Problems with Chipamp (LM3886) BrianGT

Puffin · 18th November 2007, 09:48 AM

I have just completed the Dual Mono 3886 kit with dual power supplies. Power Supplies work, the amp boards are getting DC, but I get no sound. I am measuring <47milliamps at the speaker terminals (at least that's what the meter is showing me), but when connected to speakers, they just sound dead, no hiss, no hum. Any ideas ?

I am intending to use it as a power amp. Have I missed something ?

The amp is in standard configuration (i.e no feedback cap used)

I am getting about 22vDC to the amp board. Is this enough (twin 15v AC taps) I have a larger 30+30 vac if it needs it ?

Nuuk · 18th November 2007, 11:05 AM

Can you show us some hi-res close-ups of the amp? Sounds like a wiring problem somewhere.

Puffin · 18th November 2007, 11:37 AM

NuuK. Not sure if these are good enough. I would assume that by the fact that I am getting DC at the amp board, that the wiring to that is o.k. The Red & Blue wires to the mid right are Sig in+Sig Gnd and to the left Sig Out and Gnd Out.

http://i73.photobucket.com/albums/i2...x/PowerBd1.jpg

http://i73.photobucket.com/albums/i239/saxonsex/Amp.jpg

Nuuk · 18th November 2007, 11:49 AM

Have you checked both rails to make sure that you get the +/- voltages? If so (with something playing) measure the signal at the input phono socket, see if you have a signal at the amp inputs.

Check for a short between the signal wires too!

Puffin · 18th November 2007, 01:08 PM

NuuK. between PG- and V- I am only getting 0.9v Pg+ and V+ are giving me 24v. Is this the problem ?

audio1st · 18th November 2007, 01:21 PM

Have you got the polarity right? Does V- goto V- on the power supply board and the same with V+, PG+ and PG-. Using the same colour wires make it difficult to tell. Between V+ and V- should be over 30V.

Nuuk · 18th November 2007, 01:31 PM

Quote:

Between V+ and V- should be over 30V.

43-44 volts to be precise! Or in other words between ground (PG+) and positive you should get +21-22 volts and between ground (PG-) and negative you should get -21-22 volts.

Puffin · 18th November 2007, 01:33 PM

Audio1st. the instructions on Brian's site are to wire the PS wires like for like e.g V+ to V+ on Amp Bd, V- to V-, PGND to PGND etc.

I have measured the voltage between V+ and V- and I get 21volts.

What has just occurred to me is that the PS borad is designed for Stereo applications. It has 2 AC connection points AC1 and AC2. I could only get the LED to light (which is said to confirm that the PS is working) by connecting one set of secondarys to the same side (AC1). It may be that I have only got power to one side of the PSU board.

Here is a link to Chipamp.com

http://www.chipamp.com/docs/lm3886-manual.pdf

Here is a picture from the site. AC1 and AC2 are between the Diodes. If you click on the picture it will enlarge.

http://www.briangt.com/gallery/lm3886amp/proto_amp_4

john65b · 18th November 2007, 01:37 PM

Do you have a Center tapped transformer or is it a dual secondary?

The conections to the PS board for the two are quite different

Puffin · 18th November 2007, 01:38 PM

Dual Secondary.

18th November 2007, 09:48 AM	#1
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	Problems with Chipamp (LM3886) BrianGT I have just completed the Dual Mono 3886 kit with dual power supplies. Power Supplies work, the amp boards are getting DC, but I get no sound. I am measuring <47milliamps at the speaker terminals (at least that's what the meter is showing me), but when connected to speakers, they just sound dead, no hiss, no hum. Any ideas ? I am intending to use it as a power amp. Have I missed something ? The amp is in standard configuration (i.e no feedback cap used) I am getting about 22vDC to the amp board. Is this enough (twin 15v AC taps) I have a larger 30+30 vac if it needs it ?

18th November 2007, 11:05 AM	#2
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	Can you show us some hi-res close-ups of the amp? Sounds like a wiring problem somewhere. __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

18th November 2007, 11:49 AM	#4
Nuuk diyAudio Member Join Date: Feb 2003 Location: Somerset, SW England	Have you checked both rails to make sure that you get the +/- voltages? If so (with something playing) measure the signal at the input phono socket, see if you have a signal at the amp inputs. Check for a short between the signal wires too! __________________ The truth need not be veiled, for it veils itself from the eyes of the ignorant.

18th November 2007, 01:37 PM	#9
john65b diyAudio Member Join Date: Jan 2005 Location: Chicago	Do you have a Center tapped transformer or is it a dual secondary? The conections to the PS board for the two are quite different __________________ "I speak Spanish to God, Italian to Women, French to Men, and German to my Horse" - Charles V

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18th November 2007, 11:37 AM	#3
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	NuuK. Not sure if these are good enough. I would assume that by the fact that I am getting DC at the amp board, that the wiring to that is o.k. The Red & Blue wires to the mid right are Sig in+Sig Gnd and to the left Sig Out and Gnd Out. http://i73.photobucket.com/albums/i2...x/PowerBd1.jpg http://i73.photobucket.com/albums/i239/saxonsex/Amp.jpg

18th November 2007, 01:08 PM	#5
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	NuuK. between PG- and V- I am only getting 0.9v Pg+ and V+ are giving me 24v. Is this the problem ?

18th November 2007, 01:21 PM	#6
audio1st diyAudio Member Join Date: May 2005 Location: Foxton, CAMBS..	Have you got the polarity right? Does V- goto V- on the power supply board and the same with V+, PG+ and PG-. Using the same colour wires make it difficult to tell. Between V+ and V- should be over 30V.

18th November 2007, 01:33 PM	#8
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	Audio1st. the instructions on Brian's site are to wire the PS wires like for like e.g V+ to V+ on Amp Bd, V- to V-, PGND to PGND etc. I have measured the voltage between V+ and V- and I get 21volts. What has just occurred to me is that the PS borad is designed for Stereo applications. It has 2 AC connection points AC1 and AC2. I could only get the LED to light (which is said to confirm that the PS is working) by connecting one set of secondarys to the same side (AC1). It may be that I have only got power to one side of the PSU board. Here is a link to Chipamp.com http://www.chipamp.com/docs/lm3886-manual.pdf Here is a picture from the site. AC1 and AC2 are between the Diodes. If you click on the picture it will enlarge. http://www.briangt.com/gallery/lm3886amp/proto_amp_4

18th November 2007, 01:38 PM	#10
Puffin diyAudio Member Join Date: Feb 2006 Location: U.K	Dual Secondary.

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