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Topping A90 Discrete Review (Headphone Amp & Preamp)

Rate this Headphone Amp/Pre-amp

  • 1. Poor (headless panther)

    Votes: 9 3.1%
  • 2. Not terrible (postman panther)

    Votes: 9 3.1%
  • 3. Fine (happy panther)

    Votes: 49 17.1%
  • 4. Great (golfing panther)

    Votes: 220 76.7%

  • Total voters
    287

Moderate Dionysianism

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The latter is better (more precise, perfect channel matching) and also what the a90d has.

Is it that simple? Because I remember the Loxjie P20 driving me crazy with X being too quiet and X+1 being too loud. It was the main reason I sold it. Similar thing with the BT volume control on my V40. They were able to do 75 steps for the 'quad DAC' mode, but BT has 15:facepalm:

Of course there are trade-offs. I'm currently using a THX 887 and it had lasted ~6 months before the pot developed a noise issue. I know I can clean it, but that's super quick for a new device. My HUD-MX1 took >5 years before I had to clean the volume pot. I wonder how the pots on the A90s are faring.
 

nyxnyxnyx

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Whoops, yup, still my point stands. Actually, it's even a step backwards then compared to some other gadgets from them.

I still stick with my opinion that we're sliding into a marketing scheme - not just Topping - where every year a new gadget with slight improvements is released and sold for a higher price.

We only can hope that audio gear lasts longer than smartphones and consumers are more reasonable. But seeing how people still buy +1000$ phones just as a camera + expensive instant messaging and social media machine, my hopes are dim.
Please do NOT forget that we are only reaching the 'stalemate' lately. Prior to this we've never had such a swift step-up in the headgear market. This 'slight improvements' thing you are talking right here could have easily costed 50%-100% or even more 7-8 years ago. Now we have constant improvements and alternative options for very affordable price, and it's a good thing overall.

I say, as long as companies don't scam people with misguided specs and confusing marketing schemes they are doing a good job and it is up to the consumers to decide for themselves.
 

enricoclaudio

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I think you have swapped linear and logarithmic.

My assumption was based on a response from Parasound regarding the implementation of the Burr Brown analog resistor ladder volume control found in my Halo P6 Preamp:

The P 6 and HINT 6 volume control and Zpre 3 and 200PRE mapping results in turning the volume to a higher number for all sources.
70 or higher is typical.
The number has nothing to do with the % of the maximum possible volume.

Please note that relative to the displayed Volume Control indicator:

VOLUME DISPLAYED INCREMENTAL CHANGE in dB

0-20 +/-2 dB increments from one displayed number to the next

21-60 +/-0.5 dB increments from one displayed number to the next

61-100 +/-1 dB increments from one displayed number to the next

The P 6 and HINT 6 volume setting may appear to be set higher than other stereo products you are familiar with. In particular stereo equipment that use a potentiometer for the volume control (like the P 5 and Halo Integrated) may seem to be playing louder at a relatively lower setting of the volume knob. This is because potentiometer based volume controls are usually based on linear voltage gains rather than based on the way humans perceive sound which is logarithmic. Most potentiometer volume controls have very little increase in loudness past the 1 o’clock position. The P 6 and HINT 6 volume scale works in dB (logarithmic) so the volume increases significantly all the way to the maximum of 99. In addition we have designed the P 6 and HINT 6 to have finer adjustments in the middle of the volume range since this is where a listener would appreciate smaller (0.5dB) step. Generally all of Parasound’s products have the same maximum gain (~10dB) but the P 6 and HINT 6 simply get to that same maximum gain slower and gives the listener finer control over the volume level. Depending on the efficiency of the speakers and the type of music being played the typically “loud” listening range may vary anywhere from 60-90 which leaves plenty of headroom should you wish to listen even louder.

Let me know this helps you to better understand the VC implementation of selected Parasound products. I appreciate your curiosity.

Thanks for being a valued Parasound customer.
 

Haruko

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Sep 14, 2021
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Is it that simple? Because I remember the Loxjie P20 driving me crazy with X being too quiet and X+1 being too loud. It was the main reason I sold it. Similar thing with the BT volume control on my V40. They were able to do 75 steps for the 'quad DAC' mode, but BT has 15:facepalm:

Of course there are trade-offs. I'm currently using a THX 887 and it had lasted ~6 months before the pot developed a noise issue. I know I can clean it, but that's super quick for a new device. My HUD-MX1 took >5 years before I had to clean the volume pot. I wonder how the pots on the A90s are faring.
lol i had similar problem with thx789.. pot was noisy only after 4-5 months

i have 0 problems with L30 tho
 

nagster

Active Member
Joined
Jan 24, 2021
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380
Looking at the image of the A90D board, it seems that the number of relays for volume control is one less than that of Pre90.
I touched my acquaintance's A90D. The volume adjustment was 100 steps. (The number of steps of Pre90 is 233, 0.5dB even step)
By the way, when the maximum gain is 0dBr, the gain measurement value one step before mute is about -115dBr for Pre90 and about -96dBr for A90D.

