Hi all.
On my third day with my new ADA1250 3channel. Totally awesome unit. First day cranked it so far seems a little more dynamic{details in the music} than my previous A|B pro power Amp.

But now I have a noticeable noise floor from the ADA.
It's not a ground loop as I'm already using an isolator through my cable box{had that issue with my old Amp}.
It's similar to the feedback from a guitar amp just a quiet buzz in the background.

Also it seems to be through the center channel or 3rd channel unplugged it to see in stereo and buzz was not noticeable. And gone when I turn of the power switch

Any ideas greatly appreciated.

Now in the process of organizing the mess my cable monster put behind the entertainment center. To funny how they can get to a holly cow state so easily.

Oh boy!

Did you try swapping one of the L/R channel boards into the center channel?

When you said that you unplugged it, are you talking about removing the cable from your pre-amp to your ADA center channel?

I would as mojo said, try moving the center channel cable to either the left or right channel and see if the hum moves to that speaker. Likewise, try running the left or right channel cable to the center without the center cable plugged in. Does it make the hum. If it was a power problem inside the ADA then it would more likely be system wide and the hum would come from all your speakers.

You also didn't say if you are using RCA or XLR to connect between the pre-amp and your ADA. It should not make a difference, but if there is something up inside your pre-amp then this might help isolate the deficiency

I'm using RCA Monster ultra audio cables.
So I switched the channels around and swapped the RCA's and as I was doing so the hum went to almost gone, as long as the one on my center stayed stretched. As soon as I pushed it back on my stand the hum becomes very noticeable.
With that RCA removed from the ADA nothing just clean sound from my M80s. On any channel that I have tried on the ADA. My remaining surround channels through my AVR are not getting this hum at all.{Front height and sides}

It's pretty easy for my to try an RCA to mic.{XLR} though I've read that that can actually degrade the sound quality

Confused?

So what speaker is the hum coming from? is it just the center speaker or is it all the speakers?

I get that when you have just the left and the right hooked up, it sounds silent. That is what is should sound all the time.

I think you are saying when you hook up the center channel RCA that you start to get the hum. I am going to gather that you have tried moving the RCA connectors to different plug spots on the back of the ADA to see if that changes the characteristic or amount of hum that you are hearing.

Have you tried just hooking up the center channel RCA only and seeing if you are getting any hum.

Just trying to figure if it has anything to do with a signal or ground issue coming from your Pre-Amp that the ADA is sensative to that perhaps any of your prior amps were not.

Also, have you tried pulling all your other inputs from your pre-amp to see if the sound goes away. These would all be steps to look into before you can start to diagnose what to do. You really need to isolate what is connected. For instance, I had a wicked hum with an Rotel amp that went away when I unplugged the HTPC media player computer that I was using for music streaming.

And BTW, going from RCA to XLR doesn't reduce the sound quality, it just reduces the gain by about -10db

It comes from all 3 L,C,R, though only when I connect my center.
haven't tried only the center yet. When I put the ADA back in my rack the hum gets louder so possibly EMI/RFI.
Swapped through all the inputs on my ADAs RCAs

If you have a spare speaker you could substitute it for you center as a test.

In my last house which was older 1960ish I had to do all kinds of dumb stuff because of noise in my bedroom system. I had to run a separate extension cord from the hall way outlet into the bedroom for certain things like all the wall warts and used ground lift so no loopback . My newer house is dead silent , has a really well designed electrical system. Can you run a cord from another room and only power up the pre/pro and the amp with all else turned off. Like you say maybe some EMI.

sorry

[quote=MatManBobbleHead]Confused?

So what speaker is the hum coming from? is it just the center speaker or is it all the speakers?

I get that when you have just the left and the right hooked up, it sounds silent. That is what is should sound all the time.

I think you are saying when you hook up the center channel RCA that you start to get the hum. I am going to gather that you have tried moving the RCA connectors to different plug spots on the back of the ADA to see if that changes the characteristic or amount of hum that you are hearing.

