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Old 7th September 2015, 12:35 AM   #1
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Default My LM3886 Build

Decided to make this thread to consolidate my ongoing progress and questions related to the LM3886 amplifier I'm building over the next month.

I ordered the stereo LM3886 kit from chipamp.com and should have it in a few days. I also ordered an Antek 300VA 2x25v toroidal transformer.

I ordered quality rca connectors, speaker binding posts and power connector from chipamp as well.

First question:
Brian doesn't sell a fuse holder and I am in need of one. I see 5 for like $7 on amazon, but these are just generic ones. Is there a particularly high quality fuse holder for my build that is on par with the quality of the other parts I just bought?
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Old 7th September 2015, 01:27 AM   #2
infinia is offline infinia  United States
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look into a IEC AC inlet with a built in fuse. compact and less wires to mess with

OK you shop Amazon , added link ( not sure if these are safety rated or not.
http://www.amazon.com/Inlet-Module-S.../dp/B00F4MFMXE
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Last edited by infinia; 7th September 2015 at 01:33 AM. Reason: added link
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Old 7th September 2015, 02:17 AM   #3
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Quote:
Originally Posted by infinia View Post
look into a IEC AC inlet with a built in fuse. compact and less wires to mess with

OK you shop Amazon , added link ( not sure if these are safety rated or not.
Amazon.com: Inlet Module Plug Fuse Switch Male Power Socket 10A 250V 3 Pin IEC320 C14: Automotive
Okay, just ordered that inlet/fuse/switch from Amazon for my LM3886. Makes for a great bench/testing setup as well. I might order more of these for other projects.. like a replacement linear power supply for my 1983 Commodore 64.
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Old 7th September 2015, 02:29 AM   #4
nezbleu is offline nezbleu  Canada
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For things like that i have purchased from Apex Jr, Apex Jr.Home Page. They are in the vendors forum here. They have switched, fused IEC receptacles for $0.99
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Old 10th September 2015, 01:53 PM   #5
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I received the parts the day before yesterday and spend all day yesterday working on this amp. So far it sounds great! This is my first power supply I've ever made and first amplifier ever

Click the image to open in full size.

It's a face panel from an old HP 400D vacuum tube multimeter (1/8" thick or so aluminum). And it is clamped to a piece of poplar.
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Old 10th September 2015, 02:16 PM   #6
infinia is offline infinia  United States
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Congrats Jennifer!

a fine home until a donor case arrives.
look forward to any new hardware developments or listening impressions.
twisted wires are great
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Old 10th September 2015, 02:41 PM   #7
AndrewT is online now AndrewT  Scotland
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do not use multiple wires under the Safety Earth nut.
Use a dedicated bolt fixing for the Safety Earth.
Stick a couple of layers of insulating tape over the exposed MAINS terminals. You don't want to touch these nor drop a metal tool on them.

Change the label on the mains input. Either PE (Protective Earth), if that means anything to you, or "Safety Earth" if that sticks in your head better.

It is not GND. That is too easily confused with other parts of the audio circuits.


Use a separate bolt/lug for the Main Audio Ground. This can float as long as you can SEE that the mains transformer is not faulty.

Then after you have the amplifier working and tested you can take an extra wire (or Disconnecting Network) to the earthed panel with it's own separate fixing.

Are you using a single 4diode bridge rectifier? Or is that an 8diode dual bridge rectifier? Once I have this answer I am going to expand on Infinia's "twisted wires are great"

Have you built up a Mains Bulb Tester yet?
Do you know how to use it?
Do you know how to interpret the messages that the bulb gives you?
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Last edited by AndrewT; 10th September 2015 at 02:49 PM.
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Old 10th September 2015, 02:43 PM   #8
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Are you using a single 4diode bridge rectifier? Or is that an 8diode dual bridge rectifier?
8 diodes, dual bridge. One side provides positive voltage and the other is negative voltage.
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Old 10th September 2015, 02:43 PM   #9
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regarding the audio & ground, the amp board itself tie the ins and outs to chassis ground if I recall correctly.
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Old 10th September 2015, 02:46 PM   #10
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I'm going to have to read up more about this audio grounding vs chassis grounding.. it's confusing.

I'm not getting any hum right now as is. Although I am wishing the sound was a bit more clear than it is. It sounds better than what I had before I believe.
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