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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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Tweakers' Asylum Tweaks for systems, rooms and Do It Yourself (DIY) help. FAQ. |
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In Reply to: Bridge Rectifier Challenge - Viewpoints Welcome! posted by spindrifter on May 15, 2007 at 22:24:58:
You state that you have built a "Full duo mono phono stage". In order to have a 'full dual mono' circuit you must also have an isolated Central Ground Point for EACH CHANNEL. By isolated 'central ground point' I mean that each CGP is "floating", i.e. it is not grounded to anything other than the power supply. Many people do not understand the importance of "ground". "Ground" is the other half of the circuit. Hum in a circuit is often due to poor grounding techniques. Ideally, each component requiring grounding should be connected DIRECTLY to the CGP. The simplest nethod of achieving this is to use a double-sided pcb (a copper sheet on both sides of the pcb). The top plane of the pcb then becomes the CGP. Ground busses are anathema as they often pick up noise on the way to the CGP and often result in a pcb much larger than necessary due to the number of components requiring grounding. David Clark, a highly respected tube circuit designer) used a separate ground line for each component requiring grounding in his circuits. As far as shielding, Texas Instruments' "T.I. Shielding Material" is claimed by T.I. to block 98+% of BOTH EMI and RFI when properly grounded. It is composed of two layers of copper sheeting with a layer of proprietary metal in the middle. It is available from Percy in sheet form 12" wide and any length desired and is available in various thicknesses. It is easily worked with tin snips and solders easily.As to bypassing capacitors, few people seem to understand the reason for bypassing caps. Caps, especially electrolytics, have a resonant frequency. When they reach their resonant frequency they electrically drop out of the circuit as if they weren't there. To prevent this a small value cap is installed accross the cap to be bypassed to shunt these high frequencies to ground. I have found that the best value for bypasses in audio circuits is 0.01 uF. The best type of bypass cap is silver mica, followed by stacked film as they have exceedingly low inductance. Silve mica caps are available from Hosfelt Electronics (800/264-6464 & 888/264-6464) at very low prices.
Happy Listening !
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Follow Ups
- Re: Bridge Rectifier Challenge - Viewpoints Welcome! - pkell44 18:58:35 05/16/07 (1)
- Re: Bridge Rectifier Challenge - Viewpoints Welcome! - spindrifter 20:01:53 05/16/07 (0)
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