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Topping D90 Balanced USB DAC Review

Scintilla said:
I just received my D90 last evening and I also have hum from both channels when the unit is in standby. I will be tracing when I have some time.

This unit replaced an NAD M51, and I simply removed the NAD box and used the existing power cord and input and output cables previously connected to the NAD which exhibited no hum. I do believe the NAD has an output relay enabled in powered-on mode vs. standby. Perhaps this is the issue.
Click to expand...
The output analogue switch is always powered on regardless being on or standby. There shouldn't be any difference when it's in standby mode.
 
JohnYang1997 said:
Was the rca cable close to power chords? Maybe swap left and right cables?
Click to expand...
I think the amp is in cause.
I unplugged the RCA (so that no incoming signal) and it still didn't switch off.
I will check this issue this morning.
Thanks for your concern and sorry for pointing out the Topping.

PS- The power cords are all shielded.
 
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Seems like my issue is the same. When I removed xlr's from the Krell, the ground loop appeared only when the right channel xlr was plugged in, absent the left channel cable. Trading the right xlr cables still induced some hum although less from the left channel with the right channel cable. So, it appears that it is induced by the right channel cable or there is a ground fault in the right channel of the amplifier. This unit has tripped ground fault breakers too and I suspect it may have a fault internally on that channel if the cable is not to blame. Will check with another xlr cable. It is curious why the NAD didn't haver the problem, but it doesn't appear to be the fault of the D90 in any case. It appears that the right channle is susceptible to induced hum from input cable susceptibility to stray power fields. I will try shielded cables.

Also like to add that this is a really good product. It definitely meets and probably exceeds the NAD M51 for SQ and feels like an upgrade with HQPlayer providing DSD 128x with ASDM7EC and Sinc-M in DSD direct. It is so clean and I am really happy with it so far.
 
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As indicated, I think it's my amp.
I just opened it, introduced some fresh air as it hasn't been opened since over a decade or so and I think the relay works again.

Try to isolate your components and find the faulty one.
Doubtful that it's the D90 to be the cause as JohnYang indicated. Schnell RCA Right (6).jpg
 
Anyone know the max voltage out at highest volume level of the D90 in balanced mode - is it 4v?
 
I verified that the cause of the hum was an unshielded XLR cable from the D90 to my amplifier in the presence of AC fields. With a shielded interconnect, the D90 was silent into the amplifier in standby. I will be replacing my aging balanced cables with some new ones that are shielded. I am really enjoying the D90. It has been a clear step up from my NAD M51, especially in clarity. I can now understand some spoken parts and lyrics that I could not before because the voices are more readily understandable and delineated from the music. Pretty nifty. This thing is a bargain.
 
@Scintilla
My mono's are OK and both trigger on and off :) and just RCA. My 2 other mono's are XLR - but they are actually unbalanced. A modified RCA >> XLR and even their cabling is not standard, so that I'm now careful to connect these, though I was using all 4 of them to bi-amp passively.

Unshielded XLR ? Does that exist ?

About your D90 : Are you running it as DAC (fixed output) or as Preamp (variable output) ?
 
Goertz tourmaline XLR cables are unshielded. I am running in DAC mode using HQPlayer and Purevinyl for volume. I currently use the rca outputs for my subwoofer and have an RC convolution filter built in Acourate that equalizes the voltage difference in outputs by adjusting amplitude over the frequency range covered by my main speakers. I will probably add a splitter for each channel and do XLR-->rca for the subwoofer when I get new speakers in house next month. For now the system is working and I have no desire to break out measurement gear and do sweeps again. Might as well wait until I have new speakers to measure.
 
Veri said:
Worse still, there's an entire brand devoted to making unshielded cables and pushing them for professional use.
For optimal audiophile sound you know. Shielded cables sound so edgy and veiled :facepalm::facepalm::facepalm:. sigh
Click to expand...

Well, if they are unshielded then at the very least the braiding should be very very tight and good. The resulting cable will have less pole to pole capacitance and therefore less roll off at very high frequency – but would be audible only at ludicrous lengths... so.... no, useless exercise.
 
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