Great deal on a 6 channel amp

[scottw]

Marbles,

I don't get a thump when I turn the amp on and off BUT if I leave the amp on and put the computer in standby I get a thump from the speakers and the same when I bring it out of standby, scared the *@#T out of me the first time. I assume that is what you mean by thump, right?? I was thinking of getting an X10 to turn the amp off before standby and back on when I click the music button in XL.

Unless you come up with something cheaper and easier

Sharp sorry I cannot help but this is not my area but I do not notice any hum in mine.

[sharp_1]

Sharp sorry I cannot help but this is not my area but I do not notice any hum in mine.

You can only hear the hum at very little or no volume...I have the master volume at 20% and the winamp volume at only the first or second notch in baddabings Heavy Metal skin...that's why I was thinking the amp was turned up too high at first.

scottw: How did you do your inputs to the amp...does your adapter have the ground wire built into it?

[scottw]

I have my master volume all the way up (needed it to hear audio thru zoom for movies), using the KX drivers and have the pre-amp for them ( I think that is what it's called) set to 25% and the amp is set to what I believe is the factory settings:

[quote]
Mine does not seems to hum. I had messed with all of the input gains while trying to get the amp to work (turned out to be something else) so I was not sure what they were set to by default. I had ordered another amp since then and noticed by default they were turned just above all the way down so I set all of mine to that.


Hope this helps!!!
[/quote

I keep my winamp vol pretty low most of the time and still don't hear a hum.

Hope that helps you some.

Oh and I wired all the grounds to the one ground on the input cable.

[scottw]

After checking back on what I did. I wired up rca cables to the input cable that was supplied. I connected the +'s to the 6 numbered pins and all of the -'s to the single shield wire.

[Marbles_00]

Sorry I haven't written back on this. Did a first major test trial of running the system on the livingroom zone for a New Years party, which went on fine, and I finally got the wife to admit that it is pretty cool . I just didn't do the test with one of these amps yet. And then, I wasn't in any frame of mind to type anything on a keyboard *hic*.

Anyways Sharp,

Connecting a shield at both ends could induce a ground loop and this could cause the hum. Not sure what you mean

What I mean there is that typically the shield is used to...well...shield against unwanted external signals inducing noise onto the cables being shielded. The shield only requires to be tied to ground at one end. If the cable has a dedicated return for the audio path, which could be grounded in some other fashion than a direct path to earth, then tie the shield at both ends, which should be a direct path to earth at one end, and it may connect up to the returns at the other end, you have now created a ground loop, where current could find multiple paths to ground. Crap that is hard to explain...hopefully I did it ok.

Now some companies, like with this amps inputs, and cheaper RCA will use the shield, not as it was intended, but as a return for the the music signals.

Another usual thing to try is to star ground to one point but try and seperate that ground return from earth ground. Usually something like a 10ohm 5watt resistor between the two (though difficult to acheive with a computer power supply). This is the only thing I have left to try...can you explain a bit more on how I could do this?[/b]

What a star ground is, is that all returns go to ONE common point and that is the only point that is grounded. I now realize that seperating the audio return path from earth ground is impossible at the amp. I measured the input shield ring to the AC ground prong and measured close to 0 ohms. What I have read (and makes sense) is that the AC earth ground is for taking care of the problem of an electrical short and us, the users, getting shocked and killed. Audio return paths, though technically grounded, are not grounded for the purpose of protecting the user against electrical shock, but rather as a path for the signals to return to ground. These two "grounds" though both mean the same thing, are really two seperate types of entities and using some resistance isolates one from the other.

Here is a good article that may help out:
http://sound.westhost.com/earthing.htm

I'm also tring to find the article and circuit discription that explains better about isolating true "earth" ground from the rest of the circuit ground. Thought it was an Elliot Sound Product article, but now I can't seem to find it. I think it was building a better power supply.

Unplug your source from the amp. Does the hum go away? Yes

Try a different source input like the line-outs from your receiver. Connected my receiver no improvements to hum

In both cases, is your interface box still connected, or are you disconnecting that from the amplifier?

Scottw,

I don't get a thump when I turn the amp on and off BUT if I leave the amp on and put the computer in standby I get a thump from the speakers and the same when I bring it out of standby

Yeah, that is what I wanted to know. I may build a circuit like this:
http://sound.westhost.com/project118.htm
And control the relay via a parallel port data line.

Or I may look more into the amps Mute circuit connection and figure out how those two pins work. Then just mute the outputs prior to sending the system into sleep.