PS: Volume change is now knob rotation + speed type. In other words, even if the angle changes the same, if turn it quickly, the volume will change significantly. (I think it is essential for the encoder type. Otherwise 300° type like mola-mola)
Pre90 is unresponsive to the rotation speed, so I had to turn it a lot, which was one of the drawbacks for me...

edit: 231 => 233
 
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restorer-john

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I appreciate that there a are no high order harmonics visible in the spectrum of the discrete A90 version, compared to the one with IC's. And also the cleaner noise bottom.

View attachment 215560 View attachment 215561

Did you notice the input impedance of the analyzer is different for each one of Amir's tests? 200k for the discrete, 600R for the OPAMP version.
 
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carlcamper

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Just started testing my A90 Discrete plugged into my Topping D10 Balanced, and so far so good.

No hiss on my Moondrop Chu in Single Ended, and no trace of crosstalk in balanced.

The only issue I've encountered so far is when plugging and unplugging on the 1/4 Jack, the unit seems to reset, as if it shorted. I then need to turn it back on, and everything works normally. @JohnYang1997 is this expected behavior?
 

pma

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Did you notice the input impedance of the analyzer is different for each one of Amir's tests? 200k for the discrete, 600R for the OPAMP version.
Good point, John. Anyway, opamps tend to create higher amount of high order harmonics than a good discrete design. Good discrete design may intentionally maximize circuit linearity before the feedback is applied. Opamps rely on heavy feedback, which tends to push disrtortion energy into high order harmonics. Take it as a circuit designer’s comment.
 

tritopia

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I found one thing to improve.
When operating in headphone mode or headphone mode + preamp mode, In this mode, when the connected headphones are unplugged, the unit will stop working with a roaring sound from the speaker.

After that, it stops working and turns off the power. If you turn the power back on, it will work normally, but it can put a lot of stress on the speaker. Perhaps the protection is being applied too strongly.

Turning the volume down and unplugging the headphones doesn't seem to be a problem, but it's a disappointment.

I have no doubt that it will be fixed with a new firmware system sooner or later. Topping, please solve this problem well~
 

enricoclaudio

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I use Hart Audio cables with all my headphones and I keep the single ended and balanced connectors always plugged in and switch only between headphones cables so I'm curious to know what would happen when switching only headphones and not unplugging the adapters. I guess I will find out as soon my A90D arrives.
 

xema

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Dec 1, 2019
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Ah OK.
Maybe just at 3 fixed levels ?
-20dB, -40dB, and -60dB, as an example ?

That's basically SNR at low level, isn't it?

@nagster has published an interesting comparison with pre90 at 12 levels here:
would you try behringer's monitor2usb by chance? It is has a VCA volume which is intersting.
index.php
 

Rja4000

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Well
I had a look at specs of the Behringer Monitor2usb...
85dB A SNR
Not vey inspiring...
20220701_203856.jpg


The Volume2, which does look "beaten" in above comparison plot, still reaches 110dB SINAD
 
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carlcamper

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I use Hart Audio cables with all my headphones and I keep the single ended and balanced connectors always plugged in and switch only between headphones cables so I'm curious to know what would happen when switching only headphones and not unplugging the adapters. I guess I will find out as soon my A90D arrives.
I'm here to confirm that keeping my 1/4 to 3.5mm Ugreen adapter plugged and just plugging and unplugging to it does not trigger the reset. But I still hope @JohnYang1997 can patch this issue, together with adding Gain change to the volume button.
 

mocenigo

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Is this why on the Schitt Frey+ the volume seems to jump exponentially the higher on the scale I go? Everything's chill until about 2 o'clock then each click is an enormous increase in volume. Or is it my imagination?

Probably that's the reason.
 

tiramisu

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The A90 needs a Lexan clear top and the ability to mount it on the wall for display. At this point, the real differentiator is how pretty that fully balanced PCB is. I'm not even being sarcastic. My A50 is more than enough but the A90 is a work of art.
 

Acerun

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I don't know about you but clicks and ticks when you quickly increase the volume is a no thank you for me. Given that a used a90 is between 300 and $350 I'm not sure what the attraction is here
 

carlcamper

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I don't know about you but clicks and ticks when you quickly increase the volume is a no thank you for me. Given that a used a90 is between 300 and $350 I'm not sure what the attraction is here
Id rather have the slight ticks during volume changes with perfect volume matching than scratchy volume pots and channel imbalance that some A90 units can develop over time.
 
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