My first non-inverted gainclone circuit - 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 16th June 2005, 04:55 PM   #1
diyAudio Member
 
Join Date: Jun 2003
Location: Haifa, Israel
Send a message via ICQ to eranrund
Default My first non-inverted gainclone circuit

Hello people.

Below is my first non-inverted gainclone circuit. It is powered from a toroid-based power supply which will supply around 25-30v to it (still need to decide - any help will be appritiated). The power supply has 10000uf of total capacitence on each rail (shared by two copies of this circuit...)
I plan to power 6-8ohm speakers with it.
Volume controll will be established using an external, active, pre-amplifier yet to be built

Please - try be realistic. This is my first project - dont kill me

Thanks a lot
Attached Images
File Type: png amp.png (8.6 KB, 896 views)
  Reply With Quote
Old 16th June 2005, 06:57 PM   #2
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Not sure what to say. It looks OK but I would use a smaller film capacitor for the DC blocker.

If you are using 10K caps in the PSU, I suggest that you have a look at Carlos' snubberized PSU.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 17th June 2005, 09:54 AM   #3
diyAudio Member
 
Join Date: Jun 2003
Location: Haifa, Israel
Send a message via ICQ to eranrund
Heya.

I did put snubbers on the PSU
Ok, I will use a smaller capacitor. How about 4.7uF?
Except that. will it be ok?
Any other things worth adding/changing/removing?

Thanks.
  Reply With Quote
Old 17th June 2005, 10:02 AM   #4
Nuuk is offline Nuuk  United Kingdom
diyAudio Member
 
Nuuk's Avatar
 
Join Date: Feb 2003
Location: Somerset, SW England
Quote:
How about 4.7uF?
That's fine and do make sure it is a good film type as this is the most important cap as regards sound quality.

Anything else need changing? No, I don't think so but you can always read my thoughts on GC's at Decibel Dungeon.
__________________
The truth need not be veiled, for it veils itself from the eyes of the ignorant.
  Reply With Quote
Old 17th June 2005, 10:47 AM   #5
diyAudio Member
 
Join Date: Jun 2003
Location: Haifa, Israel
Send a message via ICQ to eranrund
Thanks dude
Ofcourse I've read your site. An excellent one, I must say!
  Reply With Quote
Old 17th June 2005, 12:55 PM   #6
diyAudio Member
 
Join Date: Jun 2003
Location: Haifa, Israel
Send a message via ICQ to eranrund
Hey guys.
I've made some more changes and designed a PCB:
Attached Images
File Type: png amp2.png (13.0 KB, 624 views)
  Reply With Quote
Old 17th June 2005, 02:32 PM   #7
diyAudio Member
 
Join Date: Mar 2003
Location: Austin
Send a message via AIM to ScottRHinson
Default Re: My first non-inverted gainclone circuit

Quote:
Originally posted by eranrund
Hello people.

Below is my first non-inverted gainclone circuit. It is powered from a toroid-based power supply which will supply around 25-30v to it (still need to decide - any help will be appritiated). The power supply has 10000uf of total capacitence on each rail (shared by two copies of this circuit...)
I plan to power 6-8ohm speakers with it.
Volume controll will be established using an external, active, pre-amplifier yet to be built

Please - try be realistic. This is my first project - dont kill me

Thanks a lot

Eranrund,

If you don't mind...a couple of suggestions:

1. I don't see a path for DC bias currents for the input. I would move C2 directly accross pin 7 and 8. Also move R2 to the other side of C1.

2. R3 and R1 are somewhat high in value, try 22K for R3, 1K for R1 and 100uF for C3.

3. The National application note for the 3886 mentions the potential need for a resistor accross the input terminals, at the input terminals to prevent oscillations when there is nothing connected to those input terminals. Leave yourself a spot on the PCB for a 10K or a 5K resistor and a small cap (to filter RF) right at the input terminals.

4. Try to get your feedback and input components closer to the 3875 chip on your circuit layout.

5. Provide separate ground returns to the star point of your chassis for signal ground (R2 and C3 return) than power ground (R4, C7, C8, C5, C6). Study the suggested layout for the 4870.

6. The power supply bypass capacitors need to be closer to the chip.

I have just finished putting together a 3886 board. When I first started it up I was using some linearly regulated supplies with test leads that were longer than I would have liked. In the process I discovered how sensitive the high gain, wide bandwidth chip is. I had oscillation issues with that test supply even though I had all of my bypass capacitors as close as physically possible to the chip, my feedback and input circuitry was in a tight loop around the chip pins, and I had separated my signal and power grounds all the way back to the star point.

When I switched to the real supply with shorter, heavier gauge wiring all of these issues went away, but it did give me a better appreciation for the warnings posted in the data sheet.


Scott
  Reply With Quote
Old 17th June 2005, 02:36 PM   #8
diyAudio Member
 
Russ White's Avatar
 
Join Date: Jan 2005
Location: Nashville, TN, USA
Send a message via Yahoo to Russ White
Quite a good start!
__________________
Less pulp more juice Twisted Pear Audio.
  Reply With Quote
Old 17th June 2005, 07:11 PM   #9
diyAudio Member
 
Join Date: Jun 2003
Location: Haifa, Israel
Send a message via ICQ to eranrund
Heya.

New versions:
- still need to figure out how to do star grounds - no idea how :-(
i think i'm gonna solder directly to the chip extra capacitors for +ve and -ve. i might solder the feedbacks on it as well.

Please give some more comments

Click the image to open in full size.
Click the image to open in full size.
  Reply With Quote
Old 17th June 2005, 07:20 PM   #10
diyAudio Member
 
Join Date: Mar 2003
Location: Austin
Send a message via AIM to ScottRHinson
Quote:
Originally posted by eranrund
Heya.

New versions:
- still need to figure out how to do star grounds - no idea how :-(
i think i'm gonna solder directly to the chip extra capacitors for +ve and -ve. i might solder the feedbacks on it as well.

Please give some more comments


For an excellent example of star grounding look at the datasheet for the LM4870 (4780?). When doing your layout I suggest the following steps.

1. Place amplifier chip.
2. Place feedback parts next to the pins they are connected to.
3. Place input parts next to the pins they are connected to.
4. Place bypass parts next to the pins they are connected to.
5. Place everything else.
6. Route bypass capacitors with wide traces.
7. Route feedback nets keeping all traces as short as possible.
8. Route input nets keeping all traces as short as possible.
9. Route everything else.

Scott
  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
Inverted GainClone question? 5150ed Chip Amps 35 10th July 2006 08:16 AM
PCB for Inverted Gainclone 2Bak Chip Amps 8 19th February 2004 09:09 AM
Non-Buffered Non-Inverted Gainclone (LM3875) fpr 47K Pot Circuit Wanted krishu Chip Amps 42 5th January 2004 12:14 PM
Circuit questions - Inverted vs non-inverted (again) alvinlim Chip Amps 4 1st July 2003 11:27 AM
Non-inverted Gainclone jpask Chip Amps 1 29th March 2003 08:01 AM


New To Site? Need Help?

All times are GMT. The time now is 05:13 PM.


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