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Chip Amps Amplifiers based on integrated circuits

LM3886 opinions sought
LM3886 opinions sought
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Old 8th January 2018, 10:51 AM   #11
AndrewT is offline AndrewT  Scotland
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I like your signature line with the links to three sites I have used a lot.
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Old 8th January 2018, 12:08 PM   #12
john blackburn is offline john blackburn  United Kingdom
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Decibel Dungeon was the first place I saw the word Gainclone which eventually lead me to this forum. Even the bathroom has speakers now.
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Old 8th January 2018, 12:46 PM   #13
bullittstang is offline bullittstang  United States
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I currently run 2 inexpensive LM3886 from eBay with a 28VAC toroidal, with an iPhone as the only input. They will take full power from the iPhone with only a very rare clip (2-3 times in the last 2 months) but have to run the iPhone at 100% to get it to clip. I typically listen at 40-50% on the iPhone though and they do just fine.
I have both chips on a 7-1/2 x 2-1/4 x 2 inch finned heatsink, running in my basement (60 degrees F right now)
I am running a Mauro Penasa LM3886 with 22VAC torroidal (same size heatsink) - and it certainly sounds better, it will be up to you if $150 compared to $20 is worth the difference, just more refined in most every way.

Edit - this is running on 4-ohm DIY speakers (4-ohm woofer, 4-ohm tweeter), but the industry would probably say they are 6-ohm nominal.

Last edited by bullittstang; 8th January 2018 at 12:51 PM.
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Old 8th January 2018, 07:19 PM   #14
john blackburn is offline john blackburn  United Kingdom
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If the budget was available I would love to hear a Myref or Modulus implementation of the 3886 but I can't justify the costs as things are.

The amps I have are at the minimalist end of things. My first was a chipamp.com LM3875 which is still playing daily some 11 years later and taught me all about the invisible lacquer on transformer secondaries. That was followed by a couple of point to point builds with more of the "optional" stability components included, so I have yet to hear the best sound you can get from them.

Interesting to hear you are running on even higher voltages than I was proposing too.
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Old 8th January 2018, 07:36 PM   #15
bullittstang is offline bullittstang  United States
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There are way smarter people on this forum than I, so I can only say that it works...not that it is the best long-term solution.
For me - $20 is not enough to warrant not using the toiroidal I already had, even if they get destroyed. I did make sure to have speaker protection, just in case.
After being a mosfet guy in all my previous amps - I was surprised and have been very happy with the LM3886 amps. Much better and stronger bass than I expected and easy to listen to. My previous Class D cheap amps always seemed to be shrill and my ears got tired of listening to them after 30-45 minutes.
Good Luck on whatever you build - sure it will sound great and give you years of entertainment.
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Old 11th January 2018, 10:08 PM   #16
tomchr is offline tomchr  Canada
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2x25VAC is a bit much for a single LM3886 as you'll get about 35-36 V DC out of it. I explain my reasoning here: LM3886 Output Power. You could choose to drop the supply voltage a bit using a 5.6 V, 5 W zener in series with each supply lead.
You could also implement a simple zener regulator with a transistor (requires four components). You'll probably want a darlington transistor as shown here - or a MOSFET. You'd want the transistor on a heat sink ... which it could share with the LM3886.
Click the image to open in full size.
Then you get the bragging rights to having a regulated supply... Read the full circuit description here: Transistor-Zener Diode Regulator Circuits

Should you later decide to drop in a MOD286 in mono configuration for 100 W into 4 Ω, you'd have the supply and heat sink ready to go. Just remove the zener diode or regulator and drop in the MOD286.

Tom
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Last edited by tomchr; 11th January 2018 at 10:11 PM.
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Old 14th January 2018, 01:55 AM   #17
john blackburn is offline john blackburn  United Kingdom
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Hi Tom, sorry for the delayed reply. Thanks for the advice and links, I will have a proper read of them later when I get chance.

I have been reading your site recently, that's some grasp of maths you've got.
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Old 31st January 2018, 02:56 PM   #18
john blackburn is offline john blackburn  United Kingdom
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A bit of an update.

Further biscuit tin rummaging turned up four LM338s that I bought years ago to try a regulated chipamp using CarlosFMs design. I didn't get round to it at the time so I think I will try those at 28 volts to start with, and maybe try discrete regulators eventually.

What are your collective thoughts on the best way and place to create a signal ground when point to pointing? I can't do it on the RCAs due to the distance.

I have used a one ohm resistor from the power ground as a signal ground point on a previous build which seemed to work nicely, so that is probably the plan unless I've missed something.

John
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Old 31st January 2018, 03:44 PM   #19
AndrewT is offline AndrewT  Scotland
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Placing the main audio ground reference point on the speaker output terminal is probably better for a discrete P2P assembly.
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Old 1st February 2018, 05:11 AM   #20
Nenola is offline Nenola  Finland
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Quote:
Originally Posted by bullittstang View Post
I currently run 2 inexpensive LM3886 from eBay
Do you have a picture of what they looked like? I was going through the options one day and ordered one mono board for about 5, so not a big loss if it's no good.

LM3886TF AC 20~28V 60W Sound Audio Amplifier Mono Digital Power AMP DIY Kit | eBay

I know that there are better designs out there, but I just need a mono amp that does the job decently. Need to upgrade one LM1876 from my 2.1 amp to this, so it can better drive a 4 ohm subwoofer.
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