Topping A90 Headphone Amplifier Review

[Veri]

As far as I understand D90 based on AKM 4499 and D70S on AKM 4497. Is there any valuable difference between those chips ?

AK4499 has more maximum potentional comparing both specs, but D70s squeezed everything out of AK4497, more than any other product accomplished so far. So D70s is definitely up there in terms of performance. Absolutely perfect multitone.

 

[Rantenti]

Since I got some EMI probably due to ground loops when using the A90, I am trying to diagnose where the ground loop is.

I placed my hand on my equipment and disconnected the printer, LED screen and active speakers, the buzz persists in my IEMs. I turned OFF the DAC while keeping the headphone amp on, the buzz got softer but it was same kind of buzz which varies with GPU workload.

The buzz disappears when I do any one of these things:
1. unplug the USB cable from the DAC.
2. shut down the headphone amp.
3. shut down the computer mains

What should I do further to ascertain whether the ground loop is at the USB or at the power supply of the A90 or the computer? Thanks.

 

[foxxx0]

Since I got some EMI probably due to ground loops when using the A90, I am trying to diagnose where the ground loop is.

I placed my hand on my equipment and disconnected the printer, LED screen and active speakers, the buzz persists in my IEMs. I turned OFF the DAC while keeping the headphone amp on, the buzz got softer but it was same kind of buzz which varies with GPU workload.

The buzz disappears when I do any one of these things:
1. unplug the USB cable from the DAC.
2. shut down the headphone amp.
3. shut down the computer mains

What should I do further to ascertain whether the ground loop is at the USB or at the power supply of the A90 or the computer? Thanks.

Try a galvanically decoupled connection from your PC to the DAC, e.g. by using optical toslink spdif connection. That should prevent any interference or ground loop (PSU, USB, GPU, CPU, ...) from reaching your DAC since the digital audio signal is transmitted optically.

If that resolves your issues but you want to switch back to USB connection for higher bandwidth / DSD / whatever, you might give these usb ifi defender / ground-decouplers a try, combined with an external 5V power supply (e.g. phone charger for some first tests).
These use a transformer-like connection for ground/5V-USB and thus can help resolve ground loops but are in turn highly restricted in current delivery, hence the need for an external 5V power supply, at least for USB bus-powered consumer devices.
If your DAC has already an external/internal PSU supplied with it, that might suffice because the USB connection is likely used for data transmission only and not current.

 

[Rantenti]

Thank you for suggesting going optical to decouple the PC/ DAC electrical connection!
Now I'll know whether I need an iDefender or a GND defender.
Thanks again.

 

[hmscott]

Since I got some EMI probably due to ground loops when using the A90, I am trying to diagnose where the ground loop is.

I placed my hand on my equipment and disconnected the printer, LED screen and active speakers, the buzz persists in my IEMs. I turned OFF the DAC while keeping the headphone amp on, the buzz got softer but it was same kind of buzz which varies with GPU workload.

The buzz disappears when I do any one of these things:
1. unplug the USB cable from the DAC.
2. shut down the headphone amp.
3. shut down the computer mains

What should I do further to ascertain whether the ground loop is at the USB or at the power supply of the A90 or the computer? Thanks.

Thank you for suggesting going optical to decouple the PC/ DAC electrical connection!
Now I'll know whether I need an iDefender or a GND defender.
Thanks again.

I've used the ifi iDefender + Mogami shielded XLR / RCA cables (WBC cables) successfully to stop the GPU / PC noise carried on the USB power wires, and most of the incidental ground loop noise. ifi asked me to try the iSilencer in series, it's subtle, but it also helps if used in series with the iDefender - yeah, I know.

