LM3886 running inverting only and bridged - for 8 Ohms only - diyAudio
Go Back   Home > Forums > Amplifiers > Chip Amps

Chip Amps Amplifiers based on integrated circuits

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
Reply
 
Thread Tools Search this Thread
Old 30th October 2012, 12:37 PM   #1
astx is offline astx  Austria
diyAudio Member
 
Join Date: Jan 2011
Location: Tyrol / Austria
Default LM3886 running inverting only and bridged - for 8 Ohms only

Dear diy'ers,

attached you can find my diy version of a very good and warm sounding 4 channel gainclone based on LM4562 and 2 x LM3886.
Feel free to re-use my schematics and pcb for DIY!
To manage mains there is a pic microcontroller based control circuit.

Best regards,

Toni

lm3886_bridging_amplifier.png

amp2012_inrush_mains.png amp2012_inrush_control.png 1024x768-2012-10-21 16.34.50.jpg

1024x768-2012-09-29 16.58.55.jpg 1024x768-2012-10-21 16.28.00.jpg 1024x768-2012-10-21 16.34.05.jpg

1024x768-2012-10-21 16.38.42.jpg 1024x718-IMD_19_20kHz_CH_A_LE.PNG

lm3886_inv_btl_schematics_and_pcb.zip

Last edited by astx; 10th September 2013 at 08:27 PM.
  Reply With Quote
Old 30th October 2012, 12:55 PM   #2
astx is offline astx  Austria
diyAudio Member
 
Join Date: Jan 2011
Location: Tyrol / Austria
some more pictures:

1024x768-2012-09-20 23.25.14.jpg 1024x718-THD+N_5W_8_OHM.PNG

1024x718-THD+N_50W_8_OHM.PNG 1024x768-2012-10-21 16.29.15.jpg
  Reply With Quote
Old 30th October 2012, 01:13 PM   #3
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
I'm not allowed to put in the word I am thinking !!!

I had a post written and clicked on a pic. The Forum downloaded a revised page with the pic. When I returned to where I was, my post was lost.
Why does the Forum sometimes on clicking superimpose the pic alongside where one currently is and at other times take one to a new page?
__________________
regards Andrew T.

Last edited by AndrewT; 30th October 2012 at 01:16 PM.
  Reply With Quote
Old 30th October 2012, 01:18 PM   #4
AndrewT is offline AndrewT  Scotland
diyAudio Member
 
Join Date: Jul 2004
Location: Scottish Borders
How about adding a note that the decoupling caps Cs are located on the amp PCBs and not as shown on the PSU schematic.

How does output offset vary with time from start up and/or with temperature?

Can you include details of the MCU operation and how we can duplicate that functionality?

Why does the FFT show both 50Hz and 60Hz and the harmonics of both?

And congrats on the super drawings.

Clever use of the sawn in half heatsink to fit all 4 amplifiers inside your chassis and still give adequate cooling. Nice.

I have a similar sink but it's only 50mm tall. If instead of having 12 @ 50mm I had 6 @ 100mm high I would never have any cooling problems. What height is your extrusion?
__________________
regards Andrew T.

Last edited by AndrewT; 30th October 2012 at 01:26 PM.
  Reply With Quote
Old 30th October 2012, 01:21 PM   #5
astx is offline astx  Austria
diyAudio Member
 
Join Date: Jan 2011
Location: Tyrol / Austria
Dear AndrewT,

thank you for your response - but I am not responsible for any forum problems ...


If you have any comment on the project - try again to post your ideas.


Regards,
Toni
  Reply With Quote
Old 30th October 2012, 01:22 PM   #6
diyAudio Member
 
Join Date: Feb 2008
Location: Jackson,michigan
I like this method of design and is the way I have been planing driving my chipamp design for a BTL configuration.
Thanks for posting the THD graphs.

Cheers!!!

jer
  Reply With Quote
Old 30th October 2012, 01:52 PM   #7
astx is offline astx  Austria
diyAudio Member
 
Join Date: Jan 2011
Location: Tyrol / Austria
Quote:
Originally Posted by AndrewT View Post
How about adding a note that the decoupling caps Cs are located on the amp PCBs and not as shown on the PSU schematic.

How does output offset vary with time from start up and/or with temperature?

Can you include details of the MCU operational and how we can duplicate that functionality?

Why does the FFT show both 50Hz and 50Hz and the harmonics of both?

