Lynx 3

[dodi_firman]

Dear, Mr. Jan
I had bulid your LYNX 3 amp...

If I use 8 transistor output 5200/1943..with rail voltages +/-65 V 15 Amp traffo..at bias 300mv...

The sound are quite good and so powerfull..but I hear liltle hum at the ouput..no loud but its can be heard at night...

What should I do to remove the hum..? I isolated the main ground form the input with 10/1W R...but still ican hear the hum..

If I Put 8 Tr for the ouput..how many watts output for thats ?.. How I can measure for that..

Thanks...Dodi

[Jan Dupont]

Hi Dodi,

I have just read your email and this post here.

Lets take the main issue first: Hum

It would a be a big help, if you can make a drawing of the way you have connected the wires (Supply and Ground) to the PCB.
Hum can be caused by the Power Supply, the Ground wiring and by bad shielding..... Lots of possibillities......

Is your layout the same as the original, or have you made a different layout ?

Edit: Added photo of the original layout

[dodi_firman]

Dear Mr. Jan.

Thanks to repply my email..

I had put away all the wires on the input..and only on min capasitor ground conected to ground via R10Ohm to chasis..

I conected the ground input on the PCB to power supply ground for the opamp and driver near them...because if I dont conenct them the DC Voltages are raise at the output stages...

According on your PCB layout, that ground input are not connected to anywhere..accept the feedback capasitor....

There's mistake on the layout..? I just download form the website in Grebers files...

Thank for your attention...
Dodi

[Jan Dupont]

As described to you in my email to you, there are no mistakes in the layout. The Input Gnd is made this way, so you can make the Gnd connection to fit your specific Amp internal connection

[peranders]

Jan, good work For curious reasons, I checked your Gerber files in Viewmate but the pads are minimal

I have used also GC-Preview with wierd results.

[Jan Dupont]

Hi Peranders and thanks
I'm not sure what you meen with Pad are minimal ??
Here is a view of the bottom copper in viewmate

[peranders]

Both my gerber wiever has problems with reading the files. I see now that the unit system seems to be wrong. Maybe I can configure the viewers to fit your files.

[Jan Dupont]

I opened a local file on my network disk, and had no problems with unit system......
Maybe I should try to check with the files on my website.
Perhaps they are corrupted in some way ........

Edit: Yes the files online are corrupted
Maybe the zip conversion did it??
I'll put up new files right away

[peranders]

It works now.... have you noticed my remark on Jens' pcb layout about the feedback? Your feedback point is a bit unsymmetrial, are you aware of that? You have also a couple of disturbing elements on the way to R120. A microscopic(?) improvement would be to "sniff" the feedback signal just before the inductor and have a clean trace directly to R120 with nothing else connected.

[Jan Dupont]

Yes I did notice your remark, and you are right about it being unsymmetrial
I will remember your point when making next layout