I've made further isolation and noise reduction running disconnected from the AC mains with the D90 MQA + Xduoo TA-20 / A90 plugged in to a pure sine wave 110VAC inverter / battery + iDefender + iSilencer at the PC USB-A port:

Spoiler: Portable Power Station 252.7Wh Power House - Model: RP-PB187

Portable Power Station 252.7Wh Power House - Model: RP-PB187
https://www.ravpower.com/products/rp-pb187-portable-power-station

The Ravpower RP-PB187 runs 2 of my D90/A90/TA-20 units paired up DAC/AMP for up to 10 hours - varies with audio listening use, or I can run them indefinitely with a passthrough charge from the included AC adapter (2 prong - no ground wire) *or* charging via an up to 60W PD charger throught the the RP-PB187 USB-C PD port - which allows passthrough charging via the USB-C port, as well as delivering PD60W output from that port.

I picked this Ravpower device over others due to the $159 price + pure sine-wave output - vs others in the price range with modified square-wave AC. Ravpower frequently emails site wide and specific product discounts via their newsletter bringing the price down as low as $159 recently - currently at $179 on Amazon / $189 on RAVpower.com. I signed up for their newsletter and waited for about a month for a specific RP-PB187 discount - $80 off = $169. Ravpower increased the discount by $10 just after I purchased, and Ravpower when asked refunded me that additional $10! Very nice people to work with.

It requires some user monitoring to make sure it keeps charging while varying your use. For example if it "catches up" and becomes fully charged it can stop charging and not resume charging after the battery runs down a bit. This can happen when I stop listening for a while without turning off the AC inverter. Minor grump, but it's a lapse in user friendly automated management - you need to monitor manually. The result is after 10+ hours it may run out of power while in use, and you then need to recharge it with the AC inverter disabled for a short while before using it with the DAC/AMP - or plug them back into AC power temporarily.

Other than that if works great for breaking ground loops when used with the iDefender+iSilencer. Oh, and you'll want to get 2 "cheater adapters" as the RP-PB187 doesn't include a ground pin hole for the AC 2 prong sockets:

Commercial Electric 15 Amp Single Outlet Grounding Adapter, Gray Model # U-09 Store SKU # 224676
https://www.homedepot.com/p/Commerc...-Outlet-Grounding-Adapter-Gray-U-09/203456716

YMMV, and if you use those "cheater" plugs with AC directly, be careful! - I don't use them that way at all!! - really!

Here is a Hobotech review of the Ravpower RP-PB187

Also, use careful cable + device management to make sure you aren't connecting cables from grounded devices with your RCA / XLR / power cables / device cases connected to the floating ground of the RP-PB187. Don't cross the streams!

And, keep the A90 / D90 away from your PC / Wifi router / Cell booster / etc to reduce EMI / RFI as another potential noise source.

Good luck

 

[Atanasi]

Oh, and you'll want to get 2 "cheater adapters" as the RP-PB187 doesn't include a ground pin hole for the AC 2 prong sockets

I am not sure if omitting the ground wire would affect the performance or safety of A90. There is a way to wire a grounded plug with an inverter, but the details should be checked. Isolated systems like car electricity use it.

 

[instinctafk]

I have a question with the A90 + D90 stack.

If I connect both together with XLR (balanced), can I still connect RCA (unbalanced) powered speakers to the back of the A90 and use the pre-amp switch? From what I understand, the source is balanced and the connection to the amp is balanced, so this would not work since my speakers are unbalanced? (or at least not be ideal and could damage the amp/dac?)

The goal is to use the pre-amp switch to switch between my balanced headphones and powered unbalanced speakers without having to unplug anything. Also ideally, sound is not playing in both speakers and headphones at the same time.

 

[GeorgeWalk]

I have a question with the A90 + D90 stack.

If I connect both together with XLR (balanced), can I still connect RCA (unbalanced) powered speakers to the back of the A90 and use the pre-amp switch? From what I understand, the source is balanced and the connection to the amp is balanced, so this would not work since my speakers are unbalanced? (or at least not be ideal and could damage the amp/dac?)

The goal is to use the pre-amp switch to switch between my balanced headphones and powered unbalanced speakers without having to unplug anything. Also ideally, sound is not playing in both speakers and headphones at the same time.

