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previous: DD Wiring has the potential for lots o... -- 8/17/2004 3:06 AM View Thread

Re: Lacquer covered cloth wire over PVC insulation?

8/17/2004 12:17 AM
Bruce /Mission Amps
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Re: Lacquer covered cloth wire over PVC insulation?
Ha ha.. OK DD!! I get it. You aren't going to give up, you like overkill and lots of teflon. :)  
 
By the way the <30pF of "distributed capacitance" of co-ax per foot is more of a problem with impedance matching and or db loss per 100' at RF freqs not audio.  
If not, your 30pF per foot would result in no signal at the end of the 100 feet!!  
 
Co-ax used like this is an unbalanced transmission line. At low or base band audio freqs, it's fairly unimportant.  
Used the way most co-ax is used in audio circuits, the capacitance is shunted to ground not to another stage for possible amplification. Therefore, as far as instability is concerned, it's unlikely to cause any problems what so ever.  
IMHO, used in short runs for audio coupling in guitar amps, it is nearly a total moot point.  
A well designed amp only has one side of the shield grounded anyhow... at the signal origination point, not the amplification end.  
For those inclined to do the math.... a one foot of co-ax with a 30pF/per foot rating, shunted across a 1M grounded grid load resistor has a -3dB point of aprox 5300 Hz.  
However, that doesn't mean the circuit bandwidth drops -3dB at 5300Hz because of the 12" of shielded co-ax.  
There are other reactive components in there that can negate or add to this effect .  
 
Bruce

 
Replies:
DD you like overkill and lots of te... -- 8/17/2004 3:34 AM