[TonyRoma]

Hi all, bit of a newcomer to this amp, i currently have a Bryston BHA-1 with HD800s, just wondering if the M9 would be a step up rather than sideways soundwise, cheers.

 

[Ergoforce]

Hi,
 
I wonder if someone has tried connecting Etymotic ER-4PT, ER-4S or ER4SR to M9? 
 
I hear low humming noise when I connect these. The noise is louder with ER-4P than with ER4SR. 
 
I don't hear any noise when I connect HD650 or HD800 single end.
 
Could it be due to the lower impedance on Etymotic in-ear phones or is it something wrong with my M9?
 
No matter what, it's annoying as the subtle piano play, pp or ppp gets disturbed.

 

[mtoc]

The amp in the M11 ain't no the same as M9. 
 
for exmp, output transistors
 
M11: 8
M9 : 12
 
Different number

 

[PeterCraig]

Could it be due to the lower impedance on Etymotic in-ear phones or is it something wrong with my M9?

Most likely it's not due to your IEM or the M9.

The noise is probably coming from your upstream source and the M9 is just amplifying it.

You can't hear it on the higher impedance headphones but it may be there also. Stop the music and crank the volume on the HD800 and see if you can detect the noise.

Try another source if you are able and you may find the sound is gone (or it may be even louder).

 

[Ergoforce]

Most likely it's not due to your IEM or the M9.

The noise is probably coming from your upstream source and the M9 is just amplifying it.

You can't hear it on the higher impedance headphones but it may be there also. Stop the music and crank the volume on the HD800 and see if you can detect the noise.

Try another source if you are able and you may find the sound is gone (or it may be even louder).

Hi and thanks for your suggestions, I have tried it and some more:
 
Neither HD650 nor HD800 causes noise even with volume maxed out on M9. With Etymotics however, the noise is present and constant regardless of volume level and also when all the analog inputs are shorted. So I'd say it is a ground loop problem within M9 for the single end jack. If I use the ER-4PT conversion cable ( -> raises the resistance as  far as I know), the humming ( = 100 Hz) gets lower in volume.
 
As I open M9, I see the output cables are relayed from the balanced XLR jacks to to the single ended jack and that short cabling is not shielded nor twisted. I wonder if this ground loop hum is picked up from the tranformer(s) nearby.

 

[PeterCraig]

So I'd say it is a ground loop problem within M9 for the single end jack.

Are you able to try operating the amp with the ground lifted in your power cable? That will help narrow down the problem a little further. I'm in a building without ground and have operated all my gear with a lifted ground because it always introduced some sort of noise problem.

 

[Ergoforce]

Are you able to try operating the amp with the ground lifted in your power cable? That will help narrow down the problem a little further. I'm in a building without ground and have operated all my gear with a lifted ground because it always introduced some sort of noise problem.

Yes, I tried that too. HE-350 also have a ground lift switch, which also didn't make any difference.
 
Is it time to contact Audio-gd?

 

[PeterCraig]

Yes, I tried that too. HE-350 also have a ground lift switch, which also didn't make any difference.

Is it time to contact Audio-gd?

Well you certainly have done your trouble shooting. I'm pretty confident it's not a M9 design issue so I wouldn't suggest that to Kingwa But AG will likely have some suggestions as to what the issue may be.

 

[Ergoforce]

Well you certainly have done your trouble shooting. I'm pretty confident it's not a M9 design issue so I wouldn't suggest that to Kingwa

But AG will likely have some suggestions as to what the issue may be.

It could be assembly/wiring issue with my M9. As the hum exists even when only M9 is switched on, all analog inputs are shorted and volume set to zero. Maybe I should inspect how wiring goes from XLR jacks to 1/4" jack and how chassis- and signal ground are connected.

But first I will wait for reply from Audio-gd. I wonder what S/N is supposed to be for single end as specification only shows for XLR with "input short". With Etymotic ER4* on my M9, S/N is barely 90 dB or less.

 

[Sabenza]

Hi guys.  When I adjust the volume knob on my Master 9,  I heard popping noises through the headphone (I'm not referring to the deliberate "clicking" sound made by volume adjusting mechanism).  Does anyone have similar experience or is my volume adjuster faulty?  I am using Audirvana + ==> Hugo TT ==> Master 9 ==> LCD-4/Abyss

 

[Articnoise]

  Hi guys.  When I adjust the volume knob on my Master 9,  I heard popping noises through the headphone (I'm not referring to the deliberate "clicking" sound made by volume adjusting mechanism).  Does anyone have similar experience or is my volume adjuster faulty?  I am using Audirvana + ==> Hugo TT ==> Master 9 ==> LCD-4/Abyss

 

Very nice gear you have!

 

A minor poping sound is “normal” with this type of volume pot.  M9 use a step attenuator volume pot and the pop comes from changing from one contact surface to another, mechanically. 

 

[Articnoise]

  Yes, I tried that too. HE-350 also have a ground lift switch, which also didn't make any difference.
 
Is it time to contact Audio-gd?

 

I’m very interested in your thought about HE-350.

 

Do you turn it on/off every day?

 

Does it get very hot, like the M9?

 

And how is the SQ difference to other regenerator or power conditioner you may have tried?

 

[Sabenza]

Articnoise, thanks for sharing your knowledge and experience and I feel much better after knowing this is normal.  The amp is 9 months old and I live in a very humid area so I was a bit concerned that something went wrong due to the humidity.

 

[Ergoforce]

 

It could be assembly/wiring issue with my M9. As the hum exists even when only M9 is switched on, all analog inputs are shorted and volume set to zero. Maybe I should inspect how wiring goes from XLR jacks to 1/4" jack and how chassis- and signal ground are connected.

But first I will wait for reply from Audio-gd. I wonder what S/N is supposed to be for single end as specification only shows for XLR with "input short". With Etymotic ER4* on my M9, S/N is barely 90 dB or less.

I got an answer back from Kingwa. I quote:
 
"Audio-gd headamp product models had high power output and high gain, they are not suited in ear headphones.
Kingwa"
 
A disappointing answer. During the years, I have tried around 10-15 different high-end headphone amplifiers. None of them had problems with hum noise using ER-4*.
 
So it is by design that low impedance headphones (even as high as 100 Ohm), will generate hum noise on M9 if connected single end.
 
I wonder if the hum noise also would be present for Sennheihser HD700 with impedance of 150 ohm. My guess is it would be audible.

 

[Ergoforce]

   

I’m very interested in your thought about HE-350.

 

Do you turn it on/off every day?

 

Does it get very hot, like the M9?

 

And how is the SQ difference to other regenerator or power conditioner you may have tried?

 
HE-350 gets much hotter. You can keep your hand on M9 indefinitely. With HE-350 you cannot. The temperature gets above 60 C / 140 F in my configuration (room temperature of 25-27 C / 77-80.6 F).
 
I turn it on few hours before I start to listen then turns it off during night. My gear sounds at it's best after at least 4 hours of warming up.
 
This is the only regenerator I've tried. I've used passive power filters before.