Unfortunately, we arent able to search just this thread 
So Im about to ask a question that has probably been asked a few times before in this thread (Sorry! It will take a week to read through the whole thing)
I have a ground loop hum issue.
I built the LM4780 4 channel version wth two amp boards. ( 2 channels off each board and one transformer).I followed the directions and did the star ground. My RCA's are isolated from the chassis with plastic isolation washers. When I have my PC connected via RCA as a source to the amp, I get alot of hum, even at low volumes. If I disconect the power cord from the PC and run just off the battery the hum goes away instantly. Is there a modification I can make to the amp to eliminate this issue?
Sounds fantastc when its not humming!
So Im about to ask a question that has probably been asked a few times before in this thread (Sorry! It will take a week to read through the whole thing)I have a ground loop hum issue.
I built the LM4780 4 channel version wth two amp boards. ( 2 channels off each board and one transformer).I followed the directions and did the star ground. My RCA's are isolated from the chassis with plastic isolation washers. When I have my PC connected via RCA as a source to the amp, I get alot of hum, even at low volumes. If I disconect the power cord from the PC and run just off the battery the hum goes away instantly. Is there a modification I can make to the amp to eliminate this issue?
Sounds fantastc when its not humming!
Did you use both rectifier boards or just one as recommended?
Is your star ground as described here: http://www.diyaudio.com/forums/audi...-kit-building-instructions-4.html#post1518369
Is your star ground as described here: http://www.diyaudio.com/forums/audi...-kit-building-instructions-4.html#post1518369
Yessir, one rectifier board as you suggested. And yes to the star ground model as well.
Okay, with all due kindness but a bit of hilarity I have to say
"Hey CaptainObvious, in fact you can search this thread. Up at the top where it says "search this thread."
Thats odd. Yesterday all I saw up there was thread tools, today I see the search option and the thread rating...
Thats odd. Yesterday all I saw up there was thread tools, today I see the search option and the thread rating...
I think you have to be logged in for those to appear.
Hi all
How can I add a "sub out" to my integrated (with source selector and volume att.) gainclone? I have a subwoofer that needs a line input, can be full frequency, filtering is done inside the subwoofer. Just split the signal after volume and before amp boards?
Kind regards
Erik Blokpoel
How can I add a "sub out" to my integrated (with source selector and volume att.) gainclone? I have a subwoofer that needs a line input, can be full frequency, filtering is done inside the subwoofer. Just split the signal after volume and before amp boards?
Kind regards
Erik Blokpoel
Hello everyone,
I'm a newbie who just bought the LM3875 kit. I reading the thread while I'm waiting fot it to be delivered and have a question in mind.
Right now, I have an old Pionner amp that (if I remember correctly) was stated to output 100W per channel.
First tought : commercial amp = not really 100W.
Second : At half power, its more than loud enoughin a party, so theorically, I use 50W.
Third : I want to build this amp mainly to listen to MP3 throught a multi-zone systems of in-celling and in-wall speakers, so not that loud.
So, my quesion is : if I use a smaller transformer (example 12V instead of 24) with less VA (example 120 VA for 6 amps) will I get a good sound but less loud?
Or should I buy the 300 VA 25Vx2?
I'm not sure if my speakers will be 8ohms or 4 ohms...
Thanks
I'm a newbie who just bought the LM3875 kit. I reading the thread while I'm waiting fot it to be delivered and have a question in mind.
Right now, I have an old Pionner amp that (if I remember correctly) was stated to output 100W per channel.
First tought : commercial amp = not really 100W.
Second : At half power, its more than loud enoughin a party, so theorically, I use 50W.
Third : I want to build this amp mainly to listen to MP3 throught a multi-zone systems of in-celling and in-wall speakers, so not that loud.
So, my quesion is : if I use a smaller transformer (example 12V instead of 24) with less VA (example 120 VA for 6 amps) will I get a good sound but less loud?
Or should I buy the 300 VA 25Vx2?
I'm not sure if my speakers will be 8ohms or 4 ohms...
Thanks
How do you know it's at half power? Are you actually measuring the power output electrically, or just judging by the position of the volume knob? The position of a volume knob would not be a meaningful way of gauging power output since most potentiometers used in this application have a logarithmic taper.
I was just judging by the position of the knob.
My goal is to amplify my computer's sound cards for in-wall speakers. I don't need them to play very loud and since toroids are expensive, I was wandering if Volts and/or Amps (or VA) can be reduce and still get a good result.
I saw a Toroid in Montreal for $19,99 which is 12volts and 150VA. I was planning to buy two of thoses.
From what I can understand, the amps will help mostly the sound quality and volts the volume? Is that right?
Thanks
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I cannot recommed to power this amp with less than 18V transformer secondary voltage. I made one with 15V and although it works perfectly can run out of power during peaks in an irritating way, not limiting distortion but a kind of overall limiting.
If you are concerned about the maximum power, buy something between 18V and 21V secondary. One toroid with approx. 160VA is sufficient in your case, I think.
If you are concerned about the maximum power, buy something between 18V and 21V secondary. One toroid with approx. 160VA is sufficient in your case, I think.