Whistling Coldamp

[SimonInd]

Hi
I connected up a pair of ColdAmp's BP4078 modules with a single SPS80 switch mode power supply last night and found that I was getting some whistling at the speaker outputs. When I cut the power and the modules were running on the PSU's capacitors for a few seconds it disappeared suggesting the PSU was the source.

I've emailed technical support but if anyone has any tips I'd be grateful? The power supply wires are twisted but I haven't used the supplied chokes yet - I will try this tonight.

Thanks
Simon

[BWRX]

Can you post a picture of the physical layout of your amp? If not, how close is the supply module to the amp modules? Does the whistling still occur if only one channel connected to the supply?

It would be best if you could get rid of the whistling without using the chokes, but do try them and see if they help.

[SimonInd]

They're about 8 or 9 inches from the PSU - nothing is in an enclosure yet, just flat out on the floor. The whistling occurs with one or both of the modules connected.

I've tried moving things around and it does have some effect on the whistling but it always remains audible.

Thanks
Simon

[luka]

Hi

Put chokes in. This will help a lot, probaby problem will go away

[ssanmor]

Hello, Simon.

Usually, no whistles are produced, but depending on the layout, the fact that you don't have any earth that may act as shield, etc, may increase chances. It is usually solved at first attempt with the chokes, though.
You may want to connect everything as you plan in your case, etc, and, if you still experience the issue, cut the wires and insert the chokes.

We provide 4 chokes per supply, you have to connect them in series with VCC and with VSS, one per rail, and the same for the other module. Have a look at page 12 of this document: (except for the aux supplies):

http://www.coldamp.com/opencms/openc...ppnotes_en.pdf


BTW: We haven't received any technical support question from you about this, Simon. Please check that you sent it to info@coldamp.com or to sales@coldamp.com

Best regards
Sergio
www.coldamp.com

[SimonInd]

Thanks for the replies everyone, no joy I'm afraid even with the chokes I'm still getting the whistling. I've got 1 module connected with chokes at the module end.

Should I try earthing the ground in case there's noise on that?

Sergio, I mailed technical.support@coldamp.com as per your DIY web page: http://www.coldamp.com/opencms/openc...elf/index.html

Thanks
Simon

[ssanmor]

Please post your question with all the info you can, and if possible a photo, to info@coldamp.com , the other account seems to be down.

[SimonInd]

Got to the bottom of the problem last night, something to do with PSU earthing as tightening the screws that secure the SPS80 PCB to its Aluminium base plate got rid of the whistling even with no chokes on the PSU lines.

I'll be trying it against my TAG 5x100R tonight to see how it compares. From last night's listening the bass seems very good giving a full sound with plenty of scale.

Simon

[ssanmor]

Thanks.
Here is the explanation: there are some capacitors that AC-couple switching nodes to earth chassis in order to minimize HF emissions. The connection is made by means of the PCB screws at the corners. If one of the screws was not tight due to transport or whatever, that could cause the problem.

Nice to hear that everything is ok now.