3886 oscillating?

mantisory · 27th December 2006, 03:34 PM

Hi there,
I built a chipamp from BriantGT and everything was in good working order. However, i have connected it to my new rogue preamp, which is said to be 'inverting' and now the amp is (I think) oscillating. I am not sure I have inverted the inputs from the pre to the amp, but if i didn't would it cause this behaviour?
The other thing that i changed was to put the jumpers back onto my speakers to remove the bi-wiring...
Thanks,
Mantisory

I_Forgot · 27th December 2006, 04:11 PM

What makes you think the amp is oscillating? Are you hearing hum or other noise? Is the chip getting hot even with no signal applied to the input?

I_F

Nordic · 27th December 2006, 04:23 PM

do you mean you are not sure if input wires are the wrong way around? yes, this would cause some noise...

mantisory · 27th December 2006, 04:31 PM

the chip is not overheating - i checked that early on.
there is audible periodic (1 second frequency maybe?) noise coming from the speakers even with no signal.

CarlosT · 27th December 2006, 04:39 PM

1 second? Hhhhmmm...sounds like a long interval for the usual 60Hz stuff from the power side.

I got a terrible loud buzzing sound (prolly like 60 Hz) when I grounded the metal mounting tab on an LM3875T the other night. Could something be grounded that shouldn't?

mantisory · 27th December 2006, 04:44 PM

yeah, maybe, i dunno - i am going to try some different speaker cables and also switch the inputs around.
it may be as wmuch as 2hz, but no more than that i think...i remeber that i had a similar problem in one channel when it wasn't connected to my speaker (I have read elsewhere that the chipamp doesn't like to be un-loaded), so i wonder if maybe my cabling is an issue..

halo0925 · 27th December 2006, 05:19 PM

Disconnect your pre amp and short the input to the chip amp to ground and see if you get the same result, if you do its the chip amp if not its probably the pre or a cableing issue

mantisory · 27th December 2006, 05:22 PM

will give 'er a go after work - thanks.

27th December 2006, 03:34 PM	#1
mantisory diyAudio Member Join Date: May 2002 Location: toronto	3886 oscillating? Hi there, I built a chipamp from BriantGT and everything was in good working order. However, i have connected it to my new rogue preamp, which is said to be 'inverting' and now the amp is (I think) oscillating. I am not sure I have inverted the inputs from the pre to the amp, but if i didn't would it cause this behaviour? The other thing that i changed was to put the jumpers back onto my speakers to remove the bi-wiring... Thanks, Mantisory

27th December 2006, 05:19 PM	#7
halo0925 diyAudio Member Join Date: Aug 2006	oscillating Disconnect your pre amp and short the input to the chip amp to ground and see if you get the same result, if you do its the chip amp if not its probably the pre or a cableing issue

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
please help with an oscillating amp	ballai.tibi	Solid State	101	19th June 2010 09:19 AM
Self oscillating fun	Eva	Class D	92	17th November 2008 06:21 PM
Impressions of Snubbered BrianGT 3886 vs Reg 3886	moving_electron	Chip Amps	1	23rd March 2005 06:51 AM
oscillating...always oscillating	WoulYaShassu	Solid State	30	9th April 2004 05:31 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


	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 December 2006, 04:11 PM	#2
I_Forgot diyAudio Member Join Date: Jan 2005 Location: Phoenix, Az.	What makes you think the amp is oscillating? Are you hearing hum or other noise? Is the chip getting hot even with no signal applied to the input? I_F

27th December 2006, 04:23 PM	#3
Nordic diyAudio Member Join Date: Sep 2005	do you mean you are not sure if input wires are the wrong way around? yes, this would cause some noise...

27th December 2006, 04:31 PM	#4
mantisory diyAudio Member Join Date: May 2002 Location: toronto	the chip is not overheating - i checked that early on. there is audible periodic (1 second frequency maybe?) noise coming from the speakers even with no signal.

27th December 2006, 04:39 PM	#5
CarlosT diyAudio Member Join Date: Oct 2006	1 second? Hhhhmmm...sounds like a long interval for the usual 60Hz stuff from the power side. I got a terrible loud buzzing sound (prolly like 60 Hz) when I grounded the metal mounting tab on an LM3875T the other night. Could something be grounded that shouldn't?

27th December 2006, 04:44 PM	#6
mantisory diyAudio Member Join Date: May 2002 Location: toronto	yeah, maybe, i dunno - i am going to try some different speaker cables and also switch the inputs around. it may be as wmuch as 2hz, but no more than that i think...i remeber that i had a similar problem in one channel when it wasn't connected to my speaker (I have read elsewhere that the chipamp doesn't like to be un-loaded), so i wonder if maybe my cabling is an issue..

27th December 2006, 05:22 PM	#8
mantisory diyAudio Member Join Date: May 2002 Location: toronto	will give 'er a go after work - thanks.