And congrats on the super drawings.

Many questions in one post ...

1) The "PSU" that you mean are the bypass capacitors already located on the amplifier pcb. As we have here 2 types of GND (power GND and analog GND) I have decided to draw this an the amp circuit.

2) I have built 4 amplifiers and the output DC offset varies from 1mV to 35 mV. As the amp warms up the DC offset is getting lower. The DC offset depends mainly on the LM4562 input stage. If one would match/check the used input opamps, there would be nearly no DC offset as the two LM3886 are galvanically coupled to the input/inverter stage.

3) Maybe someday you will find the firmware and C source-code using SDCC compiler to self edit the firmware. As the "mains inrush controller" is not directly needed for this project, I will open a new thread if there is enough interest on it.
What is controlled by the MCU/inrush controller (which itself is always powered by a small PSU):
  • Controls the 2 mains relays to suppress inrush current. Supports two high power toroids. Timing is configurable. (typically 250ms delay)
  • mute signal during power on/off.
  • power on/off button (on switch or push button with power state saving in eeprom)
  • external power on/off (e.g.: needs additional optocoupler)
  • 3 configurable temperature sensors (e.g.: left/right heatsink; case temperature)
  • DC speaker controll - emergency power off - locked
  • RS232-TTL-Level-Interface for configuration only or for connection to another MCU (e.g.: to support IR remote control, Voltage sensors etc.)
4) The 50Hz and its harmonics are introduced by the measurement setup: PC running ARTA/STEPS and using an ASUS Xonar Essence STX Soundcard. During measurements a Hameg HM1507 OSC was also connected. The amp itself is totally silent with shorted inputs.

Thank you,

Toni
  Reply With Quote
Old 30th October 2012, 02:09 PM   #8
astx is offline astx  Austria
diyAudio Member
 
Join Date: Jan 2011
Location: Tyrol / Austria
Quote:
Originally Posted by AndrewT View Post

Clever use of the sawn in half heatsink to fit all 4 amplifiers inside your chassis and still give adequate cooling. Nice.

I have a similar sink but it's only 50mm tall. If instead of having 12 @ 50mm I had 6 @ 100mm high I would never have any cooling problems. What height is your extrusion?
Dear AndrewT,

sorry I have overseen your last question:
The heat sink model: KS216-100E (0.4 K/W) before "saw in action". Size: 216x83x100mm.
An LR24 stateful variable active crossover divides the signal before amp input into bass and mid/treble (crossover point 400Hz). So the heat sinks are big enough as only 2 amplifiers are providing high power.

Regards,
Toni
  Reply With Quote
Old 30th October 2012, 03:02 PM   #9
astx is offline astx  Austria
diyAudio Member
 
Join Date: Jan 2011
Location: Tyrol / Austria
Quote:
Originally Posted by geraldfryjr View Post
I like this method of design and is the way I have been planing driving my chipamp design for a BTL configuration.
Thanks for posting the THD graphs.

Cheers!!!

jer
Dear jer,

you mean you already have a similar design ...

Regards, Toni


lm3886_bridging_amplifier_pcb.png
  Reply With Quote
Old 30th October 2012, 04:05 PM   #10
astx is offline astx  Austria
diyAudio Member
 
Join Date: Jan 2011
Location: Tyrol / Austria
Quote:
Originally Posted by AndrewT View Post
Why does the FFT show both 50Hz and 60Hz and the harmonics of both?
Dear AndrewT,

about the 50 Hz: our mains is running 50Hz. I thought about the 60Hz artefacts and the only source with 60Hz:
The connected LCD monitor get it's video signal with 60Hz refresh ... could it be the video card generating a sharp 60 Hz pulse?

Regards, Toni
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Bridged LM4780 kit: 5 Ohms (Min) at 300Hz = smoke? Plammox Audio Sector 5 10th December 2009 03:44 PM
Bridged ClassD 800W in 4 ohms - oscillation problem Zoors Class D 24 10th May 2008 07:16 PM
Bridged Lm4780. Up and running. sachi Chip Amps 0 15th December 2005 05:27 AM
Bridged Lm4780. Up and running! sachi Chip Amps 5 14th December 2005 04:37 PM
Bridged/Stereo, w or w/o servo, inverting 3886, inverting buffer PCB Alexander Rice Chip Amps 9 27th March 2004 06:53 PM


New To Site? Need Help?

All times are GMT. The time now is 04:51 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2