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Topping A90 Headphone Amplifier Review

Mikechw

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My Topping A90 arrived yesterday.
I hooked it up from D90 -> A90 -> AHB2.
First impression is very clean sound.
May be too clear..
I think need some time to get used to..
 

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Atanasi

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Would A90 work with unbalanced inputs without grounding problems if I used RCA-XLR cables and lifted pin 1 with an adapter if necessary?
 

Veri

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Would A90 work with unbalanced inputs without grounding problems if I used RCA-XLR cables and lifted pin 1 with an adapter if necessary?
Situation dependent probably, but I used it this way with zero noise.
 

Mikechw

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The A90 unit runs a little warm... Almost same temperature as my D90..
 

SloPoke

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The A90 unit runs a little warm... Almost same temperature as my D90..
My A90 runs cool.

Does a forehead thermometer work to take the surface temp of an object?

With such an infrared thermometer I'm getting a 81.7 degree F temp from the top of the A90
 

YSC

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Better solution? Try packing that amount of power in the small box. Try 40W transformer, what's the size of it. Not even considering the heat.
Also considering that the noise is really faint. I have two A90 on the desk and I can't hear anything even in the night. I can only hear it when I put my ear up against the power supply section.
Ic, then it sounds reasonable, I just a bit surprised you didn’t make a larger box and make it a complete no compromise solution which even you sell at 10x the price there will be a market
 

JohnYang1997

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YSC

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yea I know the bryston and holo azure did not measure as well, but I am getting confused, you mentioned that you do noticed a noise at 10khz which didn't appear in the measurement here, was that something related to interference ? and for both holo and byrston I didn't notice to hear anything even at max volume in silence, so just wondering how prominent that noise in the power supply in A90 was
 

JohnYang1997

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yea I know the bryston and holo azure did not measure as well, but I am getting confused, you mentioned that you do noticed a noise at 10khz which didn't appear in the measurement here, was that something related to interference ? and for both holo and byrston I didn't notice to hear anything even at max volume in silence, so just wondering how prominent that noise in the power supply in A90 was
I linked these two as being good not bad.
The noise is physical noise not in the circuit.
 

YSC

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I linked these two as being good not bad.
The noise is physical noise not in the circuit.
I see than! if so despite your preference of small box, a big box solution like holo and bryston might made the ultimate amp in my book, and tbh I feel audiophiles don't mind traditional size as we usually own some sort of gear with that size in the first place
 

Atanasi

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How much is the power supply noise in dB at 1 m?
 

pplum

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Better solution? Try packing that amount of power in the small box. Try 40W transformer, what's the size of it. Not even considering the heat.
Also considering that the noise is really faint. I have two A90 on the desk and I can't hear anything even in the night. I can only hear it when I put my ear up against the power supply section.
Just bought an irm-20-15 module, the same as a90 used and found it's actually very quiet, only with some low frequency noise, maybe this 10k noise is from inductance on the pcb, or i just pick a good quality module.
 

Atanasi

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Is there any problem running A90 when there is no true ground connection, for example in a car where AC comes from a battery through an inverter?
 
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JohnYang1997

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Just bought an irm-20-15 module, the same as a90 used and found it's actually very quiet, only with some low frequency noise, maybe this 10k noise is from inductance on the pcb, or i just pick a good quality module.
Unit variation. Some modules have higher noise. The noise also usually gets eliminated/reduced after driving some load after turning on. But overall not an issue to consider. Irm-20-15 is not cheap itself let alone two of them.
 

Mikechw

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I suspect noise level of Topping D90 does rises vs temperature of unit.
I am stacking my A90 over D90 and after awhile, audio does seems not as clear and clean.
May be someone can measure noise level of D90 vs temperature.
Now I am stacking my AC Infinity fan under them to keep the units cool.
 

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JohnYang1997

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I suspect noise level of Topping D90 does rises vs temperature of unit.
I am stacking my A90 over D90 and after awhile, audio does seems not as clear and clean.
May be someone can measure noise level of D90 vs temperature.
Now I am stacking my AC Infinity fan under them to keep the units cool.
No, that doesn't happen...
Instead, quite the opposite, fan will introduce profound interference to the signal at hundred Hz range. Avoid.
 

Doodski

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Is there any problem running A90 when there is no true ground connection, for example in a car where AC comes from a battery through an inverter?
It should work fine. Although if there is a ground issue in the system the amplifiers will source ground through the RCA cable. I've seen it hundreds of times when I specialized in high end car audio gear repairs. Make sure the amp grounds are very good or you'll let out some smoke.
 
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