More information about connecting your system.
True about some older model color TV sets especially the one manufactured during the 1980s. These particular sets had a live chassis with a very basic mains isolation circuit for connecting aerial and video into the set. They work fine with double insulated mains appliances but problems arise when you connect an earthed (mains grounded appliance such as a PC) where if the components are old such as 25 years the possibilities of ground to mains leakage are apparent, causing mains to earth current loop and in worst case short circuit and if the PC is not earthed properly a very live PC. I have measured the isolated input ground to earth ground and have read about 90 volt AC potential difference between the two points, although the current is small and the worse you would feel is a pricking sensation. However this potential is significant enough to cause ground loop interference, which would cause PC crashes and mains hum or buzz in audio amplifiers. My recommendations would be never use this particular model of TV set for this application. In fact (and take this seriously from a TV tech) a live chassis TV set is a danger, electrical hazard, especially that this type of set is 20 years old and should be disposed of or used as a door stop period. Fortunately the TV sets made today and 10 years have an isolated chassis and if you want a cheap replacement; Brands such as Samsung, TVON, TEAC/ROWA, SANYO, TOSHIBA aren't too bad.
A few tips to help performance: The biggest problem I have found is interference in the audio, this is mainly mains hum or buzz as well as noise such as hiss and PC function whether it is cause by PC interrupt command or just processor noise.
To cure the main hum or buzz, this probably the most pain in the ass problem this is caused by earth looping. To start attach a wire to every ground plane you have, start with PC case, Amplifier case, DVD case, Turntable and any other accessory you have attached. Then with these wires, which should be about the same length connect them to a common point and attach to the mains earth. The next part which is tricky if you not electronically inclined and that is to attach a 2.2 ohm resistor in parallel with a 470 pico farad ceramic type capacitor from the electronic ground to mains earth or chassis.
Sound card noise this is dependent on type of sound card used and where the sound card is positioned on the PC mother board. Further away from the video card and processor the better. Cheap cards will allow processor or interrupt noise to be present, you can hear with headphones on and by turning the volume up to max then inserting a CD ROM or running a program, where you will hear a squealing or buzzing sound that is obviously computer generated. The only solution is to get a better sound card such a Sound Blaster or better.
Isolating the sound card by placing the sound card between two unused
mother board slots then make up two blank PCB cards to fit and tying the copper planes to chassis. These blank PCB cards should not be inserted into the slots but rigidly mounted, both sides of the sound card. I would like to draw a diagram here but damn these blogging sites for being so text only, can't even place a .bmp file. Stupid bulletin board formats, so last century, grow up and let have some HTML graphics to play with.
With sound card hiss I have been given several suggestions on how to fix this problem again this is for the electronically minded and begins with changing every capacitor on the sound card board from the cheap ceramic and electrolytic type to the audio quality silver mica and bipolar electrolytic. Then change the generic commercial analogue output IC to high grade military, industrial spec types. A bit far fetched I know but theoretically there should be no noise, even with all levels cranked up to the max. A good electronics tech should help you with this problem and we usually prefer hash or cash.
Again with your AV connections the cables you use on the inputs are more important, as small signals can be subject to noise interference. So optimizing shielding and contact quality i.e using gold plated connectors can play an important role. In regards to speaker cable, which is large signal and where small signal noise is less apparent but factors such as resistance play a more important role for power delivery. Personally I would forget about using monster cable unless you are using 1000 Watt RMS or greater, power amplifiers. Don't listen to the sales reps about promoting this (tell them they are full of sh*t)(AHH yes sale reps I just love chewing them up and spitting them out, making the ******** sweat and pissing them off, them in there stupid suit and tie. (Cant help it I'm an electronics tech)).
I found that ordinary multi core 10 Amp mains flex such as the type used in lamp flex or vaccum cleaners and mains extension leads is more than adequate. From what I know mains flex, it does have a higher resistance per meter than monster cable but it also has a higher high frequency roll off that is better than monster cable. In fact I would recommend this type of cable as a cheap and reliable alternative in any amplifier to speaker installation.
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