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School Project: Off-the-shelf EQ module board

Demondayuk

Jul 22, 2021
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Hi Folks,

I'm helping out with a school project using an off-the-shelf EQ module board from Amazon/eBay.

https://www.ebay.co.uk/itm/265122265065

We got it working and it sounds great but after a few minutes the output distorts, mostly to white noise. Suspecting a faulty module we bought a different one from a different supplier but ran into the same issues.

A power cycle of the board resets it for another few mins and then it distorts again. We tried semi-isolating the input and outputs by employing a battery-powered MP3 player for input and a battery-powered mini-amplifier for output and even tried running the boards via a battery but the same thing happens. We've also tried various other input sources, and various amplifiers on the output and even switched to a bench power supply but no luck so far. Obviously it could be a fault with the two modules so we've ordered a third one (they are very cheap!).

Considering these graphic eq modules are for sale all over the internet there doesn't seem to be any useful information on connecting them up, though it does seem pretty logical looking at the terminals on the board. Maybe we're doing something fundamentally wrong, like needing a resistor and/or capacitor on the input and outputs? The only thing I can think of is that we're not using a power supply with a ground (only +ve & -ve) but there is no noise interference or hum when it's working.

Anyway, I just wondered if anyone here has come across these modules, and if so had any success in getting them to work properly? If not, thanks for taking the time to read this, I know we're all busy people!

Best Regards,
Emily & Darren.
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hevans1944

Hop - AC8NS
Jun 21, 2012
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The only thing I can think of is that we're not using a power supply with a ground (only +ve & -ve) but there is no noise interference or hum when it's working.
Could be that something is charging up and causing the output to distort because the board requires two power supply voltages of opposite voltage with a common ground. Try powering the equalizer from two 9V batteries, using one battery as the (+15V) supply and the other as the (-15V) supply with a common "G" connection. This may work but cause the output to distort with large signal inputs. If that happens, you have no choice but to increase the (+9V) and (-9V) batteries to (+15V) and (-15V) as specified for your equalizer board.
 

Demondayuk

Jul 22, 2021
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Jul 22, 2021
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Thank you for your prompt reply.
That's a great idea, I'll give it a try and see what happens.
 

Audioguru

Sep 24, 2016
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Without having a ground then one of the power supply voltages probably far exceeded the rated 15V and caused a problem.
I think it stopped working when one or more opamps got too hot with the over-voltage.
 

Demondayuk

Jul 22, 2021
4
Joined
Jul 22, 2021
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Thank you so much for your input and suggestions.
The module is now working great with the 2 x 9v battery solution.
Emily is over the moon that it's working... and more importantly, why it wasn't working in the first place!
Thanks again, and best regards.
Darren & Emily

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VenomBallistics

Aug 30, 2018
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Aug 30, 2018
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Now that you have discovered the power supply type was the issue .... Part number MAX1044 may be of interest to you
 
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