Buzz Noise on outputs with inputs attached

akunec · 6th March 2005, 12:15 AM

I have a noise problem on my parelleled 4780 amp. I have a lot of noise coming out the outputs. I hooked up the outputs to my scope and it looks like a half sine wave ~ 60hz, then 0 v then another half sine wave in the other direction. There is a gap of about 2 periods between these half sine waves. Does anyone know what is causing this?

peranders · 6th March 2005, 06:14 AM

Have you checked youir supply voltage? Is it "DC" or something else".

What happens if you shorten your input? Have the two channels the same behavior?

akunec · 6th March 2005, 07:15 PM

Yah, both channels have the same behaviour (both use the same tranny and rectifier), the noise doesn't change when I short the inputs?

akunec · 7th March 2005, 12:31 AM

Thanks for the help. I checked out the 2 supply voltages on the scope and they seem pretty bad. (looks like lines going up and down like ^^^^^^. )

I'm currently using a 400VA toroidal transformer with dual secondary 21V outs. The 2 coils are attached together to form the ground, while the other 2 wires are rectified using 4 MUR860 diodes.

Would it be better to leave the 2 coils seperated and rectify them individually using 8 diodes?

I have 17600uF total between 2 parelleled LM4780s. Is this enough?

6th March 2005, 12:15 AM	#1
akunec diyAudio Member Join Date: Aug 2004 Location: Alberta	Buzz Noise on outputs with inputs attached I have a noise problem on my parelleled 4780 amp. I have a lot of noise coming out the outputs. I hooked up the outputs to my scope and it looks like a half sine wave ~ 60hz, then 0 v then another half sine wave in the other direction. There is a gap of about 2 periods between these half sine waves. Does anyone know what is causing this?

6th March 2005, 06:14 AM	#2
peranders Electrons are yellow and more is better! diyAudio Member Join Date: Apr 2002 Location: Göteborg, Sweden Blog Entries: 4	Have you checked youir supply voltage? Is it "DC" or something else". What happens if you shorten your input? Have the two channels the same behavior? __________________ /Per-Anders (my first name) or P-A as my friends call me

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
What components has to be present on the balanced inputs/outputs of an audio ADC/DAC?	skpb	Analog Line Level	3	12th October 2006 07:30 PM
Changing inputs and outputs on DH-200	jakelm3075	Solid State	4	30th March 2006 10:28 PM
designing inputs + outputs of electronic crossover	stinkpot	Parts	12	14th May 2005 05:07 PM
buzz noise on outputs with no input attached	akunec	Chip Amps	9	28th February 2005 11:18 AM
Why are XLR outputs male, and inputs female?	Bricolo	Parts	5	30th August 2004 01:43 AM

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


	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

6th March 2005, 07:15 PM	#3
akunec diyAudio Member Join Date: Aug 2004 Location: Alberta	Yah, both channels have the same behaviour (both use the same tranny and rectifier), the noise doesn't change when I short the inputs?

7th March 2005, 12:31 AM	#4
akunec diyAudio Member Join Date: Aug 2004 Location: Alberta	Thanks for the help. I checked out the 2 supply voltages on the scope and they seem pretty bad. (looks like lines going up and down like ^^^^^^. ) I'm currently using a 400VA toroidal transformer with dual secondary 21V outs. The 2 coils are attached together to form the ground, while the other 2 wires are rectified using 4 MUR860 diodes. Would it be better to leave the 2 coils seperated and rectify them individually using 8 diodes? I have 17600uF total between 2 parelleled LM4780s. Is this enough?

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