Yes, you can. That is how I have my D90/A90 stack connected. I am driving a pair of Bose Desktop speakers from the RCA output on the A90.

 

[instinctafk]

Yes, you can. That is how I have my D90/A90 stack connected. I am driving a pair of Bose Desktop speakers from the RCA output on the A90.

Awesome thanks!

Did you have to connect both RCA and XLR cables between the A90 and D90? And then switch the Pre-Amp switch AND the Input switch from XLR to RCA to switch to speakers? (Assuming your headphones are balanced)

 

[GeorgeWalk]

No. Mac->USB->D90->XLR->A90-> RCA -> Bose. I also use headphones. On the A90 just switch the front panel selector between pre and hpa for speakers or headphonse. Leave the input set to XLR. My headphones are not balanced.

 

[AdamG]

Awesome thanks!

Did you have to connect both RCA and XLR cables between the A90 and D90? And then switch the Pre-Amp switch AND the Input switch from XLR to RCA to switch to speakers? (Assuming your headphones are balanced)

Welcome Aboard @instinctafk.

 

[Rantenti]

I've used the ifi iDefender + Mogami shielded XLR / RCA cables (WBC cables) successfully to stop the GPU / PC noise carried on the USB power wires, and most of the incidental ground loop noise. ifi asked me to try the iSilencer in series, it's subtle, but it also helps if used in series with the iDefender - yeah, I know.

I've made further isolation and noise reduction running disconnected from the AC mains with the D90 MQA + Xduoo TA-20 / A90 plugged in to a pure sine wave 110VAC inverter / battery + iDefender + iSilencer at the PC USB-A port:

Spoiler: Portable Power Station 252.7Wh Power House - Model: RP-PB187

Portable Power Station 252.7Wh Power House - Model: RP-PB187
https://www.ravpower.com/products/rp-pb187-portable-power-station

The Ravpower RP-PB187 runs 2 of my D90/A90/TA-20 units paired up DAC/AMP for up to 10 hours - varies with audio listening use, or I can run them indefinitely with a passthrough charge from the included AC adapter (2 prong - no ground wire) *or* charging via an up to 60W PD charger throught the the RP-PB187 USB-C PD port - which allows passthrough charging via the USB-C port, as well as delivering PD60W output from that port.

I picked this Ravpower device over others due to the $159 price + pure sine-wave output - vs others in the price range with modified square-wave AC. Ravpower frequently emails site wide and specific product discounts via their newsletter bringing the price down as low as $159 recently - currently at $179 on Amazon / $189 on RAVpower.com. I signed up for their newsletter and waited for about a month for a specific RP-PB187 discount - $80 off = $169. Ravpower increased the discount by $10 just after I purchased, and Ravpower when asked refunded me that additional $10! Very nice people to work with.

It requires some user monitoring to make sure it keeps charging while varying your use. For example if it "catches up" and becomes fully charged it can stop charging and not resume charging after the battery runs down a bit. This can happen when I stop listening for a while without turning off the AC inverter. Minor grump, but it's a lapse in user friendly automated management - you need to monitor manually. The result is after 10+ hours it may run out of power while in use, and you then need to recharge it with the AC inverter disabled for a short while before using it with the DAC/AMP - or plug them back into AC power temporarily.

Other than that if works great for breaking ground loops when used with the iDefender+iSilencer. Oh, and you'll want to get 2 "cheater adapters" as the RP-PB187 doesn't include a ground pin hole for the AC 2 prong sockets:

Commercial Electric 15 Amp Single Outlet Grounding Adapter, Gray Model # U-09 Store SKU # 224676
https://www.homedepot.com/p/Commerc...-Outlet-Grounding-Adapter-Gray-U-09/203456716

YMMV, and if you use those "cheater" plugs with AC directly, be careful! - I don't use them that way at all!! - really!

