strange problem

[amallalone]

Recently I have brought 3 circuit from eight audio..one preamp module and one active subwoofer crossover and psu with crc filter..when I try to connect an 12-0-12v transformer to the psu and to the preamp or sub crossover the input or output passing dc current..the screwdriver tester confirms it..do I have grounding problem..
Whenever I tried to connect input or output from my pc the transformer stops passing any current at all..after removing the jack from input or output the transformer again started passing current..I tried 2 transformer..same result..

 

[avesbilal]

Recently I have brought 3 circuit from eight audio..one preamp module and one active subwoofer crossover and psu with crc filter..when I try to connect an 12-0-12v transformer to the psu and to the preamp or sub crossover the input or output passing dc current..the screwdriver tester confirms it..do I have grounding problem..
Whenever I tried to connect input or output from my pc the transformer stops passing any current at all..after removing the jack from input or output the transformer again started passing current..I tried 2 transformer..same result..

Please provide the web links of the 3 modules you bought so people can review what you're trying to archive is possible with those modules.

Sent from my Redmi Note 3 using Tapatalk

 

[amallalone]

https://www.eightaudio.in/collections/tone-controls-eqs/products/ea-two-band-tone-control
https://www.eightaudio.in/collections/power-supply-modules/products/15volts-dual-crc-filter-psu
https://www.eightaudio.in/collectio...subwoofer-crossover-filter?variant=7622049028

 

[avesbilal]

I'm no expert, check the output of your PC with multimeter if it has DC voltage on it when idle, have you tested it with any other sources.

Sent from my Redmi Note 3 using Tapatalk

 

[amallalone]

I have checked it with mobile output jack also

 

[sadik]

I am not an expert...its my suggestion to you that, It will be Better if you can just Draw a simple sketch of your wiring connection so that the Gurus can understand your Problem Properly.

I mean to say draw a simple sketch, take a photo of it and upload the same on this thread.

 

[amallalone]

It's 2 pin ac to transformer to 3 output transformer to ac input psu 3 pin ..to 3 pin dc output to dc preamp 3 pin input

 

[omishra]

First of all , please elaborate your confidence in electronics. I mean what tools you have and your previous hands on experience. Also your understanding about Voltage polarity, ground etc. Your descriptions are too vague to understand and give solution. Screw driver tester is not indicator of DC at output.

Don't assume me wrong but I feel something reverse polarity of +15, -15V might be reason for opamp delivering DC at output.

 

[shravanth]

Hello, this is shravanth from eightaudio.in, can you please share the wiring diagram

 

[amallalone]

Yes man am a beginner In diy audio..got few knowledge from from Hfv and net..that's why I need help of senior s..

 

[omishra]

Ok, being new to DIY is not a problem.
Welcome.

Please post a high resolution picture of your wiring to us. Or describe which output of power supply +15, 0, -15v connected where on other module.

Remember, you are dealing with dual power supply. Which has 3 terminals ->
+15v, ground or 0, -15V.
How to measure this?
Use DMM(digital multimeter) on DC Volts 20V or 200V range.
Common wire, at DMM marked as Earth ground symbol also, use as black probe wire of DMM. Red wire as Voltage measure terminal, call it's other end red probe of DMM.

Now always use black probe of DMM on ground of PCB where it would be measured. By using red probe on other terminal find out which is +15 and -15.

These same +15&-15 from power supply needs to be connected to other PCB module at same place marked + & -. Your PS(power supply) output and preamplifier module has marking +, G and -.

Same markings are on power input of preamplifier too. So + wire from power supply goes to + on preamplifier module, G wire from PS to G wire on preamplifier and - wire from PS to - wire on preamplifier. Use 3 different colour wires so that you can identify it clearly.

Screw driver Tester light showing presence of Voltage until you touch it and make it ground. It's not a problem until you encase it and connect G of PS to mains earth ground.

 

[amallalone]

I did everything as u r saying....and yes tester shows until I touch it...just yesterday I noticed one thing.. output of from pc or mobile to active speakers..no humm..pc or mobile both are offmode..but if I connect preamp out to active speakers ..humm reappear and increasing its volume with volume up..even the preamp is without power

 

[omishra]

Your speakers are active speakers. It means they have pre and power amplifier inside. So any hanging wire or open circuit at its input will act as an antenna to surrounding noise and catch main 230VAC line interference. It will be amplified and fed to speaker. That's why you hear hum or buzz. In case of direct connection to speaker, you use interconnect wire which is closed circuit and most probably shielded wire. So no noise.

Did you power on and measure output DC voltage after correction again? Did it play music?

One more thing, each input and output wire has 2 wires marked +/- on PCB. It means live wire goes to + and ground or shield goes to - or G. Though this marking is misleading, no issues in understanding. Reverse connections at any point may lead to hum or noise.

See 3 wire connect on PCB
Middle wire is common ground, red is right channel and black is left. Same pattern for input and output

Subwoofer module has +/- marking at output, input has no marking but fine, it's as above.

PS: If you/anyone likes my suggestion then please acknowledge it by thanking to my post as courtesy. Otherwise I don't understand, if I am on correct path or not.

 

[amallalone]

Yes my preamp board is open ..I played music from pc as well as from mobile..no sound coming out of active speakers..only humm

 

[omishra]

Ok, now disconnect speakers and measure DC voltage at output of both channels at preamplifier module.

Also verify wiring of input and output as per above diagram.

Before that I strongly recommend to post picture of wiring.

 

[amallalone]

Psu to sub crossover and transformer to psu wiring

 

[omishra]

Okay, this wiring is correct. I don't see any issue here.
This is Subwoofer filter board. It will filter high frequency. So at the output of it you can expect only low frequency below 250Hz, not full range music. So hum is expected, not an issue. It's output is not correct candidate for active speakers input.

Same question again, did you measure DC voltage at output terminals of this filter before connecting to active speaker?

How the input and output are connected?
(If possible, please take the picture, mark using paint or any picture editor software.)

 

[amallalone]

Output from preamp board showing 0.0 voltage

 

[amallalone]

Thanks...I found the problem..thanks for giving the idea of audio wire shielding@omishra

 

[omishra]

Output from preamp board showing 0.0 voltage

Good, then you have everything seems okay. No problems.

Now adjust crossover frequency and cutoff correctly, and use with speaker. It will sound only drums and below.