Poor man's guide to remove power supply noise from audio

**Gip** · 11-23-2006, 01:44 PM

Originally Posted by Ruffy

I have spare modems, many of them. Most people that have build computers through the years have at least one.

I also I have RCA jacks and mini 1/8" plugs, same thing as above.

With alittle knowledge of the tools anyone can make it in like 10 minutes or less. I know I could.

A Premade one can be bought for under $20. But wheres the thrill of making something yourself with that?

Hell you can buy those transformers for $2-5 each and make your own for under $10

Well, I must admit it, this tutorial is mainly for people like you (and me), who have tons of "junkies" too hard to throw away because "you never know..."!
And I must ABSOLUTELY quote "A Premade one can be bought for under $20. But wheres the thrill of making something yourself with that?"!!! Are we the same person?

Btw, I'm not really a "poor man", and I don't think that everyone having enough money and effort to spend in a carputer is a REAL poor man, but I simply LOVE the challenge of efficiency. I always want to obtain the best results with the smallest effort... And I succeed most of the time! Sorry for you guys that prefer to buy premade things, paying more and learning nothing, but I'm a geek and I'm proud of it! Well, actually I'm not a real geek, since I have a girlfriend, but who cares!

PS: my circuit is wrapped up in 19 cent red electrical tape...

**Rob Withey** · 11-23-2006, 02:31 PM

Originally Posted by Gip

Sorry for you guys that prefer to buy premade things, paying more and learning nothing, but I'm a geek and I'm proud of it!

Some of us are geeks that already know how stuff works, and recognise that sometimes the most efficient way to get stuff done is to buy a mass produced device.
I'm surprised you didn't wind your own transformers...!

**Gip** · 11-23-2006, 04:10 PM

Originally Posted by Rob Withey

Some of us are geeks that already know how stuff works, and recognise that sometimes the most efficient way to get stuff done is to buy a mass produced device.
I'm surprised you didn't wind your own transformers...!

Touche...

But what about the satiafaction! Btw, I myself already know how and why this stuff works, you surely can imagine that I haven't tried to put every single component of a modem pc board in series of the audio cable to find out tha the transformer works better!

You will be surprised to know that in the past i even wond (mmmh... past of "to wind"? sorry for my english.....) my own transormers...

**Ruffy** · 11-23-2006, 05:20 PM

Originally Posted by Gip

Touche...

But what about the satiafaction! Btw, I myself already know how and why this stuff works, you surely can imagine that I haven't tried to put every single component of a modem pc board in series of the audio cable to find out tha the transformer works better!

You will be surprised to know that in the past i even wond (mmmh... past of "to wind"? sorry for my english.....) my own transormers...

wound. You were on the right track with the word. The English language is not friendly.

**miwise** · 11-23-2006, 05:37 PM

worked nicely for me. I already had a ground loop isolator (from radio shack) b/w the computer and both amps, but I was getting a loop b/w the sub amp and highs amp. I installed this b/w the 2 amps. Worked great!

**Skum** · 01-19-2007, 03:23 PM

I had tons of problems with the generator noise, and had tried a lot of stuff (but apparently gone in the wrong direction). Then finally turning to the net (where I of course should have started) I found this, which works perfectly! Thanks a million man!

**ROMbler** · 01-19-2007, 03:41 PM

Arg! I just threw away two modems I had kept for the longest time. I have tons of parts that I finally decided to organize and consolidate. The only stuff I chucked were the modems and an 8MB graphics card. I should have known better. I like your tutorial and would have preferred to build the isolator over junking the parts. Never fails when you decide to chuck something

**RedGTiVR6** · 01-19-2007, 04:13 PM

Induced noise/Ground loop trouble shooting guide.

some of you should venture into the Car Audio forum more often...

**raxy** · 01-22-2007, 03:44 AM

sorry to disagree with the solution.

telephone/modem coupling tranformers are good only for telephony,
that mean they are made for telephony bandwidth : 300-4000Hz

below and above this range, nothing is guaranted and the cheaper the device, the narrower its frequency response.

Did you measure 20Khz and 20Hz output levels compared to a reference @ 1KHz ?

**spuzzdawg** · 01-22-2007, 10:07 AM

I might be making a big assumption but I would have thought that the interference noise had a relationship to the RPM of the engine, in which case the telephony bandwidth is almost perfect - I guess it could go a little higher

Spuzzdawg