SMSL M500 DAC and HP Amp Review

[Shoaibexpert]

@Shoaibexpert
Could you please try this to check if you're having the same problem I had.
Disconnect the M500 from everything except power cord and headphones. Switch the M500 off to standby with the remote. Are you now hearing a hum in your phones?

Yes, just tried it. The hum is there even if i have nothing connected to the DAC except power...even through the DAC's own quarter inch output...just like its there with the AMP not connected to anything but power.

The only time i dont hear a hum (btw which comes and goes, its NOT a constant hum) is when i disconnect the power to both AMP and DAC...its strange!

 

[Shoaibexpert]

I'm confused. Can't you just buy the correct type power cables and eliminate all those white converter boxes? Surely there exist UAE power cables that can plug right into your devices?

I have those, I just wanted to plug my DAC and AMP to the first strip in a daisy chain of power strips to cater to all my electrical items under the hood...

 

[Veri]

Try to multi-quote few posts please, no need to post four times in a row this needlessly clutters up this thread.

 

[Oklei]

Yes, just tried it. The hum is there even if i have nothing connected to the DAC except power...even through the DAC's own quarter inch output...just like its there with the AMP not connected to anything but power.

This really looks like a problem that can be solved by grounding the system at one place. I did exactly this and the hum went away. I won't tell you how to ground it directly to power earth because if you electrocute yourself while doing this, you will haunt me in my dreams. And my dreams are already a nightmare. Don't you know someone who can help you with the grounding?

 

[Jimbob54]

Yes, just tried it. The hum is there even if i have nothing connected to the DAC except power...even through the DAC's own quarter inch output...just like its there with the AMP not connected to anything but power.

The only time i dont hear a hum (btw which comes and goes, its NOT a constant hum) is when i disconnect the power to both AMP and DAC...its strange!

Id be very worried if you heard a hum in headphones without the amp plugged in! But the EMI type whirring/ clicking I could see with nothing connected but wearing the HP.

 

[Jimbob54]

I have those, I just wanted to plug my DAC and AMP to the first strip in a daisy chain of power strips to cater to all my electrical items under the hood...

Take your M500, 789 and chromecast audio to another room with little / nothing else there. Definitely no power bricks or anything with a transformer Find a wall socket with nothing else in. First, plug in the M500 on its own, turn on, plug into HP socket and increase volume to low end of normal- hum? Try this directly into wall socket, not power strip

If yes, problems!

If no, connect 789 to power and to m500, plug HP into 789. Turn up volume on 789 Hum? If yes- problems!

If no, connect CCA to power and to M500 optical- repeat above.

You get the drift.

My suspicion is that rig in an electrically quiet room will be silent. Ruling out issues with your components but issues with how you have it all wired up in a cluttered room.

 

[Shoaibexpert]

Take your M500, 789 and chromecast audio to another room with little / nothing else there. Definitely no power bricks or anything with a transformer Find a wall socket with nothing else in. First, plug in the M500 on its own, turn on, plug into HP socket and increase volume to low end of normal- hum? Try this directly into wall socket, not power strip

If yes, problems!

If no, connect 789 to power and to m500, plug HP into 789. Turn up volume on 789 Hum? If yes- problems!

If no, connect CCA to power and to M500 optical- repeat above.

You get the drift.

My suspicion is that rig in an electrically quiet room will be silent. Ruling out issues with your components but issues with how you have it all wired up in a cluttered room.

Looks like this is the only option left coz nothing else works.

 

[Shoaibexpert]

This really looks like a problem that can be solved by grounding the system at one place. I did exactly this and the hum went away. I won't tell you how to ground it directly to power earth because if you electrocute yourself while doing this, you will haunt me in my dreams. And my dreams are already a nightmare. Don't you know someone who can help you with the grounding?

Nope. Have to see youtube and see if its doable myself... Thanks anyways

 

[Shoaibexpert]

Alright just to update, i took my THX 789 on a home tour. Turns out the same buzz is heard on all my home sockets. Could there be something wrong with the Amp power supply?