Here is a Hobotech review of the Ravpower RP-PB187

Also, use careful cable + device management to make sure you aren't paralleling power cables with your RCA / XLR / power cables / device cases.

And, keep the A90 / D90 away from your PC / Wifi router / Cell booster / etc to reduce EMI / RFI as another potential noise source.

Good luck

Thanks for the suggestion about the power bank! I'll definitely look into it. There's so much to learn from you guys!

May I also ask, if I change the three-pronged UK plug AC power cords of my DAC and A90 to 2-pronged AC power cords, while keep using a 3-prong UK plug for my PC (connected via USB +/- iDefender to DAC) and plugging all these into one AC power strip, so that there is only ONE ground left in the whole connected chain, is this move essentially the same as "lifting the ground" or "ground cheating"? Is it dangerous like I'll get an electric shock or burn up my DAC/ headamp?

Thanks!

 

[Atanasi]

May I also ask, if I change the three-pronged UK plug AC power cords of my DAC and A90 to 2-pronged AC power cords, while keep using a 3-prong UK plug for my PC (connected via USB +/- iDefender to DAC) and plugging all these into one AC power strip, so that there is only ONE ground left in the whole connected chain, is this move essentially the same as "lifting the ground" or "ground cheating"? Is it dangerous like I'll get an electric shock or burn up my DAC/ headamp?

This is unsafe, because if there are currents to ground, they would flow through audio and data cables instead of power cords, which are designed for safety ground. For example, high currents would burn audio cables in cases where power cords are safe.

 

[Rantenti]

This is unsafe, because if there are currents to ground, they would flow through audio and data cables instead of power cords, which are designed for safety ground. For example, high currents would burn audio cables in cases where power cords are safe.

Thank you very much!
Safety is paramount. Everything else comes second.

 

[hmscott]

Thanks for the suggestion about the power bank! I'll definitely look into it. There's so much to learn from you guys!

May I also ask, if I change the three-pronged UK plug AC power cords of my DAC and A90 to 2-pronged AC power cords, while keep using a 3-prong UK plug for my PC (connected via USB +/- iDefender to DAC) and plugging all these into one AC power strip, so that there is only ONE ground left in the whole connected chain, is this move essentially the same as "lifting the ground" or "ground cheating"? Is it dangerous like I'll get an electric shock or burn up my DAC/ headamp?

Thanks!

I am not sure if omitting the ground wire would affect the performance or safety of A90. There is a way to wire a grounded plug with an inverter, but the details should be checked. Isolated systems like car electricity use it.

There is no ground for a portable battery bank inverter. They usually have a "hole" to contain the ground pin, but the Ravpower RP-PB187 doesn't have that accomodation.

I'm also blocking the power from the PC USB-A connection to the D90 via the ifi iDefender. AFAIK I don't have any paths to ground, including the 2 prong Ravpower RP-PC144 PD charger or my 2 prong Samsung 25w PD charger, or the included 2 prong charger for the RP-PB187 - none of the devices in the chain have a ground connection/path.

When I use the RP-PB187 off AC mains - AC charger disconnected - it supplies 10+ hours of listening time with both the D90 MQA and TA-20 powering my headphones.

There are large system battery backups with a designed-in grounding system - like the "BLUETTI EP500 Pro" (more info below) for fixed installations - meant to use a ground bar and physical earthing, and for RV/Cars where they use the chassis as the ground, but not for portable devices like the RP-PB187.

I don't use the cheater plugs with an AC power strip, and I don't recommend anyone else does that either. Be safe, and sound!!

