t-amp is pushing speaker cone out

MisterTwister · 17th December 2010, 03:02 AM

Hello. when I connect speakers to my t-amp, speaker cones are pushed out quite a bit and stay in this position. does anyone know why this is happening?

Pano · 17th December 2010, 03:33 AM

I can sure guess! DC offset.
What can happen, and probably has in your case, it that there is a path to ground after the input caps. You do have input caps, right? There is about 2.5V on the inputs. If this gets pulled down toward ground, you'll see DC at the outputs. That DC will push your speaker cone. It only takes a small "leak" to ground to do this. Be sure there is no DC path to ground between the input caps and the chip. If the amp works OK otherwise, this is likely the problem.

Note:
You should see 1/2 the power supply voltage (above ground) on the speaker terminals of most T-amps. But you should see this on both neg AND pos terminals from ground, but not between the neg and pos. This is normal. The DC offset mentioned above is not.

Poindexter · 17th December 2010, 03:40 AM

Whut he sed.

Poinz

MisterTwister · 17th December 2010, 07:21 PM

thank you for reply.
I did modify my amp according to these instructions
sureelectronics Tripath boards?
removed c3 and c24. could this cause a problem?
I measured voltage across speaker terminals, it's about 1volt.

cjkpkg · 19th December 2010, 11:36 PM

yes you have DC across your speaker terminals. You should have no more than 10 or 20 mA DC on your terminals *in general*

Work from your speaker terminals backwards and the first place that DC could get into the output.

Pano · 20th December 2010, 08:18 PM

Check to see if you find about 2.5V on the volume pot or the inputs. There should not be.

MisterTwister · 22nd December 2010, 02:35 AM

there was 0v on input.
oops, I just accidentally killed the amp.

shortened chip's pins with voltmeter's probe

theAnonymous1 · 22nd December 2010, 03:07 AM

Quote:

Originally Posted by MisterTwister

shortened chip's pins with voltmeter's probe

Heh, been there plenty of times.

17th December 2010, 03:02 AM	#1
MisterTwister diyAudio Member Join Date: Feb 2006 Location: usa Blog Entries: 1	t-amp is pushing speaker cone out Hello. when I connect speakers to my t-amp, speaker cones are pushed out quite a bit and stay in this position. does anyone know why this is happening?

17th December 2010, 03:33 AM	#2
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	I can sure guess! DC offset. What can happen, and probably has in your case, it that there is a path to ground after the input caps. You do have input caps, right? There is about 2.5V on the inputs. If this gets pulled down toward ground, you'll see DC at the outputs. That DC will push your speaker cone. It only takes a small "leak" to ground to do this. Be sure there is no DC path to ground between the input caps and the chip. If the amp works OK otherwise, this is likely the problem. Note: You should see 1/2 the power supply voltage (above ground) on the speaker terminals of most T-amps. But you should see this on both neg AND pos terminals from ground, but not between the neg and pos. This is normal. The DC offset mentioned above is not. __________________ Take the Speaker Voltage Test!

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17th December 2010, 03:40 AM	#3
Poindexter diyAudio Member Join Date: Oct 2004 Location: Maui, Hawai'i, USA	Whut he sed. Poinz

17th December 2010, 07:21 PM	#4
MisterTwister diyAudio Member Join Date: Feb 2006 Location: usa Blog Entries: 1	thank you for reply. I did modify my amp according to these instructions sureelectronics Tripath boards? removed c3 and c24. could this cause a problem? I measured voltage across speaker terminals, it's about 1volt.

19th December 2010, 11:36 PM	#5
cjkpkg diyAudio Member Join Date: Aug 2008 Location: Roswell GA	yes you have DC across your speaker terminals. You should have no more than 10 or 20 mA DC on your terminals in general Work from your speaker terminals backwards and the first place that DC could get into the output.

20th December 2010, 08:18 PM	#6
Pano diyAudio Moderator Join Date: Oct 2004 Location: North Carolina Blog Entries: 4	Check to see if you find about 2.5V on the volume pot or the inputs. There should not be.

22nd December 2010, 02:35 AM	#7
MisterTwister diyAudio Member Join Date: Feb 2006 Location: usa Blog Entries: 1	there was 0v on input. oops, I just accidentally killed the amp. shortened chip's pins with voltmeter's probe

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