Help on Brute force

Ryssen · 9th March 2004, 06:52 PM

I have done some messuring on my Brute force (Glass Audio) headphone amp and as I can see there is something with 50 and
100hz that I don´t like.It must be something whit the power feeding or?I do not use any stabilizator in the power,but I am planing to use one will it help for this?I am messuring through my souncard,and when I messure only the soundcard there´s almost a straight line even at 50 and 100Hz.But when I listen with headphones (No signal) I hear hum,then I disconnect the line in to the headamp.the hum dissapears,what´s this hum from the computer?Is it some grounding problem how to solve this?

fdegrove · 9th March 2004, 10:51 PM

Hi,

Quote:

what´s this hum from the computer?Is it some grounding problem how to solve this?

The PC PSU is a switched mode supply rectifying at HF so 50/60 or 100/120Hz shouldn't originate from that one.

It sounds as if you have a groundloop somewhere.

Cheers,

Ryssen · 1st May 2004, 10:27 AM

A tips and a question.I have made some changes on my brute force,I have added a ground loop breaker: http://headwize2.powerpill.org/projects/meier_prj.htm
and an extra ground wire to from the amp to the coumputer chassie,so now it is a little bit better,but I am wondering about the thing from ca 40-500hz it´s a little bit higher than the rest.I have tried to change the capacistors in the signal path to different values,but there was no difference.When I mesaure just with the soundcard it is a flat line,so it must be the brute force.Any suggestions?

SY · 1st May 2004, 01:40 PM

I think you still have a ground loop, but inside the amp. Are you returning all grounds to a single point?

Ryssen · 1st May 2004, 06:13 PM

Yes,from the input and output RCA´s,they are isolated from the chassis,I have thick solid wire,where the cathode resitors are soldered to,and from that solid wire another solid wire to the first
e-lyt in the power supply where all other grounds meet,eccept for mains ground wich is connected to chassis.and between chassis and the solid wire is the ground loop breaker.

Ryssen · 2nd May 2004, 10:07 AM

I have now moved around the grounds in the amp and now I cannot hear any hum at all,I coul´d even remove the extra wires to the PC chassis,in fact I got more hum if they where there.But the peak in the frekv.response is stil there.The frekv.rexponse is from +1.6db-0,75db,what is good ,(acceptable)?The next step is to try Regulated supply.
Thank´s for the answers.

1st May 2004, 01:40 PM	#4
SY diyAudio Moderator Join Date: Oct 2002 Location: Chicagoland Blog Entries: 1	I think you still have a ground loop, but inside the amp. Are you returning all grounds to a single point? __________________ If there's a sucker born every minute, where do the rest of them come from?

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1st May 2004, 06:13 PM	#5
Ryssen diyAudio Member Join Date: Dec 2003 Location: Sweden--> Here	Yes,from the input and output RCA´s,they are isolated from the chassis,I have thick solid wire,where the cathode resitors are soldered to,and from that solid wire another solid wire to the first e-lyt in the power supply where all other grounds meet,eccept for mains ground wich is connected to chassis.and between chassis and the solid wire is the ground loop breaker.

2nd May 2004, 10:07 AM	#6
Ryssen diyAudio Member Join Date: Dec 2003 Location: Sweden--> Here	I have now moved around the grounds in the amp and now I cannot hear any hum at all,I coul´d even remove the extra wires to the PC chassis,in fact I got more hum if they where there.But the peak in the frekv.response is stil there.The frekv.rexponse is from +1.6db-0,75db,what is good ,(acceptable)?The next step is to try Regulated supply. Thank´s for the answers.