36 V DC offset when source connected

revell · 27th February 2005, 12:53 PM

The problem has probably been disussed before but I couldn't find it:
when no source is connected I have 54 mV dc offset on my GT kit when I connect a source (DVD player) the offset jumps to 36 volts

anyone who knows what to do?

jaudio · 27th February 2005, 12:57 PM

Make sure signal ground is connected

peranders · 27th February 2005, 12:58 PM

Do you have any resistor from the input down to ground?

janneman · 27th February 2005, 01:02 PM

Meneer Revell,

Gij zoudt kunnen trachten de source met een condensator in the koppelen, als het dan goed is weten we dat het ofwel de source is, ofwel de ingangsschakeling van de versterker.

Jan Didden

revell · 27th February 2005, 01:04 PM

Quote:

Do you have any resistor from the input down to ground?

I'm not sure what you mean, isn't the BrianGT kit an all-in package? I connected SG to - of the rca connector and IN to the+ of the rca connector

revell · 27th February 2005, 01:14 PM

Ok I tried a different source (very old walkman) and the dc remains low but when nothing is playing and the source is still connected I get a very loud hum. Maybe because it is not yet in a case?

janneman · 27th February 2005, 01:14 PM

You may want to post the circuit. Then we can check. Not everyone here is familiar with that particular kit you mentioned.

Jan Didden

revell · 27th February 2005, 01:21 PM

a diagram and more can be found here: http://www.chipamp.com/lm3875.shtml

Tube_Dude · 27th February 2005, 01:37 PM

Hi Revell

Use a cap at the input or a cap in series between the 620 Ohm resistor and ground.

paologatto · 27th February 2005, 02:08 PM

Probably a ground-loop problem.
Try connecting the 2 devices chassis/ground together with a wire.

I had a similar problem (70 V AC between 2 audio devices, also not pleasant to feel on my fingers!) and resolved with the chassis connection.

Bye

27th February 2005, 12:53 PM	#1
revell diyAudio Member Join Date: Jun 2004 Location: Kemzeke	36 V DC offset when source connected The problem has probably been disussed before but I couldn't find it: when no source is connected I have 54 mV dc offset on my GT kit when I connect a source (DVD player) the offset jumps to 36 volts anyone who knows what to do?

27th February 2005, 12:58 PM	#3
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Do you have any resistor from the input down to ground? __________________ /Per-Anders (my first name) or P-A as my friends call me

27th February 2005, 01:02 PM	#4
janneman diyAudio Member Join Date: May 2002 Location: Where Germany, The Netherlands and Belgium meet Blog Entries: 6	Meneer Revell, Gij zoudt kunnen trachten de source met een condensator in the koppelen, als het dan goed is weten we dat het ofwel de source is, ofwel de ingangsschakeling van de versterker. Jan Didden __________________ /New Linear Audio publication: Baxandall & Self on Audio Power!

27th February 2005, 01:14 PM	#7
janneman diyAudio Member Join Date: May 2002 Location: Where Germany, The Netherlands and Belgium meet Blog Entries: 6	You may want to post the circuit. Then we can check. Not everyone here is familiar with that particular kit you mentioned. Jan Didden __________________ /New Linear Audio publication: Baxandall & Self on Audio Power!

27th February 2005, 01:37 PM	#9
Tube_Dude diyAudio Member Join Date: Mar 2002 Location: Aveiro-Portugal	Hi Revell Use a cap at the input or a cap in series between the 620 Ohm resistor and ground. __________________ Jorge


	Please consider donating to help us continue to serve you. Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving

27th February 2005, 12:57 PM	#2
jaudio diyAudio Member Join Date: Oct 2004	Make sure signal ground is connected

27th February 2005, 01:21 PM	#8
revell diyAudio Member Join Date: Jun 2004 Location: Kemzeke	a diagram and more can be found here: http://www.chipamp.com/lm3875.shtml

27th February 2005, 02:08 PM	#10
paologatto diyAudio Member Join Date: Jun 2004 Location: Italy	Probably a ground-loop problem. Try connecting the 2 devices chassis/ground together with a wire. I had a similar problem (70 V AC between 2 audio devices, also not pleasant to feel on my fingers!) and resolved with the chassis connection. Bye

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Rotel RCD-971: Anyone revised the PCM63 Current Output Config-Source of DC Offset???	dtm1962	Digital Source	3	25th November 2010 09:39 PM
cmoy with 1uF input cap, DC offset from source still getting through	morfic	Solid State	11	5th August 2009 02:41 PM
Question about DC offset from source.	theAnonymous1	Solid State	2	12th November 2006 08:07 PM
Not connected yet	Andy G	Multi-Way	2	14th October 2006 10:20 AM
Must I have a TV connected?	Timn8ter	Digital Source	2	16th March 2004 07:27 PM

New To Site?	Need Help?
Register to Participate Search Privacy Statement Contact Us	Frequently Asked Questions Did you forget your password? Mark Forums Read