 

[Jimbob54]

1. If you plug the M500 into a wall socket without any adapters etc - and plug HP in, buzz? If your mains voltage is within parameters for the M500- (220-240 in UAE?) get a kettle cord or similar if not already using.
2. Any region adapter used when plugging the 789 PSU in? Im in the UK, 3 pin, cheap adapter to 2 pin, no issues. BUT the adapter is the weakest link in your chain. Let me dig out what I use and link it

 

[Shoaibexpert]

1. If you plug the M500 into a wall socket without any adapters etc - and plug HP in, buzz?

Yes in all cases...but much more pronounced with my higher impedence HD800S...and the mainly the noise is from the AMP...even when only connected to the mains in any room across the house. It becomes less noticeable ahen the amp in ON but is still very much heard...

BUT the adapter is the weakest link in your chain. Let me dig out what I use and link it

Sure, I would like to explore any options possible. I have already emailed THX and they say that replacing ths SMPS to a Linear and regulated PSU would solve the problem ... does it work like that?

 

[Jimbob54]

Yes in all cases...but much more pronounced with my higher impedence HD800S...and the mainly the noise is from the AMP...even when only connected to the mains in any room across the house. It becomes less noticeable ahen the amp in ON but is still very much heard...

Sure, I would like to explore any options possible. I have already emailed THX and they say that replacing ths SMPS to a Linear and regulated PSU would solve the problem ... does it work like that?

No, I mean the M500, connected to nothing but power and headphones. If this buzzes, its not your 789 power brick, is it?

I think you're saying the highest buzz is from the 789 into headphones? And it's the same buzz whether the M500 is there in the room and connected to 789 or unplugged and totally unconnected?

Edit, adapters I use for us plug to UK including 789 and geshelli amps, no issues
https://www.amazon.co.uk/Adapter-Vi...d=1597258075&sprefix=us+to+uk+,aps,168&sr=8-6

 

[Oklei]

Turns out the same buzz is heard on all my home sockets. Could there be something wrong with the Amp power supply?

Just another idea: Is your mobile phone always with you while you're testing? If I remember correctly there was something like that in this forum with a thx amp. Maybe you find that post via the forum search function. Anyway it might be a good idea to test if the buzz is still there when your phone is in another room.

 

[Shoaibexpert]

No, I mean the M500, connected to nothing but power and headphones. If this buzzes, its not your 789 power brick, is it?

Yes, tried that too. The Buzz from M500 headphone jack was not as loud as that from the AMP but was noticeable.

I think you're saying the highest buzz is from the 789 into headphones? And it's the same buzz whether the M500 is there in the room and connected to 789 or unplugged and totally unconnected?

Yes thats correct. I get the Buzz whether I am in any room using any socket to the AMP only. I moved the AMP alone around the house, same alternating buzzing sound comes...gets lower when i touch the AMP though!

Just another idea: Is your mobile phone always with you while you're testing? If I remember correctly there was something like that in this forum with a thx amp. Maybe you find that post via the forum search function. Anyway it might be a good idea to test if the buzz is still there when your phone is in another room.

Tried that too...As soon as i connect the power to the AMP, the buzzing starts, gets lower when i either touch the AMP by hand or turn the AMP ON...but still is very much noticeable. Could connecting the AMP RCAs (unused) to the TV's component in help ground things? Although i dont think its a grounding issue....as the AMP has a US style +/- 2 cables and no ground cable...nor does my M500...

Btw, I have another DAC (FiiO D07 TV DAC), totally unconnected from the THX/M500 Setup but connected to the same power strip...that too gives the same Buzz...seems any audio device connected to power is giving the same type of Buzz.

Its a god damn riddle i cant seem to solve with my level of knowledge...but my music listening sessions have stopped for now!

 

[icsi85]

Yes, tried that too. The Buzz from M500 headphone jack was not as loud as that from the AMP but was noticeable.

