[denjo]

Hi Dusty
After a late night listening session, I had my ear very near the D200 monos which I leave on 24/7, and heard a slight humming sound coming from the pair. I wonder if this is normal or should the monos be dead quiet. My preamp was on but the "mute" button was activated so I don't think it could have been the preamp. I would appreciate your advice please!

Merry Christmas!

Best Regards
Dennis

[DaveX]

Hello denjo, when I first had my D200's the hum was very very obvious at times. Now that I have had them a while, most of the time there is only a slight hum from my D200's, however, the hum can be louder for a few minutes at certain times of the day but I notice it much less these days. Cheers.

[denjo]

Hi Dave

Thanks for your response. The problem of hum is like one dead pixel on a 19 inch computer monitor! If you don't pay attention to it, the "problem" hardly draws any attention. Trouble is, now that I know the hum is there, I tend to focus on that "detail" and ignore the other 99% that is just perfect! I am sure there must be a reasonable explanation and a simple solution to the "hum". I have since read up a bit about toroidal transformers and it seems ALL toroids manifest hum to a lesser or greater degree.
As for your observation, it seems that what you are saying is that the audibility of the hum fluctuates with the time of the day/night. The other possibility is that with time we can become more immune and less affected by the hum, sort of become conditioned to the situation. I will try to get to the bottom of this and, hopefully, I will be able to solve the problem which I will be happy to share with you and others.

Best Regards
Dennis

[CIAudio]

A very slight hum is normal if you have your ear next to the chassis or vents. If you hear it from further away, my guess is you have some small DC on your AC line.
This is the most common cause of mechanical hum although other things can also cause it.

We will soon be releasing an AC enhancement filter (XDC•2/$299), which will block DC.
It's a small box with a single IEC inlet on the rear and duplex AC outlet on the front, and will have two individually fused 120v/7.5A circuits (or 240v/4.0A). This will easily accommodate a pair of D•100 or D•200 amplifiers.

[denjo]

Hi Dusty
Thanks for the info and the announcement of a new DC buster. I am using the Hydra-6 and am quite surprised that the Hydras do not seem to eliminate DC, notwithstanding their Trident defense system! Can your new XDC*2 piggy back the Hydras or would you suggest using the XDC*2 as a standalone? Lastly, when can we expect release of the unit?

Best Regards
Dennis

[CIAudio]

I don't think the Shunyata has any DC blocking...you could use the XDC•2 connected to one of it's outputs, or stand-alone. XDC•2 should be available in a couple of weeks.

[denjo]

Thanks Dusty! Look forward to more news of the XDC*2 by and by!

DaveX: I have also observed that the loudness of the hum varies with the time of day!

Best Regards
Dennis

[denjo]

And, one other thing which might significantly contribute to the hum ... in Singapore which uses 230v the right pin is live and the left is neutral. As I understand, in the US it is the reverse - left is live and right is neutral. My power cord is most likely configured for the US voltage system and this polarity mismatch may explain the hum I'm hearing.

While I would consider investing in a DC buster (like the XDC*2) if this would cure the hum problem, I am naturally concerned about what minuses such a device would have to the wondrous sound of the D200s. I have read from some that their experience of a DC buster was some compromise to the midrange.

Best Regards
Dennis

DaveX: Since the UK uses 230v too, I was wondering what kind of power cords you are using with your D200s and whether you have tried the monos with a UK terminated power cord?

[CIAudio]

And, one other thing which might significantly contribute to the hum ... in Singapore which uses 230v the right pin is live and the left is neutral. As I understand, in the US it is the reverse - left is live and right is neutral. My power cord is most likely configured for the US voltage system and this polarity mismatch may explain the hum I'm hearing.

Reversing polarity will most likely have no affect on mechanical hum.

While I would consider investing in a DC buster (like the XDC*2) if this would cure the hum problem, I am naturally concerned about what minuses such a device would have to the wondrous sound of the D200s. I have read from some that their experience of a DC buster was some compromise to the midrange.

A properly designed DC blocking device will actually improve sound quality by improving the transformers efficiency. Some devices will raise the line impedance enough to hurt dynamics in high-current drawing amplifiers. Due to their efficiency, most Class D amplifiers are insensitive to the line impedance issue.

In addition to this, XDC-2 has about half the impedance of traditional devices and uses two separate circuits (rather than sharing one for two channels) and works well with any amplifier that is within it's current limits.

[denjo]

Hi Dusty
One more query if I may: can the XDC*2 be placed before my Hydra instead of after it? If it can, I can use the XDC*2 outlet to feed both a Hydra and a Power Wedge. I have heard that the elimination of DC enhances picture quality of TVs. Needless to say, I am aware that I should not overload the XDC*2 and ensure I operate it within the power capability.

Best Regards
Dennis

[CIAudio]

One more query if I may: can the XDC*2 be placed before my Hydra instead of after it? If it can, I can use the XDC*2 outlet to feed both a Hydra and a Power Wedge. I have heard that the elimination of DC enhances picture quality of TVs. Needless to say, I am aware that I should not overload the XDC*2 and ensure I operate it within the power capability.

I would recommend using it after the Hydra so you can still use the separate outlets for each amp. You could also try it for your TV and get a second one if it proves effective there.

[denjo]

Hi Dusty

You wrote earlier that "(a) very slight hum is normal if you have your ear next to the chassis or vents. If you hear it from further away, my guess is you have some small DC on your AC line."

With the XDC*2 in place feeding the D*200s, would DC induced hum be entirely eradicated by the conditioner? It should right?  So, if I still hear hum from the D*200s, then it cannot be the DC in the AC that is the culprit and that the cause must be attributed to something else ...

I have already placed my order with Steve and am looking forward to its arrival!  aa

Best Regards
Dennis

[CIAudio]

You wrote earlier that "(a) very slight hum is normal if you have your ear next to the chassis or vents. If you hear it from further away, my guess is you have some small DC on your AC line."

With the XDC*2 in place feeding the D*200s, would DC induced hum be entirely eradicated by the conditioner? It should right?   So, if I still hear hum from the D*200s, then it cannot be the DC in the AC that is the culprit and that the cause must be attributed to something else ...

I have already placed my order with Steve and am looking forward to its arrival! 

XDC-2 will eliminate all DC induced hum, which is usually the cause. All transformers hum to a certain degree in normal operation (with no DC), but is usually only heard with your ear against the chassis...DC induced hum can sometimes be heard several feet away, and be distracting when listening to music.

[denjo]

Dusty

Thanks for the prompt reply.
Comprehendo ...

Best regards
Dennis