FYI - BETTER Solar Generator Than JACKERY? Ravpower 252wh Portable Power Station Review

BTW, I've been watching these PowerBen devices which are pretty awesome too, much more expensive as configured for this audio application, but can be used with their optional power inverter(s) - I'm thinking of getting some for portable / bench use:

Spoiler: PowerBen options, I'm looking at Workbench / Team options + extra 1500w inverter

https://www.indiegogo.com/projects/powerben-world-s-first-pd200w-input-powerbank--2/x/23504862

Power Ben - MODULAR Programmable DUAL 100w USB Power! 360w PowerBen MPPT Solar Power Bank Review

The new EP500/Pro from Bluetti has AC sockets for AC connectors with "ground" prongs, and the ability to connect two units through their "Fusion Box" (with 120v/240v US) to your "Fusebox" and earthling ground bar, to provide UPS service for Home Power Backup:

Spoiler: Dual EP500/Pro + Fusion Box = Home Power Backup

https://www.bluetti.com/pages/ep500-p

BLUETTI EP500 & EP500Pro - The New Era of Home Backup Power
5100Wh LiFePO4 /1200W or 2400W MPPT Solar /Seamless UPS /240V Split Phase /6000+ Cycles /App & OTA Upgrade /100W USB-C /Charge Tesla

BLUETTI EP500 5120wh LiFePO4 UPS BACKUP Off Grid Solar Generator Kickstarter Review

Educate yourself before getting into trouble! If you aren't sure what you are doing, please find a trained Electrician or Technician, or EL / EE Engineer that can help you "hands-on" in person and/or can set it up for you safely. It can be easy to "mess up", or worse, get it set up professionally, and down the road "hook up" something else yourself and get into trouble. Please be safe!!

 

[gpardede]

Hi all, first-time poster here but have been a reader since a couple of years ago. The reason I'm posting is that my A90 suddenly went dead on the left channel this morning. Also if no music is on and I turn the volume knob I can hear a distortion/crackle on the left channel. This only happens when I have the RCA line-in though, the music from the XLR line-in can be heard from both channels but the sound quality has deteriorated quite a bit on both channels even on XLR input.

The above is the same if I used the single-ended or the balanced 4.4 output. I haven't tried the XLR output. Has anyone experienced the same issue?

I live in Indonesia and have emailed Topping's service email. I bought it from an Indonesian seller, he is trying to check with Topping as well he said. Fingers crossed.

DAC is D90 and I'm using a regular power socket. Never had this issue with the other electronics I have in the house.

Thanks for any help!

 

[Veri]

I live in Indonesia and have emailed Topping's service email. I bought it from an Indonesian seller, he is trying to check with Topping as well he said. Fingers crossed.

DAC is D90 and I'm using a regular power socket. Never had this issue with the other electronics I have in the house.

Thanks for any help!

How long did you own it? Looks like your unit just died.. I'm sure your reseller/customer support will help you out.

 

[gpardede]

How long did you own it? Looks like your unit just died.. I'm sure your reseller/customer support will help you out.

Hi - I bought it just this January 2021 so fairly new. I may have left it on for a long period +- 6 hours.

Yes, I'm hoping he can help me out.

 

[bahamot]

Hi - I bought it just this January 2021 so fairly new. I may have left it on for a long period +- 6 hours.

Yes, I'm hoping he can help me out.

If you bought from CSI (CASEI), I'm sure they'll honour the warranty as long as they can replicate the issue (which mean you are covered).
Usually they (CSI) will ask to send the item back to them and they will try to replicate the issue. If they can replicate it, they will RMA the item. After it gets back, you will need to pay some fee before they send the item back to you.

 

[gpardede]

If you bought from CSI (CASEI), I'm sure they'll honour the warranty as long as they can replicate the issue (which mean you are covered).
Usually they (CSI) will ask to send the item back to them and they will try to replicate the issue. If they can replicate it, they will RMA the item. After it gets back, you will need to pay some fee before they send the item back to you.

Hi - thanks for this info. Is CSI an authorized Indonesian distributor?

Unfortunately no. I bought it from an individual seller on one of Indonesia's online marketplace. It seems my seller bought it directly from a Chinese reseller online and was able to ship it to Indonesia with a lower customs cost (compared to if I buy directly from shenzenaudio.com for example).