Yes thats correct. I get the Buzz whether I am in any room using any socket to the AMP only. I moved the AMP alone around the house, same alternating buzzing sound comes...gets lower when i touch the AMP though!

Tried that too...As soon as i connect the power to the AMP, the buzzing starts, gets lower when i either touch the AMP by hand or turn the AMP ON...but still is very much noticeable. Could connecting the AMP RCAs (unused) to the TV's component in help ground things? Although i dont think its a grounding issue....as the AMP has a US style +/- 2 cables and no ground cable...nor does my M500...

Btw, I have another DAC (FiiO D07 TV DAC), totally unconnected from the THX/M500 Setup but connected to the same power strip...that too gives the same Buzz...seems any audio device connected to power is giving the same type of Buzz.

Its a god damn riddle i cant seem to solve with my level of knowledge...but my music listening sessions have stopped for now!

I would turn of all the short circuit brake, just leave 1 room/outlet. And try like that.
If you cant find the problem, you can call your electric service provider. They need to look after it.

 

[Jimbob54]

Yes, tried that too. The Buzz from M500 headphone jack was not as loud as that from the AMP but was noticeable.

Yes thats correct. I get the Buzz whether I am in any room using any socket to the AMP only. I moved the AMP alone around the house, same alternating buzzing sound comes...gets lower when i touch the AMP though!

Tried that too...As soon as i connect the power to the AMP, the buzzing starts, gets lower when i either touch the AMP by hand or turn the AMP ON...but still is very much noticeable. Could connecting the AMP RCAs (unused) to the TV's component in help ground things? Although i dont think its a grounding issue....as the AMP has a US style +/- 2 cables and no ground cable...nor does my M500...

Btw, I have another DAC (FiiO D07 TV DAC), totally unconnected from the THX/M500 Setup but connected to the same power strip...that too gives the same Buzz...seems any audio device connected to power is giving the same type of Buzz.

Its a god damn riddle i cant seem to solve with my level of knowledge...but my music listening sessions have stopped for now!

Wow, again , Im no electrician, but if you are getting audible hum through headphones connected to both the 789 and M500 when those devices are plugged into the mains but not powered on the device, you have incredibly dirty power. Luckily both devices are pretty portable- so looks like they need to go on a tour around friends and family. That will at least tell you whether its specific to your home wiring or UAE mains in general.

I do know if I am in my car, have a DAP connected to the power socket but not playing, and I plug the car audio into the jack and have the car stereo on and turned up, thats noisy. But that stops when I play / turn on the DAP and the filtering must kick in

 

[Shoaibexpert]

I would turn of all the short circuit brake, just leave 1 room/outlet. And try like that.
If you cant find the problem, you can call your electric service provider. They need to look after it.

Yup...will need to do that Thanks

 

[Shoaibexpert]

Wow, again , Im no electrician, but if you are getting audible hum through headphones connected to both the 789 and M500 when those devices are plugged into the mains but not powered on the device, you have incredibly dirty power. Luckily both devices are pretty portable- so looks like they need to go on a tour around friends and family. That will at least tell you whether its specific to your home wiring or UAE mains in general.

I do know if I am in my car, have a DAP connected to the power socket but not playing, and I plug the car audio into the jack and have the car stereo on and turned up, thats noisy. But that stops when I play / turn on the DAP and the filtering must kick in

You are right. I am gonna be moving soon and hopefully these US spec plug and devices run fine down there...

 

[osasglo]

Anyone know how much SINAD and other measurements are affected by lowering output on the knob in pre-amp mode? If I used the preamp at 25 output level, would that greatly affect measurements?

 

[Jimbob54]

Anyone know how much SINAD and other measurements are affected by lowering output on the knob in pre-amp mode? If I used the preamp at 25 output level, would that greatly affect measurements?

In theory and practice, not a lot, but if youre going into a noisy amp you'll just be emphasising that noise as you'll be making it work harder.

Theres a few posts here and elsewhere (think Archimago has done something ) on digital volume in DACs. When we are talking about transparent kit such as this, I would do whatever works best for you for your use case.