My "audiophile" LM3886 approach

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#2,921
:shy:
Hi all,
I am back in to the project again!
Why?
I made a pair of 3875 GC with onboard Pedja Rogic buffer a while ago.. In the beginning I liked it too much.. But day after day its sound getting boring and non-analytical to me! May be its a component selection problem or just psychological..
Then started to listen my old LM4780 GC with some audio grade component upgrade and a LM4562 preamp and its sound was more better than buffered 3875.
Anyway,
Now I want to retry Rev.C. Last time I had to stop project because of PCB design problems. And at the moment it looks solved.. So this is my last PCB design for Rev.C:
An externally hosted image should be here but it was not working when we last tested it.

Its a single sided design and a ground plane may be added on the top side if requested..
As you will see, there is no connection between signal GND and power GND.. Because I will use a single regulated supply for both channels and the GND s will be connected on this PSU board with a 1R resistor.
Any comments or anybody wants to do this with me?
 
#2,923
Hey Nordic.
Well, I am a prolific starter 🙂 Have a few 90% done. HRII and F5 for instance only need 2 or 3 more parts each. K502 and LM3886 amps are done and sound nice. Fostex Fonkens and Audio Nirvana BRs are done and B1 buffer pre is done. I am happy with all of them that are finished.
I want to build the C to take on vacation with me to have my friends listen to how great a DIY can sound. They are a bunch of doubters and from what I read this is probably one of the best implementations of LM3886.
Uriah
 
#2,924
Hi Ozgur and Udaley,

IMHO, high quality PS for the LM318 is critical for Hi quality sound on RevC. I have tried so far:
*simple lm317/337: better bass and impact than stock unit but still "hard" sound.
*TeddyReg with BC550/560 DIY Darlington: better sound overall, softer, more elegant. Bass is good which adds depth to the image.
*TeddyReg with BC550->BD139 Darlington: outstanding bass with less extended HF.

What I'm trying to say is use your preferred high quality regulated supply (LM317 and the like won't qualify as it). 😎
It is worth it.

Good luck,
M
 
#2,925
Yep its pretty good, maybe not as smooth as the HRII you are nearly done with, but pretty good for a chipamp. I would say it would kill anything commercial south of $300.

DX, bypass the pre, with this amp I believe the best solution is just a pot infront of it. At least this is how mine ended up... remove the pre and give your ear a day to adjust... also let the amp burn in a bit more. Some people do not believe in burn in... I say they can go suck my elbow.

I have pointed it out before, on advice from Mauro, I replaced the 220uf Caps at the chip with a low ESR Vishay cap, made the world's diffirence.
 
#2,926
South of $300? They must sell really great amps for super cheap in S. Africa. The sound of my plain old LM3886 blows away my Harmon Kardon AVR135 which is now in storage. And I dont think I have listened to $1000 amps that were any better. I am talking Yamaha, Sony, and the like down at the Big Box stores like Best Buy and Circuit City or Tweeter. I never expected those amps to be great but was pleased the LM3886 pounded them for quality of sound.
Hmm. But you like it better than maybe a chipamp.com version? Really, I dont want to build it if the sonics wont be much better. I can put my money into... I dunno yet, maybe a better DMM.

Max, Thanks for the hints on the PSU I will take that into consideration.

URiah
 
#2,927
Yep it is better than a standard LM3886 config, and can be tuned further...

What it isn't, is a good discrete amp. Don't get me wrong it is going to blow many other commercial chip amps out of the water... but after enough time or with exposure to better equipment you may realise the diffirence in sound quality.

Without much exposure to high class audio I would say this amp would sound astounding, especialy when coupled with an adequate transformer... once again not something you see until you reach a big price ticket in a shop.
 
#2,933
Dear Udailey,
You haven't completed the amp yet, right?
If so, I recommend you do this first, enjoy it, and when you feel the bite again, tweak it 😉

Yes, the TeddyReg needs an out board like stripboard. You can see them on my very bad pick for which a link was poted above.

http://picasaweb.google.com/maxlorenz24/TeddyReg/photo#5234754717241252978
Here a view of de desoldering of the zener wich will feed the Reg:
http://picasaweb.google.com/maxlorenz24/TeddyReg/photo#5233960546067228434

The guys at PFM have a groupbuy with dedicated boards but I'm stuck to my stripboard instead. It is complicated as a first attempt regulated PS...

