DC Offset Blocker/Killer - where to buy in the USA

Hi Jim,

They both appear to be reasonable values for this purpose.  The 10 uF/100K combination will charge up to the final value about twice as fast as the 22 uF/100K combination, which isn't important, but it won't be down quite as far at 60 Hz as the latter.  That difference probably isn't important either, although I can't say that with certainty as I'm not familiar with the internal design of modern digital multimeters.

Specifically, the 3 db bandwidth of the low pass filter (i.e., the frequency at which 3 db of rolloff will have occurred) = 1/(2 x pi x R x C).  Let's refer to that as "bw" (bandwidth).

For 10 uF/100K, bw = 0.16 Hz

For 22 uF/100K, bw = 0.07 Hz

The rolloff at 60 Hz will be 1/(square root(1 + ((60/bw)squared))), converted into db based on 20 x logarithm of the resulting numerical value.

(That looks more complicated than it really is; it could be illustrated more simply if it didn't have to be shown as text.  Some people depict "squared" as "^2" and "square root" as "^(1/2)", but I'm not sure if for most people that would make the equation more clear or less clear).

For 10 uF/100K that calculates to -52 db at 60 Hz, which would reduce 120 volts to about 0.3 volts.

For 22 uF/100K that calculates to -59 db at 60 Hz, which would reduce 120 volts to about 0.14 volts.

Also, the time to charge to very close to the full value of the DC that is present will be approximately RC x 5, which is how I derived the 10 or 15 second figure for the 22 uF/100K combination.

Best regards,
-- Al

Thanks Al.

Jim

.

P.S. to my previous post: I didn’t mention the units that should be used for R and C in the various calculations. If R is expressed in ohms and C is expressed in Farads, the calculation described in my last paragraph will provide an answer expressed in seconds, and the calculation of bandwidth that is described earlier in the post will provide an answer expressed in Hz.

Best,
-- Al

I am curious how the OP made out.  I believe he was going to the dealer earlier this week to get it sorted out.  I hope he sees this and replies.

Here is the update and it’s a surprising one:

Went to the dealer today with the MC8207 and right away I was taken upstairs to their tech department where they plugged this amp and the result was a dead quite none buzzing transformer and I mean dead quite not even a small buzz. Now I don’t know if their outlets have been treated since this is the tech department and not any other place in the store, it was the only place that we tested it. I was very surprised and happy at the same time knowing that this amp can be quite so I guess it leads me back to my house or the outside power.

I am in a search of somebody that really knows how to measure DC offset in the AC lines, I did what McIntosh told me to do and it returned 0.9mV which is nothing to make the transformer buzz but it could've been a wrong measurement.

As for the LED Lights that were not illuminating equal Left Side to Center to Right, there was a slight shift of an inside part that the tech had to open the front and fix it to make it all Illuminate the same, bear in mind this is a brand new amp and it needed to be open to be fixed.

I have already spoken to my electrician who is coming back to the house to do an extensive checking and we would be unplugging everything from the outlets and I mean everything, and will be turning off all the breakers off except the one for the amp and see if we can finally find the problem and if that doesn’t help than it would be the right time to call the electric company to do their part, because otherwise it would be very hard to convince them to come out just because I have a buzz.

I am a person that do not give up and would like to find a solution to fix this problem no matter what it takes as long as it is fixable.

And if anyone from here ever had to deal with their electric company would you be kind to share the steps taken to convince them to come out.