Topping A90 Discrete Review (Headphone Amp & Preamp)

[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?

 

[KeithPhantom]

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?

No difference, it sounds exactly the same as an "unbalanced" amplifier.

 

[Veri]

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?

Two independent amplifier modules for each channel will have more power on tap, should some device need loads of power (there's plenty of very powerful single ended devices out there, though, so it really depends on what you're using it for). Also some devices have just plain bad SE performance (Magnius comes to mind) while its BAL is much better. This varies on the design.

But in theory using one amplifier for both L+R will have the least self-noise, as long as power is sufficient..

 

[shrimp_dude]

Thankfully Topping included the remote to go with the relay volume... spinning the knob quickly and having volumes erratically change up and down is always a terrible experience with this volume tech.

 

[okok]

the fly says the output voltage: BAL 49vpp, SE 25vpp, does that mean the power supply is +/- 25v?

 

[Arnas]

I keep hearing from audiophools that all these ''China amps'' have ''weak switched power supplies'' very small capacitors banks'' and thus dynamics suck because of that.
Amir, John stance on such myths?

 

[Doodski]

have ''weak switched power supplies'' very small capacitors banks''

The switched mode power supplies in these amps have small capacitors because the power supplies operate at high frequencies and that means that small capacitors may be used for smoothing. It is normal and nothing is amiss. If it where a linear 50 or 60 Hz power supply then big capacitors are required but not for switch mode power supplies.

 

[metasharp]

If I plug my DAC in RCA on my A90d =>low volume + lot of distortion
If I plug my DAC in XLR on my A90d => windows volume at 100%, DAC @0db (2db is max), gain in high, volume at 90 is ok on my Stealth. But even at +2 at 99 (all max) it's not super loud... sometimes it's even say it's barely an average volume.

I tried a sonometre app of my phone put on the speaker : strangely the stealth outputs more db than my bluetooth B&W PX7.... but I would swear at ear the B&W (60db) was at least 2 times louder... impossible to keep the headphone on whereas the Stealth felt at a moderate volume (62db).

I don't get it.

 

[lazarian]

If I plug my DAC in RCA on my A90d =>low volume + lot of distortion
If I plug my DAC in XLR on my A90d => windows volume at 100%, DAC @0db (2db is max), gain in high, volume at 90 is ok on my Stealth. But even at +2 at 99 (all max) it's not super loud... sometimes it's even say it's barely an average volume.

I tried a sonometre app of my phone put on the speaker : strangely the stealth outputs more db than my bluetooth B&W PX7.... but I would swear at ear the B&W (60db) was at least 2 times louder... impossible to keep the headphone on whereas the Stealth felt at a moderate volume (62db).

I don't get it.

Very likely ground loop and I'd assume very likely through your PC. Try the ground shunt, otherwise put it on a separate power outlet from your PC, otherwise buy something like the Topping HS01

 

[metasharp]

Ground loops changes nothing. Separate power plug nothing either.
The A90 Discrete is just not strong enough to drive properly a DCA Stealth.

 

[ObjectiveSubjectivist]

Ground loops changes nothing. Separate power plug nothing either.
The A90 Discrete is just not strong enough to drive properly a DCA Stealth.

I tried it with stealth and have to strongly disagree.

Power handling into Stealth was superb, you can get very very loud listening without hint of any distortion.

Something must be wrong with your unit or something else.

Control that this amplifier has was really amazing, I agree with Amir's words:
"This is the first time I have seen an amplifier have such an upper hand over these headphones."

 

[staticV3]

The A90 Discrete is just not strong enough to drive properly a DCA Stealth.

The A90D is strong enough to drive the Stealth to an ear-shattering 122dB Peak.
If you are missing volume, then either your hearing is considerably damaged, or your DAC is outputting barely any voltage.
A doctor can check the former, the latter you can check yourself with a $10 multimeter.

 

[metasharp]

Well using a soundmeter app on my android phone, at max volume the stealth gives 60 to 65db.

I have a multimeter. How should I plug it on the SU-9 Pro to verify the voltage?

https://www.smsl-audio.com/upload/ueditor/20221021/202210211433393711.jpg

 

[roundsound]

Check the volume curve setting of the amplifier as well. Button B on the remote.

 

[solderdude]

Ground loops changes nothing. Separate power plug nothing either.
The A90 Discrete is just not strong enough to drive properly a DCA Stealth.

Something must be defective or seriously wrong somewhere or some settings are very wrong.
Plug the stealth in a different amplifier.

Even a phone should be able to create a decent output level (70dB average) and 10V should give you about 100dB average (very loud) and 120dB peaks.

 

[staticV3]

Well using a soundmeter app on my android phone, at max volume the stealth gives 60 to 65db.

I have a multimeter. How should I plug it on the SU-9 Pro to verify the voltage?

That's a start, even though Android Soundmeter Apps are generally unreliable due to a lack of calibration.
iOS is more reliable in this case, because there are few hardware models and devs can calibrate.

Next, get a cheap multimeter, play a 60Hz, 0dBFS test tone just like you would your normal tracks, then set your multimeter to V(AC) and measure the voltage both at the output of your DAC and at the output of your A90D.

 

[metasharp]

In windows I use the SMSL SU9-Pro USB driver 5.5.0 and foobar uses that proper output.
It means that if I change the volume in Windows, the volume doesn't change.
(However if I change it in foobar, it does change)

In the DAC I'm in fixed mode, it show -0.0dB. In variable mode I gain a little something, but not much by being able to raise it to +2.0dB.
Output with RCA cables gives low volume + early distorsion.
Output with XLR produces the described result around 60dB at 99 volume (max).
My Stealth is plugged with an XLR cable.

 

[Veri]

In the DAC I'm in fixed mode, it show -0.0dB. In variable mode I gain a little something, but not much by being able to raise it to +2.0dB.
Output with RCA cables gives low volume + early distorsion.
Output with XLR produces the described result around 60dB at 99 volume (max).
My Stealth is plugged with an XLR cable.

Are there official specs/measures on the output impedance of your DAC? Because this all seems pretty very weird.

 

[metasharp]

That's it! It's button B of the A90D that changes everything. It says invalid button on the documentation but actually it changes A LOT the volume setting it to 1.

 

[metasharp]

Check the volume curve setting of the amplifier as well. Button B on the remote.

Thanks.
The online doc states invalid button...

A90 Discrete user manual-TOPPING

www.tpdz.net

The paper one (that i didn't check before) says volume curve with no further explaination.
Do you know where is the proper doc that explains it?

With Volume Curve 1 it goes the highest. Curve 2 : there I understand Amir's comment. Curve 3 to 5 : max volume is far too little.
I'll go back to RCA to test more then.