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Hum from my Amp, solution...Emotiva CMX-2

Razz

Razz

Well-Known Member
So I recently moved into a older home and after getting all set up I noticed a loud hum coming from my amp itself. The hum was not a steady one. It was rhythmic. Cycling up and down in frequency and sometimes was very loud as I heard it in my kitchen 3o feet away. Other times I could barely notice it. There was no noise at all coming from my speakers... dead silent.

I brought my amp (ATI 2007) into the manufacturer here in L.A. and ran into none other but our own @rammisframmis. He recognized the problem right away and told me it's not a problem with the amp but a problem with my power lines as there is probably DC feedback in them. It's not a problem for the amp but super annoying to listen to your nice gear sounding like shit!!!

The solution was know by rammisframmis and recently brought up in a thread by @team_tsp who was having a similar problem. Unfortunately for him, his sounded more an amp problem. The Emotiva CMX-2 was the perfect solution in my case.

The Emotiva CMX-2 did a fantastic job of completely blocking all the DC in the line and my amp hum is GONE!

It's $119 including shipping from Emotiva website and for this type of problem is an excellent solution. It's a solid heavy piece, about the size of a power strip but as soon as you pick it up you realize it's not. IT'S HEAVY!

Now Emotiva also makes a CMX-6 which has six plugs instead of 2, don't be fooled here. The CMX-6 does NOT have the DC blocker, only the CMX-2. They actually recommend you buy both and plug your CMX-6 into the CMX-2. I know... LAME!!!

One downfall... rammisframmis warned me about this and he was right. There is a power drain and I noticed my normal listening levels needed to be turned up. This is not a problem for me as my ATI 2007 has lots of power to spare but those with demanding speakers and light amps might suffer a bit.

I have noticed no difference at all in dynamic range and/or sound of my speakers. Just needed to turn it up a bit.

 
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Does that thing run warm? I'm surprised to see cooling fins.
Glad it solved your hum problem!
 
I would also like to know more about "Power Drain". Is it really a Voltage Drop?

Glad it solved your problem Russ!
 
Zing said:
I don't understand how and why such a thing can happen.
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This is a DC blocker, and it does this by inserting back-to-back electrolytic capacitors (of at least 250V rating) in series with the AC power line. Since these capacitors cannot be of an infinite value, there is a slight voltage loss because of the capacitive reactance. It is essentially a very low frequency high pass filter. Although the loss is relatively small, the loss of power capability of the amplifier can be quite large. During our lab testing of amplifiers using a variac to regulate the AC voltage to 120 VAC, there can be significant power losses even if the AC voltage slips down to 119 VAC. Roughly, the loss incurred by using a DC blocker can be like adding a hundred feet or so of AC house wiring before the amplifier. Its something you don't want to do unless its really necessary because of a grossly distorted AC power line waveform which is heavy in 2nd order harmonic distortion, which is what makes the DC offset. Power transformers absolutely HATE to be fed DC!

I don't see how this could affect the gain of an amplifier since that's set by the ratio of feedback resistors. Weird.

The Emotiva device looks interesting; I'd love to take one apart to see exactly how they implemented this. Russ, can you bring it down to the factory - I'll give you the super deluxe factory tour! :rtfm:
 
^ Your R&D budget should be able to buy and few of these, evaluate them and develop a much better product...............Right?
 
heeman said:
^ Your R&D budget should be able to buy and few of these, evaluate them and develop a much better product...............Right?
Click to expand...
I would imagine so if the company wanted to get into that business, but they don't. We've made a few "one offs" for some customers in the past, but nothing commercial.
 
Can we assume detailed pics and a report will follow?

Jeff (Extremely Curious) Mackwood
 
Nice compliment to your product line, but I am not a business development professional.
 
heeman said:
Nice compliment to your product line, but I am not a business development professional.
Click to expand...
We've got more stuff going on what with new designs than the available people can handle; remember, we design for a lot of other companies too in addition to our own brands like ATI, BGW, Theta, B&K, SAE, and probably some I've forgotten.
 
Glad the CMX-2 worked for you @Razz! I was going to reply in my thread to ask whether it worked for you.

Everything you described in your original post is spot on, including the differences compared to the CMX-6, very informative post :thumbsup: For the brief amount of time I had mine, I too felt the build quality of the CMX-2 is excellent. I really wanted to find a reason to keep it, but it just didn't help in my case.
 
rammisframmis said:
We've got more stuff going on what with new designs than the available people can handle; remember, we design for a lot of other companies too in addition to our own brands like ATI, BGW, Theta, B&K, SAE, and probably some I've forgotten.
Click to expand...

B&K is still alive?
 
Did you guys clean up the rats nest of wires in their units?

BTW - Their 125.2 was the first power amp I owned. No problems with it, and sounded fine.
 
Not from a marketing stand point but from a design and quality standpoint, where does the B&K vs. ATI stack up?
 
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