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-   -   Speaker Hum issue? - SE TK2050 Amp - Project (http://www.diyaudio.com/forums/class-d/222180-speaker-hum-issue-se-tk2050-amp-project.html)

kirtangl 24th October 2012 10:51 PM

Speaker Hum issue? - SE TK2050 Amp - Project
 
Hi everyone

I have been reading a lot of threads on this forum for the past couple of years, working on making a fairly large Speaker Box that we use for camping trips etc. Everything I need help with is here, but I am now stuck on a problem that seems to be very specific to setup.

Basically I have a hum front he speakers, reading into this on this site, I hear things about Ground Loop, and other forms of interference, but I wanted to get a little more info on this for my situation.

I am running 2 a.audio HP-10w, and 2... er tweeter? they are a rip off of the Motorola ones, I am actually unsure of what they are called.

These are connected through a 2*100w Sure Electronics TK2050 Amp, the input into this amp was a cheap pre-amp, but has since been changed to a JVC KD-X40 Head Unit, connecting to the amp using the Pre-Outs (Not amplified). Since changing the hum has come considerable less audible.

At the heart of the entire system is a 24v 40AH LiFePO4 Battery, running direct to the amp through a line of caps, and to the Head Unit through a Switching Relay (I thought the switching regulator could have been the issue, but since a head unit is designed to run on a choppy car battery, I'm hoping this wont be the issue).

I also have a Spectrum Analyzer build using 40 x 10 row LEDs, 20 Bands wide, 20 levels high. I found that when I connected this to the second pre-out, the hum/buzz is horrible, it's almost a whine/sequel, and is very audible, to the point where I have just left it disconnected.

OK, ill make a list of everything I have at the bottom, but first here is what I have tried so far to eliminate the issue.
  • Disconnecting the inputs from the amp does remove the hum.
  • The volume on the Head Unit does not seem to affect the hum.
  • Adding a Ground Loop Isolater did appear at first to fix the issue, but after further testing, the hum does appear to be the same (it is rather quiet)
  • The Ground Isolater has no affect on the Spectrum Analyzer
  • moved all power cables away from the audio cables, but in a box 400x290x300... that's easier said then done.
  • Moved the entire thing out side, away from any electrical equipment.
  • New pre-amp (As mentioned, seemed to help a bit)

Things I am yet yo try;
  • Upgrading cables to Shielded Cables.
  • Grounding Everything (Although I am unsure of how to do this to each device)

And here is my Equipment List;
  • Sure Electronics TK2050 2*100w Class D Amp
  • JVC KD-X40 Head Unit (Pre-Amp)
  • HP-10w, 50w Tweeters
  • Spectrum Analyzer (Essentially this one Here)
  • 24v 40ah LiFePO4 Battery
  • Power Supply Board is just a couple of Terminals, wire, and a 12v regulator. (Caps to amp)

I look forward to hearing what everyone has to say, I am really lost for what else I could try, or if there is something I missed, im sure its common Knowledge and I just missed it haha.

p.s. Important bit of information, I just remembered the Spectrum Analyzer is Mono in, If I am using a Y RCA to 3.5mm Stereo plug, is it possible its accepting only the one channel, then sending the signal back to the second channel causing the noise? Will disconnecting one of the channels fix this if its the case, or will I need a mono plug? (Probably a stupid question, but I gotta ask)

dangus 25th October 2012 12:15 AM

A Y cable usually will short the Left and Right channels together, which shouldn't cause hum, but might cause distortion. If you want to mix them down to mono, use a couple of resistors in the 10k to 100k range as a crude mixer.

Can you run the head unit from a separate 12V supply and see what happens?

kirtangl 25th October 2012 01:25 AM

I haven't tested the head unit on a separate power supply, to be honest, the buzz/hum from the head unit it so low I am not really worried about it at this point, its more the hum caused by the S/A. I tested the the S/A on a separate battery (12v SLA) and it did cut out the noise (Unfortunately I cant run a second battery, no room, and makes charging and leveling an issue). I tried a Ground Isolator on it when it was on the same power supply, but it didn't seem to help.

Reason I am focusing on the S/A is, I believe what ever fixes it will probably work on the H/U as well.

kirtangl 25th October 2012 05:49 AM

An Electrical Engineering mate of mine just provided some input. He said I need to try and keep digital and analog signals separate, the cpu on the s/a might be causing interference that is feeding back to the pre-amp through the regulator. Apparently I should have used a separate regulator for each device, as this will cause a lot of digital noise, not the normal hum, but a high pitched noise (Pretty much described my issue). He said it might be work a try setting up a dedicated regulator for the S/A and try to keep the grounds from each device straight to the battery.

Ill give this a go. Ill also try the amp on a second battery to test sound or hum differences as mentioned.

Ill keep you guys posted.

kirtangl 25th October 2012 10:54 AM

Sweet, all good now, thatx dangus, ypur trick also helped so if the little hum that's left anoys me, I know where too start ;)

Here's what I got so fat (obviously it won't be taped together in the end)

Video

Priva 3rd December 2012 05:37 PM

Hi folks!


I got the same hum problem with my Sure Tk2050 4*100w board. So what was the actual mean - to get rid of the most noise ?


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