Have you tried just hooking up the center channel RCA only and seeing if you are getting any hum.

Just trying to figure if it has anything to do with a signal or ground issue coming from your Pre-Amp that the ADA is sensative to that perhaps any of your prior amps were not.

Also, have you tried pulling all your other inputs from your pre-amp to see if the sound goes away. These would all be steps to look into before you can start to diagnose what to do. You really need to isolate what is connected. For instance, I had a wicked hum with an Rotel amp that went away when I unplugged the HTPC media player computer that I was using for music streaming.

And BTW, going from RCA to XLR doesn't reduce the sound quality, it just reduces the gain by about -10db [/quote

If you used an adapter from unbalanced to balanced this could limit your amp since balanced connections have much higher output voltage on pre/pro's and higher input impedance on the amp. Is that what you meant to say or am I talkin out my backside.

Yes. And I found when you work it out it comes in at around -10db loss of sound level.

I was using for a long while a Pioneer receiver that only had RCA pre-outs and had to use RCA-XLR cables as there was something that caused a wicked hum between the LFR1100 speakers DSP and the Anthem amp that I had purchased. If you play with the room correction sound levels you can compensate by putting the channels to +db for the ones that are on the RCA-XLR and -db for the ones that are not.

If you can try just the Center to see if you get a hum. While you are at it, try the center with either just the left or just the right.

The issue might be caused by your pre-amp in there might be a grounding issue inside the circuit that is causing the ADA not to like it. This can come from differences in the way that the ADA does it's grounding vs the way that the pre-amp does that in turn causes this headache. The awful down side to this hifi game that we are playing.

In my past experience, I had a Marantz AV7005 that just did not want to play nice with me. I bought it used and it had no issues with the previous owner who was running it with an Emotiva amp, but got it home and even looking at it the wrong way caused it to generate a horrible background hum. At the time I had the Anthem MCA5 amp and two AmpOneAs. All of them just did not like this pre-amp. As long as I did not plug any input source into the Marantz it was fine, but as soon as I plugged in a source (even a toslink optical cable) the unit would make the speakers buzz. I ended up selling it and the gentleman who bought it has no problems what so ever. It just doesn't like my room.

My new Anthem AVM60 works like a charm and no issues what so ever. Different pre-amp from a different company but the exact same power, input components and speakers and everything worked perfect. I did upgrade to new ADA1000 and sold the Anthem MCA5 along the way.

HA!!!
Dang interference went through many steps.
Wound up cleaning all my wires from the playing with equipment Troll that gets into them when we play.
Fed every thing into my Monster HDP1800 power center, cleaned my coaxial cables made shure they were connected to my Ground loop isolator properly. Separated all the speaker wires.

Presto Dang hum gone.

Thank you for the advice, especially older building wiring. My building is also 60s built. So that led my to think it was fixable with the power conditioning{isolation} in my power center.

Still listening to V. tuner radio at only 20 Db on my dial and shocked it worked actually. No more buzz YAY!!!

Thanks for all the thoughts and help made my trouble shooting much easier.

Brendo

Glad that you got it all worked out. Background hum is the death of many. I spent a good 20+ hours trying many different things when I had the case of it. I eventually decided that I'd spent enough and it would have been cheaper to just buy new equipment than try and diagnose where the problem was coming from.

And now I have an Anthem AVM60 ;-)

The Buzz was through all the speakers when it was occurring, and specifically when I put my center RCA into the ADA1250 any channel. when I was trying as suggested to just swap the RCAs to different channels, without swapping the speaker wires it would make the hum softer but not gone. In doing so I moved my amp. out of the rack and noticed that while the RCA was stretched the hum would almost disappear.

Thanks again for suggesting to isolate everything.

Socketman saved me a lot of trouble with mention of his 60s building wiring troubles.

