[HAL]

One interesting experiment would be to put the XDC2 at the output of a PS Audio PPP.  This should give a low distortion sinewave output and remove any DC on the line.  The new PS Audio Humbuster is also designed to remove DC on the AC power line.

I have D200's that hummed.  Found the DC problem on the AC power line into the house.  It was the power meter connections that were corroded. After the power company corrected the problem, no more humming toroidal transformers!

[designdude]

As I wrote, for what I spent I expect something that sounds fantastic.   I am not interested in spending time tracking down a problem that only affects one component, nor am I interested in spending another $300-400 on another little box that might offer an improvement.

I am going to cut my losses. I just listed them on ebay. If anyone is is interested, here is the link: http://cgi.ebay.com/Channel-Islands-Audio-D-100-monoblock-amps_W0QQitemZ280303840893.

[wilsynet]

If I recall correctly, Dusty has a 30 day return policy, so I'm not sure why there's so much bitterness.

As suggested before, you should probably talk to Dusty.  Give him a ring, send him email, see what he says and if he can help fix the problem.  When I dealt with Dusty in the past he was a total class act.  Maybe he'll send you an XDC2  to try without you having to fork over more money.

[madisonears]

I owned a pair of the D200's and I had to sell them because their humming made me crazy.  I don't expect to hear that loud of a noise coming from a $20k stereo.  None of my other gear makes any noise.  The only solution Dusty offered me was to buy another one of their products that he told me "might" stop the amps from humming.  I tried reclamping and tightening the xformer mounting bolts and plates, but I never did buy the band-aid magic box, and the amp humming got worse over time until I couldn't stand it any longer.  The hum from one amp was clearly audible over a low level signal and completely spoiled listening to music, and the other amp could be heard between tracks.  The buyer never complained, so I guess his power supply was better suited to their sensitivity to DC or whatever.  Maybe he hid them in another room.

Pity, because otherwise they actually sounded pretty good.  There are better sounding amps, but these were pleasantly efficient and compact.  Too bad they used problematic xformers.  There doesn't seem to be any consistency to these complaints, so I wonder if it was a random supplier quality problem, spec problem, marginal design problem, or if the problem really lies in the individual's home power supply.  Strange that other toroids here don't make more than a very faint hum, easily contained by an enclosure.

[CIAudio]

We've sold several thousand amplifiers and have only heard of 20-25 cases of humming, which is cured by XDC-2 in most cases. DC on the AC line is usually the culprit. XDC-2 is not a "band-aid" fix, and eliminates the problem at the source. The XDC circuit is so effective, we now have it built-in to all our amplifiers.

Over-voltage and/or distorted waveform can also cause hum.
As another poster mentioned, using a variac to reduce the line voltage will eliminate the hum. Even with distorted waveform, reducing line voltage will keep the transformer from saturating and humming.

We get calls everyday from customers with humming components made by other manufacturers...9 times out of 10, XDC-2 cures the problem. 

[stu]

I have had a new pair of dusty's D-500's for about two months now, and they are dead quiet.  Not even a hint of transformer hum.  I quess the built-in XDC circuit is doing its job.

Mark

[NewBuyer]

...DC on the AC line is usually the culprit... The XDC circuit is so effective, we now have it built-in to all our amplifiers...

Dusty, when approximately did you start putting the DC-blocking circuitry into your D-100 and D-200 amplifiers please? 

[CIAudio]

We started shipping the latest version about 3 months ago.

[gme109]

We started shipping the latest version about 3 months ago.

So the next question would be, can the XDC circuit be retro fitted to the older D200's?

[timind]

As I wrote, for what I spent I expect something that sounds fantastic.   I am not interested in spending time tracking down a problem that only affects one component, nor am I interested in spending another $300-400 on another little box that might offer an improvement.

I am going to cut my losses. I just listed them on ebay. If anyone is is interested, here is the link: http://cgi.ebay.com/Channel-Islands-Audio-D-100-monoblock-amps_W0QQitemZ280303840893.

I understand your concern with fixing an intolerable situation but why no mention of the hum in the ebay ad? You may be asked for a refund from the buyer if they hum for him also.

[designdude]

"You may be asked for a refund from the buyer if they hum for him also."

I doubt that will occur. The fundamental premise of buying used goods can be found in the phrase Caveat emptor, roughly translated as Let the buyer beware. Any time I sell something used I stick to the facts: what it is, what it does, how long I have owned it, what I did with it, how it is described in the press, why I am selling it. I also answer any questions a buyer asks.

In this case, the amps do pretty much what most people want them to do. Under "normal" operating conditions, e.g. connected to a wall socket using a Home Depot power cord, they provide decent sound at a decent price.

The point I was trying to make (and I apologize if I sound jaded or disillusioned or "bitter") is that at this price point I expect a certain level of performance and an ability to synchronize with other gear. After all, anyone who is going to spend $1,000 to $1,500 on an audio amplifier (or a pair of monoblock amplifiers), is probably also going to spend a a lot of money on other gear in their system. System synergy is an elusive gremlin. Sometimes you get it, sometimes you don't. When you do find it, that's awesome. Hell, our whole hobby it about that. But to have an entire post dedicated to a piece of gear that flat out prevents system synergy? That is very unusual. 

Bottom line, the D-100 mono block amplifiers do not meet my expectations. So I am selling them as used audio equipment. This is not the first time that I have sold some used gear, but it is the first time that I have seen a thread with 30+ posts addressing the very reason why I am selling that gear.

[CIAudio]

So the next question would be, can the XDC circuit be retro fitted to the older D200's?

It could be done but would require replacing the entire power supply board in each amplifier. This would be costly, more than twice the cost of purchasing an XDC-2. There is really no benefit unless you have DC on your AC line.