Actually, I'm having trouble with one of my amp's regs. The other channel is OK. I will try the gyrator after the 20V zener diode, without the pre-regulator to see how it sounds. I think(hope) LM318 can handle the V (around 19V)

Cheers,
M
 
#2,934
Actually I just got my copper clad board in the mail today. I would like to try to transfer a toner image to it and dip it by this weekend. Might take a few tries. Never tried this before.
So, good idea Max. I will build it the Twisted Pear way and then try to tweak the PSU your way after a bit of a listen. BTW complicated PSUs dont scare me they just make me feel like your signature 🙂
Uriah
 
#2,935
maxlorenz said:
Hi Ozgur and Udaley,

IMHO, high quality PS for the LM318 is critical for Hi quality sound on RevC. I have tried so far:
*simple lm317/337: better bass and impact than stock unit but still "hard" sound.
*TeddyReg with BC550/560 DIY Darlington: better sound overall, softer, more elegant. Bass is good which adds depth to the image.
*TeddyReg with BC550->BD139 Darlington: outstanding bass with less extended HF.

What I'm trying to say is use your preferred high quality regulated supply (LM317 and the like won't qualify as it). 😎
It is worth it.

Good luck,
M
Click to expand...

Dear Max,
This is why I did not put the PSU on board... I will use my LM3617/337 PSU first then if I dont like I will use the TeddyReg..
But you did not say anything about my new PCB layout?
THX..

Nordic said:
Yep its pretty good, maybe not as smooth as the HRII you are nearly done with, but pretty good for a chipamp. I would say it would kill anything commercial south of $300.

DX, bypass the pre, with this amp I believe the best solution is just a pot infront of it. At least this is how mine ended up... remove the pre and give your ear a day to adjust... also let the amp burn in a bit more. Some people do not believe in burn in... I say they can go suck my elbow.

I have pointed it out before, on advice from Mauro, I replaced the 220uf Caps at the chip with a low ESR Vishay cap, made the world's diffirence.
Click to expand...

Dear Nordic,

I do believe in burning! Especially for the power stages.. Because I have tested and heard with my ears..
Anyway,
I wont use my preamp with this amp.. It was for my LM4780 and LM4702 amps.. However I have tested it with my 3875+buffer amp but did not see any difference with or without preamp.. Thats interesting. Because I heard a lot of sound differences with LM4780 and LM4702 amplifiers..
THX...
 
#2,936
Ozgur,
One nice thing about a preamp is to NOT hear it. Another nice thing, for me anyway, is to use unity gain buffered preamp. To me a pre is not much more than an input selector and handy for changing volume. However, if you want a nice sound added overtop of the music by your pre you might consider putting a tube in there somewhere. I love tube sound.
Uriah

PS your layout looks nice to me, but I have not compared it to the schematic to make sure pin to pin is correct.
 
#2,937
Separate PSU for LM318 - please advise

What Russ told me is clear so far:
Remove R1 and R4, remove the two zeners ZD1 and ZD2.
Connect your negative supply to the R1 pad on the LM318 side of things.
Connect your positive supply to the R4 pad on the LM318 side of things.
Connect your PSU GND at power gnd on the REVC.
Click to expand...

I intend to use a complete regulated PSU with own transformer and rectifier. Will it work in that way? 😕
 
#2,940
Dear Dxvideo,

This is why I did not put the PSU on board... I will use my LM3617/337 PSU first then if I dont like I will use the TeddyReg..
But you did not say anything about my new PCB layout?
Click to expand...

I did not comment about your PCB layout because I am not expert...at all...
Look at the tool that I use to make my own PCB's:

http://www.amazon.co.uk/Dremel-Rotary-Tool-300-acces/dp/B000KJRQN0

Am I primitive or what? 😀

You could use other regs instead of TeddyReg, like shunt-reg, which look simple.

Good luck with your PCB/project :up:
M
 
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