That got my thinking about EMI/RFI. Figured already have a power conditioner. Time to clean up and put all the equipment through
it's designated outlets and get it as isolated as possible.
Even took the extra steps to make sure the inputs HDMI, RCA, digital, and tos were all separated.

Wow thank you guys those simple steps solved all my EMI/RFI troubles. It's now silent:}:}:}

Thank you again:}
Brendan

I really don't know why there is so much cord sex goin on behind my audio gear. I put it all nice when I set it up 3 months ago and its a mess now. Damn gremlins. Good to hear its all working again, such a great relief when a plan comes together.

Hurry to at least put some form of contraception between those cables, mine weren't to busy doing the nasty and it still caused them to moan a lot.

Happy to say that my cables are no longer a problem and man is this Amp. awesome at any level it just takes authority and commands every detail to come through. Have run it for the whole day with movies and music back and forth and it doesn't even get very warm.

Thanks again for the help with my woes.
Cheers

So many people argue that amps make no difference though my experience has been different. I really found my sound became effortless for lack of a better description. It been my experience that I don't have to play my movies as loud to get the same enjoyment, much more dynamic.Now if you sat me down and did a blind test I don't know if I could A/B 2 amps but as I upgraded over the years the differences are subtle but noticeable. Its not like switching a light on but the sound seems less strained. If anyone wants to cast doubt on my observation that's fine but you wont change my mind and I probly wont change yours . Glad to hear everything is working to your pleasure, enjoy your system .

Richard

Hi Richard,

The amp debate is an ongoing saga and I think the reason is that everyone is correct. It all comes down to what you want from your system and how large a space you have it in. It is the logarithmic nature of power (both amp power and inversely distance) that makes it a bit confusing. If we use 15 dB as a safe range of dynamic headroom then in a small room at lower average listening levels the performance is highly likely to be indistinguishable between most amplifiers. For example; if you are seated 3 meters away from your speakers and you want a maximum average listening level of 86 dB then around 65 watts of dynamic power is going to work just fine. Since most receivers have the same continuous output as they do dynamic output a 70 watt per channel receiver is lots assuming it is rated with both channels driven broadband at less than 1% distortion. Now lets assume you are 6 meters away from your speakers and you want an average listening level of 92 dB. Now you will require around 1,000 watts per channel of dynamic power. This is where big continuous output with lots of dynamic headroom is going to be critical or your listening experience will be severely compromised. Since 1,000 watts of continuous power would require big mono blocks on separate circuits, the amount of available dynamic headroom becomes very important. A good guide to judging an amp's dynamic headroom available is found in the amount of storage capacitance combined with the type and/or sizing of the power supply. I have left a lot of the finer detail out here; but I think it gives the basic picture of what is going on and how everyone can be correct.

Ian, how about the slew rating of amplifiers or is this proportional to it's output?

Hi Adrian,

I would not be too concerned about the slew rate. This is one of those specs that gets far more attention then it deserves. It is a measurement of voltage rise achieved before being off by 1 microsecond or one one-millionth of a second; again, one one-millionth of a second. Generally 20 volts or better in most amplifiers.

6V per microsecond for an amp with 50V rails and you're good to the high end of the human hearing range.

Now that I've fixed my feedback issue, it's time for some real feedback.

I totally agree with you Socketman in switching from my A/B Pro amp. to the ADA it does seem like I'm getting more power and detail at lower volume levels.

My seating is around 4meters from my mains. Now at say 40Db it's so much cleaner and legible, where I would have gone to say 50 or 60Db.s for the same effects. Strange considering my older Pro and the ADA1250 are rated to similar 450watts, probably due to heat dissipation from the A/B class Amp. Almost like it's given my pre/pro the freedom to reach it's full bandwidth range without limitations, maybe even extend it a little to the ADA's. Though I'm aware that is set by the range the pre/pro has.

Happy to say for all of us drooling over these Amp's. They are fantastic!!! Highly recommended.