally result in about 50% higher loudness. That is excluding any potential issues related to Zo and Zi.

 

[ObjectiveSubjectivist]

Ohh, it's just on the unbalanced out? Well, I can live with that. I'll probably still be getting it since it allows me to easily switch between the outs and memorises the volume level.

Maybe I'll wait until @amirm manages to find some time and get his hands on an L70. Also, you never know what's on sale during Black Friday.

I cannot test balanced 4,4mm.
I'm waiting for XLR cable for my Stealths but I believe there won't be any problem with XLR output.

 

[Music1969]

I'm waiting for XLR cable for my Stealths but I believe there won't be any problem with XLR output.

Yes YouTube video review I linked on previous page said balanced was not issue with latest firmware.

Unbalanced was issue for him with latest firmware.

I didn't expect this from @JohnYang1997 since it's not his first headphone amp design

Hopefully they can fix it in a hardware revision (which will upset some early buyers)

 

[lazarian]

Yes YouTube video review I linked on previous page said balanced was not issue with latest firmware.

Unbalanced was issue for him with latest firmware.

I didn't expect this from @JohnYang1997 since it's not his first headphone amp design

Hopefully they can fix it in a hardware revision (which will upset some early buyers)

Whilst it definitely isn't a good look for an amp at this price point to have this style of issue, I will say that majority of users likely wouldn't hit this. I know I basically never unplug my headphones from the amp, and when I do I've always had the habit of turning down / off any amp anyway.
I'd also suggest many users of this amp would be on balanced as it's one of its main selling points.

 

[Music1969]

Whilst it definitely isn't a good look for an amp at this price point to have this style of issue, I will say that majority of users likely wouldn't hit this. I know I basically never unplug my headphones from the amp, and when I do I've always had the habit of turning down / off any amp anyway.
I'd also suggest many users of this amp would be on balanced as it's one of its main selling points.

I'm not sure about 'many users would be on balanced'. We don't have any such data about how many.

My SMSL SP400 doesn't have any firmware related issues - no firwmare updates , which is what I expect from a headphone amp.

While my SP400 doesn't power off if I unplug 6.3mm plug, I agree it is bad practise with any amp to do this with amp powered on.

It's more of an engineering complaint than practical one.

I expected more form Johnyang considering his experience now.

I don't expect to see firmware updates on a purely analogue headphone amp - this should absolutely not, ever, become a thing...

Get it right, in the factory.

 

[ObjectiveSubjectivist]

Get it right, in the factory

Exactly

 

[lazarian]

I suppose all I'm really saying is its not a huge issue unless you're a person that is swapping headphones quite alot and aren't switching the amp off when you do it.
Not defending it beyond that, it shouldn't be an issue to begin with.

I will say that you only need to be blasted with static or a loud pop once in your life to always be cautious after... some of us probably showing our age with that of course being more of an issue on older amps.

 

[ObjectiveSubjectivist]

Has anyone compared XLR output to 6,3mm on the same headphones?
Any differences? (other than power)

 

[Veri]

Any differences? (other than power)

None.

 

[tarikuz]

Has anyone compared XLR output to 6,3mm on the same headphones?
Any differences? (other than power)

None (i didn't check the 4.4 because I have only XLR balanced cable).

 

[scociu]

Does A90D still have the ground loop issue when using unbalanced inputs (RCA), or was it fixed?
I just got home with an A90 and have to return it due to the noise.
Using balanced inputs is not an option as my use case is macbook -> jack to RCA -> Amp -> Hifiman Arya

 

[tomelex]

Does A90D still have the ground loop issue when using unbalanced inputs (RCA), or was it fixed?
I just got home with an A90 and have to return it due to the noise.
Using balanced inputs is not an option as my use case is macbook -> jack to RCA -> Amp -> Hifiman Arya

All I can tell you is there is a ground lift switch on the back of the unit

 

[tarikuz]

I never faced any ground loop (i had a90) with a90d. Anyway the 90d has the ground loop switch (i never used it). For me was not necessary in RCA and as well for the XLR.

 

[scociu]

Update: exchanged the A90 for the A90d. No hissing regardless of how I set the ground lift switch. ‍
Can't notice any difference in sound quality.

 

[bearcatsandor]

What difference does it make that the A90 descrete is fully balanced? I know it gives you a little more power, but is there any sonic or other benefit to it?