My LM4766 + 6p15p project, and LM1875 project. - diyAudio
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Old 12th June 2013, 06:20 PM   #1
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Join Date: Jun 2012
Location: Lithuania
Default My LM4766 + 6p15p project, and LM1875 project.

Hi.
I thought it would be interesting to show my pcb to others, hear opinions, etc.
After failed search for LM4766 pcb on internet, i decided to route myself. Because all pcb's i found on net was really bad...
I need to say, that i don't believe in expensive parts.
Only thing i care - no ceramics or electrolytics in signal path.

This PCB uses three stages of power supply bypassing:
1. 2x2200uF
2. 3x22uF
3. 3x0.22uF (smd)
Bypassing scheme based on LM4780 datasheet

input bias resistor to gnd 47K
input resistor 1K
input capacitor 0.68uF (-3db at 5Hz)

feedback 4k7 and 47K (smd) gives gain of 11
feedback caps 100uF
zobel 4r7 and 0.1uF
mute resistor 8k2 (smd) pulls about 2mA, 1mA per ch.
signal ground separated from power with 3r3

All smd 0805.

Amp sounds awesome, very strong and accurate bass and clean highs.
Probably a little better than my LM1875, which runs down to 1.5Hz what is too low on my poor small test speakers. But with normal speakers everything probably be different.
This LM4766 pcb is interchangeable with my LM1875 PCB, so i tested it with same power supply that my LM1875 uses (8 x mbr340 and 6x2200uF)

I going to try bi-amping with LM4766 to 310hz, and from 310hz with 6P15P tube amp.
Tube amp is tested and works really nice
And later i will post photos of almost finished LM1875 amp. < EDIT. No i will not post LM1875 photos here. It would become messy. I dedicate this topic to my LM4766 - 6p15p BiAmp.

LM4766 pics:
http://img189.imageshack.us/img189/686/p1060447f.jpg
http://img839.imageshack.us/img839/561/p1060448wt.jpg
http://img268.imageshack.us/img268/6849/p1060449.JPG
http://imageshack.us/a/img14/2341/lm4766lay.png

6p15p Tube amp (PCB routed by me too)
http://imageshack.us/a/img845/1649/p1060387n.jpg
http://imageshack.us/a/img855/4548/p1060388e.jpg
http://imageshack.us/a/img825/1682/tubelay.png
Tube power amplifier (I do not own this website)

If someone copy my layout, would be nice if you let me know. Or even show a photo if you build something with it






Last edited by valtra103; 15th August 2013 at 06:00 PM. Reason: added pics
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Old 19th June 2013, 12:18 AM   #2
IG81 is offline IG81  Canada
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Pretty cool! I was not finding much on people having used the LM4766 too, while looking at the various Overture chips on the Digikey page. Glad to hear something good about it. I might try to configure it for current drive on small fullrange drivers if I go with this project.

IG
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Old 24th June 2013, 05:41 PM   #3
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Quote:
Originally Posted by IG81 View Post
Pretty cool! I was not finding much on people having used the LM4766 too, while looking at the various Overture chips on the Digikey page. Glad to hear something good about it. I might try to configure it for current drive on small fullrange drivers if I go with this project.

IG
Thanks. I will post more pictures when i make some progress.
What advantage current drive have?

And i allmost forgot to mention: In my experience all chip amps hate high gains. I think gain of 11 is optimum, because with every bit of aditional gain chips sound worse, so i like to set gain just a little higher than minimum recommended and use preamp.

Last edited by valtra103; 24th June 2013 at 05:49 PM.
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Old 25th June 2013, 10:47 AM   #4
AndrewT is offline AndrewT  Scotland
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What about attaching your most informative pics to DIYaudio?
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regards Andrew T.
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Old 25th June 2013, 06:44 PM   #5
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Yes, I'd like to hear about current drive as well, I am using LM3886, and although it measures worse, is not so linear, I love the sonics of that amplifier driven by tube preamp.
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Old 27th June 2013, 08:50 PM   #6
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Quote:
Originally Posted by Headbanger View Post
Yes, I'd like to hear about current drive as well, I am using LM3886, and although it measures worse, is not so linear, I love the sonics of that amplifier driven by tube preamp.
Actually i don't use tube preamp. My active crossover have some gain in this case.
I tested crossover with one channel of LM4766 conected to high frequency output, and other channel to low freq output. In other words bi-amping.
And it sounded really good.
Now i need to make power supply for tube amp. Then i will be able to test bi-amping with tube amp for highs and 4766 for low frequencies.

Last edited by valtra103; 27th June 2013 at 08:52 PM.
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Old 2nd July 2013, 07:53 PM   #7
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Quote:
Originally Posted by valtra103 View Post
I tested crossover with one channel of LM4766 conected to high frequency output, and other channel to low freq output. In other words bi-amping.
And it sounded really good.
I guess that is the most important part, if it sounds good to you, then it is good.
Measurements often do not correlate with how appealing the sound of amp is. Maybe due to non-linearity of speakers or something. I'd like to get some info about crossovers for current driven speakers.
Good luck with tube amp.
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Old 25th July 2013, 12:30 AM   #8
lsheng is offline lsheng  United States
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Very good one. Very clear power and signal ground. Much better than most ebay PCB, where even double side PCBs do not have clear signal flows.

If this PCB does not have good sound, it must be the chip's fault.
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Old 30th July 2013, 07:05 AM   #9
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Quote:
Originally Posted by lsheng View Post
Very good one. Very clear power and signal ground. Much better than most ebay PCB, where even double side PCBs do not have clear signal flows.

If this PCB does not have good sound, it must be the chip's fault.

Thank you for good words

P.S. Project is not freezed, but my camera and/or memory card died... And
project is in my grandparents village... So when i go there i will take pictures.

Now box is half made. And most of pcb's mounted.
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Old 28th August 2013, 04:12 PM   #10
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Location: Lithuania
Amp tested...
And sounds awesome.
Need to make:
1) Control PCB with:
*ON/OF using pushbutton
*Fan based on temperature
*Delayed B+ transformer
*Maybe something more...

2) USB port for charging (have 5V st-by supply anyways, so why not And i like to use smart phone as music player...
3) Cover
4) Something i forgot to mention lol

If someone ask why i'm making it so complex: I do this not only for music, but for learning purposes, because I'm 18 years old. I like electronics not only music And try to make something new every time, to learn new things. This year i'm going to university to study electronics engineering.

Photos:

Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.
Click the image to open in full size.

Last edited by valtra103; 28th August 2013 at 04:38 PM. Reason: Messed up with photos
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