[scottw]

Yeah, that is what I wanted to know. I may build a circuit like this:
http://sound.westhost.com/project118.htm
And control the relay via a parallel port data line.

Or I may look more into the amps Mute circuit connection and figure out how those two pins work. Then just mute the outputs prior to sending the system into sleep.

Looks like I can use an X10 controller with the xSleep plugin to turn the amp off before sleep and back on after it comes out of Standby

Pretty cool stuff!!!!

[Marbles_00]

I really like the simplicity of the XSleep plugin, but the problem I found with it, and maybe it's just myself not having the time to play with it, is that the countdown timer is only triggered at midnight. I wanted to set the computer to sleep at 3:00 am, but the event would not trigger the timer unless it was after 12:00 midnight.

I ended up setting up an Xevent script to execute a program called sleep.exe. It has been working great. In your case Xevent could be used to trigger the X10 command, then place the system to sleep.

Hope this helps.

[jryan1776]

I bought 3 of these amps and they are great! Has anyone heard/seen/used a remote sensing circuit to power off/on an amp? I'd like to know if there is a circuit that could sense changes to the speaker knob dial and react to controls. Maybe it's a silly idea or the wrong way, but I would like to turn the amp off automatically if all of the volume knobs are turned all the way down. I'd also like it to power back on if the knob is turned up… Not sure if something like this exists, but it would be nice to save the power/heat from the amps.

[Marbles_00]

jryan,

Not exactly what you want, but check out this circuit. This may work by using this to power some relays in the AC lines, or it may be the ticket for muting the amp using the amps mute inputs (haven't looked at that circuit yet to fully understand how to utilize it). Though I guess a problem with this circuit is to which stereo pair do you use to control the amp? Or it could be as simple as adding addtional inputs through 10k resistors.

Another auto turn on/off circuit is this

or this, which is not as good but works.

Hope this was helpful.

*EDIT*
I stand corrected, in order to use the signal detection circuit would require that the first op-amp stage would most likely need to be copied over, so each stereo pair would have their own first stage, seperating the output of each first stage via a diode. Then you would adjust the reference voltage for the second stage (going into the non-inverting input) to take in account the voltage drop of the diodes. Hmm, I've got some TL072 and TL074 op-amps, I just might have to play when I get a chance.

[jryan1776]

thanks for the circuit references. looks like a cool site. the both of the circuits appear to use the a/c side of the preamps to turn on the output relays. i was looking for something to use the actual preamp audio signal going into the power amps. this is mainly because my main source will be my computer serving mp3's which is always on.

[Marbles_00]

I think you missed the signal detection circuit (first one listed). It detects audio signals and if the signals exceed a pre-determined level, a relay closes...powering the amps. It is the sort of circuit used in a power subwoofer. Since looking over the circuit more, I'm not too sure if it is designed for stereo use as both left and right channels goto the same point. In my eyes that would allow the left channel to drift to the right and vise versa. Though for a powered amp, who cares, but for something like how you'd want to use it, then you would only want to hook up one channel...still requiring three seperate first stages.

[scottw]

Marbles,

What do you think of the sound quality of the amp, I think it sounds good

[Marbles_00]

Actually, when I did my first true zone test for my New Year's party, I used a car audio amp rigged to some power supplies that I put together a few years ago. I've been waiting to hook up the these amps until I get my volume control circuit put together...but I'm starting to get a little impatient, and may just have to use the AIP and connect them up to the system. Which phone cord is required to connect the AIP to the amp? A 4-wire or 6-wire? I think the ones that were included were only 2-wire.

I think also that the Mute pins are for muting the AIP and have nothing to do with the circuitry of the amp. The 2-pin connector on the amp goes to pins 1 and 2 of an 4N25 opto-isolator. Pin 5 of the 4N25 is the output and the trace goes through a 20k resitor and back out to a pin of the RJ11 connector (that connects to the AIP unit). Now I did see a trace that goes to a via, and then I'm not too sure where it ends up.

P.S. For who may be concerned, I was able to find these at Digikey, so one doesn't have to hack the DIN harness that came with the amps.

[sharp_1]

I replaced the 6 wire that came with the unit with a 4 wire and thats what made mine work.

[Marbles_00]

Well, I had my first listen to one of the amps last night...though it was late so I couldn't crank it, and I'm using it with the AIP right now. I will have to adjust the gain levels for sure, once I have everything hooked up, but it sounded good. Nice and clear. I see why people would criticize the low frequency performance, but other than that it has a pleasent sound.

I also didn't experience any turn on/off thumps either when powering the amp up/down or computer out/into sleep. Maybe the AIP has something to do with that, I'm not to sure.